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Elemental Mass Balance of the Hydrothermal Alteration Associated with the

Baturappe Epithermal Silver-Base Metal Prospect, South Sulawesi, Indonesia

Article · January 2013

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Elemental Mass Balance of the Hydrothermal Alteration

Associated with the Baturappe Epithermal Silver-Base

Metal Prospect, South Sulawesi, Indonesia

1Irzal Nur

*,

2Arifudin Idrus,

2Subagyo Pramumijoyo,

2Agung Harijoko

2, Koichiro

3Watanabe,

4Akira

Imai, 1Sufriadin,

1Asri Jaya HS,

1Ulva Ria Irfan

1Department of Geological Engineering, Hasanuddin University, Makassar 90245, Indonesia

2Department of Geological Engineering, Gadjah Mada University, Yogyakarta 55281, Indonesia

3Department of Earth Resources Engineering, Kyushu University, Fukuoka 819-0395, Japan

4Department of Earth Science and Technology, Akita University, Akita 010-8502, Japan

Email address: irzal_nur@yahoo.com

Abstrak

Prospek Baturappe yang terletak di ujung selatan Pulau Sulawesi, Indonesia, adalah sebuah distrik mineralisasi hidrotermal

yang dicirikan dengan kehadiran mineralisasi perak-logam dasar epitermal. Mineralisasi ini terbentuk pada batuan volkanik

basaltik-andesitik anggota Formasi Volkanik Baturappe yang berumur akhir Miosen Tengah. Makalah ini membahas hasil

studi terkini tentang hubungan antara mineralogi alterasi dan komposisi geokimia batuan, yang difokuskan pada kalkulasi

kesetimbangan massa, pada zona-zona alterasi hidrotermal prospek Baturappe. Alterasi hidrotermal pada prospek Baturappe

terzonasi di sekitar mineralisasi dari proksimal ke distal: zona kuarsa-karbonat dan illit-kuarsa (argilik), zona propilitik yang

berhubungan genetik dengan urat termineralisasi (epidot-klorit-kasit), dan zona propilitik berskala distrik (klorit). Hasil

evaluasi kalkulasi kesetimbangan massa menunjukkan bahwa pada zona propilitik yang berhubungan genetik dengan urat

termineralisasi terjadi sedikit penurunan komposisi kimia total pada batuan yang teralterasi dibandingkan dengan batuan

ekuivalen tak-teralterasinya. Sebaliknya, batuan yang teralterasi kuarsa-karbonat mengalami peningkatan komposisi kimia

total dibandingkan dengan batuan ekuivalen tak-teralterasinya. Peningkatan dan penurunan konsentrasi oksida-oksida mayor

dan unsur-unsur jejak pada kedua zona alterasi tersebut secara umum konsisten, baik terhadap himpunan mineral alterasi

hidrotermal yang terbentuk, indikasi-indikasi proses alterasi hidrotermal seperti destruksi mineral-mineral primer dan

absorpsi unsur-unsur tertentu pada mineral-mineral teralterasi, maupun perilaku geokimia sulfida-sulfida logam pra-alterasi.

Kata kunci: Baturappe epithermal silver-base metal prospect, Indonesia, hydrothermal alteration, mass balance.

Abstract

The Baturappe prospect situated in southernmost part of Sulawesi island, Indonesia, is a hydrothermal mineralization district

which is characterized by occurrences of epithermal silver-base metal mineralizations. The mineralizations hosted in

basaltic-andesitic volcanic rocks of the late Middle-Miocene Baturappe Volcanics. This paper discusses a recent study of

relationships between alteration mineralogy and whole-rock geochemistry, which focused on elemental mass balance

calculation, of the hydrothermal alteration zones within the prospect. Hydrothermal alteration is zoned around the

mineralizations from proximal quartz-carbonate and illite-quartz (argillic) to vein-related propylitic (epidote-chlorite-calcite)

to distal-district propylitic (chlorite) alteration. Mass balance calculation indicates that in the vein-related propylitic altered

zone there is a little decrease in bulk composition of the altered rock with respect to the least-altered rock. In contrast, the

quartz-carbonate altered rocks show an increasing in bulk composition with respect to the least-altered rocks. The gains and

losses of the major oxides and trace elements in the both alteration zones are generally consistent either with the

hydrothermal alteration mineral assemblages of each alteration zone, indications of the hydrothermal alteration processes

such as destruction of primary minerals and absorption of certain elements in altered minerals, and the behaviours of early

metal-bearing sulphides.

