RADIOACTIVE MINERALS SPECIES OF MAISAHTERTIARY GRANITE, SOUTH SULAWESI

Soeprapto Tjokrokardono *

Abstract

RADIOACTIVE MINERALS SPECIES OF MAISAH TERTIARY GRANITE,

SOUTH SULAWESI. As a part of the supporting program for radioactive mineralexploration' in South Sulawesi, an attempt has been made to identify species and possiblesource of the minerals discovered in heavy mineral concentrates taken from Binuang River.The study was performed by petrographic observation on thin sections and grain counting

analysis of crushe~ granite samples. Identification of minerals was done by autoradiographyand x-ray diffraction methods. Radioactive minerals within the granite, such as monazite,zircon, apatite, allanite, and thorite, are similar to those found in heavy mineral concentratesamples, meaning that Maisah granite is the source rock of radioactive minerals deposited atthe river bank of Binuang River.

INTRODUCTION

Background of studyGeneral prospection stages for uranium exploration had been carried out

previously by BAT AN at North Luwu Area, South Sulawesi. Radiometricand geochemical anomalies were found on heavy mineral concentratesamples taken from river bank deposits of Binuang River, South Sulawesi(Sarwiyana et al.1982 [1]). The concentrates consisted of monazite, zircon,allanite, thorite, magnetite, and biotite (Sarijah 1993 [2]). Althoughradioactivity and uranium content of the samples were high, nomineralization was found in the detail stages program(M.Siregar et al. 1983 [3]).

The following study was carried out for identifying radioactive mineralspecies within the granite and finding the possible source of the minerals tosupport the development of exploration program in Sulawesi.

HypothesisGenerally, high proportion of total uranium content of granitic rock is

held in accessory minerals such as rutil, apatite, sphene, epidote, allanite,zircon, monazite, thorite, uraninite (Basham 1983 [4]). It is calculated thatthe proportional content of uraninite and/or thorite as the main contributorsto the whole rock value , are several tiiTIes higher than those of monazite,zircon, apatite, etc.

• Nuclear Minerals Development Centre - BAT AN

25

Theoretically, heavy minerals concentrate come from upper riverstream. They are derived from exposed rocks suffered mechanical andchemical weathering process and transported down stream and deposited at ariver bank where the potential energy is low.

Chemically, Maisah granite contains 8.00 to 30.92 ppm U (Siregar et al.1983 [3]) higher than the average ~ranium content in a normal granite, whichis 4 to 5 ppm. Based on the above data and the concept that uraninite and/orthorite are the main uranium constributors in uranium bearing granite, theMaisah granite, if fresh rock samples were available, should contain someuraninite or thorite.

Accordingly, because of the absence of either mineralization out cropsand their characteristically derived minerals such us beryl, tourmaline,garnet, andalusite, and the granite was, the only rock exposed, this meansthat the source of tha radioactive minerals within the heavy mineralconcentrates was that rock namely Maisah granite.

EXPERIMENTALThis experiment was executed at the Nuclear Minerals Development

Centre (PPBGN)-BATAN.Granite samples taken from the field (Figure I) were cut into three

pieces for petrographic study, grain counting analysis and collections.Petrographic study was carried out by microscopic observations through thinsection of the rocks. Grain counting analysis was proceded by crushingsamples to separate mineral grains into heavy and light fractions using liquidtetrabromoethane (TBE) at 2.96 specific gravity.

The heavy fractions was separated manually using horse shoe magnetinto magnetic and non magnetic fractions. Furthermore, the latter wasclassified into three fraction of < 0.2 Amp.,0.2-1.2 Amp.,and > 1.2 Amp.using isodynamic magnetic separator "COOK" at the condition of 150 slideoslope and 25 forward slope.

Radioactivity of mineral was identified by using selulose nitrate CN 85as a detector autoradiographically. Polarized Carl Zeiss and unpolarizedbinocular Olimpus microscopes are the main instruments used for themicroscopic observations and Shimadzu X-ray diffraction is the instrumentwas used for the mineral identification. The identification use the conditionof 40 mA and 40 kV.

