Geophysical Characterization of Uranium-REE · PDF fileDharmapuri Shear Zone, in the Northern part of Tamil Nadu, India ... Suplide mineral galena (G) and millerite(Mi) (F) Grain mount

A.K.Chaturvedi and P.S.Parihar

Geophysical Characterization of Uranium-REE Mineralization

associated with Alkaline-Carbonatite Complex along North

Singhbhum Shear Zone, Singhbhum Craton, Jharkhand and

West Bengal, India.

Department of Atomic Energy

Atomic Minerals Directorate for Exploration & Research

Government of India

Technical Meeting on Uranium from Unconventional Resources 4-7 November 2014

International Atomic Energy Agency (IAEA), Vienna, Austria

Introduction on Alkaline-Carbonatite Complexes

(ACC) of India.

ACC areas under exploration

1. Dharmapuri Shear Zone (DSZ), and

2. North Singhbhum Shear Zone (NSSZ)

Geophysical Characterization of NSSZ

1. Using High Resolution Heliborne Survey

2. Interpretation and modeling of Heliborne TEM,

Magnetic, Radiometric data.

3. Integrated interpretation of Geophysical,

geological and drilling data for further

subsurface exploration.

Scheme of Presentation

Alkaline-Carbonatite Complex (ACC) of India holds considerable

potential and few of them are being explored to establish low-grade

polymetallic U-REE deposits.

Important Alkaline Complex of India :

Ambadongar related to late stage Deccan alkaline magmatism,

Gujarat.

Newania within Archaean basement granite, Rajasthan

Beldih and Kutni along North Singhbhum Shear Zone (NSSZ),

West Bengal.

Sevattur and Rasimallai along Dharmpuri Shear Zone, Tamil

Nadu.

Sung Valley along Um Ngot lineament, Meghalaya and

Samchampi along Kalyani lineament, Assam.

Alkaline-Carbonatite Complex (ACC) of India

75°E

22°N

Ambadonagar Village

(Map modified after Deans et al., 1972)

•The sub-volcanic alkaline ring

complex of Amba Dongar (~ 65 m.y.)

consists of carbonatites,

nephelinites and phonolites, and is

well known for hosting the largest

fluorite deposits (av. 30% CaF2) of

India.

•It is a part of the Chotta-Udaipur

alkaline province and is located at

the northern periphery of the Deccan

flood basalts besetting the western

edge of the Narmada Rift Zone.

•Fluorite, Apatite, Magnetite/Hematite

Pyrochlore, Barite, Monazite and

thorogummite are common minerals

recovered from Ambadongar

Carbonatite Complex.

•The Newania carbonatite , located

about 40 km east of Udaipur town,

Rajasthan and is situated within the

structurally highly deformed Aravalli

Mountain Range.

•The Newania carbonatite consists

mainly of dolomite (rauhaugite, ~ 2.27

Ga, Pb-Pb age) and younger,

differentiated ankerite carbonatite

(~1.55 Ga, Pb-Pb age), and dykelets of

calcite carbonatite (sovite).

• Apatite is the main economic

mineral mined from Newania

Carbonatite Complex. Associated by-

products are magnetite, pyrochlore

and traces U-REE bearing minerals.

25°N

24°N

74°E

0 50Km

GEOLOGICAL MAP OF MEGHALAYA PLATEAU AND THE MIKIR HILLS

ALLUVIUM

GARO GROUP & EQ.

JAINTIA GROUP

KHASI GROUP

CARBONATITE COMP.

SYLHET TRAP KHASI GREENStonne

INTRUSIVE GRANITE SHILLONG GROUP

BASEMENT GNEISSIC COMP.

90° 91° 92° 93° 94°

90° 91° 92° 93° 94°

25°

26°

25°

26°

F

F F

F

F

F F F

F

F

F

F

F

JA

MU

NA

F

GUWAHATI

DAUKI F

SUNG VALLEY

COMPLEX

SHILLONG

(AFTER NANDY, D.R., 2001)

F

SAMCHAMPI

COMPLEX

Barpung

Jasra

Sankri, Nongcharam

• The Sung Valley ultramafic-alkaline–carbonatite complex

(~115 Ma) is an oval shaped body covering an area of about 26

Sq. Km and is emplaced within the Shillong Plateau, an

uplifted horst-like feature in Meghalaya state.

• Sung Valley complex consists of pyroxenite, serpentinized

peridotite, ijolite, nepheline syenite and carbonatite.

