IRON ORE DEPOSITS IN EGYPT

Lecture 9:

Hassan Z. [email protected]

2016- 2017

@ Hassan Harraz 2017

mailto:[email protected]

Outline of Lecture 9:EGYPTIAN IRON ORE DEPOSITS

Iron ore deposit of sedimentary nature

Sinai: Gabal Halal iron ore deposit

Western Desert:

Aswan iron Ore Deposits

Bahariya iron Ore Deposits

• The Banded Iron ore deposits (BIFs)• Geologic Setting

• General Characteristics of the Egyptian Banded Iron Ores

• Are the Egyptian Banded Iron Ores Unique? Genesis of Egyptian Banded Iron Formation

We will explore all of the above in Topic 9.

2

@ Hassan Harraz 2017 3

Figure 1: Distribution of iron deposits in Egypt .

This figure shows the distribution of iron ores and iron oxide traces all over Egypt. Most of the

locations are inter-related in origin to each other. The trend of the iron oxides in Western Desert points

out to a common source of the iron deposits in this area.


EGYPTIAN IRON ORE DEPOSITSIn Egypt economic iron ore deposits occur in two natures (or forms):

i) Iron ore deposit of sedimentary nature (Ironstone)

(Sedimentary iron ore deposit is a very limited occurrence, being found only in the 2 localities in the Western Desert and one locality in Sinai):- Sinai: Gabal Halal iron ore depositWestern Desert:



and

ii) The Banded Iron ore deposits (BIFs) (BIFs have being found only in the 13 localities in the central Eastern

Desert)


I) Iron ore deposit of sedimentary natureSedimentary iron ore deposit is a very limited occurrence, being found only in the:-

One locality in Sinai : Gabal Halal iron ore depositTwo localities in the Western Desert



Sinai: Gabal Halal iron ore deposit

It is located ~4 km NW Sir Hadhira, Sinai (El-Far, 1965).

This area contain oolitic iron ores of lower Cretaceous age that

extending ~8 km.

The iron ore were found in two beds separated by 14 m sandstones:

The lower bed (~2.65 m in thickness) is a yellowish-brown

and compact bed mainly oolitic.

The upper bed (~5 m in thickness) is a typical oolitic iron ore.

Main ore minerals: goethite and hematite.

Gangue minerals: clay minerals, quartz, calcite-dolomite, and sulphate

minerals.


I) Iron ore deposit of sedimentary nature

Gabal Halal iron ore deposit

It is located ~4 km NW Sir Hadhira, Sinai (El-Far, 1965).

This area contain oolitic iron ores of lower Cretaceous age that extending ~8

km.

The iron ore were found in two beds separated by 14 m sandstones:

The lower bed (~2.65 m in thickness) is a yellowish-brown and

compact bed mainly oolitic.

The upper bed (~5 m in thickness) is a typical oolitic iron ore.

Main ore minerals: goethite and hematite.

Gangue minerals: clay minerals, quartz, calcite-dolomite, and sulphate minerals.

Sinai:

Iron associated with manganese east of Abu Zenima has economic significance as a by-product of manganese extraction, potentially accounting for the difference between profit and loss.

Passing references occur in some reports to ferruginous horizons with oolitichematite in Cretaceous Nubian sandstones of the Plateau Province.

Micaceous hematite is known to occur in quartz veins in eastern Sinai, in granite at Gebel Abu Mesud.


Iron ore deposit in Western DesertEconomic iron ore deposit of sedimentary nature, being found in the 2 localities in the Western Desert.

Sedimentary iron ore types only occur in

Upper Cretaceous (Senonian) sediments East of Aswan

Middle Eocene sediments north of the Bahariya oases

Note:

Senonian The final Cretaceous epoch which is dated at 88.5–

65 Ma ( Harland et al., 1989) and comprises the Coniacian,

Santonian, Campanian, and Maastrichtian Ages.

Some authors do not include the Maastrichtian Age within the

Senonian.


Egyptian Ore Deposits

Items Bahariya Oasis mine Aswan mine

Age Middle Eocene Senonian (Upper Cretaceous)

Ore Type Hard-massive, Banded-cavernous,

Friable, and Oolitic- pisolitic

Oolitic hematite (dark red with a bluish

metallic tinge in place)

Ore Minerals • Mainly of hematite, goethite, and

hydrogoethite, with occasional

pockets of softly ochre and

lepidocordite, chamosite,

magnetite, psilomelane, and

pyrolusite.

• Pyrite and chalcopyrite occur as

rare minute single grains.

Mainly hematite with minor goethite

Gangue minerals Barite, kaolinite, glauconite, alunite,

chert, gypsum, calcite, chlorite, and

Tripoli

Quartz, gypsum, halite, glauconite and

clay minerals

Average iron content (%) 53.4 43

Average silica content (%) 6.1 18

Average phosphorous content (%) 0.21 1.1

Specific gravity (gm/cc) 3.45-4.35

Mineable Geological Reserve

(m.t.)

140

(126.7?)

El-Gedida 14

136

(142.6?)

Ghorabi

Nasser

El-Harra

Average thickness of iron bed (m) 13 0.7

Stripping ratio 0.185 2.5

Mine area (km2) 6 600

Ultimate Annual production (m.t.) 3.3 (2.5) 0.5

Distance from mine to plant at Helwan

(km)

330 850

Production cost of one ton

(Egyptian pound)

18.020

On 2004

8.865

On 1975

Number of labourers 503

on 2004

1400

On 1975

Compared between Aswan and Bahariya iron ore Deposits



Western Deserti) Aswan iron Ore Deposits

Economic iron has been produced from East Aswan regions since Pharaonic times (1580 to 1380 B.C.) until 1973.

In recent years it was the main supply of iron ores for the Egyptian iron and steel industry till 1973 when it was replaced by Bahariya iron ore.

The main occurrence located East of Aswan(Kom-Ombo, Lake Naser), while small deposits are also encountered in the variegated shales along the Nile Valley to the south at Kalabsha, Garf Hussein, Kurusko, and Abu Simbil.


Fig. 2. (A) Geological map of East Aswan shows the location of study samples from Wadi Abu Sobera and Wadi Abu Agag areas. (B) Geological map of the Um Hibal area showing the locality of the iron-bearing formation. (A: after Mucke (2000); B: after Ghazaly et al. (2015)). 12

Fig. 3. General stratigraphic column of the late Cretaceous sedimentary cover in Aswan area. (After El Sharkawi et al., 1996).

13

Figure 1. Location map of the study area (up left), its main geologic topographic and iron ore localities illustrated on Landsat 8 false

color bands 7,4,2.

