47735716-Philippines-Coal-Resources-101130

Report On Coal Resources of the Philippines, November 1985

Sufficient exploration and development drilling has been done to indicate that new sources of supply could come from one or several potential new mines:

A. Western MindanaoPNO-CC has indicated sufficient in-situ reserve for the construction of a 200.000 tpa to 300.000 tpa underground mine at Lalat, which would use semi-mechanised longwall methods. The construction of the Lalat mine is particularly important, as it is the only new mine, scheduled for development, that would produce higher heating value (+10,000 Btu/ lb ar) coal.

B. Eastern Mindanao1. Several open pit properties with capacities of between 50.000 tpa and 300.000 tpa, could be

developed by the private sector in the Bislig-Tandag-Tago-Lianga area.2. Installation of PNOC-CC’s 300.000 tpa underground, Bislig III mine which would use semi-

mechanised longwall mining methods. An open pit in Sicahoy/ Junction area could be installed as an interim measure whilst the underground mine is being constructed.

C. Semirara IslandSufficient development drilling and preliminary feasibility studies have been undertaken to indicate that a new 1.0 million tpa to 1.5 million tpa open pit mine could be developed at Himalian, or possibly at Panian. The areas, however, need to be checking drilled and the recommended machine system re-evaluated, in light of the mining experience gained in SCC’s Unong open pit.

D. Cagayan ValleyThe Isabela Coal Consortium (backed by Burnett & Hallamshire) have indicated sufficient reserves of lower heating value (c. 5,000 Btu/lb ar) coal which could be mined at a rate of say 0.5 million to 1.0 million tpa, by open pit methods. Burnett & Hallamshire have recently indicated that they plan to carry out drying test on a bulk sample, which could confirm whether the heating content of the lignitic coal could be improved by reducing the total moisture content (40% to 60%) of the mine product

Information, amassed since 1977, has further emphasized that the Philippine’s coal deposits lay in difficult geological conditions. The complicated sedimentary and structural setting of the Philippines’ coal deposits does not lend itself to the installation of high capacity mines which can make use of modern coal mining technology and equipment.

The percentage of the country’s re-estimated 359 million tones of demonstrated, in-situ coal reserves which could be mined at a profit. Over 70% of the country’s demonstrated, in-situ reserve base comprises lower heating value (less than 9,000 Btu/lb ar) coals in Semirara, in Eastern Mindanao, and in the Cagayan Valley, which are likely to support the generation of coal mines.

Some of 78% of the 1984, potential coal resource is represented by coals of Miocene age (with minor tonnage of Oligocene and Eocene age). Almost half of the Miocene coal, and other coals, pre-date the Middle-Miocene, pan-Philippines tectonic event and are therefore likely to be structurally disturbed. The remaining 22% is Plio-Pleistocene in age and predominantly comprises the lignitic to sub-bituminous coal of the Cagayan Valley. Although these coal are low in heating value and relatively undeformed.

The potential coal resource contains 42% lignitic to sub-bituminous coals, 55% sub-bituminous to bituminous coals and 3% bituminous to semi-anthracitic coals. The scarce resources of the high ranking coals are largely found in the Malangas coalfield of western Mindanao, where seams have been locally affected by thermal metamorphism associated with cold intrusion of andesitic magma along major faults.

Pinch and swell structure, compaction and erosional feature are common. Seam thicknesses rarely exceed 1.5 to 2.0m. The main seam in the Unong pit of Samirara Island is an exception where the thickness locally reaches 20m or more over a 1.3km2 area.

The coal deposits of the Philippines exhibit a full range of dips. Younger coals of Plio-Pleistocene age are generally flat lying, although dips can be locally as much as 75° on the edges of the basins, and in strata affected by diapiric folding. Dips in the older deposits are generally severe (20° to 75°and overturned strata can be occasionally found in coal measures found close to the structural highs at the edges of basins. Many seams undulate down dip; undulations commonly have dips varying between 15° and 35°.

Underground, the operation of semi-mechanized longwall faces at Bislig and Malangas in Mindanao has been affected by minor scale faulting which cannot be identified by surface exploration techniques.

Coal Areas and Resources (BEB 1984)

A. Western Mindanao

The Sibuguey Peninsula contains the only coals of medium volatile bituminous and high rank in the Philippines, apart from the Eocene coals found on Catanduanes.

PNOCC_CC has undertaken the following work since acquiring the exploration rights to the Sibuguey Peninsula.

Geological mapping of the peninsula at scale 1:10,000 and preparation 1:50,000 scale composite sheets.

Topographical survey at 1:1,000. Drilling of some 400 diamond drillholes in the mining and selected exploration area. 30 kms (11 lines) of Mini-sosie Seismic reflection traversing carried out on April-May 1982. Pre-feasibility study of the Lalat prospect for an underground coal mine.

The following prospects, largely belonging to PNOC-CC, are active on the Peninsula;

Lalat (Main) North Lalat South Lalat Little Baguio (North Limb) Kauswagan Balian South Limb

Stratigraphy

The Lumbog Formation (Lower Miocene), conformably overlies the Sibuguey Formation, and comprises coal measures and volcaniclastic units laid down under paralic condition. The Formation is divided into three members.

Members: Lalat, Gotas, Dumagok Lithology: Mudstone, shale, sandstone with interbeds of pyroclastic rocks, limestone and coalStratigraphic relations: Conformable over the Sibuguey FormationDistribution: Sibuguey River Valley; Dipili-Lake Wood area, Sibuguey PeninsulaThickness: 525 mAge: Early Miocene

The Lumbog Formation was named by Ibañez and others (1956) for the sequence of clastic and pyroclastic rocks with interbeds of coal in the Malangas-Kabasalan region. The Lumbog rests conformably over the Sibuguey Formation. It is Early Miocene in age and estimated to have a maximum thickness of 525 m (Ibañez and others, 1956). It is divided into three members, namely: lower Lalat, middle Gotas and upper Dumagok.

The Lalat member was originally defined as a separate formation by Brown (1950) for the exposures along Lalat Creek, a tributary of Sibuguey River. It consists of mudstone, sandy shale and sandstone with interbeds of pyroclastic rocks, coal and limestone. The mudstone and shale are medium to dark gray, thin to medium bedded, but massive in places. The sandstone is light to dark gray, generally poorly bedded, and in places shows cross-bedding. It is composed of fine to coarse subangular to subrounded grains of quartz, feldspar and chloritized lithic fragments. The coal beds attain a thickness of 3 m. The Lalat is well exposed at the Diplahan-Butog and Lalat areas and is estimated to be 285 m thick. Fossils in this member reported by Brown (1950) include Vicarya callosa, Ceritheum herklotsi, Cerithium kenkinsi, Cerithium bandongensis and Terebra bicinncta.

The Gotas member is well-exposed along Gotas creek. It consists of mudstones, shale and sandstone. Unlike the Lalat member, Gotas has thick interbeds of coarse pyroclastic rocks and has no coal beds.

The Dumagok member consists mainly of sandstones, including medium grained arkosic sandstone with few interbeds of mudstone, coal and pyroclastic rocks.

Strata dips are variable, commonly ranging from 10° to 60° and locally overturned. Undulations in the seams are found downdip. Dip reversals over small areas are common and have been interpreted on occasions as a limb of folds.

a. PNOC-CC Mining Areas (Kauswagan Colliery, Diplahan Colliery and Little Baguio Colliery); The LA and LC1 seams have been thermally affected by igneous intrusion present in the area. The normally sub-bituminous rank of the coal has been upgraded to bituminous to semi-anthracite with an average heating value of some 10,000 Btu/lb (adb).

Coal Quality

The Lalat member contains five named seams (Seam A to E) and two named seams (LA and LC1) in the PNO-CC mining area. LA and LC1 have been thermally affected by igneous intrusions present in the area. The normally sub-bituminous rank of the coal has been upgraded to bituminous to semi-anthracite with an average heating value of some 10,300 Btu/lb on air dried basis.

In-situ Reserves

As on February 1985, PNOC-CC reported 15.1 million tones of demonstrated in-situ reserves for the corporation’s mining area. Some 84% of the reserves lie in the area to be worked by Diplahan Colliery. The in-situ reserves, proved in the LC1 seam, account for some 70% of the demonstrated in-situ reserve base.

Mining Condition

Mining conditions are moderately difficult in the mines. Both small scale faulting and larger displacement faults along the axis of the “Lumbog Anticline” hamper mine development and face layouts. Face layouts are also made difficult by the irregular boundaries of the igneous intrusions. Some of the mudstone roof and floor strata are slacking. Isolated blocks of igneous rock cause difficulties in roof support.

b. Lalat Prospect, The Lalat prospect is generally lower than the 25% ash content of the seams currently being minded by PNO-CC. The heating value is generally about 12,000 Btu/lb adb where the coal has an ash content of some 11% to 13%. The heating value of seam A is generally less than 10,000 Btu/lb adb because of the higher ash content (25%). The sulphur contents of seams are generally less than 1%.

Statigraphy

Three mineable seams (Seam A, B and E) are located in a 120m to 150m thickness of the Lalat Member of the Lumbog Formation (Lower Miocene). The mineable seams average some one meter

in thickness although in places they can attain thicknesses in excess of 3.0m. Partings are few, although in some of the thicker seam section, they can attain thicknesses of up to 0.8m.

Structure

A slightly displaced, normal axial plane fault (lower Colgran Fault) dips at 60° to the south. Strata on the southern limb dip between 10 and 30. The northern limb dips at 30° to 80°, is locally sheared and possibly overturned and affected by a major reverse strike fault (upper Colgran Fault). The structure is cut by a number of major transverse faults, orientated variously northwest, north-northwest and northeast.

c. PNOC-CC Exploration Areas:

Balian Prospect, PNOC-CC drilled six boreholes in 1982/3, and have proved the presence of two seams, equivalent to the LA seam and LC1 seam. Both seams have variable thicknesses ranging between 0.6m and 4.4m. Partings vary between 0.28m and 0.43m in thickness. The heating is some 10,000 Btu/lb adb. Ash content varies between 13% and 16% ad and sulphur is below 1%

North Lalat Prospect, The coal measures are block faulted and the strata have dips varying from 20C to 30°, thin seams with thicknesses between 0.3m and 1.22m, coal heating value of some 12,000 Btu/lb adb, ash content 10.9% and total sulphur 0.29%.

South Lalat Prospect, The inlier is affected by block faulting and dips range from 20° to 55°. Eight boreholes drilled in 1981/83 found several seams up to 1.2m thick which could be equivalent to Seam E, F and G found in the Lalat Prospect. No reserves are estimated and need to recommend deeper drilling to prove further seams at depth.

North Limb Prospect, The seam LC1 is commonly 2.1m thick (maximum 3.39m thick) and contains one to four mudstone parting, each one up to 0.2m thick. The lower LA seam lies some 15m above the Lalat member/Sibuguey Formation boundary). The seam is commonly 0.9m thick (maximum 1.58m thick) and has a mudstone parting of up to 0.1m thick. Dips on the north limb undulate between 5° and 20°. The heating value between 11,900 Btu/lb and 13,000 Btu/lb adb with ash content 22.3% to 24.8%.

South Limb Prospect, Only the LC1 seam and LA seam in the prospect are considered mineable. The upper LC1 seam has an average thickness of 2.1m (maximum 3.68m) and contains few partings which can reach 0.4m in thickness. The underlying LA seam averages 0.79m in thickness (maximum of 1.69m) and also contains few partings which can reach up to 0.31m in thickness. Heating values vary between 11,700 Btu/lb and 13,500 Btu/lb adb. Ash content 9.7% to 20.6%, Moisture 0.9% to 1.4% and Volatile Matter between of 27.1% to 22.7%.

PNOC-CC has proven that are amount 3.0 million tonnes for the LC1 seam and 1.5 million tonnes for LA seam.

Kauswagan Prospect; both of the LC1 seam and LA seam occur in the Kauswagan colliery area but only LA seam is mined. LC1 seam was invasion by micro-diorite intrusion which makes much of the seam unworkable. LA seam ranges 0.4m to 1.5m thick. Whilst the LC1 seam located some 15m above the LA seam, ranges from 0.38m to 2.63m in thickness. Ash content less than 5%, the heating value of the coal is only some 7,000 Btu/lb to 9,800 Btu/lb on an air dried basis.

Minor PNOC-CC Exploration Areas; Sibuguey Coal Quality, the rank of the normally sub-bituminous coal has in certain areas been upgraded to semi-anthracite and even naturally occurring coke. The volatile Matter from some 5% to 39%, heating values are commonly between 9,400 Btu/lb and 13,600 Btu/lb and Carbon contents ranges from some 80% to 92% on a dry, ash free basis and HGI are very variable and range from 34° to 105°.

Sibuguey Coal Quality

The rank of the normally sub-bituminous but in certain areas has been upgraded to semi-anthracite and even naturally occurring coke. Heating values are commonly 9,400 Btu/lb and 13,600 Btu/lb (adb), carbon content also varies range from some 80% to 92%, HGI range from 34 to 105 and ash free basis.

In-situ Reserves

PNO-CC, as of February 1985 estimated 35.26 million tones of demonstrated, in-situ reserves for its mining area and prospect on the Sibuguey Peninsula. Some 43% of the reserves base (15.10 million tonnes) lies in the mining area of the Diplahan, Little Baguio and Kauswagan Collieries. The Lalat prospect containing some 17.06 million tonnes accounts for more than three quarters of the reserves found in the prospecting areas of the Peninsula.

Zamboanga Del Norte

Two cyclical sequences of sediments rest on a volcanic-igneous basement. The lower of these known as the Anugan Clastic Group (Lower to Middle Miocene) contains coal-bearing sediments (Tupiloc Unit). The upper sequence known as the Curuan Group (Upper Miocene) is some 1,000m thick and is not known to contain coal. The clastical units are overlain by andesitic and basaltic volcanic, of the Soleplep Formation (Upper Miocene), Panganuran Formation (Pliocene) and Mt. Maria Formation (Quatenary).