Keywords: Baturappe epithermal silver-base metal prospect, Indonesia, hydrothermal alteration, mass balance.

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I. Introduction

The Baturappe prospect is situated in

Baturappe Village, Gowa Regency, South

Sulawesi Province, Indonesia. It lies in the

southwesternmost part of Sulawesi Island, about

50 km southeast of Makassar, the capital city of

South Sulawesi Province. The prospect is

characterized by occurences of epithermal silver-

base metal mineralizations which are hosted in

basaltic-andesitic volcanic rocks of the late

Middle-Miocene Baturappe Volcanics (Nur et al.,

2009). The most significant mineralization in the

prospect, the Bincanai vein, contains an average

grade of: Pb 17.51 %, Zn 0.35 %, Cu 0.66 %, Ag

713 g/t, and Bi 308 g/t (Nur et al., 2010, 2011a,b).

Earlier works on the prospect and its vicinity

included the regional geology around the area

(Sukamto and Supriatna, 1982); studies of

volcanism and geodynamic evolution of south

Sulawesi, as well as petrology, geochemistry, and

dating of the volcanics (Yuwono et al., 1985,

1988; Leterrier et al., 1990; Priadi et al., 1994;

Polvé et al., 1997.); preliminary investigations of

base metal mineralizations in the prospect and

vicinity (Sutisna, 1990; Sukmana et al., 2002;

Zulkifli et al., 2002); and occurences and

distribution of significant hydrothermal ore

mineralizations in the Western Sulawesi Arc in

related to its tectonic setting and metallogenesis

(Idrus et al., 2011).

The works are generally based on regional

scale studies and preliminary investigations, no

detailed study has been conducted on genetic

aspects of the prospect. A detailed investigation of

some genetic aspects including alteration

geochemistry and elemental mass balance is

needed to improve understanding of the prospect.

This paper discusses a recent study of

relationships between alteration mineralogy and

whole-rock geochemistry, which focused on

elemental mass balance calculation, of the

hydrothermal alteration zones within the

Baturappe epithermal silver-base metal prospect.

Mass balance calculation following the example

of Grant (1986) were used to quantify the effects

of hydrothermal alteration on the host rock. The

present study allows better understanding of the

behaviour (enrichment or depletion) of the

elements during hydrothermal alteration

processes.

III. Geology and Mineralization Zones

Regionally, the Baturappe area is situated in

the southwestern part of the regional geologic

map of the Ujung Pandang, Benteng and Sinjai

quadrangles, Sulawesi (Sukamto and Supriatna,

1982). A detailed surface geological mapping has

then conducted in an area of 1000 ha to study the

geological background of the mineralization in the

prospect. The older rock unit broadly distributed

in the study area is lava of dominantly basalt and

less andesite, mostly porphyritic, with general

orientations of N(80-85)oE/(18-20)

oSE at the

centre and east of the study area, and

N120oE/65

oSW at the west. Locally, blocks of

volcanic breccia also exposed in the lava. Based

on its lithological characteristics, this unit is

interpreted as a member of lava, Tpbl (Sukamto

and Supriatna, 1982) which according to K-Ar

dating indicates age of 12.38 to 12.81 Ma or late

Middle-Miocene (Yuwono et al., 1985; Priadi et

al., 1994). The basaltic-andesitic lava which

distributed from Bincanai and Ritapayung area at

the west, through Bangkowa to the east, and

Taloto at the south portions of the study area, is

identified as the host rock of the epithermal

mineralizations in the prospect. At the north, the

lava was intruded by a gabbroic-dioritic stock;