Salem, S.A. and E.A. El Gammal, E.A. (2015): Iron ore prospection East Aswan, Egypt, using remote sensing techniques. The

Egyptian Journal of Remote Sensing and Space Science, Volume 18, Issue 2,, 195–206. http://dx.doi.org/10.1016/j.ejrs.2015.04.003


Types of iron-ore tThe ore is a bedded oolitic type of Senonian age in the form of three bands

interbedded with Ferruginous sandstone and clay/Ferruginous concretioncapping Precambrian rocks.

Three ypes of iron-ore have been distinguished in the provided areas (Salem and ElGammal, 2015) :

(1) Ferruginous sandstone iron-ore (up to 70.46% Fe2O3 content),

(2) Oolitic iron-ore (attains 54.24% Fe2O3 content); and

(3) Ferruginous concretion iron-ore(up to 63.2% Fe2O3 content).

The Oolitic iron-ore shows P2O5 and S contents exist in relatively higher proportionsthan in the ferruginous sandstone and ferruginous concretions. This is due to theparticular bioactivity in the marine environment of formation of the Oolitic ore.Its low manganese content may be attributed to the low pH exhibited by theleaching solutions, which dissolved the slightly basic iron with small amounts ofstrongly acidic manganese.

In spite of the less contents of Fe2O3 = 54.24 and Fe = 37.94 in the Ooloitic iron orerelative to the other ore types, it is considered as an important type due to itsdominance and distribution in the east of Aswan district, as well as thedeficiency in silica and MnO add a promise potential to the Ooloitic iron ore.


Figure 7. Ferruginous sandstone iron ore illustrations (Salem and El Gammal, 2015). (a) Ferruginous sandstone thin beds in

Wadi Timsah hill. (b) Paleosole surface rich in iron oxides in the Nubian sandstone beds, Wadi Anid. (c) Ferruginous

sandstone cracked beds hand specimen (hs). (d) Ferruginous sandstone hs. (e) Limonite rich ferruginous sandstone hs. (f)

Ferruginous sandstone with calcite and Gibbsite.

Iron ore prospection East Aswan,

1) Ferruginous sandstone occurred and

was distributed in the lower parts of Timsah

Fm which was composed of fluviatile near-

shore marine and locally eolian fine-to

medium-grained sandstone with interbedded

channel and soil deposits.

Iron ore was found as inliers and caps and

in the paleosole surfaces of the Nubian

sandstone beds, forming hematite and

goethite strata having thickness varying from

50 cm to 4 m occuring at Gabal Timsah, Wadi

Timsah and Wadi Anid (Fig. 7a and b).

The iron ore is syn-genetic bedded of

Senomanian age, formed under lacustrine

environment. The gangue minerals

associated with the iron ore deposits include

quartz, gypsum, glauconite, and clay

minerals.

The hand specimens exhibit fine bedding

and plugs in red and brown to black colors

including limonite patches in yellow color (Fig.

7c–f).


Figure 8. The Oolitic iron-ore illustrations (Salem and El Gammal, 2015). (a) General view, Gabal Abu

Hashim. (b) Spherical Oolitic grains hs. (c) Oolitic hematitic glauconitic coarse grains hs. (d) Hematitic

rich Oolites hs.


2) Oolitic iron-ore is the more

dominant, most important and

valuable iron ore type in the study

district in spite of its low content of the

Fe2O3 relative to the other types.

It is found as compact beds vary in

thicknesses from 1–3 m. distributed

and alternated through the upper parts

of the Temsah Fm in Gabal Abu

Hashim, Gabal Nugur and Gabal

Naag areas of dark-red, Oolitic

hematite (Fig. 8a).

The oolites are cemented by pure

amorphous hematitic material and

ferruginous silica; therefore the iron-

content of the matrix is less than that

of oolites.

In the hand specimens, the Oolitic

hematitic grains are easily seen by the

naked eye varying in sizes in different

specimens and even in the same

specimen (Fig. 8b–d).


Figure 9. The Ferruginous concretion iron-ore illustrations (Salem and El Gammal, 2015). (a) Ferric-duricrust surfaces of

ferruginous concretion and substratum in Wadi Quffa. (b) Hard compact masses of ferruginous concretion beds. (c) Fine

intersected beds in Ferruginous concretion in Wadi Timsah. (d) Hematite-goethite coarse grained in Ferruginous concretion hs.

(e) Blocky Ferruginous concretion hs. (f) Gebsite, and clay minerals in Ferruginous concretion hs.


3) Ferruginous concretion iron-ore The Ferruginous concretion iron-ore form hard

compact masses of concretion beds and substratumrich in iron-ore, found as ferric-duricrust surfacesbetween isolated Nubia sandstone hills andmountains through Wadis Timsah, Quffa, Anid,Umm Udi and Abu Aggag (Fig. 9a,b).

The ferric-duricrust beds formed fromfragments accumulation of ferruginous sandstone,Oolitic iron-ore and ferruginous concretions whichwas already formed due to the action of surfacewater on the valleys floor (in wadi fill).

The thicknesses of the glauconitic coarse grainshs. (Fig. 9d) Hematitic rich Oolites hs. ferric-duricrustbeds vary from 10 to 60 cm, showing fantasticoutlines formed by precipitations from aqueoussolution in porous sedimentary rocks.

Due to the denudation of the sandstonecontaining hematite concretions and owing to theirresistance to weathering, they were often seenaccumulating in great quantities in places on theground surface giving it black and red colors. In thehand specimens, the concretions show hematite-goethite rich grain aggregations cemented in coarsegrained matrix of black and brown color s (Fig. 9c–f).


Over hanging layer of oolitic

Iron, Wadi Abu Aggag Aswan



The thickness of the bands varies from 20 up to 350 m.

Iron ore deposits occur in Senonian (upper Cretaceous) sediments ~7,000,000 tonnes were produced between 1956 and 1973.

The estimated reserves are 121 to 135 million tonnes with 20 million tonnes proved reserves with average content of 46.8% Fe (Attia. 1955).

Ore

The ore is oolitic hematite, dark red with a bluish metallic tinge in place, compact and dense (Sp.gr. 3.45-4.35 gm/cc).

Ore minerals: are mainly hematite with minor goethite. The hematite is occur in oolitic form range from 1-1.5 mm in diameter and is cemented by a compact hematitic matrix.

Gangue minerals: include quartz, gypsum, halite, glauconiteand clay minerals.