The coal measures occur in a 160m thick interval within the Malungon Formation of the Anugan Group. Four seams have been recognized in the 2,000 ha Siocon area and are variously reported to have a thickness from few centimeters up to 2.2m.

The seams could have been affected by high heat flows associated with the nearby magmatic belt. Heating values are between 11,000 Btu/lb and 11,900 Btu/lb (ad) with an ash content varying from 12% to 23% (ad). The sulphur content is high and varies from 2% to 3%.

Pagadian

An arcuate belt of potentially coal-bearing sediments of Lower Miocene age is located some 20km west and possibly northeast of Pagadian city and described a stratigraphic succession similar to that found on the Sibuguey Peninsula.

Antonio et al. (1950), describe a one metre thick seam, dipping 15° to 40°, in Bigon Creek, some 20km west-northwest og Pagadian. Valasquez and Rosario (1971), describe two seams at Barrio Bigon, near the town of Dumalinao some 10km west of Pagadian. Both seams dip at 35°. The upper seam wich is 1.5m thick is separated from the lower seam (2.5m thick) by 20m of barren strata. The upper seam has the following analysis on an as received basis; Moisture 19.0%; Ash 10.1%; Volatile Matter 34.8%; Fixed Carbon 36.2%; Heating value 8,600 Btu/lb (ar)/ 12,130 Btu/lb (daf) as received basis.

B. Central Mindanao

Geological Setting

Much of the geology of Central Mindanao is necessarily complex because of the close proximity of a number of major crustal structures. On the eastern side of the region lies the Agusan-Davao Basin which was the original site of the ancestral Philippine Trench. The north trending, Phillippine Fault extends along the eastern margin of the Agusan-Davao Basin. The fault separates Central Mindanao from the uplifted block of basement strata and Cenozoic volcanic and sediments which now comprise the Samar-East Mindanao ridge. The Cotabato Basin is separates from the Agusan-Davao basin by the Mindanao Central Cordillera. Even further westward, lies the canezoic shallow marine platform which joins the Zamboanga Ridge with the deep basins of Centaral Mindanao.

Coal Occurances

1. KapataganThe Kapatagan coal occurances lie east Lake Lanao and were noted by Tupaz (1951, 19520) in his regional investigations of Lanao del Norte and the southtern part of Misamis Oriental Provinces. Little is known of the occurances, except that they might occur in the eastward extension of the Lower Miocene, paralic sediments which are found on the Sibuguey Peninsula

2. KapaiThe Kapai area lies some 20km southern of Iligan City, on the southern tip of a massif of pre-Cenozoic strata which lies between Iligan and Cagayan de Oro. The area was investigated by Tupaz (1951), who recorded a number of seam outcrops which stratigraphically occur some 100m above the basement. Dips vary from 10° to 35° and the maximum seam thickness is 1.5m. No

analyses of the coal are available, although Tupaz mentions some flat-flying seams at Siri which have semi-coking properties and heating value of about 10,000 Btu/lb (ad).

3. Manicao/ KilablabCoal occurances, located some 20km north of Iligan City, were reported by Antonio (1957) and Pacis (1962). They occur on the western flank of a massif of pre-Cenozoic strata which forms the coastal range between Iligan and Cagayan de Oro. Antonio found some 27 seam outcrops from which he identified six or seven seams with thicknesses varying from 0.2m to 0.46m. The seams are laterally very variable and contain several partings 0.01m to 0.13m thick with strata dips varying from 15° to 85°.The average analysis on an as received basis of ten analyses carried out by Antonio in 1957 is:

-Total Moisture 7.5%-Ash 10.8%-Volatile Matter 34.7%-Fixed Carbon 37.0%-Sulphur 3.99%-Heating Value 9,000 Btu/lb (ar)-Phosphorous 0.0008%

The coals are largely sub-bituminous A and B in rank.

4. Allah Valley/ Roxas Matulas RangeCoal occurrences have been found in the southeastern part of the Cotabato Basin during oil exploration field work (RRI, 1977). “Coal interbeds” are recorded on the edge of the Basin in a 1500m thick, clastic Lower Miocene sequence which overlies a re-crystallized limestone unit. The locality is thought to be in the Allah Valley.

D. Eastern Mindanao

Stratigraphy

The Cenozoic sedimentary and volcanic cover strata of Eastern Mindanao rest unconformably on a Pre-Miocene, spilitic and non-spilitic basaltic volcanic basement, known locally as either the Barcelona Formation or the Suba Formation.

Lithology: Basalt, agglomerate, breccia, clastic rocks

Stratigraphic relations: Not reported

Distribution: Eastern coast from Bislig to Lingig, Surigao del Sur

Age: Cretaceous-Paleocene (?)

Previous name: Barcelona Basalt (Vergara and Spencer, 1957)

Renamed by: MGB (2004)

The term Barcelona Basalt was used by Vergara and Spencer (1957) while MMAJ-JICA (1974) used the

term Barcelona Group for the volcanic and sedimentary suite in the Bislig-Lingig coastal area. The term

Barcelona Formation was introduced in MGB (2004). Vergara and Spencer (1957) described the unit

exposed along the eastern coast from Bislig to Lingig as consisting of basalt flows with intercalated

agglomerates, breccias and highly indurated clastic sedimentary rocks. The presence of columnar and

pillow structures were noted. The age of this formation is poorly constrained and may range from

Cretaceous to Paleogene. It might be equivalent to the Bacuag Formation in the north.

Regional mapping by PNOC-CC and PODCO has shown that the sediments in the Tago Basin comprise three major cycles of sedimentation. The lower two, each comprise continental clastics, coal bearing paralic sediments, carbonate reefs and deeper basinal clastics, as facies equivalents and were deposited in Upper Oligocene-Lower Miocene and Middle Miocene times. The Diuata Range to the west acted as the sediments source to the Tago Basin, as demonstrated by the increasing amount of arenaceous strata from east to west throughout the basin.

Towards the end of the Miocene, the area was affected by the pan-Philippine tectonic event. The basin was uplifted, faulted and the upper sediments were eroded and covered by terrestrial volcanic which originated from the Diuata Range. During Plio-Pleistocene times, the basin was once again inundated and covered with a thick sequence of massive biohermal limestone.

Previous Investigation

The Tago Basin, until recently has not been a coal mining area. Early geological work was undertaken by Alberding (1993) and Vergara and Spencer (1957) in the Bislig area.

Recent investigations of the geology have been largely confined to the central part of Surigao del Sur, between Bislig and San Isidro. At this time, PNOC-CC started exploration in the Bislig area and by 1981, PNOC-CC has drilled some 236 fully cored boreholes and completed 35km of semi-sosie seismic survey traversing.

PNOC-CC work in the area encouraged a number private sector mining companies to contract coal exploration block both around and to the north of the Bislig mining area. Recently some of coal contractors such as; ………………………………………………

PNOC-CC Mining and Exploration Activity

1. Bislig Area

The Bislig area lies some 23km south Mangagoy, near Bislig town and is reached by graded and well maintained PICOP logging road. PNOC-CC has developed a mining camp at Mendoza. A coal terminal is operated by PNOC-CC at Mangagoy.

Stratigraphy

The best development of paralic coal seams occurs in the Lower Pamaypayan Formation (Lower Miocene). The underlying Mekoupe Formation, some 500m thick, contains only a poor development of seams which are uneconomic to work. Similarly, the upper Pamaypayan Formation which is more than 800m thick, contains poor coal development.

The Pamaypayan Formation is described by Vergara and Spencer (1957) as a 500 meter-thick sequence of interbedded conglomerate, sandstone, shale, coal and corralline limestone outcropping in Pamaypayan. Petrified logs are reported to be common. As described, there seems to be no major difference between the Mekoupe and Pamaypayan formations and even Vergara and Spencer (1957) admit little difference between the sandstone of the Mekoupe and Pamaypayan formations. The Pamaypayan is considered equivalent to the Bislig Formation.

The Lower Pamaypayan Fomation is some 400m thick (380m to 410m). To the west it s dominantly arenaceous and to the east it is dominantly argillaceous – indicating a sediment source to the west. The formation contains four persistent limestone beds, indicative of minor marine incursion over the swamp lands of the paralic environment. Up to 15 persistent coal seams (with coal splits) occur with thicknesses up to 2.5m. PNOC-CC has identified coal reserves in eleven of the seams of which four are being currently mined. The coal measure are locally affected by sills of intrusive rock which can be as thick as 50m and cover areas of +3km² in the Bislig area.

Structure

The structure of the Bilslig mine area is dominated by three, near vertical, normal, east-northeast trending faults. The San Jose Fault, with a vertical displacement of 300m, limits the mining area to the north. The Mendoza Fault with a vertical displacement of 80m limits the mining area to south. The Pamaypayan Fault lies mid-way between the two bounding faults, and has a vertical displacement of 120m. Minor faulting with displacement up to 50m and commonly in the 1 m to 5m range, trends north and northwest and is common in the mining area.

Strata dips vary between 10° and 22° (average 15°) to the northwest.

Coal Seam

PNOC-CC has identified in-situ coal reserves in eleven seams within the Bislig mining area.Seam thicknesses for the six major seams vary from 2m to 3m and commonly average 1.5m thick. The six major seams lie in coal measures with a stratigraphic thickness of about 400m. Seam K lies 50m below the top of the Pamaypayan Formation, whilst seam 5 lies 15m above its base.

Mudstone partings commonly comprise some 5% to 15% of the seams. Seam H is least contaminated with only 1% partings, whilst seam 5 is the most contaminated with 22% partings.

Coal Quality

The coal from the Bislig mining area is sub-bituminous A to C in rank. Samples from seams intersected in a preliminary diamond drilling programme, show heating values ranging from 7,700 Btu/lb to 10,200 Btu/lb, on an air dried basis. Ash content of the coals is commonly around 20% (ad), and the Volatile Matter varies from 37% to 41% (ad). The sulphur content is generally about 1%.

Cross-over temperatures for Bislig coals vary from 148° to 155°C. This temperature range is intermediate between coals which are safe from spontaneous combustion (greater than 200°C) and those which are liable to spontaneous combustion (less than 130°C).

In-situ Reverse

Some 53 million tones of in-situ reserve are reported by PNOC-CC for explored areas in the Luguimit, Central Bislig and Sicahoy areas of which 83% are in the demonstrated category. Seam H with an average heating value of 7,714 Btu/lb (adb), comprises some 38% of the in-situ reserve base. The remaining ten seams included in the reserve base have reserve tonnages varying from 1.0 million tonnes to 8.79 million tones. The demonstrated reserves in the six major seams (Seam K, I, H, H1, 5 and 51) are amount to 36.33 million tones or 86% of the total demonstrated reserve base of 44.27 million tonnes.

2. Rajah Cabungsoan-Mekoupe Prospect

The Rajah Cabungsoan/ Mekoupe prospect lies in Coal Block 372 and 373 on sheet Xii-8, some 8km south of the Bislig mining area. Both ANSCOR in the 1950s and PNOC-CC in 1981 undertook exploration in the area to determine the potential for seam development in the Mekoupe Formation. The Mekoupe Formation underlies the coal bearing, Pamaypayan Formation of the Bislig mining area and rest unconformably on the basement rock of the Barcelona Formation. The strata are intruded by Lower Miocene micro-diorites and are affected by block faulting. Strata dips are 10° to the south in the Rajah Cabungsoan area and become more variable in the Mekoupe area (5° to 28°). The area is bounded on all sides, except to the north by outcrops of the volcanic basement. PNOC-CC has drilled six boreholes in the prospect, covering an area 1000m by 600m located about a fault block which is bounded by northeast trending faults. Seam development was found to be impersistent and only one seam of significant thickness- the RC1 Seam –could be correlated with any degree of certainty. The RC1 Seam varies from 1.49m to 2.49m and has up to 25% mudstone partings. The coal quality data indicate that the coal has been thermally metamorphosed by micro-diorite intrusions and now has s high volatile bituminous rank. Locally the coal has coking properties with a Free Swelling Index of up to 3 ½. Coal analyses, derived from three outcrop samples and three cored samples are reported on an air dried basis for the RC1 Seam;

-Moisture 5.4% to 12.8%-Ash 31.6% to 56.6%-Volatile Matter 18.7% to 29.6%-Total Sulphur 0.8% to 1.1%-Heating Value 5,069 Btu/lb to 9,377 Btu/lb (ad)

In-situ measured reserves are estimated by PNOC-CC to be 210,000 tonnes for the prospect

PNOC-CC Reserves in the Bislig Area

PNOC-CC has estimated an in-situ reserve base of 54.29 million tonnes for the Bislig mining area and the Rajah Cabungsoan-Mekoupe prospect. Some 82% of the in-situ reserve are demonstrated, the larger proportion of which comprise the reserve base for the Bislig III mine project.More recently, PNOC-CC has recalculated the in-situ reserves to give a new global reserve figure of 53.83 million tonnes. Some 53 million tonnes (99%) lie in the Bislig mining area and the small tonnage is represented by poor quality coal found in the Junction and Rajah Cabungsoan-Mekoupe prospect.

PNOC-CC Prospects Elsewhere in the Tago River Basin

PNOC-CC has prospected two other areas in the Tago Basin, but which are remote from the Bislig area. These are the Manay Prospect located on the Casauman River in Davao Oriental province, and the San Miguel prospect located on the north bank of the Tago River in Suriago del Sur province.