• Carbonatite is the youngest member of the complex as it

intrudes in other rock types as small dykes, veins and oval

shaped bodies.

• Carbonatite from Sung valley indicated moderate uranium

contents (95–165 ppm), low thorium contents (45–284 ppm)

and quite variable Th/U (0.27– 1.96).

Geological map of Alkaline Carbonatite Complex along

Dharmapuri Shear Zone, in the Northern part of Tamil Nadu,

India

The NE-SW trending Dharmapuri Shear Zone (DSZ), located in the northern part of Tamilnadu and

characterized by the presence of a number of Alkaline-Carbonatite Intrusions (~700-900 Ma age)

such as Pakkanadu, Samalpatti, Sevattur, Elagiri, Rasimalai, Paravaimalai and Pallikonda.

Subsurface exploration at Pakkanadu and Rasimalai areas by AMD has indicated significant

polymetallic U-REE mineralisation.

Rasimalai

M R

B Alpha track

O O

O

Sy

Car

Py Py Cpy

G

Mi

Mi Ba

Hy

Cai-Str

Microphotographs of Rasimalai Alkali Syenite (A) with microcline (M) ,

riebeckite (R), hypersthene (H) (B) Betafite (B) with alpha track (C)

Carbonate (Car) injections in syenite with sulphide opaque (O) (D) same as

Fig.C in reflected light containing pyrite (Py) and chalcopyrite (Cpy) (E)

Suplide mineral galena (G) and millerite(Mi) (F) Grain mount of heavy

mineral showing baryte (Ba), hypersthene(Hy), opaque(O) (G) Calcite-

strontianite (cal-Str) in grain mount .

H

O

B A C

D E

F

G

676

m

RASIMALAI

Radio active Pink syeniteNon Radioactive Grey syenite

Element (ppm) Min Max

Cr 11 418

Cu 10 1056

Zn 10 411

Sr 80 23208

Y 10 133

Zr 11 3038

Nb 10 2797

Ba(%) 0.01 17.33

Ce 16 48430

Th 10 1549

U 10 1074

U - n=524 <10 ppm, n=114 10-1000 ppm, n=409 >1000 ppm, n=1

Nb - n=524 <10 ppm , n=48 10-1000 ppm, n=468 >1000 ppm, n=8

Sr - n=524 <0.01%, n=2 0.01-0.1%, n=196 >0.1-1%, n=317 >1%, n=9

Trace Element Concentration in Rasimalai area, Tamilnadu

Inferences

Betafite has been identified as the main radioactive phase at

Rasimalai hill.

Higher concentration of Nb, Pb, Ba and Sr associated with

the radioactive syenite (Galena, Barite, Strontianite).

Uranium mineralisation is syn to epigenetic disseminated in

nature

Sulphide phases are epigenetic in origin.

Radioactive phase is associated with alkali syenite (aegirine,

acmite and riebeckite).

INFERENCES FROM RASIMALAI AREA, TAMILNADU

Geophysical Characterization of U-REE Mineralisation

Associated with Alkaline-Carbonatite Complex along

North Singhbhum Shear Zone

High Resolution Heliborne Geophysical Survey over North Singhbhum

Shear Zone, Jharkhand and West Bengal, Eastern India

VTEM Measure vertical component of time derivative of the

electromagnetic induction (dB/dt) & compute the vertical

component of electromagnetic induction (B-Field) .

Specification : sampling at 0.1 sec, base frequency at 25

Hz, diapole moment : 4,25,000 NIA, 40 time gates; Half

period : 20 ms

MAGNETIC : Measure the total magnetic field.

Specification : sampling at 0.1 sec, Cs-vapour

Magnetometer, operational range : 15,000 – 1,05,000 nT

Gamma Ray Spectrometer : Measure the gamma radiation

from U, Th & K from top 30 cm of ground.

Specification : sampling at 1 sec, NaI crystals,

Data in 1024 channels over 0 to 3 MeV energy

Survey Specifications

Line Spacing: 200 m (North - South)

Tie line Spacing: 4 Km (East – West)

Survey Height: 60 meter (AGL)

TDEM: VTEM System (Geotech Airborne Ltd.)

Magnetic: Cs Vapour Magnetometer (Geometrics)

Gamma Ray Spectrometer: RSX-5 (Radiation Solution

Ltd.)

GPS: Dual Frequency GPS

Helicopter: A350 B3 Squirrel - VT VAD (Global Vectra)

Survey Operations EM, Magnetic and Radiometric Data Acquisition

Magnetic Base Station – to observe the diurnal variation in magnetic data

Ground Radiometric Calibration - pre and post survey using Uranium,

Thorium and Cesium standards to check the spectrometer functioning.