26

RESULT AND DISCUSSION

Maisah granite MassiveMaisah massive is the Neogen granite exposed at the valley between

Bulu Reketabuan and Bulu Kambuno peaks located at the 'upper stream ofMaisah River, one of the letf tributaries of Binuang River, 50 km north ofSabang village, south Sulawesi.

Geologically, Maisah granite intruded the Cretaceous metamorphicseries consisted of phyllite, slate, quartzite, gneiss, schist and the volcanicproducts composed of trachytic to trachyandesitic lavas, tuffs, breccias, andconglomerates. Then they are unconformably overlined by trachytic tosphilitic, dacitic, and andesitic volcanic sediments of Plio Plistocene age(Figure 2). In the field the massive granite shows dark to light-grey colours,equigranular shape, and medium grain size. Some samples of biotite graniteand biotite adamelite have porphyritic and pegmatitic textures that ahow agradual contact [2]. The granite was composed of quartz, K-feldspar,plagioclase, biotite, titanite, small amount of monazite, zircon, apatite, andopaque minerals. Crystalline schist was found as xenolith fragments withinthe granite.

The radioactivity average of the granite out crops varies from 266 to286 cps with a maximum valu~ of 500 cps of SPP2NF. Uranium content ofthe samples was relatively high, varying from 8.00 ppm to 30.92 ppm [3].

Radioactive Minerals within the Granite

Petrographic study on 51 samples of Maisah Granite revealed someradioactive minerals e.g. zircon, apatite, monazite, allanite, thorite, andbrannerite. Monazite occurs in almost all samples, whereas allanite andthorite are observed respectively in 13 and 2 samples.

Grain counting analysis on 10 samples of the crushed granite showedzircon and apatite in all samples, monazite and allanite in 9 samples, andthorite in 6 samples (Table I). Figure 3 indicates some grains of heavyminerals taken from crushed granite sample No.Cs 3/4/703 B,fraction 0.6-1.2 Amp.

Monazite

Monazite is homogeneously distributed within the granite. Theconcentration is about 0.01 to 0.4 permil weight, about 0.2 mm in diameter,yellowish white to white, vitreous to resinous luster, conchoidal fractures,brittle, tabular to irregular fragments, monoclinic crystal shape and lowradioactivity (Figure 4). The existence of monazite in heavies is indicated byhigh value of the rare earth and phospor elements in heavy mineral

27

concentrates as shown in Table 6. In thin sections, monazite is observed as

small subtransparant mineral inclusions within biotite, feldspar or amphiboleand shows some pleochroic haloes.

Physical characters observed under ultra violet light show green andyellowish flourescenced colour. X-ray diffraction pattern of the mineral isshown in Table 2.

Zircon

Zircon is discovered as minute crystals, about 0.02 to 0.1 permil weightof concentration, of 0.1 mm diameter average size, reddish to colourless,vitreous to adamantin luster, brittle, conchoidal fractures, euhedral shapefrom tetragonal bipiramid to rounded, 4.7 specific gravity (Figure 4), andlow radioactivity.

In thin sections, zircon exists as the inclusion within biotite, amphibole,and feldspar minerals and show transparent, sometimes zonal structures,weak pleochroic haloes character, and the shell is metamic.

X-ray pattern of the mineral is shown in Table 3.

Apatite

Apatite shows prismatic shape of hexagonal tripyramid, transparent,white to colourless, vitreous to resinous luster, brittle, conchoidal fractures,short to long prismatic shape (Figure 4), homogeneously distributed, verylow radioactivity, no pleochroic haloes and metamic (isotropic) characters asfluorapatite minerals (CaF)Ca4(P04h.

Allanite

Allanite is the dominant component within the heavies, acicularprismatic shape, brittle, reddish brown, resinous luster, subtranslucent toopaque, 1-2 mm in diameter (Figure 5), and more radioactive than both

monazite and zircon. Observation under transmitted polarized microscopeshows strong pleochroism, Z: brownish yellow,Y: reddish brown, and X:greenish brown.