and followed by a group of basaltic-andesitic

dykes. At least 50 units of dykes with a thickness

range of 8 cm to 2.5 m are cropped-out in the

study area, distributed radially centered to the

stock, forming a radial swarm of dyke. K-Ar

dating on two samples of basalt indicate ages of

7.5 Ma and 6.99 Ma, and 7.36 Ma on gabbro

(Sukamto and Supriatna, 1982). The basaltic-

andesitic stock and dykes are interpreted as the

mineralization-bearing rocks in the study area,

which is indicated by the occurences of

disseminated ore (i.e., pyrite, chalcopyrite,

sphalerite, galena, covellite, magnetite, hematite)

recognized in the field and microscopic

observations. Due to the orientation of the dykes

that are consistent to the trends of the fractures, it

is interpreted that the emplacement and

distribution of the dykes brought mineralization is

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highly controlled by geological structures (Nur et

al., 2009; Figure 1).

More than 20 units of quartz veins along with

disseminated sulphide and sulphide stringer are

distributed around the periphery of the stock in

the study area, hosted in the lava and dyke units.

Among these, eight significant mineralizations are

distributed in four zones: Bincanai-, Baturappe-,

Bangkowa- and Ritapayung zone. The

mineralizations namely: Bincanai vein, Baturappe

vein-1, Baturappe vein-2, Bungolo vein,

Paranglambere vein (all clustered in the

Baturappe zone); Bangkowa vein and Bangkowa

stringer (in the Bangkowa zone); and Ritapayung

dissemination (in the Ritapayung zone). The

Bincanai vein and Baturappe veins are distributed

and clustered along the main fault in the study

area, the NW-SE trend Bincanai-Baturappe

normal fault; whereas the Bangkowa- vein and

stringer are hosted in NW-SE dykes. Distribution

of the mineralizations and orientation of the veins

are shown in Figure 1.

The veins display the typical primary texture

of epithermal veins: crustiform banding texture;

from symmetric-, multiphase- to simple

crustiform of quartz ± carbonate – sulphide

(dominated by galena). In general, sulphide

assemblages identified in the mineralizations

indicate a range of intermediate- to high

sulphidation epithermal assemblages. The

sulphides include: galena, sphalerite, chalcopyrite,

pyrite, tennantite, tetrahedrite, bornite, enargite,

freieslebenite, and polybasite. Very fine-grained

silver and bismuth minerals which occupy

fractures of the early-stage minerals, were also

identified by SEM-EDX analysis; the minerals

include bismuthinite, cupropolybasite, jalpaite,

angelaite, cuprobismutite, sorbyite, and launayite.

Figure 1. Geological map of the study area and distribution of significant

mineralizations in the prospect: (1) Bincanai vein, (2) Ritapayung dissemination,

(3) Baturappe vein-1, (4) Baturappe vein-2, (5) Bungolo vein, (6) Paranglambere

vein, (7) Bangkowa vein, (8) Bangkowa stringer.

1

2

6

3 4

5

7

8

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Supergene minerals such as covellite, chalcocite,

iodargyrite, anglesite, cerrusite, as well as

manganese coronadite and chalcophanite were

also identified. Bulk-ore chemical composition

determined by XRF analysis indicates a highest

grade of: Pb 17.51%, Zn 0.35%, Cu 0.66%, Ag

713 g/t, Bi 308 g/t for the veins, and Pb 0.11%, Zn

0.15%, Cu 5.83%, Ag 140 g/t, Bi 60 g/t for the

dissemination (Nur et al., 2010, 2011a,b).