Manay Prospect

The Manay Prospect is located some 120km south of the Bislig mining area and covers Coal Block 95 to 99, 136 to 139 and 178 & 9 on Sheet XII-16. Irregular and impersistent development of coal seams occur in paralic coal measures of the middle and Upper Members of the Bactinan Formation (Lower Miocene), which are probably equivalent to the Mekoupe Formation and Pamaypayan Formation, respectively of the Bislig area. The Mambusco Formation, comprising massive limestone, overlies the Bactinan Formation and is probably equivalent to the Sanco Formation of the Bislig area.Three poorly developed seams have been identified in the Bactian Formation, of which two (Seam A and B) lie in the Middle Member and one (Seam C) lies in the Upper Member of the Formation. Seam A has a thickness of 1.43m to 2.26m, as identified in one borehole and one outcrop. Seam B varies from 0.3m to 1.3m and has been located in six outcrops and two boreholes. Seam C is 0.5m thick or less, as identified in two boreholes.The area is block-faulted and dips are variable (8° to 47°). Several minor intrusive bodies were noted in the south of the area.One sample from Seam A and four samples from Seam B were analyzed. The results are only for clean coal and are reported on air dried basis;

Seam A B-Total Moisture 13.5% 18.0%-Ash 9.6% 9.4%-Volatile Matter 37.5% 36.3%-Total Sulphur 0.48% 1.29%-Heating Value 10,180 Btu/lb (ad) 9,649 Btu/lb (ad)

San Miguel Prospect

IntroductionThe Sam Miguel Prospect lies on the north bank of the Tago River, southwest of Tandag. The exploration is covered by nine Coal Block (CBS 361 to 363 on Sheet XIII-4, CBS 1 to 3 and CBS 41 to 43 on Sheet XIII-5). PNOC-CC started mapping work in 1982 and has completed in a 20km2 areas.

Stratigraphy Some of 18 named seams and seam split have been identified by drilling, in the Tagbalogo Formation (Upper Oligocene to Middle Miocene). The stratigraphic column bears remarkable similarities to that of the Bislig area. The coal-bearing succession contains a relatively high proportion of sandstones, and volcaniclastic units appear towards the top indicating the prospect’s close proximity to the Diuata Range.

StructureBlock faulting is more intense that at Bislig. The northwest corner of the area is cut by two major, north-northeast trending faults (northeast Tagbalogo Fault and the North Tagbalogo Fault), which are spaced about one kilometer apart and have vertical displacements of 70m. Major faults, trending west-northwest, north-northwest and northwest also occur in the area.Strata dips are generally 20° to the northeast in the area southeast of the North Tagbalogo Fault.

Seam DevelopmentExploration has been concentrated on four seams (Seams 5, 8u, 10 and 12u) lying in faulted coal measures, some 170m thick.

Seam 5 reaches its best development against the North Tagbalogo Fault where seam thicknesses exceed 3.0m. The seam deteriorates in thickness towards the south and southeast. The average seam thickness in the reserve blocks is 2.33m, using a thickness cut-off of 1.0m.

Seam 8u, is less well developed than the underlying Seam 5. It largely lies south of the South Tagbalogo Fault. Some section reaches a thickness in excess of 2.0m and the average thickness is 1.76m for the reserve blocks.

During Seam 10 times, coal development had again migrated further to the south of the South Tagbalogo Fault. Seam thicknesses do not exceed 2.0m and the average seam thickness in the reserve blocks is 1.34m.

Areas of Seam 12u, where the seam thickness exceeds 1.0m, lie within the fault block bounded by the Northeast Tagbalogo Fault and the North Tagbalogo Fault, and in a small area immediately to the east of the North Tagbalogo Fault. The seam thickness locally exceeds 3.0m and the average thickness for the reserve areas is 2.15m.

Coal QualityPNOC-CC’s coal quality data, reported on an air dried basis, are only available for clean coal samples for seam 5 and 12u. The heating value of clean coal sample is about 8,010 Btu/lb (ad) and similar to that found in the Bislig mining area. Sulphur contents, however, vary between 1% and 3% and is considerably higher than the average of 1% found at Bislig. Unfortunately the seams contain upwards of 40% partings as indicated by a specific gravity of between 1.50 and 1.77 for the seam material. Heating values for the seam material therefore range between 4,500 Btu/lb and 5,000 Btu/lb (ad) with ash contents estimated between 25% and 38% on an air dried basis.

In-situ ReserveTotal indicated in-situ reserves are estimated by PNOC-CC as 36.86 million tonnes of which some 51% lie in seam 5.A limited tonnage of Seam 5 reserves near the outcrop has been identified by PNOC-CC as having the potential for open pit mining. The open pit reserves are limited by a limiting stripping ratio of 15m³ / 1 tonne of coal.

Private Sector Exploration AreasPrivate sector exploration has been concentrated in four geographical areas in Eastern Mindanao;

Area: Province:Gigaquit Coalfield Surigao del Norte and Agusan del NorteMasepelid Island Surigao del NorteTandag-Tago-Lianga Surigao del SurBislig Surigao del Sur and Agusan del Sur

The coal prospects are located in areas where the massive limestone units of each major cycle of sedimentation have been eroded to expose the underlying coal-bearing strata. Rather the coal occurs in a number of lenses, some 0.3m to 1.3m thick in coal-bearing horizons. The Tago Basin is cut by numerous high angle faults, with trends dominantly to the northeast and northwest. Strata dips are very variable and frequently range from 5° to 30°. The strike of the strata is commonly orientated northwest or northeast.

Gigaquit CoalfieldThe Gigaquit coalfield is located on the Surigao Peninsula, some 57km south-southeast of Surigao City. The area lies at some 600m amsl on the divide between the Mindanao Sea and the Philippine

Sea. The exploration and limited mining carried out 1n 1977 by Armstrong Mining and Industrial Corp. in Coal Block 186 and 226 to 227 on Sheet XIII-2 and Jabpract Mining and Industrial Corp. (JINICO) in Coal Block 226 to 268 on Sheet XIII-2.Seams are found in the upper part of the Bacuag Formation (Upper Oligocene to Lower Miocene).A sketch geological map of JINICO’s three Coal Blocks suggests that the area is cut by major northeast trending faults. Dip measured at coal outcrops vary from 8° to 30° and the strata commonly trend northwest and northeast.Armstrong undertook exploration and development mining in its five Coal Blocks, in early 1977. The overall seam quality was found to be poor with ash contents of between 35% and 40% (ad). The corresponding heating values ranged from 5,000 Btu/lb to 5,800 Btu/lb (ad). Washability tests did suggest that the coal could be upgraded to some 18% ash (ad) at a yield some 60%.JINICO found several seams dipping 10° to 20° to the southeast of the prospecting work which ranged in thickness from 0.5m to 6.0m. Exploration was limited to x-ray drilling and trenching. The upper seams in the sequence were poorer in quality than those below;

Upper Seams Lower Seams-Moisture (%) 12.49 14.35-Ash (%) 29.95 12.41-Volatile Matter (%) 34.60 37.18-Fixed Carbon (%) 22.96 36.04-Sulphur (%) 4.47 0.87-Heating Value (Btu/lb, ar) 6,730 8,890-Heating Value (Btu/lb, ad) 7,690 10,380 as received basis (?)

Masapelid IslandMasapelid Island lies immediately off the eastern shoreline of the Surigao Peninsula some 20km southeast of Surigao City.Coal seams reported on the island by Santos-Ynigo (1944) and Santos et al. (1965), during regional geological investigations of the Peninsula. The stratigraphy is similar to other areas in the Surigao Peninsula with the minor development of paralic coal-bearing sediments (Mabuhay Formation of Lower Miocene to Mid Miocene age) associated with coralline limestone and volcanic.

Tandag-Tago-Lianga AreaThe Tandag-Tago-Lianga area lies inland between Lanuza Bay and Lianga Bay. Apart from PNOC-CC’s San Miguel prospect, it also contains the exploration areas belonging to Pauling Plc/ EEMC, Diversifed Mining Corp. (Benguet Corp.), Semirara Coal Corp, Montenegrin Mining Corp, Piedra Negra Mining Corp., and Sabena Mining Corp.

Montenegrin Mining Corp. contracted three Coal Blocks (CBS 167, 126 and 127 on Sheet XIII-5) in 1982. The company has interpreted 13 seams (0.2m to 2.1m thick) in an 80m stratigraphic thickness of strata, it is difficult to correlate the seams and the inter-seam strata over distances of much more than 100m, because of the lensoid nature of sediments. The coal is dull, conchoidally fractured, well cleated and contains few partings (generally less than 0.1m thick). In-situ measured reserves are

quoted by the company as 1.03 million tonnes. The BED (1984) recognizes 2.8 million tonnes of in-situ proven reserves and 0.5 million tonnes probable reserves.The strata dip north to northwestwards, into hillside with dips ranging from 15° to 20°.

Semirara Coal Corp. contracted Coal Blocks 128, 129 168, 169, 209, 247, 248, 287, 288, 327, 328, on the Sheet XIII-5, which were all relinquished by Montenegrin in mid-1982. A number of boreholes were drilled but no details of the exploration result are available. It is possible that the areas dropped by Montenegrin, are too far to the east of the coal-bearing paralic belt which extends in a northerly direction through the Tago Basin.

Piedra Negra Mining Corp. contracted Coal Blocks 84 to 89 on Sheet XIII-5, which lie to the north of Montenegrin’s Layug prospect in Coal Block 127. An area (Block 85), some 375m x 2500m has been identified by surface geological mapping and X-ray drilling. The area could have potential of 2 million tonnes of coal at stripping ratio of 14:1, for open pit method. Reported seams thicknesses vary from few centimeters to 1.5m and could be affected by numerous small scale faults. Dips vary from 28°NE to 6°SW, suggesting the presence of major, high angle faults in the area. One coal analysis on as received basis is given in a 1981 exploration report;

Upper Seams -Moisture (%) 12.49 14.35-Ash (%) 29.95 12.41-Volatile Matter (%) 34.60 37.18-Fixed Carbon (%) 22.96 36.04-Sulphur (%) 4.47 0.87-Heating Value (Btu/lb, ar) 6,730 8,890-Heating Value (Btu/lb, ad) 7,690 10,380 as received basis (?)

Pauling Plc. contracted Coal Blocks 327/8 and 367/8, on Sheet XIII-4. The area lies inland from Tandag and Tago, and north of Montenegrin’s and Piedra Negra’s open pit prospect. The company drilled 68 boreholes and identified a 175 ha exploration target in an area of 300 ha to 400 ha of coal-bearing paralic sediments lying in a shallow basin. Eighteen seams, varying in thickness from a few centimeters to 1.25m, were found. The seams are generally lensoid and often difficult to correlate between boreholes and test pits. Average seam thickness is commonly 0.3m to 0.6m with only two of the 18 seams having average thicknesses greater than 1.0m (1.15m and 1.31m). The seams contain numerous waste partings which are typically 0.02m to 0.23m. Average heating values are range from coals with 3,500 Btu/lb (ad) and 46% ash to coals worth 8,500 Btu/lb (ad) with 12.6% ash. Sulphur content of the seams is generally higher than 1% and can reach 5.7%.The company estimated that the 175 ha area could contain upwards of three million tonnes of coal in all 18 seams. Demonstrated in-situ reserves are estimated to be either 0.7 million tonnes with a

stripping ratio of 7m³/tone or 1.1 million tonnes with a stripping ratio of 14m³/tone. Inferred in-situ reserves were estimated to be 1.1 million tonnes with a stripping ratio of 7m³/tone.

Diversified Mining Corp. contracted Coal Blocks 161 and 204 to 205 on Sheet XIII-5, which were transferred to Benguet Corp. in 1979.The company has located two coal-bearing areas some 10km apart; namely the San Miguel prospect in Coal Blocks 161 and 162 and the Marihatag prospect in Coal Block 204 and 205. The coal-bearing horizons contain numerous lenses of coal with thicknesses from 0.05m to 1.05m, with inter-seam strata thicknesses ranging from 0.02m to 0.5m.The coal horizon in the San Miguel prospect contains possibly four identifiable seams, whilst the Marihatag prospect contains eight seams. Both areas contain major, high angle northeast and northwest trending faults. Strata dips in the fault block vary from 10° to 25° and are oriented variously to the southwest, northeast and northwest. Two discrete coal-bearing horizons were proved by Banguet Corp. The Laguntang horizon is some 65m thick and contains only two laterally discontinuous seams of any importance. Seam A is 1.4m to 6.6m thick and is separated from Seam B (0.28m to 1.5m thick) by 6.0m of barren strata. The lower, Biling-ion horizon is some 50m to 90m thick, more arenaceous than the upper horizon and contains for identifiable but laterally discontinuous seams.Diversified Mining reported the result of six coal analyses in 1979 which showed the coal to have a heating value of 10,300 Btu/lb on an air dried basis; -Total Moisture (%) 13.7-Ash (%) 11.0 -Volatile Matter (%) 44.9 -Fixed Carbon (%) 38.6 -Sulphur (%) 1.5 -Heating Value (Btu/lb) 10,321

air dried basis

The average weighted value of the 206 analyses shows a reduction in the heating value to 7,467 Btu/lb when compared to the results previously reported by Diversified;

-Total Moisture (%) 7.3-Ash (%) 21.2 -Volatile Matter (%) 46.0 -Fixed Carbon (%) 25.4 -Heating Value (Btu/lb) 7,467

air dried basis (?)

In 1983, the BED estimated that Benguet had blocked out 4.9 million tonnes of positive reserves and 2.8 million tonnes of probable reserves.

Sabena Mining Corp. contracted Coal Blocks 206 and 207 on Sheet XIII-5, which are surrounded by Coal Blocks variously belonging to Benguet, Montenegrin and Semirara.