Aluminum plate test for current polarity check before the start of survey.

Radiometric Test line (length 7-8 Km) in start of survey and end of survey

to observe the repeatability of radiometric data.

High Altitude Test – pre and post flight; in between flight,if flight is of long

duration or drift in data is not linear , which is useful in VTEM system

noise estimation, current compensation and zero level the data.

Regular Traverse lines on the basis of navigation file (*.pgn file).

First Hand Data Quality Check – at heli-base after each flight by running

Geotech proprietary software GND.

EM (VTEM) data (*.d file, each of maximum 10 minutes) of each flight were converted to

*.xyz file using GND, which was imported to Geosoft and database file was generated.

GPS QC – Checked the profile plots and statistics for longitude latitude, GPS time and

GPS altitude and by plotting on the plan map generated using nav file.

EM QC (Where we recorded the statistics of SR[10], BR[10], SR[33] and BR[33] and

observed profile plots for spikes and other noise.

Current Compensation - Raw dB/dt (SR) and B field (BR) data were compensated for

effect residual current of transmitter loop over receiver loop using the MaxB recorded

data.

Filtering - Compensated dB/dt (SC) and B field (BC) data were filtered (4 fiducial Non-

linear & 0.0001 tolerance and 10-15 fiducial low pass filter) for removal of spikes.

Leveling - To bring the every channels data at same/zero level, the leveling is done

separately for filtered dB/dt (SF) and B field (BF) data by using high altitude correction

records in the start of each flight and end of each flight.

VTEM & Magnetic Data quality Validation and Preliminary Processing

Visualization of Processing Steps on B Field Data in Log-Linear Scale

B Field Raw Data

B Field Compensated Data

B Field Filtered Data

B Field Levelled Data

Magnetic and Power Line

Power line effect on B Field data

VTEM & Magnetic Data quality Validation and Preliminary Processing

VTEM & Magnetic Data quality Validation and Preliminary Processing

Base mag – base mag data (*.txt file) imported to Geosoft and processed

(5 fiducial Non-linear & 0.0001 tolerance and 100 fiducial low pass filter)

for removal of spikes. Finally *.tbl file is created, which will be used for

diurnal correction to raw magnetic data.

Diurnal Correction – Raw Magnetic data (Mag1) was corrected for diurnal

variation by importing the *.tbl file by matching the Gtime.

Flight database is split in to lines.

Grid images generation – by using minimum curvature gridding

technique and cell size of 50m.

Interpretation of Heliborne Geophysical Datasets.

Target delineation & Prioritization on the basis of

integrated interpretation.

Ground checking of selected prioritized target areas.

Integrated study of drilled borehole results with

interpreted results from Heliborne datasets.

Planning of boreholes for Subsurface Exploration.

Evaluation of the proposed Boreholes.

Steps for Information Extraction and

Integration

Uranium anomaly Zones in NSSZ Block

Area Line No. U (ppm) Th (ppm) K% U/Th Rock Type

Beldih

15000-15060

(along 7 line,

Mine dumps)

8.4-54.6 12.5-25.7 1.15-2.11 0.62-2.1

Quartz-

magnetite

apatite rock

Dandudih-

Kutni

16260-16340

(Anomaly extent

is 1.6 km)

6.97-43.42 13.28-20.81 0.92-1.88 0.72-2.56

Ferruginous

quartzite

Rangamatiya

16500 &

16630-16380

Anomaly extent

is 1.0 km

7.34-10.99 3.91-7.67 0.30-0.90 1.05-2.30

Brecciated

ferruginous

quartz breccia

Porapahar 17520, 17530

17600, 17650,

17690

6.06-8.76 7.60-11.79 0.52-1.09 0.65-1.15

Brecciated

ferruginous

quartz breccia

Geological map of Alkaline-Carbonatite Complex around Beldih,

Purulia district, West Bengal, Eastern India

Magnetic

B-Field

dB/dt

-400

-200

0

200

400

600

800

1000

-150 -100 -50 0 50 100 150

dB

z/d

t (u

V/A

)

Station (m)

Beldih_S3

Ch21

Ch22

Ch23

Ch24

Ch25

Ch26

Ch27

Ch28

Ch29

Ch30

Ground TEM Response of Line 14980

3D Iso-surface Map of Magnetic Susceptibility 0.03 SI unit for Beldih Area by using UBC-Mag3D Software