Some allanites are altered and isotropic (metamic). X-ray diffractionpattern of the mineral is shown on Table 4.

Thorite

Distribution of thorite is relatively rare. It shows dark to light greencolour, as a hydrated mineral, metamic (isotropic), 0.2 mm in diameter,tabular and monoclinic prismatic shape as Huttonite (Figure 4 and 5) thatindicates an alkaline condition. Some of them, however, still show tetragonal

28

crystal system probably similar to Wisaksonite which was found from placerdeposits of sand at Pekorigan River, Central Sulawesi (Heinrich 1958 [5]).

X-ray pattern of mineral heated at 1100°C is shown on Table 5.

Origin of Heavy Minerals ConcentratesAlthough the variety of the mineral species discovered within Maisah

granite is more complex than that at the river banks, found within panningconcentrate, the comparative study on their radioactive minerals contentindicates that their mineral species are in the same association.

The existence of hornblende, sphalerite, pyrite, and ilmenite within theMaisah granite, but not in the panning concentrates from the river banks, ispossibly caused by a sorting process during the heavy mineralstransportation and sedimentation. Table 7. shows that Maisah Granite (B) isthe only possible source rock of A, if the characteristic minerals in C, D, andE exist in the hidden rock, having been eroded and burried.

This means that the Maisah granite (B) must be the only source rock ofradioactive minerals found within the panning concentrate of the river bankdeposits ofBinuang River.

CONCLUSION

Discussion on microscopes and X-ray diffraction data obtained leads tothe conclusion that the radioactive minerals species of Maisah granitemassive are monazite, zircon, apatite, allanite, and thorite.

Maisah granite massive is the only source rock of radioactive mineralsfound in panning concentrate samples taken from Binuang River.

ACKNOWLEDGEMENTSThe author would like to thank the Head of Nuclear Minerals

Development Centre - BATAN for the permission to publish the data andalso to Mrs. Mudiar Masdja who contributed towards the assessment of theoriginal manuscript.

REFERENCES

]. SARWIY ANA, et aI. ]982. "Laporan prospeksi umum daerah LuwuUtara, Sulawesi Tahun ]980/1 98] "(PPBGN internal report, unpublished)

2. SARIJAH, ]993."Penentuan Jenis dan Kadar Mineral radioaktif dalamcontoh tanah".(PPBGN internal report, unpublished)

29

3. M. SIREGAR, et al. 1983."Laporan akhir prospeksi detil Luwu Utara,

Sulawesi Tahun 1982/1983" (PPBGN internal report, unpublished)

4. LR. BASHAM, 1983."Uranium bearing accessory minerals and granitefertility." Methods of Identification and evaluation. Proceedings ofUranium Exploration Methods, Symposium organized by OECD Nuclearenergy Agency, Paris

5. E.Wm. HEINRICH. 1958. "Mineralogy and Geology radioactive RawMaterials". Me. Graw Hill Book Company, New York

6. R.G. YOUNG 1984. "Uranium Deposits of the World, exluding Europe,in Uranium Geochemistry, mineralogy, geology, exploration, andresources". The Institute of Mining and Metallurgy

7. J.M.DARDEL, 1986. Personal communications, IAEA Expert onUranium exploration and Development project INS 3/009

30

Tabel 1. Heavy Mineral Concentrate Composition of Crushed GraniteRocks, Maisab Massive, South Sulawesi

Sample No.598702703704761762767766769765

Mineral Name

( 0100 )(0100 )(0100 )( 0/00)(DIDO)(0100 )(0100 )( 0/00)( 0/00 )( 0/00 )