A 1979 report indicated that Sabena had located a 1.0m thick seam which could be traced over 300m. The seam locally thickens to 2.5m but can contain up to 25% waste partings.The boreholes demonstrate the presence of upwards of 11 discontinuous seams or lenses of coal in some 50m of coal-bearing strata. Although coal comprises some 10% to 12% of the succession, the thickest intersection in any one borehole were only 1.1m to 1.4m. Any reserves in the area would only be mineable at stripping ratios of between 5m³/ tone and 10m³/ tone if the company was able to mine seams with thicknesses as little as 0.2m Bislig AreaThe Bislig area lies inland from Bislig Bay. Private sector exploration has largely concentrated on Coal Blocks lying to the west of PNOC-CC’s Bislig mining area located in Coal Block 292 of Sheet XII-8. Three groups have undertaken exploration, namely the Philippine Oil Development Co. Inc. (PODCO), Atlas Consolidated Mining and Development Corp (Atlas), and A. Soriano Corp. (ANSCOR).

Philippine Oil Development Co. Inc. (PODCO)In 1979, PODCO carried out a regional reconnaissance investigation of the area east of the Agusan-Davao National highway, between Lianga Bay and Cateel Bay. The company identified an area due west of Bislig Bay which could contain paralic coal seams associated with near shore clastic units and shallow marine carbonate units which were laid down along the Lower Miocene shoreline. PODCO contracted 12 Coal Blocks 44, 84 to 86, 123 to 126, 164 to 166 and 205 on Sheet XII-8, but in 1981 reduced their holding to Coal Blocks 44, 84, 123 to 125, 164 to 165 and 205.A number of coal seams were found in arenaceous sediments, representing channel and interchannel swamp environments. Three superimposed Coal bearing horizons occur. Each contains one or two seams which vary in thickness from a few centimeters to a maximum of 1.8m (average about 1.0m). The seams are however discontinuous in extent and are cut by barren sandstones, representing the infilling of interdistributory channels with continental material.No coal reserves have been calculated by PODCO.

A.Soriano Corp. (ANSCOR)

In 1980, ANSCOR contracted 15 Coal Blocks, 206 to 208, 245 to 248, 285 to 288, 325 to 328 on Sheet XII-8. These lie to the southeast of the PODCO area. Exploration work indicated that the area contains numerous upfaulted blocks of coal-bearing strata which have been partially eroded. Two poorly developed seams were found locally, but generally the sedimentary environments were found to be unfavourable for significant coal development. The Coal Blocks were relinquished in 1982.

Atlas Consolidated Mining and Development Corp (Atlas)

In 1980, Atlas contracted six Coal Block, 209, 210, 249, 250, 289, on Sheet XII-8. These lie immediately to the east of ANSCOR’s holdings and were also relinquished in 1982, after abortive exploration. A further two Coal Blocks, 254 and 294 on Sheet XII-8 were also contracted in 1980.

The average of 71 seam borehole intersections, with thicknesses greater than 0.2m, is 1.32m. Some 42% of the intersections have thicknesses of 1.0m or greater. The thickest intersection is 6.6. In-situ reserves of the three seams, to about 100m depth, were estimated in 1984, by BED and the company to be 4 million tonnes. An average analysis has been estimated as reported by the company in 1983;

-Total Moisture (%) 16.5-Air Dried Moisture 15.1-Ash (%) 10.5 -Volatile Matter (%) 35.7 -Fixed Carbon (%) 38.6 -Sulphur (%) 1.54 -Heating Value (Btu/lb, ad) 9,156

air dried basis

Davao Oriental

The seams lie in coal-bearing strata (Bislig Formation) of Upper Oligocene to Lower Miocene age, considered to be part of the paralic belt of sediments that extends through the Bislig area along the length of Eastern Mindanao.

Utah International identified several areas containing lignitic to sub-bituminous C seams, inland from Cateel in the north to Tarragona in the south;

-Boganga District, - Outcrops of low ranking coal with high sulphur content

-BangkokaanCreek - Three seams dipping at 60° were identified with thicknesses of 0.6m, 0.3m and 0.3m. The coal contains 5,980 Btu/lb (ad) and has a high moisture, ash and sulphur content.

-Dapdan Creek - One, 0.4m thick seam, dipping at 7°W, with a high moisture and low ash content.

-Banahaw/Mahanub - One, 0.5m thick seam, dipping at 16° NE, with a high moisture content but with low ash and sulphur content.

-Pagloscon Creek - Three outcrops of a 1.2m thick seam with some waste partings. The coal contains 7,713 Btu/lb, 10.8% ash, and 21.3% moisture on an air dried basis.

Sambanganay Creek - Two seams (2m and 1m thick) separated by 5m of barren strata. The lower seam has a 0.1m and a 0.3m waste parting.

Tumugfa, Baguan River - Two seams (0.15m and 1.5m thick). The lower seam has 8,300 Btu/lb, 16.7% ash and 0.35% sulphur on an air dried basis.

A. Almendras

In 1980, A. Almendras contracted nine Coal Blocks 216 to 218, 255 to 258, 295 and 355 on sheet XII-16. The area lies immediately south of PNOC-CC’s Manay prospect and 12km from the town of Tarragona.Twelve seam outcrops with thicknesses varying from 0.7m to 2.5m (average 1.7m) were found in a coal-bearing horizon some 100m thick. The beds strike generally to the northeast and dip 12º to 40º (exceptionally at 60º) to the southeast.Trenching and limited tunneling by the company identified on potentially workable seam with an average thickness of 2.1m (1.6m to 3.5m) containing three to five partings (0.15m to 0.02m thick). The seam dips between 22º and 40º. In situ reserves, suitable for underground mining, were estimated to be 1.6 million tones but the BED has downgraded the estimate to 0.2 million tones.One analysis, reported by A. Almendras in 1980, showed the coal to have an ash content of 11.5% and a heating value of some 8,400 Btu/lb, both on an air dried basis, viz :

Total Moisture - 17.0%Air dried Moisture (105º) - 14.6%Ash - 11.5%Volatile Matter - 43.8%Fixed Carbon - 30.2%Sulphur - 1.7%Heating Value - 8,624 Btu/lb ad air dried basis

Coal Quality

The available data on the quality of coals from Eastern Mindanao have been reduced to average values of sets of analyses which have been done by various organizations in the past.Heating values for coals from Eastern Mindanao are generally in the range of 8,000 Btu/lb to 8,600 Btu/lb on an air dried basis. Ash content is moderately high and varies between 10% and 20%. The sulphur content is high and commonly varies between 1.5% and 3%.Carbon content of the coals is usually about 75% on a dry, ash free basis. Hardgrove Grindability Indices commonly vary between 35 and 65. Limited ash analysis indicate that the ash tends to be of the bituminous type with the percentage Fe2O3 generally greater than the combined percentage of CaO and MgO

In-Situ Reserves

In-Situ reserves derived from the BED (1984) estimates with those calculated for the reassessment of the reserve base, see on table. Minor differences between the two sets of figures are generally due to variations in confidence levels which have been applied to the various tonnages.

EASTERN MINDANAO

IN-SITU RESERVES(million tones)

Area BED (1984)Demonstrated

WA (1985)Reserves

Almendras Mining Corp.Atlas ConsolidatedBenquet CorporationMontenegerinPauling PlcPiedra NegraPNOC-CC BisligPNOC-CC San MiguelJinico

0.214.005.003.300.600.5415.3013.000.75

0.134.005.002.801.100.5425.4227.60-

Total 42.70 66.59

NB. BED figures adjusted to give demonstrated reserves.i.e. BED Positive + BED Probable = BED Demonstrated Reserves.

Chapter Eight

EASTERN SEABOARD

Geological Setting

Known coal-bearing areas of the Eastern Seaboard occur in two separate structural regions, viz :

- Talaud Chain : Samar, Catanduanes, Batan and Polillo (?)- Southern Luzon – Bicol Basin : Bondoc and the southeastern of the Bicol Peninsula

The coal-bearing islands of Samar, Catanduanes, and possibly Polillo and Batan, together with the Caramoan Peninsula, comprise the northern part of the Talaud island Arc which collided with the Phillipine proto-continent in Pliocene times. The island chain choked the Phillipine ancrestal Trench which was active in Mesozoic times.The development of coal in a paralic sedimentary environment appears to be restricted to the sedimentary strata laid down on a shallow shelf which developed about the collision zone between the Talaud island Arc and the Phillipine proto-continent. Few, if any, coal seams have been located in the sediments of the Southern Luzon-Bicol Basin. It is likely that the Basin, largely controlled by faulting, subsided at a rate which was too rapid to allow any extensive development of the paralic environment.

SAMAR

Regional Geology

Sedimentary strata, of decreasing age onlap the islands volcanic nucleus. The oldest sedimentary sequences, known as the Daram Formation (Upper Oligocene & Lower Miocene?), comprise folded, dominantly calcareous strata in which paralic coal measures are locally found. Field relationships in central Samar show that the felsic tuffs of Oligocene age are contemporaneous with the paralic coal measures. The Catbalogan Formation (Middle-Upper Miocene) unconformably overlies the Duran Formation and appears to comprise a second major cycle of sedimentation in which calcareous and clastic sediments both occur. The final cycle of sedimentation is represented by the Calicoan Formation (Late Pliocene to Pleistocene?) which comprises coralline limestones overlying weak, massive mudstones (Tacloban Clay Member).Stuctural lineaments, interpreted from aerial photography, confirm the presence of a northwest/northeast conjugate set of major faults. More detailed geological mapping during coal exploration in the southern part of the island as proved a set of parallel north trending shear zones along which ultramafic rocks have been intruded. It is probable that the dominant northwest trending faults in the northern part of the island swing to a more northerly orientation somewhere in the centre of the island before continuing southwards through Dinagat, Siargo Island and eventually through Eastern Mindanao. Field evidence from the coal deposits in the centre of the island suggest the sedimentary sequences are affected by high angle block faulting, typical of the Cenozoic strata throughout the Philippines.

Coal-Bearing Areas

Samar is known to contain two coal-bearing areas of dubious mining potential. The first of these, the Bagacay area, lies in the centre of the island. The second area lies in the Giporlos area of southern part of the island.

BagacayThe bagacay area, comprising five coal blocks, was extensively prospected by Marinduque which started exploration in 1977. Some four isolated areas, lying between the Taft and Ulot Rivers in the interior of the island.Each of the areas contains two or more coal seams, generally 0.5m to 2.5m thick, in a +25m paralic coal measure sequences which is heavily contaminated with felsic tuff units. The seams contain several partings of thin (less than 0.2m thick) tuffaceous material. Dips are less than 10º and the seams are affected by numerous high angle faults with displacement generally less than 0.5m.The average heating value of Bagacay coals is some 7,500 Btu/lb on an as received basis. Average analyses from individual areas range from 6,200 Btu/lb ar to 8,300 Btu/lb ar. The generally high sulphur content of the coal (1.6% to 3.8%).A feasibility study by Nonoc (Marinduque – 1980) for the Bagacay area, estimates that 2.899 million tones of coal could be recovered by open pit from the 3.411 million tones of in-situ reserves. The BED (1984) estimates the in situ demonstrated reserves in the area to be 5.42 million tones. A reassessment of the reserves indicates that the demonstrated in-situ reserves are 3.41 million tones.Some 4,000 tones were mined by Marinduque in 1980/81 from a shallow open pit in the Cansolabao area. A 1,000 tonnes stockpile remains at the site.

GiporlosThe coal occurrences at Hucnan an Kaanian in the Giporlos area appear to have been first investigated by Tavelosa of the BMG in 1980. Pitting showed that the seams dip generally 20º to 50º to the aest and lie in a 200m thick coal measure sequences. The seams vary in thickness from 0.5m to 2m (locally 3m thick) and contain some 10% waste partings.Proximate analyses of coals from the Giporlos area, reported by Javelosa (1980) and by Marinduque (1980), indicate an average heating value of 6,700 Btu/lb to 7,300 Btu/lb on an as received basis. The analytical results of the sulphur content which averages 0.85% for Javelosa’s samples and 2.68% for Marinduque’s data set.The BED has variously estimated the in-situ reserves for the Giporlos area to be 14.7 million tones (1982) , 2.9 million tones (1983) and 3.5 million tones (1984). The re-estimated demonstrated, in-situ reserves are 3.17 million tones.The area will not produce much more than 20,000 tpa to 60,000 tpa from a series of isolated openpit properties where the seams are found to be locally thickened and the topography is such that the stripping ratios are less than 10m3 / tone.

Future Potential

The principle target should be to explore outwards from the Bagacay Mines and hopefully find less disturbed coal seams in the younger clastic sediments in the northern part of the island.

CATANDUANES

Regional Geology

The Island has a central core of pre-Cenozoic strata which appear to represent an ophiolite suite (lime stone, cherts, greywackes, pyroclastics and basaltic pillow lavas). A +1,000m thick sequences of sub-greywackes, shales and conglomerates (Cabago Formation), representing basin fill, were deposited on the basement during Lower and Middle Eocene times. Shallow marine conditions then prevailed from Middle/Upper Eocene times, during which time cyclical paralic sediments were deposited (Hitoma-Payo formation), followed by a sequence of limestone which persisted to the end of Miocene times (Sipi Limestone-Upper Eocene, Bati Hill Limestone-Miocene). A depositional break occurred at the end of the Miocene before the conglomerates of the San Vicente Formation, capped ny corraline limestone, were deposited in lower Pliocene times. The stratigraphic colomn is finally completed by the Santo Domingo Shales (Middle to Upper Miocene) which contain some tuffaceous shale and lignite units.Structurally, the island is divided into two discreate areas. In the north, the northeast fault direction dominates and the parallic coal measures of the Hitoma-Payo Formation lie in fault bounded blocks. The west-northwest trending faults are more dominant in the southern part of the island.The bituminous coal seams of Catanduanes are found in the structurally deformed Hitoma-Payo Formation, which is divided into two unnamed members – a lower, 175m thick sequence of paralic coal-bearing strata which is overlain by an upper unit of fossiliferous limestones some 30m to 250m thick. The coal seams are up to 5m thick but vary rapidly in thickness along strike.Lignitic seams, some 1.2m to 1.4m thick, are found in the Santo Domingo (Pliocene) Formation on the southern most tip of the island.