Fe31.2 - 62.3 %

(average 46.8%)

SiO2

5 - 31%

(average 14.1%)

Mn up to 1.3%

S up to 0.3%

P 0.4 - 3.5%

The oolites themselves contain 60% of Fe

while matrix contains 40% of the iron.


DiscussionThe east of Aswan area is a suitable environment for iron ore occurrences due

to the following reasons:

(1) Presence of huge Nubia sandstone rocks which formed from the compilations and accumulation of old rock fragments and deposits including iron.

(2) The aquatic marine environment present in the study area is suitable for leaching, precipitating and deposition of iron oxides from the iron rich solutions in the sandstone terrain as hematite and limonite.

(3) Varied topography between the basement and sedimentary rocks traced by intermountain substratum and basins are suitable for collection and catchment of different debris, rock fragments, slags, and wadi deposits with iron constituents. These factors motivated us to study the surface geology of this area exploring and locating the iron ore deposits through the exposed rocks and landforms.

The marine encroachments in the Cretaceous part of the east of Aswan area attained N–S to SE directions forming depositional basins (Issawi, 1981). Iron ore in the east of Aswan is considered by (Hussein, 1990) to have been formed under lacustrine conditions, during the deposition of Senomanian sediments. The sedimentary iron deposits are invariably confined to the middle series of the Nubian sandstone formations which lie unconformably on the basement rocks. The iron oxide bands are often associated to ferruginous sandstones and clays. Transitions from ferruginous sandstone to Oolitic iron deposits are often encountered (Adelsberger and Smith, 2009).


Gneiss

Ore is considered to have formed undersedimentary lacustrine to fluviomarineconditions during the deposition of UpperCretaceous (Senonian) sediments of Aswanembraces all the non-marine to marginaland shallow marine siliciclastics exposed inthe Nubia area.

The iron is mostly dissolved from bottomsediments and mobilized in so-called"carbon-dioxide zone" as ferrousbicarbonate, then precipitated in anoxidizing environment as ferric hydroxide.


II) Western Desert:Bahariya iron Ore Deposits

• The Bahariya oasis is located in central plateau of Western Desert between 27° 48/ -28° 30/ N and 28° 55/ - 29° 10/ E.

• Its northern edge is located along the contact between the stable and unstable shelves.


Gebel El-MaghrafaGebel El- Dist


Geologic map of the Bahariya area



Geologic map of the northern Bahariya area (after Said and Issawi, 1964)


The iron ore of El Harra belongs to El Harra member of El HaffufFormation; whereas El Gedida iron ore belongs to Naqb Formation.

The area is covered by Bahariya Formation (unfossiliferous varicoloredsandstone of Cenomanian age) followed by El Heiz Formation(brownish limestone and sandy clay beds), and El Haffuf Formation ofsandstone, sandy clay, and ferruginous beds, which are partly taken bythe iron ore deposit, Khuman Formation (chalky limestone), and NaqbFormation of thick limestone beds with few marl and clay associations.The iron content in the ironstone deposits ranges from 30% to 58% Fe,and the manganese content ranges from 0.7% to 7.66% Mn .

The stratigraphic position of Naqb Formation is partly taken by iron oredeposits at El Gedida, El Harra, and Ghorabi; where El Gedida iron oremember belongs to iron deposits of Lower Middle Eocene (NaqbFormation) and the upper Eocene (Abu Maharik Formation. The ore islocalized in the crest of anticline.



Fig. 6. A. Panoramic view of the Naqb Formation showing ironstone beds and clay

intercalations (white arrows) arranged in two sequences. B. Outcrop view of the

ironstone succession exposed at the central part of El Gedida mine (X is the location of

the collected fossil sample). (after Afify et al., 2016)


A composite section (not at scale) of the main Eocene lithostratigraphic and chronostrigraphic units and shallow benthic foraminiferal zones (SBZs) after Serra-Kiel et al. (1998). The shallow benthic zones written in red color are re-interpreted after previous dating by Boukhary et al. (2011) and Said and Issawi (1964). The violet shaded rectangle is the relative timing proposed for the iron mineralization. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)


The other areas: Ghorabi, Nasser, El Heiz, and El Harra are of low grade ores and of high manganese content. In addition, these areas have relatively thick overburden.

These occurrences are called El Gedida, Ghorabi, Nasser and El Harra,extending over 11.7 km2; and the ore thickness varies from 2 to 25 m(averaging 9 m).

The deposits are under laid unconformably by the Bahariya formationsandstones and overlaid by the Redwan formation.

The iron ore deposits are generally irregular in outline. They form asuccession of beds which are concordant with local dips (~4°).

The ore is thought to be localized in the crests of two major anticlinestrending in a NE-direction. El Gedida and El Harra ore deposits are localizedon the eastern anticline, while Ghorabi and Nasser are on the westernanticline.

The high-grade ores exist in the crests and that low-grade ores arelocalized in the limbs of the anticlinal structures.

Major faults disturb the peripheries of the ore bodies, forming the majorwadis which surround the area of the iron ore deposits. Many small faultsaffect the iron beds in the four areas. These structure natures of the foldsapparent to be generated by faulting affiliated with the Pelsuium mega-shear, along which the Bahariya oasis are located (Neev et al., 1982).


1.1.1. Forms, Shapes and Textures

Several forms characterize the constituents of the ore deposits such as massive crystalline, crystal aggregates, granular, botryoidal-shape, kidney-shaped, oolitic, pisolitic, pseudoolites (spheroids), subspherulitic, and sponges.

Therefore, several textures are recognized in the ore deposits such as banded, disseminated, cavity filling, cavernous, andreplacing.

1.1.2. Mineralogy

Main ore minerals: hematite, goethite, Limonite, and hydrogoethite, with occasional pockets of softly ochre and lepidocordite, chamosite, magnetite, psilomelane, and pyrolusite.

Pyrite and chalcopyrite occur as rare minute single grains.