III. Hydrothermal Alteration Zoning and

Mineralogy

As an introduction to discuss the relationships

between the alteration mineralogy and whole-rock

geochemistry, i.e., the elemental mass balance,

this section briefly reviews the hydrothermal

alteration zoning and mineralogy of the Baturappe

prospect that have been previously reported on the

earlier publications of the authors (Nur et al.,

2011c,d). Zonation of hydrothermal alteration in

the study area is divided on the basis of the

dominant mineral assemblages and its spatial

distribution relative to the mineralizations, from

distal to proximal include: chlorite, epidote-

chlorite-calcite, and illite-quartz and quartz-

carbonate zones (Figure 2). The chlorite zone is a

distal-district propylitic alteration which is

characterized by a low intensity of alteration and

developed on the periphery of the hydrothermal

system in study area. The epidote-chlorite-calcite

zone is a vein-related propylitic alteration which

is characterized by a higher intensity of alteration

and developed proximal to the structural-

controlled veins in the prospect. The illite-quartz

(argillic) zone is characterized by clay mineral

assemblages which distributed proximal to the

related-veins at Baturappe- and Bangkowa area,

and interpreted as the centre of hydrothermal

activities responsible for the mineralization. The

narrow and elongated distribution of the zone

(Figure 2) indicates that the distribution is

controlled by geological structure. The quartz-

Figure 2. Hydrothermal alteration map of the Baturappe prospect.

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carbonate zone also distributed proximal to the

related-mineralization (the Bincanai vein and the

Ritapayung dissemination), and also interpreted as

the centre of the hydrothermal activities that

responsible for the mineralizations. The narrow

and elongated distribution of the quartz-carbonate

zone around the Bincanai vein indicates that the

distribution is controlled by geological structure,

i.e., the Bincanai-Baturappe fault (Figure 2). On

the other hand, at Ritapayung, regarding the

lithological host of the alteration-mineralization

(volcanic breccia), the quartz-carbonate zone in

this area is controlled by permeability of the host

rock (Nur et al., 2011c,d). The mineral

assemblages in each alteration zone is

summarized in Table 1.

Table 1. Mineral Assemblage in Each Hydrothermal Alteration Zone

Hydrothermal

mineral

Chlorite

zone

Epidote-chlorite-calcite

zone

Illite-quartz

zone

Quartz-

carbonate zone

BC BR BK BR BK BC RP

Chlorite

Epidote

Calcite

Quartz

Sericite

Albite

Biotite

Illite

Smectite

i/s

c/s

Kaolinite

Halloysite

Dolomite

Siderite

Pyrite

Magnetite

Hematite

Distance to

mineralization

(m)

District

scale 1 to 10 7 0.5 < 7 < 0.5 < 1 < 200

- Abbreviations: i/s: mixed layer illite/smectite, c/s: mixed layer chlorite/smectite; BC: Bincanai, BR:

Baturappe, BK: Bangkowa, RP: Ritapayung.

- Line weight indicates relative abundance.

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IV. Analytical Methods

In this study, the whole-rock geochemical

analysis was performed by X-ray fluorescence

spectrometry (XRF) and inductively coupled –

mass spectrometry (ICP-MS) methods. The XRF

analysis was conducted to measure the major

oxides of altered and less-altered rock samples,

whereas the ICP-MS analysis was conducted to

measure the trace element composition of the

altered and less-altered rock samples.

Sample preparation for the XRF analysis was

performed at the Laboratory of Economic

Geology, Department of Earth Resources

Engineering, Kyushu University. The samples

were firstly crushed and grinded, then pulverized

by agate mortar, and then milled by a CMT TI-

100 model of vibrating sample mill machine, and

finally were pelletized using a Rigaku pressing

machine to form pressed powder discs that ready

to be analyzed. Before the analysis conducted, one

gram of each milled samples were separated to

measure their LOI (H2O) concentration. The

analysis was then performed using an XRF

instrument of Rigaku ZSX Primus II, which

calibrated by the fundamental parameter (FP)