1100m (l) x 280m (b) x 800m (d)

3D-Modeling of Magnetic Data of U-

REE bearing Alkaline-Carbonatite

Complex (ACC) in Beldih Area

Carbonatite Drill Cores, Beldih

0

50

100

150

200

250

0 2000 4000 6000 8000 10000

Dep

th (m

)

Magnetic Susceptibilty (X10--6) SI units

Magnetic Susceptibility Log of BLD12 Magnetic Susceptibility

Measurement of BH No. BLD12

At Depth 217m to 221m

Chalcopyrite-Pyrite and magnetite

abundance

Ch Py Mag

Py

Magnetite Rich Zone± sulphides (mainly pyrite) in

Ultramafic rock with carbonatite veins

Carbonatite rich Zone with clasts of Ultramafic rock

± magnetite and specks of sulphides

Mylonitized alkali granite

with ultramafic and

carbonatite

Magnetite zone, sulphides (mainly pyrite) in

Ultramafic rock with carbonatite

RA Zone

190

195

200

205

210

215

220

1 10 100 1000 10000

De

pth

(m)

Magnetic Susceptibilty (X10-6) SI units

Magnetic Suscepetibility log of BLD-12

190

195

200

205

210

215

220

0 0.01 0.02 0.03 0.04 0.05

De

pth

(m)

%eU3O8

Uranium Mineralisation of BLD12

0.016%eU3O8 x 2.45m(201.36m-203.82m) core assay

0.021%eU3O8 x 0.42mCore assay

0.0165%eU3O8 x 0.90m(211.42m-212.30m) core assay

S

N0 10 20 30 40m

BLD-3RL-242.94m

R.L.

in m.

DATUM

D.D.

299.90m

BLD-5RL-243.12m

240

220

200

180

160

140

120

100

80

60

40

0

20

D.D.

163.55m

0.023 x 6.40m

(0.032 x 3.20m)

(0.018 x 8.40m)

0.023 x 3.20m

(0.025 x 2.80m)

0.019 x 6.20m

(0.022 x 3.60m)

VEIN QUARTZ

A

A

A

A

B

B

B

T.D.

170.00m

BLD-16&25

TRANSVERSE SECTIONS THROUGH BLD-3, 5 & 16 & 25, BELDIH AREA

Conductor

104.00m

145.00m

ULTRAMAFICS ± CARBONATITE

ALKALI GRANITE

I N D E X

OVERBURDEN/MINE DUMP

CARBONATITE ± ULTRAMAFICS

RADIOACTIVE BAND (0.010%eU3O8 cut-off)

KAOLINITE± GOETHITE

APATITE RICH ZONE

RL-243.079m

Fel

dspa

r ri

ch z

one

D.D.

338.40m

0.021 x 8.20m

(0.034 x 2.40m)

0.013 x 3.20m

0.026 x 15.20m

RADIOACTIVE BAND (0.020%eU3O8 cut-off)

(0.034 x 6.00m)

(0.033 x 2.90m)

D.D.

121.00m

VERTICAL LONGITUDINAL SECTION THROUGH BOREHOLE NOS. BLD-11, 14, 7, 8, 13, 6, 5, 9 & 10 BELDIH AREA, PURULIA DIST., WEST BENGAL T.S.No. 73 I/8W E

0 10 20 30 40m

R.L.

in m

240

220

200

180

160

140

120

100

80

60

40

DATUM

20

BLD-5BLD-6BLD-7

D.D.

283.90m

D.D.

169.60m

D.D.

299.90m

0.016 x 1.40m0.013 x 2.10m

0.016 x 1.00m

0.018 X 1.30m

0.023 x 3.20m

(0.025 x 2.80m)*

0.019 x 6.20m

(0.022 x 3.60m)*

*Values at 0.02% eU3O8 (Cut Off)

A

A

A

A

B

B

B

B

B

(Abandoned)

A

A

A

A

AA

B

B

BD.D.

280.70m

0.032 x 14.30m

(0.034 x 12.90m)*

0.014 x 2.30m

BLD-8

D.D.

293.70m

A

A

A

A

B

B

BLD-9

0.028 x 3.40m

(0.031 x 2.80m)*

0.021 x 4.40m

(0.021 x 1.80m &

0.025 x 1.60m)*

0.016 x 9.40m

0.012 x 4.60m

D.D.

289.30m

BLD-13 (P)

0.014 x 2.40m

D.D.

282.70m

A

A

A

BLD-10 (P)

BLD-14

D.D.