Biotite

1.101.163.703.700.720.600.390.210.161.38

Zircon

0.060.031.110.190.110.060.020.020.020.07

Apatite

0.130.020.110.010.020.030.010.020.040.05

Allanite

0.080.010.130.200.010.010.010.010.05-

Sphalerite

-0.000.010.02---0.01--

Monazite

0.230.130.06-0.030.030.010.000.060.48

Thorite

0.010.050.02-0.01---0.010.01

Magnetite

0.01.0.050.13-0.080.240.000.010.010.20

Hornblende

0.040.130.210.350.070.000.010.010.100.22

Pyrite

---0.01------

Ilmenite

----------

Tot a I

1.651.584.474.621.040.970.450.290.462.43

Note:

Heavy minerals = specific gravity more than 2.96598 = Sample number Cs 03/04/598/B

(%0) = Weight permillage of the minerals to the whole rock wightCalculated from five microscopic observations

31

Tabel 2. X-Ray pattern of Monoziteof Maisah Granite massive,South Sulawesi

ASTMNo.

Maisah GranitsStandard'sMonozite

Monozite

d

IdII

5.06 55.20142

4.843 104.8283

4.546 104.66184

3.348 504.17255

3.2751004.08106

3.139453.51257

3.035 603.30508

2.873 103.091009

2.634 602.991810

2.54202.8770II

2.296202.611812

2.12102.441813

2.07402.40614

1.939102.34615

1.86452.25416

1.81252.191917

1.720402.152518

1.654402.132519

1.601102.02420

1.559101.962521

1.53551.93822

1.502101.8914

231.49451.87018

241.423201.85918

251.38610I. 79710

261.34810--

271.30810--

281.27610--

291.25310--

301.23010--

Tabel3. X-Ray pattern of Zirconof Maisah Granite massive,South Sulawesi

ASTMNo.

Maisah GranitsStandard'sZircon

Zirconed

Id1I

4.571 54.43452

3.3731003.301003

2.554 202.6554

2.372 52.518455

2.242 22.336106

2.092 202.21787

1.928 22.066208

1.769101.908149

1.726351.7511210

1.668251.7124011

1.489101.6511412

1.390201.547413

1.37221.495414

1.29821.4774815

1.26621.3811016

--1.362817

--1.290618

--1.259819

- -1.248420

--1.1881221

--1.1672222

--1.10796

23

--I. 1006624

--1.0682

25

----26

----27

----28

----29

----30

----

Note:

d = Inter spacing distance in Angstrom (A)

I = Intensity in % of the maximum high

32

Tabel4. X-Ray pattern of Allaniteof Maisah Granite massive,South Sulawesi

ASTMNo.

Maisah GranitsStandard'sAllanite

Allanite

d

1d1

1

4.571 59.2402

3.704 28.040

33.463 405.1 I20

43.264 55.0130

53.184 54.7120

62.8731004.6010

72.837 603.7310

82.629 703.6010

92.590 253.5350

102.526 103.3220

112.38202.92100

122.30102.83]0

13

2.274 152.716014

2.154 152.635015

2.125 102.562016

2.106 152.511017

1.890152.451018

1.875]02.41]019

1.766102.3410

20

1.714102.301021

1.691102.1820

221.673252.1620

231.624202.1420

241.593202.1010

251.596202.0610

261.550201.9120

271.428251.8920

28

--1.771029

--1.743030

--1.7061031

--1.6771032

--1.6395033

--].61710

TabelS. X-Ray pattern of Thoriteheated I 100°C Taken from

Maisah Granite massive,South Sulawesi

ASTMNo.

Maisah GranitsStandard'sThorite

ThoriteUranoand

1d1

I4.60 404.7380

2

4.15 73.561003

3.50702.84704

3.25 102.06805

3.201002.50706

3.00202.22807

2.90 152.02408

2.80 351.87609

2.75351.83100

102.65351.78080

II2.5210I. 75760

122.42 51.64760

13

2.2020].5907014

2.15301.5804015

2.09101.5764016

2.00151.485017

1.92901.4455018

1.86151.4404019

1.8270--20

1.65100--21

1.5840--22

1.5210--23

1.4615--24

1.4415--25

1.365--26

1.3315--27

----28

----29

----30

----

Note:

d = Inter spacing distance in Angstrom (A)

I = Intensity in % of the maximum high

33

w .p.