sensibility calibration method using 15 standards

of the Geological Survey of Japan (JB-1a, JB-2,

JB-3, JGb-2, JH-1, JA-1, JA-2, JA-3, JG-1a, JG-2,

JG-3, JSy-1, JCh-1, JSd-2, JSd-3, JLs-1 and JMn-

1) and 17 synthesized standard compounds (JA-

3S, JB2-30Fe, JB2-40Fe, JB2-50Fe, JA3-20Fe,

JA3-35Fe, 6elts-2, 6elts-3, AuAg-1, AuAg-2,

AuAg-3, Na-rich, Ag5-BiPb, Ag9-BiPb and

Ag17-BiPb). Technical specification of the

analysis is, X-ray tube: Rh, voltage: 50 kV and

current: 50 mA, detection limit (for the major

oxides): 0.01%. Peak overlapping was examined,

and overlap correction coefficients were used in

the quantitative calculation in the FP sensibility

calibration. The analysis was conducted at the

Research Institute for Environment Sustainability

(RIES) Laboratory, Kyushu University.

For the ICP-MS analysis, the rest of milled

samples that have been previously prepared and

analyzed by the XRF method (for the major

element composition) were sent to a commercial

laboratory: the Actlabs (Activation Laboratories

Ltd.), Canada, to be determined their trace- and

rare earth element composition. Determination of

43 trace elements was then conducted by ICP-MS

method, with detection limit (in ppm) as follows:

Zn = 30; Cr and Ni = 20; Cu = 10; V, As and Pb =

5; Ba = 3; Sr and Mo = 2; Co, Ga, Rb, Zr and Sn

= 1; Ge, Y, Ag and W = 0.5; Nb and Sb = 0.2; In,

Cs, Hf and Bi = 0.1; La, Ce, Nd, Tl and Th =

0.05; Pr, Sm, Gd, Tb, Dy, Ho, Er, Yb, Ta and U =

0.01; Eu, Tm = 0.005; and Lu = 0.002 (analysis

package code 4B2-research, Actlabs Service

Guide 2010).

To evaluate quantitatively the chemical

composition changes (major and trace elements)

of the host rocks of the mineralization due to

hydrothermal alteration processes, the method of

mass and volume change calculation (mass

balance) of Gresens (1967) and its modification,

the isocon diagram of Grant (1986) were applied.

The Gresens’ formula for the calculation is:

Xn = {[fv(gB/g

A)Cn

B – Cn

A}100 (1)

where: Xn is mass gain or loss of an element

between an unaltered rock (A) and its altered

equivalent (B); fv is volume change factor; g is

density of the rock; and Cn is concentration of an

element.

The equation has then rearranged by Grant

(1986) to calculate the concentration changes of

elements (∆C), as well as mass and volume

changes (∆M and ∆V, respectively) of rocks as a

results of hydrothermal alteration. The formula of

the calculation is: ∆C = (MO/M

A)*[(C

A/C

O)-1];

∆M = [(MO/M

A)-1]*100; and ∆V =

(MO/M

A)*[(ρ

A/ρ

O)-1]*100; where: ∆C =

concentration change of elements (major oxides

and trace elements) from altered rock to its

unaltered equivalent (original rock), ∆M = mass

change in %, ∆V = volume change in %, MO =

mass of original rock, MA = mass of altered rock,

CO = concentration of elements in original rock,

CA = concentration of elements in altered rock, ρ

O

= specific gravity of original rock, and ρA =

concentration of elements in altered rock. Results

of the calculation (elemental gains and losses)

were expressed in a graph where a line of iso-

concentration (immobile elements) separates the

enriched elements from the depleted ones. This

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line is called isocon. Elements plot above the

reference isocon are enriched during alteration,

whereas elements plot below are depleted. The

gradient of the isocon is defined by ratio of the

mass of original (least altered) rocks against the

mass of altered rocks: MO/M

A (Grant, 1986).

In this study, data processing and imaging of

the mass balance calculation was performed using

the GEOISO software of J. Coelho (2005).

Specific gravity of rock samples was measured by

the buoyancy method (Archimedes principle).

Elements TiO2, Zr and Y were used as immobile

or inert elements (e.g., Mauk and Simpson, 2007)

when input the data to the software.