264.50m

BLD-11

D.D.

244.50m

QUARTZ - MAGNETITE - APATITE ROCK

RADIOACTIVE BAND(S)

I N D E X

OVERBURDEN/MINE DUMP

ULTRAMAFICS ± CARBONATITE

VEIN QUARTZ

CARBONATITE ± ULTRAMAFICS

ULTRAMAFICS WITH ALKALI FELDSPAR

ULTRAMAFICS WITH PODS OF BIOTITE

A

B

ALKALI GRANITE

Carbonatite of Beldih Area

Intruded within Alkali Granite prior to Shearing

Segregated Apatite rich zone (in carbonatite) hosts U mineralization

Calcite, Apatite, Amphibole, Biotite, magnetite, Pyrochlore

Varieties 1. Calciocarbonatite

2. Magnesio carbonatite 3. Carbonatite with ultramafics

Carbonatite Ultramafics (Amphibolite)

Apatite rich zone

Alkali Granite

Elements in

ppm Carbonatite (n=13)

RA Apatite rich rocks

(n=13)

Av. carbonatite

(Woolley & Kempe,

1989)

Ba 27 – 627 ( 125) 66 – 993 (244) 3400

Sr 1930 – 4600 (3584) 1500 – 5800 (4000) 8600

Zr 24 – 187 (58) 45 – 265 (150) 189

Nb 57 – 1808 (777) 2400 – 14000 (6700) 1204

Ta 5 – 112 (28) 69 – 800 (372) 5.0

U 1 – 35 (10) 70 – 1391 (570) 8.7

Th 5 – 27 (09) 5 – 40 (25) 52

Y 10 – 78 (28) 86 – 423 (218) 119

REE (T) 390 – 1973 (797) 1887 – 8757 (4719)# 776

LREE (T) 321 - 1827 (718) 1738 – 8211 (4363) # 3850

Dy 1.5 – 20 (07) 28 – 129 (71)# 34

Trace element data (ICP-AES/MS)

# N=17

Chemical Analysis of Carbonatite and Radioactive

Apatite-Magnetite rich rocks in Beldih

In Parenthesis - Average value is given

Radioactive Phases in Apatite Rich Rocks from Beldih Area

Chl

Ap Qtz

Pcl

BLD 8

BLD 8

Microphotograph of Carbonatite and Apatite bearing Rocks

Beldih area

Ap

Ap rim

Cc

Cal

Apt

Uranium Exploration

in Dandudih-Kutni

Alkaline Carbonatite

Complex, NSSZ

Deformation Stratigraphy Metamorphism/

Metasomatism

Hydrothermal

Alteration

Mineralization

Brittle

Deformation II

Kaolinite /

Ferruginised apatite rocks

(<100m depth)

Metasomatism –III :

K-feldspar

Zeolite, Hematite

Mn minerals

Goethite, vug silica

Adsorbed

Uranium

Brittle

Deformation I

Best developed with in Apatite

rich rocks (> 100m depth)

Vug silica, Chlorite

Pyrite, siderite; 2nd

gen. Apatite

Urano –

Pyrochlore

Closure of rift , ductile deformation (500 – 600

Ma?)

Amphibolite facies metamorphism, Monazite (?)

Extension of

crust and

development of

rift zone

Carbonatite and formation of

apatite-rich rock and

ultramafics

Metasomatism II:

Na metasomatism in alkali granite

Apatite, Monazite

Pyrochlore,

Cb-Ta

Syenite (0.92 Ga)

Alkali granite (1.8 Ga)

Barabazar Granite (1.8 Ga)

Sedimentation

and Early

deformation

Tuff, meta sediments Carbon

Phyllite, quarzite

Early metamophism

Metasomatism-I: Tourmalinization

Minor allanite

Schematic Evolutionary Model for NSMB/NSSZ

U fixation

DISCUSSION & CONCLUSION

• Uranium exploration is multidisciplinary activity which

requires integration of geological, geochemical and

geophysical evidences on common georeferenced GIS

platform.

• Application of high resolution multiparameter geophysical data often providing critical information in support of local or regional framework mapping and mineral exploration modeling.

• India has many promising alkaline-carbonatite complexes which can turn into viable low-grade polymetallic uranium deposits by integration of geophysical, geological, geochemical and drilling data in GIS platform. A few of them like ACC along North Singhbhum Shear Zone and Dharmapuri Shear Zone are under active exploration to prove viable uranium deposits.

Thank you

SHEARED QUARTZITE AT PORAPAHAR