Tab

le6.

Tot

alva

lue

ofel

emen

tsw

ithin

heav

ym

iner

als

conc

entr

ates

take

nfr

omri

ver

bank

depo

sit,

Bin

uang

Riv

er,

Sout

hSu

law

esi

RE

FC

uP

bW VCr

NiB GaBt

SnAsBi

AgTi

ZrLaY

ME

TH

EA

EA

EA

EAEA

EA

EA

EAEA

EA

EA

EA

EAEA

EA

EAEA

LD

ppm

I20

0 100

100

505010

40050

20050505

50010

100

Eg

ppm

ppm

ppm% % pp

mppm

ppm

ppm

ppm

ppm

ppm% % pp

m%pp

mI

1.0025.0nd

40.0 1,00

5000

50.0

10.0

4.0

1000 350

70.0

100

15.0

6.00

20.0

0040

002

60.0

40.0

nd12

0nd

20.0

60.0

nd7.0

50.0nd

50.0200

15.0

2.50

250075

0

3

2.0

50.0nd

120

nd10.0

100

10.0

5.0

60.0 nd

25.010

015

.02.

5020

00500

4

2.0

50.0nd

250

500

ndnd25.010

.075

.0nd35

010

00.

812

.080

0030

00

5

2.0

50.0 nd100

nd5.0

50.0nd2.0

75.0 nd

35.010

015

.00.

820

00600

62.

025

.0nd10

0ndnd60.0nd2.5

200 nd

30.0nd

15.0

1.20

400010

007

8.0

25.0nd

50.0 ndnd50.0nd2.0

400 nd

20.010

015

.04.

0060

0020

008

10.0

40.0nd

200

250

nd75

.020

.05.

05.

040

020

050

01.

006.

0020

.000

8000

95.

050

.0nd75

050

030

.015

.045

.012

.025

020

040

.050

01.

506.

0015

.000

6000

105.

050

.0nd 150

45.05.0

100

nd3.0

250 nd

40.010

015

.01.

2040

00 1000

11

40.0

25.0

nd65

060

030

.0nd55

.05.0

100

250

150

100

2.00

3.00

12.0

0050

0012

85.0

70.0

10.0

0030

020

0nd

10.0

35.05.0

12.0

00 180

20002.

08.

00 8.00

10.0

0050

0013

40.0

70.0

2000 15

035

010

.015

.030

.012

.030

00450

1500

200

1.00

8.00

10.0

0060

00

Not

e:m

eth

=m

etho

d;E

A=

Ato

mic

emis

sion

;C

ol=

Col

ourm

etry

;L

D=

Det

ectio

nlim

it;nd

=no

tde

tect

ed;

Ref

=el

emen

t;E

g=

elem

ent

grad

eC

OG

EM

A:

Serv

ice

deM

lNE

RA

LO

GIE

Bor

dere

auas

:77

86E

C3

DE

STIN

AT

AIL

E:

CE

A-

DA

RN

RE

FER

EN

CE

DA

MN

/DJ/

86.5

73

w VI

Tab

le6.

Con

tinue

d

RE

FC

uPbWV CrNiBGa Bt

Sn AsBi

AgTi

ZrLaY

ME

TH

EA

EA

EA

EAEA

EA

EAEA

EAEA

EAEA

EA

EAEA

EA

EA

LD

ppm

120

0100

100

505010

400 50

20050505 50010

100

Eg

ppm

ppm

ppm% % pp

mppm

ppm

ppm

ppm

ppm

ppm% % pp

m%pp

m1

1.0025

.0nd40

.0 1,00

5000

50.0

10.0

4.0

1000

350

70.0

100

15.0

6.00

20.0

0040

00

2

60.0

40.0

nd12

0nd

20.0

60.0nd

7.0

50.0nd

50.020

015

.02.

5025

0075

0

3

2.0

50.0 nd120

nd10.0100

10.0

5.0

60.0 nd

25.0 10

015

.02.