Gangue minerals: barite, kaolinite, glauconite, alunite, chert, gypsum, calcite, chlorite, and Tripoli





Glauconite and Fe-rich chlorite

Rich Ore

Wadi area

(Western)

Barite Zone

Sands and Sandy clays

(Overburden)

Quartzite sandstone and

conglomerate (Radwan

Formation)

Unconformity

Intercalations

Footwall

(Bahariya Formation)

Barite patches

Saliferous Ore

High Central Area

Intercalations of clays, sand,

chert concretions and alunites

Mn rich

Wadi area

(Eastern)

East


Detrital Barite


Detrital Barite

الباريت المتفتت فى منطقة الهضبة بمنجم الحديد بالجديدة، الواحات البحرية•

Bahariya)بالجزء العلوى للحجر الرملى التابع لتكوين البحريةيوجد أسفل طبقة الخام• Formation)

عند منطقة التالمس بين الخام وتكوين البحرية ومتداخال مع الجزء السفلى لطبقة الخام•

سم وفى بعض الحاالت إلى مترين50سم إلى 5يتراوح السمك من •

ورة غير يوجد على هيئة جيوب او تجمعات وليس على هيئة طبقات متصلة، وهذه التجمعات منتشرة بص•ملىمنتظمة ومتفاوتة فى السمك واألبعاد ويفصلها مساحات خالية من الباريت تكون من الحجر الر

ب إلى يكون الباريت مختلط بالرمال وبنسب متفاوتة من خام الحديد وتتفاوت درجة تماسكه من سائ•متماسك في حالة اختالطه بالحجر الرملى وشديد التماسك فى حالة اختالطه بخام الحديد

•


Detrital Barite


1.1.3. Ore TypesGenerally, four types of ore are distinguished based on texture, constituents and chemical composition namely:

Hard-massive ore type: This type is relatively massive hard crystalline and has a deep reddish-brown color. It consists mainly of hematite (>80%) with minor amounts of goethite and limonite. Micro- and macro-fossils which are replaced by hematite (and/or goethite) are common. Manganese minerals (mainly psilomelane) are rare in this ore type.

Banded-cavernous ore type: It has a brown or yellowish color, generally banded and cavernous. The cavities being filled with red or yellow ochre or manganiferous powder. It consists mainly of an intergrowth of goethite and hematite together with a little amorphous limonite and minor amounts of manganese minerals. The pyrite and chalcopyrite are present as minute grains within limonite or in the core of subspherulitic goethite bodies. This banded texture is attributed to pre-existing laminations in the original limestone.

Friable-ore type: Generally, bright yellow, soft, friable and has an earthy luster. The ore minerals consist mainly of goethite and limonite together with minor amounts of hematite. Glauconite is the most common gangue mineral and result in the appreciable increase Al2O3 content of these ore type.

Oolitic-pisolitic ore type: Low to moderate grade ore (49-45 % Fe) has a yellow to yellowish-brown color and oolitic to pisolitic texture. It is mainly formed of goethite, Iimonite and quartz, minor amounts of hematite, glauconite and Fe-rich chlorite.


Reserves

• Economic iron ores confined to the lower part of the middle Eocene limestone (El Naqbformation) in four major occurrences north of Bahariya oasis.

Today, the left minable reserves are estimated by only 63 Mt, which are just enough for about15-20 years at the present mining rate of 3 to 3.5 Mt/y.

Bahariya iron ores have 53% Fe that is suitable for the iron high ovens in Helwan Cityfactories, now, iron ores excavated from El-Gedida mine with an annual rate 3.3Million Tons then carried about 300 km away to Helwan City factories by a specialtrain.

It is necessary to blend the various types to obtain:

Fe 53%, SiO2 7.5%, Cl 0.7%, and MnO 1.98%,

for use in the metallurgical plants at Helwan Iron and Steel Co., Cairo.

How Geologist do this mixture???

Area Reserves Fe SiO2 Mn S P Cl

(M.Tonnes) %

El Gedida 126.7 53.6 8.9 2.3 0.9 0.2 0.6

Ghorabi 57.0 48.0 9.0 3.0 0.7 0.9 0.8

Nasser 29.0 44.7 6.7 3.9 0.6 0.1 1.3

El Harra 56.6 44.0 12.5 2.9 1.0 0.1 0.8


They classified ore blocks according to Fe-content into three categories as following:

Poor ore (17-35% Fe): Low-grade iron ore, highly ferruginous sandstones and hydrogoethite ore.

Normal ore (35-45% Fe): Oolitic and pisolitic hydrogoethite ore, banded hydrogoethite, and hydrohematite ore

Rich ore (>45% Fe): Colloform hydrogoethite ore and massive hydrogoethite-hematite ore.



Genetic Ore TypesThe largest and richest of these occurrences in that of El Gedida (~127 million tonnesproven ore). At El Gedida mine, distinguishing three genetic, types:I) Iron ore of a massive nature and a hydrothermal-metasomatic type (Type I): Represented by the high central area in El Gedida mine. The ore is high-grade, with high Fe and NaCl contents, and low Si, and high traces of Zn

and Cu. The mineralized middle Eocene limestone (El Naqb formation) is brecciated and

metasomatically replaced by hydrothermal solutions ascending along NE-SW trending fractures.

II) Iron ore is cavernous, ochreous or massive type (Type II): Following the emergence and faulting of the mineralized middle Eocene block, the

generated depressions received reworked rocks including high-grade ore from the high central area.

Fresh water lakes occupied the depressions where remobilization of Fe and Mn and their redeposition were effected, possibly through biogenic interference.

Tripoli earth and kaolinite were authigenetically deposited with the debris. Detrital barite is a common associated. Abrupt change in grade characterizes the iron ore of this genetic type

III) Iron ore is oolitic or pisolitic type (Type III): This follows type II in age and is tied to post-middle Eocene glauconitic succession

which caps the reworked iron ore of type II Enrichment of the marine depositional basin in Fe and K promoted the formation of

glauconitic. Cyclic deposition of glauconitic clays and sands was interrupted by intermittent

emergence followed by lateritic weathering of glauconite sediments Profound changes in the mineralogy of these sediments took place resulting in the

deposition of low-grade Fe ore characteristically poor in Mn and Ba.


1.1.4. OriginAmbiguity arises regarding the genesis of the iron ores in the Bahariya oases

area.Attia (1955) favored a shallow water lacustrine origin during Oligocene time.

Deposition of leached iron under lagoonal environment and subsequent replacement of the underlying middle Eocene and Cenomanian beds. Evidence of replacement is apparent where most of the calcareous fossils, especially the diagnostic nummulites of the middle Eocene, are almost completely replaced by iron oxides.

El Shazly and Hassan (1962) assumed that the Ghorabi iron ore was derived from the chemical weathering of older rocks.

Contrary of these opinions, Tosson and Saad (1974) suggested that the ores were formed by metasomatic replacement associated with impregnations and cavity filling from ascending solutions affiliated with volcanic activity. The oolitic and pisolitic iron ore outcropping in the Ghorabi area to be syngenetic, the iron being supplied by weathering processes and the high grade ores exist in the crests and that low-grade ores are localized in the limbs of the anticlinal structures.