Coal Occurrences

Salvacion – Panganiban

The salvacion – Panganiban coal occurrences lie in the north-central part of the island and are found in several localities, which have an aggregated total area of some 20km2 of potentially coal-bearing strata.The paralic strata are known to contain only one 0.17m thick seam which has erratic dips of between 20º and 50º.The Camp Ermitano area is the more important locality as some coal has been mined here in the past. Locally, the strata strike east and dip 50ºN, except in the western part of the area where the beds are overturned and dip south. Coal seams have been located also in the Concalbon and Naglobog areas, some 4km to 5km northeast of Camp Ermitano, where the strata are similarly affected by folding and faulting.

Hitoma – Manambrag

The coal localities in the Hitoma – Manambrag area, on the western side of Catanduanes. The coal-bearing strata appears to confined to three discrete sub-areas; Sirungany, Gigante Peak, Carbon Hill – Malabog Creek. The carbon hill area lies in a faulted block with strata dipping at 40ºS. Exploration of the Malabog Creek area gave a sufficient information to outline a gently southward plunging synclinal structure, lying between reverse fault. Correlation of the seams in the two limbs of the structure proved difficult. All seams showed evidence of bedding plane slip on their lower contacts. Generally, the seam thicknesses varied between 0.3m and 1.6m. the lateral continuity of the coal measures varied from a maximum of 2,000m on the western limb to a minimum of 500m on the eastern limb.

Magnesia

The seams are reported to range between 1.2m and 1.4m in thickness. The coal-bearing strata are reported to be little disturbed with strata dips varying from 5º to 20º.

Coal Quality

The three major areas of Eocene coal are similar in their coal attributes, with heating values ranging from 10,600 Btu/lb to 12,400 Btu/lb on as received basis. The average analyses of the four known data sets also indicate an average heating value of about 12,000 Btu/lb ar, with ash contents commonly about 25% ar. The average sulphur content is generally high with values ranging from 1.6% to 2.3%. the forms of sulphur analyses performed on one sample indicated that organic sulphur accounted for 1.82% and pyritic sulphur accounted for 0.64% of a total sulphur content of 2.46%.The Pliocene lignitic coals from Magnesia have a heating value of about 7,200 Btu/lb ar with a total moisture content of 33% on an as received basis.

In-Situ Reserves

The BMG (1955) estimated the in-situ reserves down to 200m below drainage level. Total demonstrated, in-situ reserves for seams thicker than 0.75m in the two areas were estimated to be about 0.6 million tones with a further 0.9 million tones of inferred reserves.BED (1984) only estimated 0.65 million tones of demonstrated, in-situ reserves in the Malabog Creek area of the island. The reassessed demonstrated, in-situ reserves have been reduced to 0.42 milllion tones because of the uncertainties of seam correlation in the difficult structural environment of the deposit.

Future Potential

The structural complexity and irregular nature of the seams indicates that, at best, only small open pit or shallow underground mines will be developed, and these are unlikely to have outputs much greater than 10,000 tpa to 20,000 tpa.BATAN

Regional Geology

Batan is one of a group of four islands which extend east-southeastward from the Bicol Pinunsula into the Phillipine Sea. Apart from a faulted block of ultramafic rock in the northeast, the island comprises Miocene coal-bearing sediments.The source of sedimentation is thought to have been from the basement high of the Talaud island Arc, lying to the east and northeast of the island. Strata are locally cut by fluvial channels infilled with coarse clastic debris.A major, conjectured northeast trending, high angle fault which dips to the southeast, divides the island into eastern and western fault blocks.The eastern block comprises a 1,300m thick Miocene sequence of gently dipping strata (0º to 15º), which is only affected by high angle normal faulting with small displacements. Locally in the northeastern part of the island, dips of 30º to 45º are found in an isolated fault block. This block is probably structurally related to the major, east trending fault, along which ultramafic rocks have been emplaced in the extreme northeast part of the island.The western fault block of the island comprises strata with higher dips (40º to 45º).

Coal-bearing Areas

A number of differences exist between the coal seams found in the eastern and western fault blocks of the island.

Western coal depositsThe western fault block of the island contains three sub-areas of coal deposits, viz :

1. Liguan – western side of the islandFour workable seams have been identified with thicknesses varying from 0.5m to 4.3m. no major faults are reported in the workings and the strata dips generall at 30º to 60º NW.2. Caracaran/Benguet - Manela – south/central part of the islandThe Caracaran-Benguet-Manela area contains three seams with dips between 10º and 20º NE. no current workings are reported in the area.3. Bahi-Bilbao – central/northwest area of the islandThe Bahi-bilbao area contains two seams which dip generally to the north-northwest at 10º to 15º. The seams are reported to average less than 0.75m thick and are not currently mined.

Generally, The western fault block contains three or more seams, each with thicknesses up to 2.5m, the coal is high volatile C bituminous.

Eastern coal deposits

The eastern fault block of the island contains two sub-areas of coal deposits, viz :

1. Calanaga-San Ramon-Mapisay – northeastern part of the islandThis area is known to contain eleven seams, with average seam thickness of 0.7m, evenly spaced in some 300m of coal measures. The strata trend west-northwest and dip at 20º to 40º to the north.2. Buri-Dap dap-Batan – south and southeastern side of the islandExploration has demonstrated the presence of some 15 seams in the area; the lowest of which outcrops at sea level on the southern coast of the island. Seam thicknesses vary from 0.3m to 2.5m and average about 1.0m thick. It is estimated that between four and seven of the seams have mineable thicknesses. The coal bearing strata dip into the hillside, generally to the north and nort-northwest at between 3º and 23º (average of less than 10º). Faulting is minor in the area.

Generally, the gentler dipping coal-bearing strata in eastern fault block contain upwards of 20 seams, again with recorded thicknesses up to 2.5m. the rank is lower than in the west, having sub-bituminous C coal.

Coal Quality

The western fault block, the coal is high volatile C bituminous in rank with heating values between 10,300 Btu/lb and 11,300 Btu/lb on an air dried basis. In the eastern area the rank is lower than in the west, having sub bituminous C coal with heating values in the range of 8,000 Btu/lb to 9,500 Btu/lb on an air dried basis.Sulphur in the coal is lower in the eastern block; ranges of sulphur content vary from between 2% and 4% for the western block and contrast with a range of between 1% and 3% for the eastern block. The younger and lower rank coals from the eastern block are known to deteroate more quickly and suffer more from spontaneous combustion than the higher ranking coals from the western fault block.The Carbon content is commonly between 70% and 75%. The Hardgrove Grindability Indices of the coals from western Batan vary between 40 and 72.

In-Situ Reserves

In-situ reserves, down to -100m amsl, were estimated by the BMG in 1955, for seams with thicknesses greather than 0.75m. total demonstrated in-situ reserves were estimated at 7.08 million tones of which some 75% lie below sea level. Approximately 90% of the island’s reserves lie in eastern Batan.The BED estimated the demonstrated, in-situ reserves of the island to be 8.34 million tones in 1982, and 9.58 million tones in 1984.

Future Potential

The production could be maintained in the 100,000 tpa to 200,000 tpa range for the foreseeable future. The development of any large mine with an output in excess of 100,000 tpa is unlikely because of the thin and often discontinuous nature of the seams.

POLILLO

Regional Geology

Polillo could represent the northenmost island in the Talaud island Arc that was welded to the Phillipine proto-continent in Pliocene times. The island is cut by northwest and northeast trending faults and the Cenozoic strata have been extensively depformed. Sediments on the west side of crystalline basement core are overturned and dip steeply to the east. Strata on the east side of the island, although folded, are in a normal attitude and generally dip also to the east.The coa-bearing strata are largely confined to a 13km long zone of folded paralic sediments, overlying the Anawan volcanic of the basement, on the east side of the island.Thin, sub-economic coal lenses, occurring in dark coloured shales and limestones, are found in small faulted inliers of the Babacolan Formation (Eocene), on the east side of the island. However, the more important coal occurrences are found in the overlying Burdeous Formation (Lower Miocene), which contains four seams which are traceable discontinuously over 8km of strike and can, on occasions, individually reach 4m in thickness. However, it is more usual to find only two of the seams sufficiently well developed (say 1.5m thick or more) in any one area. The seams commonly dip 35º to 55º to the east and are dislocated by northeast trending faults with 3m to 5m displacement.

Coal-bearing Areas

Test pitting proved the existence of two seams, probably belonging to the paralic coal measures of the Burdeous Formation. The western seam, dipping at 63º to 80º NE, averages 3.0m thick and was traced for a distance of only 50m. the eastern seam, possibly separated from the western seam by a fault, is 4.0m to 8.0m thick. The seam dip is near vertical and wavers between 70º and 80º to the southwest and northeast.The upper three seams in Pilipino Cathay’s mining areas have thicknesses between 0.6m and 1.5m and lie in a coal measures sequence some 30m to 40m thick. The lowest seam in the coal measures is variable in its extent and continuity. The coal is generally sub-bituminous A to B, although in local areas of high heat flow (near faults and intense folding) the rank can increase to high volatile C bituminous.

Coal Quality

The average heating value of coals from Polillo is between 9,500 Btu/lb and 12,600 Btu/lb on an air dried basis. Ash contents are low and commonly lie in the range 4% to 15% ad. The sulphur content is generally less than 1%, although the average of 23 samples analysed by RRI (1977) indicated a sulphur content as high as 3.75%.

The carbon content is commonly about 70% on a dry, ash free basis. Hardgrove Grindability Indices lie between 34 and 119.

In-Situ Reserves

In 1982, BED reported 0.50 million tones of demonstrated, in-situ reserves for the area explored by Pilipino-Cathay. BED’s demonstrated, in-situ reserves for the island were increased to 0.71 million tones in 1974, with the inclusion of 0.21 million tones for the area explored by Tantuco Mining Corporation.

Mining Potential

Pilipino-Cathay currently produces some 10,000 tpa from its mining operations on the east side of the island. It is likely that the ourpur from Polillo would remain between 10,000 tpa to 20,000 tpa for the foreseeable future.

GATBO PENINSULA

Regional Geology

The formation comprises shales, fine grained clastics and rare limestones (turbidite ?) which represent a typical fill in a rapidly subsiding basin. As the trough filled, the shallow marine and paralic conditions of the shelf migrated southwest, and the basinal clastics f the lower and middle parts of the Gatbo Formation grade into a sequence of lenticular clastic limestone and coal beds. Volcanism, associated with the collision of the Talaud island Arc and the proto-continent, strated at the time of coal development and the coal measures contain a number of volcaniclastic units.The end of the deposition of the Gatbo Formation was marked by a period of uplift and intense deformation. Tight folds were formed and the strata were locally translated to the vertical and occasionally overturned. A further period of deformation occurred after the deposition of the Sugod Marl, which tilted the strata some 5º to 10º. The east-southeasterly trending San Vicente-Linao Fault, are to the northwest; whilst those to the south of the Fault dip to the northeast.

Coal Occurrences

The area contains two vertically dipping seams, trending N20ºW and separated by some 200m of barren strata. The main seam could once be traced intermittently over 2.6km of strike. It varied in thickness from a few centimeters to some 7.0m, but contained numerous waste partings. The second seam was less persistent and varied in thickness up to 0.87m. it also contained a 0.13m thick waste parting.

Coal Quality

Alberding (1939) analysed eight samples from the Gatbo Peninsula which indicated that the coal has a heating value of about 9,800 Btu/lb on an air dried basis, viz :Total Moisture : 17.1%Air Dried Moisture : 12.5%Ash : 6.3%Volatile Matter : 39.2%Fixed Carbon : 42.4%Heating Value : 9806 Btu/lb adTotal Sulphur : 1.74%Air dried basis

In-Situ Reserves

In-situ reserves were estimated at 0.122 million tones in 1939 and more recently at 0.2 million tones in 1974. In 1974, the BED estimated 0.09 million tones of demonstrated, in-situ reserves for the explored by Tantuco Coal Mines. Demonstrated, in-situ reserves have been reassessed at 0.08 million tones.

Future Potential

It is unlikely that the area would produce more than 5,000 tpa to 10,000 tpa, because the structural complexity of the geology.

BONDOC AND BICOL PENINSULAS

The bondoc Peninsula and the southwestern side of the Bicol Peninsula comprise extensively deformed basinal clastic of Miocene age which are thought to have little or no potential for the discovery of mineable reserves of coal. Some coal occurrences have been reported on the Bicol Peninsula. These probably represent coal lenses developed in marginal paralic facies in the transition zone between the rapidly subsiding Southern Luzon-Bicol Basin and the shallow shelf to the northeast. The hostile, sedimentary and structural environment of the area does not augur well for the discovery of any major deposits of coal in the area.

Chapter Nine

VISAYAS BLOCK

Geological Setting

The Visayas Block is bounded on its eastern side by the Philippine Fault which in turn marks the site of the Philippine ancestral Trench with its westerly dipping subduction zone. Major Structural trends on the eastern side of the Visayas Block are orientated north-northwest and reflect the deformation which occurred in the Cenozoic cover when the Talaud island Arc collided with the Philippine proto-continent.Shear stress developed in the Visayas Block by the southeasterly movement of the Eurasian Plate and the northwesterly movement of the Philippine Sea-Pacific Ocean Plate was relieved by major north-northeast trending block faulting.The Visayas block contains a number of important Miocene coal occurrences which are found in paralic facies of clastic sequences. Notable amongst these are the coal deposits of Cebu, which have until recently been the main source of coal for the country. Minor and less well-known coal occurrences are found on the islands of Negros, Leyte, Masbate and Bohol.