5020

0050

0

4

2.0

50.0 nd

250

500

ndnd 25.010

.075

.0nd35

010

00.

812

.080

0030

00

5

2.0

50.0 nd100

nd5.0

50.0nd

2.0

75.0nd

35.010

015

.00.

820

00600

6

2.0

25.0nd 100

ndnd60.0nd

2.5

200

nd30

.0nd15

.01.

2040

001000

7

8.0

25.0nd

50.0nd nd50.0nd

2.0

400

nd20

.0100

15.0

4.00

6000

2000

8

10.0

40.0nd

200

250

nd75

.020

.05.

05.

040

020

050

01.

006.

0020

.000

8000

9

5.0

50.0 nd

750

500

30.0

15.0

45.0

12.0

250

200

40.0

500

1.50

6.00

15.0

0060

00

10

5.0

50.0 nd150

45.0 5.0

100

nd 3.0

250

nd40

.0 100

15.0

1.20

40001000

11

40.0

25.0

nd65

060

030

.0nd55

.0 5.0

100

250

150

100

2.003.00

12.0

0050

00

12

85.0

70.0

10.0

0030

020

0nd10.0

35.0

5.0

12.0

00180

20002.

08.

008.

0010

.000

5000

13

40.0

70.0

200015

035

010

.015

.030

.012

.030

0045

015

0020

01.

008.

0010

.000

6000

Not

e:m

eth

=m

etho

d;E

A=

Ato

mic

emis

sion

;C

ol=

Col

ourm

etry

;L

D=

Det

ectio

nlim

it;nd

=no

tde

tect

ed;

Ref

=el

emen

t;E

g=

elem

ent

grad

eC

OG

EM

A:

Serv

ice

deM

INE

RA

LO

GIE

Bor

dere

auas

:77

86E

C3

DE

STIN

AT

AIL

E:

CE

A-

DA

RN

RE

FER

EN

CE

:D

AM

N/D

J/86

.573

Tabel 7. Associate minerals found in Binuang river banks and thecharacteristics in each possible source rocks

Associate MineralsPossible Source Rock

Characteristics offound in Binuang riverRemarksSaaociate Minerals

banks (A)(Sarijah 1993) [2]Maisah Granite

Thorite vv = axist

(B)

Allanite v- = noneMonazite

vZircon

v

Apatite

-Biotite

vHornblende

-Sphalerite

-Magnetite

v

Hydrothermal

Fe, Zn, Pb, Sulfide-Vein deposit

Dark Fluorite-(C)

Tourmalin -Barite

-(R. Young 1984)

[6]Carbonate minerals -

Uranitite

-

PegmatiticAmphibole/pyroxenes-

deposit rockHematite -

(D)Zircon v

Apatite

-(R. Young 1984)

[6]Fluorite -Topaz

-Granite

-

Contact metasormatic

Uranitite - Thorianite-and methamorphic rock

Monazite v

(E)Zircon v

Chlorite

-(R. Young 1984)

[6]Riebeckite -

36

Figure 1. Situation map and location of rock sample within Maisah GraniteMassive, South Sulawesi (Siregar et al. 1983).Note: 598 = location sample No. CS3/04/598 B.

Figure 2. Geological map of Maisah Granite South SUlawesi(Sarwiyana et al. 1992 and Siregar et al. 1983)I"<v I = G1"anite; ~ = Metamorphic;

I~~""'I = Volcanic product; t~"-".-:":;;.-I= Aluvia1

37

Figure 3. Photo of minerals grains of heavies which taken trom crushedMaisah granite sample No. Cs 03/04/703B; 0.6. 2amp.traction (20X)

Figure 4. Photo of zircon, reddish (Z); monazite, yellow (M) apatite, white(A) and thorite, dark green (T) taken trom granite sample No. Cs03/04/703/ (35X)

38

Figure 5. Photo of allanite reddish brown (A) and thorite, light green (T)taken from granite sample No. Cs 03/04/703/B (25X)

39