On the other hand, El Aref and Lotfy (1985) suggested that the iron deposits were formed through lateritization processes during the senile stage of post Eocene karst event. Karst depressions and excavated unconformity acted as traps where iron oxides are accumulated. Iron deposits together with soil products also form surfacialcrust (duricrust), capping and cementing highly subdued and altered carbonate rocks. The evolution of megascopic and microscopic ore fabrics, the oxidation of iron bearing minerals, and their relation to the gangue and weathering products reflect the changes in the moisture regimes and the physicochemical conditions involved during the pedogenesis.


Qatrani Formation At El Gedida Mine. You can see here a

burrowing of ants then filled with iron.


• In the Eastern and Western Wadi areas, the ore successions are truncated unconformably by late Lutetian-Bartonian glauconitic sediments with lateritic ironstone interbeds of the HamraFormation.The iron ore and the overlying glauconitic sediments are folded and undulated. The iron ore sequence attains its maximum thickness, up to 35 m, in the Western and Eastern Wadi areas, reduced into 11 m in the high central area. This iron ore sequence consists of a pisolitic oolitic iron stone unit followed by highly karstified bedded ferruginous dolostones and mudstones. Ore conglomerates mixed with silicified limestone and chert overly the karst ore. The genesis of the ores has been a matter of a scientific discussion for a long time.


Glauconitic green sand at Gabal El Dist(Bahariya Formation)

Upper Eocene Hamra Formation (Glauconite and Iron beds)


Charcoal at Gabal El Dist


ii) EGYPTIAN BANDED IRON FORMATION

(BIFs)


ii) EGYPTIAN BANDED IRON FORMATION (BIFs)

The banded iron ore deposit is a very limited occurrence, being found only in the 13 localities in the central Eastern Desert, approximately between Latitude 25° 15/ - 26° 40/ N and Longitude 33° 22/ - 34° 20/ E.

These iron ore type is concentrated in five main localities: Abu Marawat, Wadi Kareim, Wadi El Dabbah, Wadi Um GhamisEl Zarqa, Gabal El Hadid, and Um Nar.

The bands are variable in thickness and extension from one locality to another and within the same occurrence.

Their extension usually vanes from some meters up to more than 2 km along the strike, and vary in thickness from a few cmsto 18 m (normally ranging between 0.5 and 3 m).

In the most cases, the ore is present in the form of bands and lenses of magnetite, martite and hematite with a gangue dominantly of quartz.

The reserves for BIF ore type in Egypt amounts to 47.6 million tonnes (Akaad and Dardir 1983) as estimated for the whole of Quseirarea.


Localities Latitude Longitude

Abu Marawat 26° 31/ N 33° 22/ E

Wadi Kareim 25o 56/ 40// N 34° 03/ E

Wadi El Dabbah 25° 48/ N 34° 09/ E

Wadi Abu Rakab 25° 48/ 30// N 34° 11/ E

Wadi El Hindusi 25° 47/ 30// N 34° 11/ E

Gabal Um Shaddad 25° 39/ 20// N 34o 20/ E

Wadi Um Ghamis El Zarqa 25° 33/ N 34° 17/ E

Wadi Sitra 25° 32/ N 34° 14/ 30// E

Wadi Siwiqat Um Lassaf 25° 21/ N 34° 08/ E

Gabal El Hadid 25° 20/ N 34° 10/ E

Um Mar 25° 18/ N 34° 15/ E

Wadi Um Hagalig 25° 15/ 30// N 34° 16/ 30// E

Map showing major iron deposits in central Eastern Desert, Egypt.

Geographic co-ordination of the Banded Iron Ore deposits in the central Eastern Desert of Egypt

Fig. 1: Thematic Landsat image of Egypt showing the location of eleven of the most important banded iron-ores (blue circles). Inset is a simplified geological map of the area outlined in the white rectangle (from Egyptian Geological Survey, 1981) .

1) Hadrabia

2) Abu Marawat,

3) Gabal Semna

4) Diwan

5) Wadi Kareim,

6) Wadi El Dabbah,

7) Gabal Um Shaddad

8) Wadi Um Ghamis El Zarqa,

9) Gabal El Hadid,

10)El Emra

11)Um Nar

12)Wadi Hammama

13)Um Anab

Wadi Abu Rakab

Wadi El Hindusi

Wadi Sitra

Wadi Siwiqat Um Lassaf

Wadi Um Hagalig

54

Table 1: Tectonostratigraphic basement units of the Egyptian Eastern Desert

Sources: Egyptian Geological Survey (1981); El-Gaby et al. (1990); Hassan and El-Hashad (1990); Stern et al. (2006); Avigad et al. (2007); Moussa et al. (2008).

Eon/

Era

Tectonic

Stage

Age

Ma

Rock Types/ Associations Granitoid intrusion

Ph

aner

o

zoic Po

st-

Oro

gen

i

c

< 5

70

. Younger Granites (post-tectonic, alkalic): Granite, granodiorite,

monzonite

Gattarian (570 – 475

Ma)

Neo

pro

tero

zoic

Pan

Afr

ican

Acc

reti

on

/

Co

llisi

o

n6

50

-

57

0

Dokhan metavolcanics (andesite, rhyolite, rhyodacite,

pyroclastics) intercalated with Hammamat metasediments

(breccias, conglomerates, greywackes, arenites, and siltstones)

Sub

du

ctio

n

75

0 -

65

0

Isla

nd

Arc

Shadhli Metavolcanics (rhyolite, dacite, tuff);

Volcaniclastic metasediments; Diamictites (Strutian: 680

– 715 Ma).

Banded Iron Ores

Meatiq (710 – 610)

Hafafit (760 – 710)

Spre

adi

ng

85

0 -

75

0

Op

hio

li

tes

Tholeiitic basalt, sheeted dykes, gabbros, serpentinites,

all weakly metamorphosed

Shaitian Granite

(850 – 800 Ma)

Arc

hea

n?/

Pale

op

rote

ro

zoic

Pre

-Pan

-

Afr

ican

<1.8

Ga

Metasedimentary schists and gneisses (Hb-, Bt-, and Chl-

schists), metagreywackes, slates, phyllites, and

metaconglomerates Some BIF? Umm Nar?Migiff – Hafafit gneiss (Hb and Bt gneiss) and migmatite


Geologic Setting Central Eastern Desert (CED) is a part of the Arabian Nubian

Shield (ANS) which constitute the northeastern sector of the Pan-African (650-550 Ma., Clifford 1970) tectonic belt. The EgyptianBanded iron formation (BIF) and the host geosynclinalmetavolcanics and/or metasediments constitute widespread andeasily recognizable sequences at 13 localities distributed in theCED.