CEBU

Regional Geology

The island of Cebu is situated near the centre of the Visayas Block. The island forms a prominent structural high and is separated from Negros and Bohol by downfaulted blocks.The basement rocks exposed in Cebu are generally metamorphosed schist (Cansi and Tunlob Formations) and are considered to be Lower Cretaceous or older in age. They are overlain by the basinal clastic and limestone units of the Pandan Formation (Upper Creatceous). The depositional history from the Upper Oligocene onwards comprises a maximum of 6,000m to 8,000m of strata in some offshore sections.Depositional environments were generally unstable throughout the Cenozoic. Most of the sedimentary sequences show rapid lateral facies changes, oftern over very short distances. A single cycle of sedimentation often shows development of shallow water carbonates interfingered and overlain by basinal fine-grained clastics and continental coarse-grained clastic. Coal formation occurred in the generally unstable paralic depositional environment, found along the sedimentary basin margins both during the transgressive and regressive phases of a single sedimentary cycle.

StratigraphyThe stratigraphy of Cebu typically exhibits rapid lateral facies changes within the same time units, and as a consequence many litho units have unfortunately been given formational names.The more important coal measures are found in the Cebu Formation (Upper Oligocene) and the Upper Malubog Formation (Lower Miocene). Minor seams are also developed in the coarse clastic sequences found at the base of the Toledo Formation (Middle Miocene) and at the base of the Barili Formation (Upper Miocene).

Cenozoic StratigraphyThe first major cycle of sedimentation (Upper Oligocene to Lower Miocene) comprises an older transgressive sequence is represented by the Cebu Formation which lies unconformably on the basement. The younger regressive sequence is represented by the Malubog Formation, and possibly by the Calagasan Formation found in an inlier in southern Cebu. The paralic-carbonate shelf-basinal clastics of the transgressive sequences are represented respectively by the Cebu Coal Measures, the Cebu limestone and the lower part of the Malubog Formation. The Cebu Coal Measures (40m to 100m thick) comprise generally of coarse clastics laid with paralic sediments containing numerous, but irregulary developed coal seams.The overlying regressive sequence is represented by the upper part of the Malubog Formation – a clastic sequence laid down in shallow marine conditions during Lower Miocene times. The Basal section (N1 and N2 Blow Zones) contains generally coarser clastics with numerous, poorly developed coal seams which represent a paralic environment.The second major sedimentary cycle, of Middle Miocene age, is represented by the Toledo Formation, and possibly by the Linut-od Formation and Butong Formation which are found in an inlier in southern Cebu. The youngest unit of the second transgressive sequence is represented by the “Luka Facies” which rests unconformably on the upper Malubog Formation. It comprises a clastic sequence containing workable coal seams which were laid down in a paralic environment.The transgression started in Cebu during N11 Blow Zone times and the episode is marked by the deposition of a predominantly calcareous sequence, called the Barili Formation. The transgressive sequence is therefore represented ny the paralic sediments of the Maingit Formation which contain sub-economic coal seams, the Barili Limestone which represents the carbonate shelf facies, and the Barili Marl which was laid down in deeper water.Upper Pliocene – Pleistocene times were characterized by yet another major marine transgression, which is represented by the Carcar Limestone. This, the final cycle of Cenozoic sedimentation contains few if any paralic sediments and no coals of this age are known on Cebu.

StructureThe principal structural trends are north-northeast in south and central Cebu, while in the north trend is more northerly or north-northwesterly. The major coal-bearing strata are exposed in the central and southern parts of the island with the younger Barili Limestone, the Carcar Limestone and marl sequences effectively covering the remaining 80% of the island surface area. Where exposed, the predominant north-northwest structural trend is present in the coal bearing strata.Deformation of the strata is most strongly developed in the Lower Miocene – Middle Miocene coal-bearing formations. Seams of Oligocene – Miocene age are often found in steeply dipping strata with dips ranging from 30º to the vertical. The upper Oligocene coal-bearing sediments, however, do not seem to have been folded to the same extent and generally exhibit lower dips.

Mining History

The island has four main coal districts where seams found in the Cebu Coal Measures and Upper Malubog Formations are worked, viz :

1. Danao – Compostela2. Toledo – Balamban3. Uling – Alpaco4. Argao – Dalaguete

Coal was first discovered in the Phillipines in 1827, on the island of Cebu, although the first recorded production of coal from the Archipelago came from Batan Island.Today there are 17 companies mining coal in Cebu. Of these, only five regularly produce more than 15,000 tpa. Despite the previous, but limited geological work and the long history of mining, there is still a lack of detailed geological knowledge on the various mining areas.

1. Danao – Compostela DistrictThe Danao-Compostela district of northern Cebu is located some five to ten kilometers west and northwest of Danao and Compostela. The district is divided into the Licos-Camansi area in the south and the Cahumayhumayan area in the north.Coal mining in the Licos-Camansi area is restricted to seams in the Malubog Formation, which lie in the western limb of a north-northeast trending syncline. Minor folding occurs on the limb and strata dips range from 25º to 70º. At least five coal seams, trending northeast and dipping around 35º to the southeast, are present in this area. The seams were apparently traced northeast from the Licos area into the Camansi area where average seam thicknesses of 0.5m to 2.0m were found.In the Cahumayhumayan area, the Malubo Formation is found in a northeast plunging syncline. The seams in the Malubog Formation dip between 30º to 60º on both limbs of the syncline, whilst the strata to the southwest dip at around 40º to 50º, coal seams in the area, which have thicknesses ranging from 0.44m to 3.35m.J.D. Almendras Corp. is mining seams of the upper Malubog Formation in the Cahumayhumayan area. The company is working two coal seams which dip at 30º to 45º to the southeast, and vary in the thickness from 1.00m to 2.00m. six coal seams are known in the area, but in general the geological definition of the mining area is poor.

2. Toledo – Balamban DistrictMost of the coal deposits in the Toledo-Balamban district of northern and central Cebu are found in the Cebu Coal Measures, although coal measures in the Malubog. In the Masaba area, at least four coal seams have been recognized from exploration and underground workings. Their thickness varies from a few centimeters to greater than 1.0m. two of these seams are persistent and can be traced along strike for several hundreds of metres.Alberding (1940) states that many waste partings occur in the seams of the Cebu coal measures. However, two seams in the Guila-Guila area range from 0.16m to 1.22m in thickness, one of which has no partings and the other has only one of 0.15m thickness. In the Mabais area, Alberding noted only one coal seam, which although variable in thickness can attain 2.0m in places.Cebu Coal Mines Inc. is the largest producer in the Toledo-Balamban District. The company’s license area occupies an area to the north of the Toledo – Tabunoc road, along the western bank of the Mananga River. Coal is mined from a number of seams in the Cebu Coal Measures. The dip of the strata is around 20º to the southeast, although locally, this levels out to very shallow dips. Coal seam thicknesses varies from 0.6m to 1.5m within the area, and are commonly affected by frequent pinching and swelling.

3. Uling – Alpaco DistrictThe Uling-Alpaco district of southern and central Cebu lies south and west of Cebu City, and about 10km northwest of Naga. Coal-bearing sediments of the Cebu Coal Measures and the Malubog Formation occur in the area.Some eleven coal seams are recognized in the area although only three are considered to be of workable thickness. The lower seams tend to be impersistent. One seam in sequence, according to Alberding (1940), has cooking qualities. It varies in thickness from 1.95m to 4.75m and averages 2.91m (excluding partings).The Malubog coal-bearing strata are also located in a north trending syncline in the Alpaco area, to the southwest of Uling. Dips on the east limb of the fold are in the range 30º to 70º whilist the west limb is affected by a fault zone associated with near vertical strata dips. At least seven seams have been located in the area, of which at least two are in excess of 1.0m in thickness.The PNOC-CC has operated its Uling mine since 1977 which produces coal from two seams – the Dona Marguarita Seam and the N-6 Seam. Seams dip in the range 45º to 60º with average thicknesses of about 2.0m for the Dona Marguarita Seam and 0.8m for the N-6 Seam. The Dona Marguarita Seam does pinch and swell rapidly. The area is structurally complex with abundant faulting.

4. Argao – Dalaguete DistrictThe Argao-Dalaguate district in southern Cebu is located some 80 km south west of Cebu City. The district consists of an inlier of Lower to Middle Miocene strata surrounded by the Barili and Carcar Formations.The Argao group is divided locally into the coal-bearing units of the Calagasan Formation and the Linut-Od Formation which are separated by the Butong Limestone.In the northern Calagasan area, seams up to 2.0 m in thickness are found east and west of the Butong Limestone outcrop. At least three seams are usually found in the Calagasan and Linut-od Formation, but these are generally only persistent for a few hundred metres of strike. Dips are commonly 45º to 70º.In the southern Mantalongan area, the strata trend more northwesterly than northerly. Seams up to 4.0 m thick occur to the west of the Butong limestone outcrop and up to 2.0 m thick to the east. Up to four seams are present to the east of the limestone, in the Calagasan Formation. Dips generally vary from 40º to 65º and can be locally overturned.To the south of the Argao-Dalaguete district, near Boljoon, another erosional window within the Barili and Carcar Formations reveals an older coal-bearing clastic sequence. The coal deposits have not been investigated in any detail but limited sampling indicitates a range of heatingvalues from 9650 Btu/lb to 10,200 Btu/lb ad. No information is available on lateral extent, continuity or thickness of the coal seams.

Coal Quality

Average coal quality data are given for the four coal regions of Cebu, namely : Danao – Compostela (northen region), Toledo – Balamban (central region), Uling – Alpaco (central region), and Argao – Dalaguate (southern region).

Air Dried ResultsArgao – Dalaguate coals show the highest heating values (10,000 Btu/lb to 14,400 Btu/lb ad) and generally the lowest ash content.The Toledo – Balamban coals are also of higher quality, and have heating values in the range of 9,000 Btu/lb to 11,600 Btu/lb ad. Ash values are afairly high at 11% to 28%. The Danau – Compostela and Uling – Alpaco coals are similar in quality, although they are geneally poorer than the other two areas. The two areas have coals with heating values of 8,800 Btu/lb to 10,900 Btu/lb ad and ash contents between 8% and 22% ad.

Total MoistureThe higher quality coals of the Argao – Dalaguate and Toledo – Balamban areas generally have lower total moisture contents, generally in the range 5% to 14%. The slightly poorer quality coals of the Danao – Compostela and Uling – Alpaco areas have a total moisture content in the range of 9% to 19%.

Ultimate AnalysesCebu coals commonly have between 5.2% and 5.6% hydrogen (daf) and 70% to 80% carbon (daf). Coals from Danao – Compostela and Toledo – Balamban are higher in sulphur (+2.5%) than those from Uling – Alpaco and Argao – Dalaguete districts (less than 1%). Nitrogen contents are high with values between 1.4% and 1.8% (daf).

Ash Fusion TemperaturesAverage temperatures of the recombined floats. A similar set of ash fusion temperatures was determined by Norwest on the raw, minus 0.6 mm fraction

Ash AnalysesThe ash from the Danao – Compostela coal is shown to be rich in SiO2/Al2O3 and poor in Fe2O3/CaO/SO3. Uling – Alpaco ash is conversely SiO2/Al2O3 poor and Fe2O3/CaO/SO3 rich. The compostion of the ash from Toledo – Balamban appears to fall midway between the other two areas.

Other AnalysesAverage Hardgrove Grindability Indices determined by Norwest (1983). The higher quality Toledo – Balamban coals show a slightly higher index range than the other two areas.

In-situ Reserves

Little or no exploration is carried out by the producers, resulting in very poor geological definition of the coal bearing areas. Although unquantified reserves of coal may be present on the island, most of exploration geological data are totally insufficient to warrant classifying tonnages stated in the various companys five year production plans at a level higher than inferred.The reassessment of reserves has generally resulted in the down grading of most of the Cebu reserves to inferred status.

NEGROS

Regional Geology

Negros lies immediately to the west of Cebu. Although similarities exist between the stratigraphy on the two islands, the developmet of coals on Negros is poor. Coal measures contain more volcaniclastic units and comprise generally coarser material than that found on Cebu.Coal seams occur in a +300m thick clastic sequence (Macasilao Formation – Lower Miocene) in eastern Negros, and in the Tapul Formation in western Negros. Coal occurrences are known in eastern Negros, inland from the coast between Toboso and Calatrava, and at a location 20km south of Kabankalan in western Negros.

Eastern Negros

Regional Geology

The Cenozoic cover starts with a 660m thick carbonate-shale-carbonate section (Escalante Formation) which is correlated with the Cebu Coal Measures (Oligocene to Miocene). Unlike in Cebu, no coal has been found in the clastic unit. A generally coarse clastic sequence (Maasilao Formation – Lower Miocene) rests on the Escalante Formation. The Macasilao Formation contains poorly developed paralic coal-bearing strata.

Coal Occurances

Four separate coal occurrences which are located, on strike, to the north and south of Macasilap. The areas are found along a 20km lonf, folded belt, trending norh-northeast, and are known as the Tababoy, Macasilao, Kabulayan and Bagongon areas.The Tababoy area contains the northernmost coal occurances on the island, Melendres & Barnes (1954) located two seams on the eastern limb of an anticline. Some old workings are locatd in the area. The seams have thicknesses up to 1.57m.Eight seams were noted in the Macasilao area. The coal-bearing strata are folded by the north plunging Macasilao anticline. Seam thickess average less than 1.0m and vary between 0.35m and 2.0m. dips are 30º to 50º.The Kabulayan area lies 4km west of Macasilao. Melendres & Barnes (1954) located four seams with thicknesses ranging from 0.3m to 1.7m thick. The seams could only be traced along strike for 100m to 200m. dips varied from 30º to 50º NW.The Bagonbon area lies 9km west of Calatrava and is the southernmost coal occurrence. Melendres & Barnes (1954) traced two to seven seams over a strike distance of some 500m. seams are commonly 0.25m to 2.0m thick and contain numerous waste partings. The strata are folded by the Bagonbon syncline. Strata dips are between 20º and 40º and are locally overturned.