The iron formations occur as sporadic deposits in layered thevolcanogenic rocks of Neoproterozoic age. The Neoproterozoicbasement complex of the CED consists largely of a crudely layeredsequence of volcanic rocks and derivative sedimentary rocks,mainly of greenschist facies metamorphism. The terrene has manylithologic similarities to the Archean greenstone terrenes.

The BIF geologic sequences are considered to be geneticallyrelated to Pan-African weakly metamorphosed island arcassemblages ( island arc volcanics and volcanoclastics ofNeoproterozoic age) which are often associated with ophioliticmélange rocks


Fig. 2: Location of Wadi Kareim (K) and El Dabbagh (D) study areas. Location of Meatiq dome (M) is also shown. Dark green area between Kareim and Dabbagh is a Hammamat basin. From Google Earth.


Figure 23: Geologic map of Wadi Kareim area (left) and Wadi El Dabbagharea (right; note north arrow (Stern and Dixon, unpublished)


Geological map of Wadi El Dabbah iron ore deposit ( after Akaad and Dardir, 1983)


• Fig. 2: Geological maps of (a) Wadi Kareim area (AFTER El-Habaak and Mahmoud, 1994) and (b) Umm Nar (after El-Aref et al., 1993). Ellipse in (a) shows location of banded iron ore. 60


General Characteristics of the Egyptian Banded Iron formation

The general characteristics of the iron formation in the central Eastern Desert are as follows:

1)The BIF occurs as sharply defined stratigraphic units within layered volcanic-volcaniclastic sequences of calc-alkaline nature and andesitic composition.

2)Some deposits (e.g. Wadi Kareim) are reportedly associated with diamictites (e.g. Stern et al., 2006) suggesting some relation to glaciations and possibly “Snowball Earth” conditions.

3)Individual bands range from a few centimeters to more than 10 m in thickness and are frequently faulted and folded with steeply limbs.

4)Frequent contemporaneous folding, faulting, brecciation and slump structures are found.

5)Microbanding occurs on a scale of centimeter or less, where iron-rich bands alternate with bands of jasper or, sometimes, of carbonates or silicates.

6)In a given area, the zone containing layers of iron-formation typically has a stratigraphic thickness of 100 to 200 m, in which the aggregate thickness of BIF is on the order of 10 to 20 m.

7)The lateral extents and thicknesses of individual ore bodies are relatively small, typically on the order of tens of meters (Fig. 2).

8)The entire sequence (iron ore + host rocks) is strongly deformed by a series of folds and thrusts, and was regionally metamorphosed under at least greenschist facies conditions.

9)Deformation evident on the regional, outcrop, and hand specimen scales (Figs. 2).

10)Rhythmic banding is either streaky (Umm Ghamis) or continuous (Hadrabia) where layers of magnetite and hematite alternate with quartz – rich layers on macro-, meso- or micro-scales.


General Characteristics of the Egyptian Banded Iron Ores

11) Hadrabia is the only deposit with oolitic and pisolitic textures. None of the other deposits have oolites, pisolites, pellets, or granules . Other wave generated primary structures are also lacking.

12) Oxide and silicate facies ubiquitous; carbonate facies usually represented by calcite is common in several deposits (e.g. Wadi Kareim, Wadi Dabbah, and Hadrabia). Sulfide facies is generally lacking.

13) Magnetite is dominant, except in a few deposits (e.g. Hadrabia) where hematite -magnetite. Most crystals of magnetite have undergone some grain coarsening attributed to metamorphism in several areas (e.g. Wadi Kareim).

14) Magnetite commonly altered to martite, specularite, or goethite due to post-metamorphic oxidation.

15) Most of the iron is present as magnetite (altered in places to martite) concentrated in steel-back bands alternating with reddish jasper or with iron-poor grey or greenish bands; hematite is less frequent. The gangue minerals present are mainly quartz, chlorite, biotite and clay minerals.

16) Silicate facies characterized by the minerals: chlorite, epidote, garnet, hornblende, and stilpnomelane.

17) Some deposits are also strongly altered, often developing a porous texture

18) Many of the iron ore deposits (e.g. Gebel Semna, Gebel Hadrabia and Abu Merwat) are characterized by high Fe and low Si contents in comparison with Algoma, Superior, or Rapitan BIF types (Fig. 7, Table 2), whereas others (e.g. Gebel El Hadid and Wadi El Dabbah) are characterized by Fe/Si ratios somewhat comparable to Rapitan BIF. Altered samples with a porous texture are typically characterized by some of the highest Fe/Si ratios (Table 2).

19) Greenschist facies metamorphism, with the development of chlorite, sericite and the iron silicate stilpnomelane and possibly minnesotaite occur. On the contact with intrusives, local metamorphism may reach amphibolite facies with the recrystallization of the iron minerals and silica and development of epidote and garnet.


Table 5: Mineralogical compositions and mode of occurrence the BIF, Central Eastern Desert, EgyptWadi Kareim Wadi El Dabbah Umm Ghamis El Zarqa Gabal El Hadid Umm Nar

Country rocks

Metavolcaniclastics,

metavolcanics,

granodiorites, Hammamt

sediments, trachytes

tetavolcanics, serpentinites,

Older Granites, Hammamat

sediments, Younger

Granites

Metasediments, metavolcanics,

serpentinites, metagabbros,

diorites, granodiorites, granites

Metasediments,

metavocanics, serpentinites,

metagabbros, granites

Shaitian granites, metasediments,

serpentinites, metagabbros, younger

gabbros, granites

Host rocks

Metavolcanic rocks

intercalated with

volcaniclastic rocks

(andesite-dacite tuffs,

metagreywackes &

metamudstones)

Tuffaceous metasediments Calcareous metamudstones

intercalated with

metagreywackes

Metasediments-

metapyroclastics (consists of

metagreywackes,

metamudstones,

metasiltstones,

metaconglomerates,

metatuffs)

Mica-schists, amphibole schists,

marbles and quartzites.

Principal iron mineralMagnetite, hematite Hematite and/or magnetite Magnetite with or without

hematite

Magnetite, hematite Magnetite, hematite, stilpnomelane

Subsidiary iron minerals

(rarer minerals in

parenthesis)

Goethite, siderite,

greenalite, ninnosotaite,

stilpnomelane, pyrite,

(pyrrhotite, chalcopyrite,

sphalerite)

Goethite, martite (pyrite) Martite, goethite Goethite, siderite, (pyrite,

chalcopyrite)

Martite, goethite

Gangue minerals

Quartz, jasper, calcite,

ankerite, dolosite, garnet,

epidote, chlorite, actinolite,

talc

Quartz, jasper, calcite,

garnet, epidote, chlorite,

actinolite

Quartz, jasper, chalcedony,

calcite, epidote, chlorite, garnet,

hornblende, feldspar

Quartz, jasper, chert, calcite,

dolomite. ankerite, chlorite,

epidote, muscovite, biotite,

feldspar, apatite

Quartz, calcite, plagioclase, muscovite,

biotite, hornblende, graphite, epidote,

garnet

Iron formation faciesOxide, carbonate, silicate,

sulfide

Oxide, oxide-silicate Oxide, oxide-silicate Oxide, carbonate (rarely

sulfide)

Oxide, oxide-silicate

Ore types

Banded siliceous Massive

magnetite

Magnetite-rich (black)

Hematite-rich (red-violet)

Magnetite-jasper-(hematite) Jasper-hematite Magnetite)

Nodular chert-magnetite-

(hematite) Siderite-magnetite)

Quartz-magnetite, Hematite-

magnetite-quartz-garnet

Fe% surface

Fe% subsurface

Reserve (m.t.)

44.6

43.0

17.8

38.2

34.9

6.0

44.6

42.1

5.6

45.7

45.0

3.6

45.8

41.8

13.7

Texture

Bedding, banding,

lamination, lensoidal, slump,

pelitic, psamo-pelitic, relics

of oolitic, granular, massive

Bedding, banding,

lamination, lensoidal,

Massive

Banding, bedding, lamination,

lenses, slump, crenulation

Banded, bedded, lensoidal,

deformation, massive,

colloform, rim veins, relict

replacement

Bedding, banding, lamination, cross-

lamination, flaser structure,

granoblastic, lense, slump, lensoidal

Band thickness 0.4 to 12 m Few cm to 10 m 10 cm to 5m Few cm to 3.8 m Few cm to 3 m@ Hassan Harraz 2017 64

BIF with japer laminations (Wadi El Kariem)

d) Meso- and (e) micro-scale banding (lamination) between alternating jasper (red) and Fe-ore in unaltered samples from Wadi Kareim.


Fig. 4: Photomicrographs showing selected textural relations. (a) through (e) taken under polarized reflected light, oil immersion; (f) - (h) under plane polarized transmitted light. (a) Magnetite coarsened by metamorphism, Wadi Kareim; (b) relicts of primary? magnetite (Mgt) replaced by hematite, Wadi Kareim; (c) coarse grained porphyroblasts of strongly martitizedmagnetite, Wadi Kareim; (d) relict magnetite strongly martitized, and transformed into platy specular hematite (Hm) Wadi Kareim; (e) primary magnetite (arrow) and quartz embedded in a matrix of secondary goethite, Gebel Semna; (f) oriented platy hematite, oxide facies, strongly altered porous sample from Gebel Semna; (g) fibrous stilpnomelane (Stp) in silicate facies; Wadi Kareim; (h) epidote (Ep; arrow) coexisting with magnetite, silicate facies; Wadi Kareim; (i) chlorite coexisting with sericite and quartz, silicate facies; Gebel Semna; cross polarized transmitted light.


Reserves

Abu

Marawat

Wadi

Kareim

Wadi

El Dabbah

Umm

Ghamis El

Zarqa

Gabal

El Hadid

Umm

NarTotal (m.t.)

Reserves* (m.t.) 6.5 17.7 6.0 5.6 3.6 13.7 53.1

Fe% surface 44.4 44.6 38.2 44.6 45.7 45.8 43.7

Fe% subsurface - 43.0 34.9 42.1 45.0 41.8 -

Fe% in concentrate - 56.4 53.5 59.7 69.0 61.0 55.3

Expected

concentrates

- 10.0 3.2 3.6 2.6 7.0 27.4


Are the Egyptian Banded Iron formations Unique? The size and general characteristics of the Egyptian BIF led to the suggestion that they are “Algoma type” deposits (e.g.

Sims and James, 1984; Table 2). However, several points suggest that the Egyptian BIFs may be unique, namely:

Algoma and Superior type deposits are Late Archean or Paleoproterozoic in age (e.g. Klein, 2005), whereas the Egyptian BIF’s are Neoproterozoic (Fig. 5). Only Umm Nar is suspected to be Paleoproterozoic (El-Aref et al., 1993).

The Neoproterozoic Rapitan/ Urucum type deposits are typically jaspilites associated with glacial deposits. Among the Egyptian iron ores, only Hadrabia is characterized by Hm >Mgt? (Essawy et al., 1997). Diamictites have only been reported from Wadi Kareim (Stern et al., 2006).

Egyptian BIFs are intercalated with calcalkalic metavolcanic and metapyroclastic rocks of island arc affinity rather than the tholeiites typical of Algoma type deposits.

Sulfide facies is lacking, carbonates minor, usually predominated by calcite (or ankerite) rather than siderite; well developed silicate facies with stilpnomelane, chlorite, epidote, and garnet; oxide facies predominated by magnetite.

Garnet in many Egyptian BIFs is grossular rich (and in some cases free of almandine; Khalil, 2001; Takla et al., 1999) unlike garnets from Algoma or Superior BIFs which are typically almandine – spessartine solid solutions (e.g. Klein and Beukes, 1993).

Amphibole in many Egyptian BIFs is a magnesiohornblende (e.g. Takla et al., 1999; Khalil, 2001) rather than cummingtonite – grunerite.

Chlorite in all Egyptian BIFs is a clinochlore – ripidolite with significantly higher Mg/(Fe + Mg) ratios (0.5 – 0.7) compared to Algoma and Superior type BIFs (Fig. 6).

All Egyptian BIFs characterized by an unusually high Fe/Si ratio (Fig. 7), as well as higher Fe3+/Fe2+ ratios compared to Algoma and Superior types (Fig. 8). Fe/Si is considerably higher for BIFs affected by alteration (hydrothermal or weathering?).

Egyptian BIFs characterized by bulk chemistries that vary considerably from one deposit to another. However, many deposits are characterized by high Al and low Cr and Ni compared to Algoma type BIFs (Table 2).

REE patterns for Egyptian BIFs vary from one deposit to another, and do not resemble those patterns characteristic of Algoma, Superior, or Rapitan BIFs. “Fresh” Umm Ghamis and Umm Shaddad have prominent negative Sm and positive Ndand Eu anomalies, and slight HREE enrichment . Hadrabia deposit (“altered”) is characterized by a positive Eu anomaly. Strongly oxidized samples from Hadrabia show LREE enrichment relative to North American Shale Composite (NASC) .