Western Negros

Coal seams on the west side of the Ilog Valley, some 15km south of Kabankalan. The seams occur in a 100m thick clastic-volcaniclastic sequence, called the Topul Formation (Middle to Upper Miocene?) and are overlain by a reefal limestone (Calesa Formation) of possible Upper Miocene age. The seams dip 10º to 15º in the area. Strata dips are to the south-southeast in the northern part of the coal-bearing area and to the east-northeast in the southern part. The seams are poorly developed. They rarely exceed 1.0m in thickness and can have up to 50% waste partings.

Coal Quality

Heating values of Negros coals vary from 6,800 Btu/lb to 9,500 Btu/lb on an air dried basis. Ash contenta are moderately high and commonly vary from 15% to 27% ad.Carbon content s commonly about 70% to 75% on a dry, ash free baisi. Hadgrove Grindability Indices lie between 30 and 54.

In-Situ Reserves

Melendres & Barnes (1954) estimated the in-situ reserves for seams thicker than 0.75m in the four main coal-bearing areas in eastern Negros. A further 2.2 million tones of additional inferred reserves were estimated, presumably with a confidence less than that for the formalized, inferred, in-situ reserves.

BOHOL

Regional Geology

The island of Bohol lies centrally in the Visayas Block, immediately east of Cebu. The Cenozoic cover rests on metavolcanic and metasedimentary basement strata (Alicia schists). The basement is overlain by volcanic strata of the Ubay Formation (Cretaceous-Eocene) which contains carbonate units (Calape Limestone) in its upper section. The remainder of the Cenozoic strata comprises two cycles of sedimentation which are separated by an unconformity in Upper Miocene times. The Lower-Middle Miocene strata comprise a lower dominantly carbonate section (Wahig Formation) which is separated from the upper clastic unit (Carmen Formation) by andesitic volcanic (Jagna Formation).The structure of Bohol comprises a major, centrally located, south plunging, and broadl flexed syncline, which is flanked by two major anticlines. The fold axes are offset along major northwest trending high angle faults. A major shear zone, called the Eastern Bohol Belt, is located on the eastern side of the island.

Coal Occurences

Coal occurrences are restricted to an area around Tubigon, inland from the northwestern coastline. The coal-bearing sediments are found in the Tubigon Member of the Carmen Formation (Middle to Upper Miocene), and lie on the flanks of a northeast trending anticline. Arco (1962) mentions there coal occurrences in the area, viz :Cantuyoc : where two seams (1.3m and 2.4m thick) dip to the northwest at 55ºBanahao : where two seams, both 1.3m to 1.5m thick dip to the east at 30ºIlihan : where three coal seams, respectively 1.5m, 1.3m and 1.0m rhick, dip to the southwest at 20º

Coal Quality

Four proximate analyses indicated that the coal has an average heating vale of 7,900 Btu/lb and contains almost 30% ash ad, viz :Total Moisture : 18.0%Air Dried Moisture : 11.3%Ash : 29.6%Volatile Matter : 50.0%Fixed Carbon : 9.1%Heating Value : 7,874 Btu/lb adTotal Sulphur : 4.26%Air dried basis

In-Situ Reserves

The BED’s 1984 estimate of demonstrated reserves (positive plus probable) for the area investigated by First Bohol Mining is 1.3 million tones.

MASBATE

Regional Geology

Masbate lies to the north of Negros and Cebu on the eastern side of the Visayas Blosk. A coal bearing clastic sequence, the Buyag Formation, was deposited in Middle Miocene times and contains paralic coal-bearing strata. The Cenozoic strata in the northwestern part of the island are not known to contain coal but those in the southeast are coal – bearing.The strata are disturbed and dips are commonly between 20º and 65º to the southwest, and to a lesser extent to noe\rtheast and southeast.

Coal Occurences

The Buyog area, coal-bearing strata lie near a major fault, are sheared and have erratic dips varying between 40º and 80º SW. one seam, averaging 1.0m in thickness can be traced over 1.5km. exploration in the Santa Teresa area, in Coal Block 359, proved the presence of a less structurally disturbed seam, some 1.0m thick and dipping erratically between 20º and 40º S.Since starting exploration in 1980, Hercules have established the occurrence of eight seams varying in thickness from 0.3m to 1.5m in a 150m thick sequence of coal bearing strata.The seams lie in a mudstone unit and grade laterally into carbonaceous mudstones. Waste partings in the seams are common.

Coal Quality

The high geothermal gradient, associated with the Philippine Fault has increased the rank of coal to high volatile C bituminous with 11,500 Btu/lb.The area was affected by high heat flow associated with the Phillipine Fault. The coal has a heating value of between 10,000 Btu/lb and 11,000 Btu/lb ad and contains 8% to 15% ad ash, some 1.5% sulphur and a total moisture content some 10%.

In-Situ Reserves

Ibalon estimated that the Buyog area could contain 185,000 tonnes of in-situ reserves. Ibalon estimated 60,000 tonnes of in-situ reserves for the Santa Teresa area.Hercules has estimated the proven, in-situ reserves in its exploration area to be some 522,300 tonnes of which 190,300 tonnes (36%) lie in the Maria seam which has the greatest continuity of strike of all the known seams. The BED, in 1984, estimated that the Hercules exploration area contained 0.29 million tones of demonstrated, in-situ reserves.

LEYTE

Leyte lies on the eastern boundary of the Visayas Block and is bisected by the Philippine Fault. No proven coal occurrences are known on the island.The peat lies in the Mahonag valley at 600m amsl – one of several northwest trending topographical lows reflecting the underlying elongated fault blocks associated with the Philippine Fault. The peat layer is 0.5m to 12m thick (averages 5.3m) and is interbedded with thin layers of sandstone in its upper section, and clay, mudstone and shale in its lower section.The peat-mudstone unit lies conformably on a coarse grained sandstone which in turn rests on weathered andesitic volcanic strata (Oligocene to Miocene). The peat is overlain by sandstones and Quaternary terrace gravels.

Two potentially mineable areas in North and South, In-situ reserves are estimated by the Company to be 3.35 million tones with an overall stripping ratio of 0.73m3/1 tonne of peat. Overburden thicknesses vary from 1.0m to 6.0m and interburden from 0.25m to 3.5mAverage analytical results were reported by Acoje on as received and air dried bases and indicate that the peat contains some 67% total moisture with a heating valur of abllut 1,000 Btu/lb on an as received basis.

Chapter Ten

WESTERN SEABOARD

Geological Setting

A group of coal deposits are found in the southern part of Mindoro, on Semirara island and on the north western tip of Panay. The coal-bearing area lies at the junction of several major structural, sedimentary, geomorphological and physiographic units.The area is dominated by two structural highs of pre-Cenozoic basement strata which are probably in-situ, but rotated, blocks of strata belonging to the Northwest Borneo Geosyncline. One structural high comprises a northern block of pre-Cenozoic strata forming the core of Mindoro (Mindoro Central Cordillera), and a southern block covered with lower Cenozoic volcanic which form the Tablas and Antique Ridges.

PANAY

Little information is available on the coal seams of Panay. Melendres (1951) mentions coal occurrences on the Buruanga Peninsula. Jagolino and Jandumon (1973) mention those further south about Lipata Point. Seam thicknesses of one metre or less and strata dips of 20º to 40º are mentioned in the reports. The coal-bearing strata appear in a clastic sequence known as the Santa Cruz (or Libacao) Formation which rests unconformably on the a Pre-Cenozoic basement of metavolcanics intruded by ophiolites and diorite.No information is available on the coal quality of the seams.Clastic sequence containing paralic coal-bearing strata are restricted to the western side of the structural highs and within a structurally low area which divides the Mindoro Cordillera from the Tablas Ridge and its southward continuation – the Antique Ridge.

MINDORO

Regional Geology

The Cenozoic strata of Mindoro lie in two basins, separated by an uplifted and rotated (?) block of pre-Cenozoic metamorphic strata, which forms the Mindoro Central Cordillera.The sedimentary strata are contaminated with andesitic volcaniclastics which are derived from volcanic episodes associated with the movements along the Manila Trench, in Middle to Upper Miocene and Pleistocene times.Paralic coal measures were developed in Middle to Upper Miocene times and are found in the Napisian Formation and Pocanil Formation of the Sablayan Group.

Stratigraphy

Known coal deposits are found only in the fore-arc basin of the Manila trench which is located on the western side of the island. Coal measures of Middle Miocene age are found in the Sabalayan Group which outcrops in a northwesterly trending belt, some 20km wide, and extending from Sablayan in the north to Bulalacao in the south.The Sablayan Group largerly comprises shallow marine limestones with lesser development of the continental, paralic and basinal clastic units. The paralic coal measures occur in the middle of the Sablayan Group, in units informall called the Napisian Coal Measures Formation and the Pocanil Formation. Their age is thought to be Middle to Upper Miocene.

Structure

The regional strike of the Sabalayan Group is northwest. It parallels the structural grain of the uplifted central massif of metamorphosed basement rocks which comprise the mountain range extending down the spine of the island. Strata dips are very variable, with a range between 20º and 70º.

Coal-bearing Areas

A belt of paralic coal measures is known to extend, northwest from Bulalacao. Within this belt, four coal-bearing areas have been identified :

1. Bulalacao – immediately southwest of the mouth of the Bulalacao River2. Napisian – west side of the Cawacat River and some 5km to 7km northwest of Bulalacao3. Siay – some 5km northeast of Bulalacao4. Alitaytayan – some 13km northesast of San Jose

Some seams have been traced over 1km of strike and thicknesses up to 3.0m have been recorded.

Bulalacao – NapisianGeological mapping has shown that seven seams occur in a structurally disturbed environment. The strata trend, generally, north to north-northwest and dip to the west at between 20º and 70º. Numerous dip reversals and changes in azimuth have been mapped.The coal quality of Napisian seams was determined from eight samples which were reported to have the following average analysis (on an as received basis?) :

Moisture : 27.7%Volatille Matter : 37.14%Ash : 3.7%Fixed Carbon : 31.0%Heating Value : 12,023 Btu/lb

SiayUp to seven coal seams, with thickness between 0.1m and 1.2m have been identified in the area. Previous production has come from three seams with thicknesses greather than 0.75mThe bureau of Mines (1955) estimated total in-situ reserves of 310,000 tonnes in seams thicker than 0.75m, one sample gave the following analysis (air dried basis?) :

Moisture : 5.8%Volatile Matter : 45.4%Fixed Carbon : 45.6%Ash : 3.2%Heating Value : 11,850 Btu/lb

AlitaytayanAt least five semas with thcknesses up to 1.2m are known to occur in the coal measures. The strata strike north-northwest and have dips of about 30º. Arganao (1976) has traced individual seams in the area for some 1km along strike.The Japanese Geological Mission (1984) reports the presence of only two seams (0.6m and 1.05m thick). An analysis of one seam (as received basis?) gave the following results :

Moisture : 18.0%Volatile Matter : 39.4%Fixed Carbon : 36.0%Ash : 6.6%Sulphur : 4.4%Heating Value : 9,432 Btu/lb

Coal Quality

The average heating value of the Mindoro coals is about 10,000 Btu/lb on an air dried basis. The ash content is low and varies from 2% to 11% ad. The sulphur content is high and varies between 3% and 4%. The carbon content is some 68%. Hardgrocve Grindability Indices vary from 62 to 74.

In-Situ Reserves

BED has estimated 4.47 million tones of demonstrated reserves for Filsystems Incorporated’s exploration area at Napisian. The reserve base has been reduces to 1.16 million tones in the reserve reassessment because of the lack of adequate data of which base the tonnage calculations.

Mining Potential

The qualified resources estimate of 100 million tones for the region should be treated with considerable caution until more formal mapping identifies the structural setting of the area and the continuity of seams in the coal measures of the Sablayan Group.

SEMIRARA ISLAND

The thicker and relatively less structurally disturbed seams found on Semirara Island contrast markedly with those found in southern Mindoro, some 40km to the north. Two other coal-bearing areas in the island, Panian and Himalian have been extensively explored and might be developed as open pits in the future.

Regional Geology

StratigraphyThe island is underlain by coal-bearing Lower to Middle Miocene strata of the Semirara Formation, which are partially covered by shallow marine limestones of the Buenavista Formation (Pliocene).Coal measures are known to exist below the depth of drilling which was carried out to determine the reserves for the Unong open pit. British Petroleum sunk an il well (Nº 1) in the south of the island and intersected and aggregated coal seam thickness of some 70m, lying 300m to 2000m below the surface. The thickest coal seam, some 10m thick was found between 1000m an 1300m below the surface. The total coal thickness in the Semirara Formation is estimated to be some 100m to 200m in a 3000m thick coal measure sequence.

StructureThe coal measures of the Semirara Formation are exposed in three, gently plunging and faulted anticlinal flexures. The regional strike of the seams is generally northwards with dips varying between 5º and 30º, both to the east and west on either side of the anticlinal flexures. The structural style of area is dominated by high angle faulting, dividing the strata into discrete structurally intact faults trend northeast and northwest.

Coal Seams

Correlation of coal seams between the three coal areas of Panian, Himalian and Unong is tenous, because of the rapid lithological variations so characteristic of unstable, paralic sedimentary environments.

PanianThe coal measures at Panian contain seven identified seams of which four are considered economically important.

Austromineral reports an aggregated average thickness of 38m of coal for the four potentially mineable seams at Panian.

HimalianHimalian contains some 19 seams, of which ten are considered potentially mineable.Average thickness of the ten potentially mineable seam at Himalian vary from 1.0m to 7.4m thick

UnongAt Unong, there is only one major seam with several minor seams in the roof and floor strata.The average coal thickness (Main Seam + rider seams) at Unong varies from 4.33m to 28.00m for the various reserve blocks. The arithmetic average seam thickness of the 56 proven and probable reserve blocks is 17.36m.

In general, the seams in each area show relatively little vertical change but have marked lateral variation. Thicker seams grade into carbonaceous shales. The thickness of inter-seam partings varies considerably. Washout structures do occur, but are relatively uncommon

Coal Quality

UnongLittle formal analysis exists on the coal data of the reserve blocks in Austromineral’s feasibility study on Unong open pit.The coal are typed as medium-soft, sub bituminous C to lignitic black coal. Austromineral gave the following estimate of the Run-of-Mine coal (0mm to 400mm) on an as received basis :

Moisture : 16% to 19%Ash : 16% to 19%Volatile Matter : 35% to 41%Fixed Carbon : 26% to 29%Total Sulphur : less than 1%Heating value : 8,000 Btu/lb ar to 9,000 Btu/lb arHGI : 40 to 50Air dried basis

PanianAn analysis of the 105 samples results used by Dames and Moore is estimated the heating value to average 8,080 Btu/lb on an air dried basis. They estimated that in 95 cases out of 100, the heating value should lie between 7,879 Btu/lb and 8,280 Btu/lb ad.

HimalianThe only available coal analytical results for Himalian are those reported by SCC in the Dames and Moore feasibility study. The coal was typed as sub bituminous A, with a heating value of 12,320 Btu/lb,

daf. The chlorine content is low (0.01% to 0.02%). Some 80% of the total sulphur is in an organic form and it therefore can not be removed by physical coal preparation methods.

The wide variation in the average values for heating value, ash and fixed carbon serve to illustrate the uncertainties which have prevailed on the quality of Semirara coal. The set of average values for total moisture appear to comprise two different populations – one with total moisture of 24% to 27% and another with total moisture of 18% to 19%. Average ultimate analyses appear also to have discrepancies with carbon contents varying between 46% to 70% on a dry, ash free basis. The HGI appears to be about 40 for Semirara coals.

In-Situ Reserves

UnongThe Austromineral’s estimate of the reserves (20.63 million tones) is some 12% less than that computed by Dames & Moore and BED, the difference is tonnage using a 0.5m and 1.0m seam thickness cut-off minimal.The overall stripping ratio for the Unong pit down to -150m amsl, is 7.4m3/1 tonne.

PanianIn-situ reserves tonnages have been estimated by SCC, Dames & Moore and Austromineral. The in-situ tonnage estimates vary from 40 million tones (lower SCC estimate) to 78.6 million tones (Austromineral). All the reserves lie below sea level and 20% of the reserve base lies beyond the coastline.The overall stripping ratio is estimated by Austromineral to be 8.4m3/1 tonne, to -230m amsl. Dames and Moore estimate an overall stripping ratio of 9.0m3/1 tonne, to -250 amsl.

HimalianThe in-pit mineable reserves are estimated to be 37.5 million tones. The over all stripping ratio is 11.3 m3/1 tonne, requiring the removal of 424.2 million m3 of over/inter-burden which covers the 10 mineable seams. Some 58.2 million m3 of limestone form part of the overburden and will require blasting.Total in-situ reserves are estimated at 60.5 million tones.

SCC and its consultants have estimated the in-situ reserves of the island to be 160.3 million tones which is identical to that estimated by BED in 1983.

Chapter Eleven

LUZON BLOCK

Geological Setting

The Luzon block is the northernmost major structural Block of the Philippine proto-continent and now lies between two, north trending and convergently dipping subduction zones. To the west of the Block, lies the Manila Trench which marks the site of the east dipping subduction zone on the border of the South China Sea.Unlike other parts of the Philippines, coal is poorly developed in the Miocene strata of the Luzon Block. Isolated occurrences of deformed coal-bearing strata are found in the northern part of the Central Luzon Basin, and in a small subbasin of sediments within the magmatic bet of the Catanduanes Ridge. The sediments, originally laid down in a fore-arc basin, were trapped when the magmatic belt moved seawards as the east coast subduction zone re-established its new position after the collision of the Talaud island Arc with the Philippine proto-continent.The only significant coal development is confined to a Plio-Pleistocene clastic unit in the Cagayan Basin, which, because,of its younger age, has escaped much of the deformation affecting the older Cenozoic sediments.

CAGAYAN BASIN

The Cagayan Basin is situated in northern Luzon and is one of the largest Cenozoic basins in the Philippines. The principal coal-bearing strata – the Upper Ulagan Formation of Plio-Pleistocene age – occupy an area of about 180km north-south, by a maximum of 50 km east-west in the San Marino embayment area.

Exploration History

Although the upper, coal – bearing strata were not logged in detail, carbonaceous horizons were identified during drilling. Seams were identified in the upper Ilagan Formation and close to the contact between the lower Ilagan Formation and the upper Cabagan Formation. For example, in oil well Nassiping No. 1, an aggregated thickness of about 12m of coal seams were identified in the upper Ilagan Formation and 1.0 m of thin coal seams were identified within the lower Ilagan Formation.

Regional Geology

The Cagayan Basin is an asymmetric basin which contains a maximum of some 10,000 m of dominantly marine sediments along its axis. Cyclical sedimentation started in Upper Oligocene – Lower Miocene

times and represents an almost continuous sequence of marine transgressions and marine regressions with few major depositional breaks.Only minor paralic coal measures, deposited along unstable shorelines, were developed in Miocene times. These are found in the Palawan Member of the Lubuagan Formation, where the seams are thin and discontinuous and considered to be of little economic importance. Major seam development is only found in the Ilagan Formation of Plio-Pleistocene age. The coal measures, at this time, were deposited during a marine regression which retreated from south to north.

Stratigraphy

The principal coal-bearing strata are found in the Ilagan Formation of Pliocene to Pleistocene age. The Formation comprises a thick sequence (2200m) of predominantly sandstone, siltstones and mudstones and contains coal seams in its upper part.The lignitic coal seams are lensoid and discontinuous, exhibit washouts and erosional features and are both interbedded and lateral equivalents to a varied suite of sediments, such as limestones, siltstones and sandstones. The Ilagan Formation has its largest outcrops areas in the northwest and southeast parts of the Basin.

Structure

The Cagayan Basin is asymmetric, infilled with 6000m to 10000m of sediments in the west and some 5000m of sediments in the east. Strata on the eastern limb of the Basin dip between 0º and 5º and those on the western limb dip at an average of 25º. Outcrops of the Cabagan and Ilagan Formations, lying in the core of the anticlines, are often found as inliers throughout the fold belt. The folds are diapiric in origin and deformation is due to gravity tectonics related to movements of the Luzon Central Cordillera.

Coal Occurences

Outcrops of the coal-bearing Ilagan Formation are found in three major areas of the Basin, viz :

Southeast : within the San Mariano EmbaymentCentral : associated with the diapiric fold beltNorthern : between the Sicalao-Cassigayan High and Paret River Embayment.

Southeast Area

The southeast area lies to the south and east of Cauayan, Isabela, on the east bank of the Cagayan River.Located some 12 seam outcrops and proved a 1.75m thick seam at Quimtabbasa and a 1.90m thick coal seam at Linglingay. Drilling proved up to nine seams in any one area, each seam varying in thickness from less than 0.1m to 1.76m. a maximum of 3.48m of coal was encountered in some 114m of strata, representing approximately 3% of the strata drilled. Grey-green mudstones with plant remains were commonly found immediately below the seams which indicated that the coals are autochtonous.

Central Area

Some eight coal outcrops were located to the west of the Liwan Syncline in the central part of the Basin. Seams were found to dip to the east and northeast at about 20º to 30º. One outcrop comprised two, 1.20m thick seams separated by a 2.0m thicknesses of shale. Other outcrops indicated seam thicknesses from 0.30m to 0.88m. four of the outcrops are distributed over 3.5km strike and it is possible that they may represent part of a north trending, continous belt of coal measures.

Northern Area

Three seams have proved to be laterally persistent in the Nassiping and Gattaran areas in the northern part of the Basin. The upper two are generally 0.15m to 0.20m thick and occasionally reach thicknesses of 0.35m to 0.60m. the lowest seam is 1.25m thick (1.55m maximum). The 24 m to 44 m thickness of strata between the upper two seams comprises a number of fining – upward sedimentary cycles with associated seams. However, these seams are lensoid and impersistent laterally. The coal – bearing strata represent between 12% and 26% of the total strata investigated, with three seams representing a maximum of 1% of the total strata.

Minor Areas

A number of coal occurrences in the Miocene (?) strata of the Cagayan Basin are known in the hills east and west of Diduyan and Cagayan Rivers in the Province of Quirino, the coal-bearing area is located near the town of Maddela.Seam thicknesses are generally 0.5m to 2.0m, although one coal intersection of 9m was recorded at less than 12m depth. The strata dip 5º to 28º to the northwest. The Company estimated some 338,000 tonnes of in-situ reserves which could be suitable for open pit mining. The coal is sub-bituminous and has a heating value of between 7,000 Btu/lb and 9,000 Btu/lb ad.

Coal Quality

The range of average heating values varies from 6,100 Btu/lb to 8,300 Btu/lb on an air dried basis. It is likely that the range is due in part to different sampling and air drying techniques which have been employed by the various investigators. Ash content varies between 8% and 33% ad and sulphur between 0.9% and 2.3%.Ultimate analyses indicate a carbon content of between 63% and 67% on a dry, ash free basis. Ash analyses show that two facies exist one which is SiO2 + Al2O3 rich and one which is CaO + MgO rich.

In-Situ Reserves

The Isabela Coal Consortium have reported a total coal tonnage of 98.19 million tones in the Cauayan area of Isabela Province. It comprises 78.23 million tones of in-situ reserves and 19.96 million tones of hypothetical resources. The 78.23 million tones of identified reserves were further sub-divided into 40.05

million tones of measured reserves, 35.89 million tones of indicated reserves and 2.29 million tones of inferred reserves. Of these, all the measured reserves, 66% of the indicated reserves, and 50% of the inferred reserves have been summed to estimate an in-situ tonnage of 64.60 million tones. The reserve classification is based on the USBM system using the following parameters: measured reserves were calculated from data points at less than 0.8km spacing; indicated reserves were calculated from data points at between 0.8km and 1.6km spacing; and inferred reserves were calculated from data points at greater than 1.6km spacing.In the area of the Pangul anticline, to the west of the Cagayan Basin, a coal reserve of 390,000 tonnes is conjectured from the German exploration. This is an optimistic estimate and assumes a 0.6 m thick seam, with a seam density of 1.30, is laterallu persistent through six outcrops over 10km of strike.Reserves of coal may be present in the Ilagan Formation in the centre of the basin where it is overlain by the Awiden Mesa Formation.

LA UNION PROVINCE

Regional Geology

Coal occurrences have been recorded in Miocene clastic strata found in the northern part of the Central Luzon Basin. The Basin lies between two massifs – the allochthonous mass of the Zambales Ridge and the magmatic belt of the Luzon Central Cordillera.The Kennon Formation contains the Twin Peaks clastic member which is not known to contain any coal development. Minor coal development, however, has been reported in the overlying Klondyke Formation which has a stratigraphic thickness of some 2,800m, outcrops over much of the land between the Luzon Central Cordillera and the coast. The Formation comprises mostly volcaniclastic units with minor development of paralic facies which contain coal seams.

Coal Occurences

Only two coal occurrences, both reported to occur in the Klondyke Formation (Upper Miocene), are known. Thin coal seams, some 0.15m to 0.25m thick, are found 20 km east – southeast of San Fernando. The seams occur in a gently dipping sandstone sequence.

LAGMAC, QUEZON PROVINCE

Regional Geology

The lagmac coal measures lie within a 70km by 20km belt of sediments (Eocene to Miocene), located in the Catanduanes Ridge. Contrary to some interpretations in reports, the area is not an intermontaine basin. It, rather, represents a pile of sediments deposited in a fore-arc basin.

The Lagmac coal measures lies in the Lambak Formation (Lower Miocene), comprising clastic beds which are contaminated with volcaniclastic units. The Lambak Formation is overlain by the fossiliferous limestones of the Buenacop Formation (Middle Miocene).High angle block faulting, orientated north, dominates the structure of the area. The faulting is probably responsible for the dip reversals which have been previously interpreted as folds. Secondary faulting also occurs which is orientated northeast and northwest.

Coal Occurences

Coal seam occurrences along the Lagmac river, athough abundant coal float is found in the streams, less than a dozen seam outcrops have been reported. Seams have been traced over a maximum strike distance of 50m. seam thickness vary from 0.3m to 1.2m and strata dips vary from 15º to 85º.

Coal Quality

The average heating value varies between 10,900 Btu/lb and 13,000 Btu/lb on an air dried basis indicating that the coal may have been subjected to abnormally high geothermal gradients. The ash content is low and varies from 4% to 13% ad. The sulphur content is below 1% and commonly ranges between 0.3% and 0.5%. the coals are reported to have good cooking properties.

In-Situ Reserves

The BED has estimated potential, in-situ reserves of 2 million tones in 1982; later revised to 93,000 tonnes of positive, in-situ reserves in 1983. Lack of exporation data precludes the inclusion of these reserves in the reserve reassessment.

Future Potential

The potential for the area remains largely unknown, until futher exploration is done. However, the structural complexity of the Lagmac coal measures suggest that the area is unlikely to become a major producer.