Table 2: BIF from the Eastern Desert of Egypt compared to the main types of BIF

O = oxide, Si = silicate, C = carbonate, Sf = sulfide, Mgt = magnetite, Hm = hematite.

Algoma Superior RapitanEgyptian BIF

Fresh Altered

Age(Ga) >2.5 2.5 - 1.9 0.8 - 0.6 0.85? - 0.65 0.75-0.6

Size small large small small small

Thickness (m) <50 >100 75 - 270 Very thin 5 -30

Deformation Very strong Undeformed Deformed Strong Strong

Facies O, Si, SfC O, Si, C O, Si,C

Oolites rare always common none none

Ore Minerals Mt>HmMt>Hm

Higher HmHm Mt>Hm MtHm

Rock

Associations

Tho to CA

vol,tuffs,

wackes/shales

Carbonaceous DiamictitesCA volcanic, tuffd, shales,

wackes; Diamictites?

ChemistryHigh, Cr, Mn,

Ni, Cu, As

Low Cr, Co, Ni,

Cu, Zn

High P, Fe,

Low Cr, Co,

Ni

Low Cr, Co, Ni, Cu,

Variable Al

REE/NASC

+Eu, -Ce, slight

HREE-

Enrichment

+Eu , strong

HREE-

Enrichment

Weak +Eu,

Very strong

HREE

Enrichment

-Sm, Ce?,

+Nd and Eu,

HREE- rich?

+Eu, -Yb,

LREE-rich

Fe/Si <1.36 <1.36 1.3 - 1.6 1.4 -2.75 3 -4.7

Fe2O3/FeO 1.9 2.76 46- 100 5.5 - 8 7 -57


Fig. 5: Schematic diagram showing age and abundance of the three main types of BIF relative to Hamersley Group as a maximum (from Klein, 2005). Note Egyptian BIF age.


Fig. 6: Compositional range for chlorites from the silicate facies of the Egyptian BIF relative to the fields of Sheikhikhou(1992).


Fig. 7: Bulk rock compositions of “Fresh” and “Altered” BIFs from Egypt relative to Algoma, Superior, and Rapitan average compositions from Gross & McLeon (1980).


Fig. 8: Bulk rock major oxide components of Wadi Kareim iron formation (solid circels) compared to overall averages for Algoma and Superior type BIFs (shaded green) from Klein (2005). All analyses recalculated on an anhydrous, CO2 – free basis.


Fig. 9: REE patterns normalized relative to North American Shale Composite (NASC) for (a) “fresh” BIF from Taklaet al. (1999); El-Habaak & Soliman, (1999); (b) “altered” BIF from Hadrabia (Essawy et al.,1997), and Kareim (El-Habaak and Soliman (1999) compared to patterns typical of Algoma (c), Superior (d), and Rapitan (e). (c) – (e) from Klein (2005).


GENESIS OF EGYPTIAN BANDED IRON FORMATION

The Egyptian banded iron formation (BIF) and the host metavolcanics or metasediments constitute widespread and easily recognizable sequences at 13 localities distributed in the Central Eastern Desert (CED) between latitudes 25° 12/ and 26° 31/ N. These BIF sequences are considered, in the recent literatures, to be genetically related to Pan-African weakly metamorphosed island arc volcanic and volcaniclastic assemblages (Late Proterozoic) which are often associated with ophiolitic mélange rocks.

However, the understanding of the environment of deposition and geologic setting of each BIF-bearing sequence is very important to unravel the origin of the related BIF facies as well as its genetic relationship with the complex history of the Pan-African rock assemblages.

Two main genetic models have been postulated for the banded Egyptian BIFs:1) a purely sedimentary origin during the accumulation of the Precambrian

geosynclinal sediments (i.e. chemical marine sediments in geosynclinalbasin; Shukari et al., 1959, and Rasmy, 1968), and

2) a volcanogenic origin related to submarine magmatism and hydrothermal activity of Pan-African island arc assemblage (i.e., subaqueous volcanogenic deposits in an island arc environment: (Sims and James, 1984; El-Gaby etal., 1988).


It is generally agreed that the BIFs are chemical precipitates from water, but there is no general agreement as to the source of the iron and silica in them or to the physical environment in which they were deposited.

The BIF and base metal sulfides of the Egyptian Eastern Desert seem to be occurring exclusively in the island arc assemblage which consists of weakly metamorphosed volcanogenic sequences, where the iron oxides represent an aerated near-shore environment to the north and the sulfides represent deeper euxinic environment to the south.

On the other hand, the two southernmost iron occurrences at Gabal El Hadid and Umm Nar contain pyrite, chalcopyrite and siderite beside iron oxide minerals (Sabet et al., 1976; El-Dougdoug et al., 1985); these occurrences may represent transitional conditions shallow or near shore facies (i.e. iron oxide).

El Aref et al. (1993) preliminary reclassified the Egyptian BIFs into two main genetic types of different ages;1) Early (?) Proterozoic BIF of pre-Pan-African shelf environment,

represented by the Umm Nar occurrence., and2) Late Proterozoic BIF of Pan-African island arc environment,

represented by Gabal El Hadid, Wadi Kareim, and Gabal El Dabbah.


Table 3: Paragenetic sequence of mineral formation of the central Eastern Desert BIFs in relation to the metamorphic history

Sedimentation and

Diagenesis

Metamorphism Hydrothermal

process

Weathering process

Regional Contact

Mineralogical

Composition

Colloidal materials of

ferruginous/

calcareous sediments,

muds, shale, silica

gel and detritus materials ?

Magnetite

(fine euhedral

crystals)

Hematite (fine

prismatic and

flaky crystals)

Stilpnomelane

Minnosotaite

Quartz

Chlorite

Muscovite

Dolomite

Ankerite

Biotite

Epidote

Hornblende

Actinolite

Talc

Garnet

Apatite

Magnetite

(large euhedral

crystals)

Magnetite

(after chlorite)

Chlorite

Epidote

Garnet

Graphite

Magnetite (veinlets)

Goethite (veinlets)

Pyrite

Chalcopyrite

Pyrrhotite

Sphalerite

Quartz (veinlets)

Calcite (veinlets)

Hematite (martite)

Goethite

Kaolinite

Sericite

Chlorite

Textures

Banded

Massive

Colloform

Pelitic and psmao-pelitic

Relics of oolitic

Nodular

Granular

Banded

Lensoidal

Massive

Granoblastic

Vein replacemet Replacenent

Colloform

77

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http://dx.doi.org/10.2113/gsecongeo.64.4.424

http://dx.doi.org/10.2113/gsecongeo.79.8.1777

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