V. Result and Discussion

In this study, four samples around the

Bincanai vein were selected to be evaluated. The

selection of the samples is because around the

Bincanai vein a systematic sampling was

conducted from proximal to distal site of the vein.

The samples include: WBC.2B, WBC.2C and

WBC.2D which were collected respectively 1 m,

2 m, and 3 m from the vein. These samples

represent altered rocks which according to their

alteration mineral assemblages (Table 1), the first

two samples represent the quartz-carbonate zone

and the rest represents the epidote-chlorite-calcite

zone or vein-related propylitic. For the least-

altered rock, sample BCFW.1 that was taken

relatively far from the vein (10 m) is selected.

From the mineral assemblage identified by

microscopic observation, this sample is relatively

weak altered compared to the other three samples.

Chemically, the sample also generally has a lower

content of H2O, Cu, Zn and Pb relative to the

other three samples (Table 2). Thus, beside

consider the relative distance from the

mineralization, the alteration mineral assemblage

and chemical composition are also considered to

select the least altered and altered rocks in this

evaluation.

Whole-rock chemical composition of the

samples are listed in Table 2, and the results of

mass balance calculation, the isocon diagram of

the three pairs of least-altered and altered rocks

(BCFW.1 vs WBC.2D, BCFW.1 vs WBC.2C, and

BCFW.1 vs WBC.2B) including their enrichment-

depletion diagram of selected elements are

respectively shown in Figure 3, 4, 5. The gradient

of isocons and results of mass and volume change

calculations are attached in each isocon diagram

(Figure 3.A, 4.A, 5.A).

The propylitic altered rock (sample WBC.2D)

indicates a little decrease in bulk composition

with respect to the least-altered rock. This is

expressed by the slight negative value of their

mass and volume changes, -0.95% and -8.75%,

respectively (Figure 3.A). K2O and Rb are

strongly enriched with enrichment factors of 0.52

and 0.60, respectively, and Ba is slightly added

with factor of 0.07 (Figure 3.B). The strong

enrichment of K2O may related to the presence of

illite and sericite; these secondary minerals are

identified in the samples of propylitic altered rock

around the Bincanai vein. The addition of Rb and

Ba indicates that the elements are probably

absorbed in altered plagioclase and sericite (Idrus

et al., 2009). MgO also moderately enriched with

enrichment factor of 0.25 (Figure 3.A), which

may related to the abundance of clinochlore in the

sample (13.61 wt.% from semi-quantitative XRD

result, Nur et al., 2011c,d). CaO is slightly

depleted (depletion factor of 0.20). The depletion

of CaO in propylitic alteration has been reported

by Idrus et al. (2009), which may indicates that

replacement of the calcic plagioclase rims is more

intense than the formation of Ca-bearing

hydrothermal minerals such as calcite and epidote

in the rocks. The depletions of Na2O, Sr and V

reflect destruction of plagioclase during the

alteration. The strong gain of Cu and slight to

moderate gain of Zn indicate a high abundance of

early copper- and zinc-bearing sulphides.

Whereas the strong depletions of Pb and Bi

suggest that lead- and bismuth-bearing sulphides

are still not well developed in this alteration zone.

Other elements such as MnO and Cs are enriched,

whereas Zr, In and Sn are depleted (Figure 3).

In contrast, the quartz-carbonate altered rocks

(WBC.2C and WBC.2B) show an increasing in

bulk composition with respect to the least-altered

rock. This is expressed by the positive values of

their mass and volume changes, +15.56% and

+6.09% respectively for sample WBC.2C, and

+20.93% and +33.87% respectively for sample

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WBC.2D (Figure 4 and 5). SiO2, CaO and FeO

are enriched which explains the development of

quartz and carbonate calcite and siderite in this

alteration zone. The enrichment of FeO (0.11 in

WBC.2C and 0.16 in WBC.2B) may also related

to the occurrence of chamosite in the alteration

zone. K2O, Rb, Cr and Ba are moderately to

strongly enriched with the average enrichment

factors for the two samples are 1.22, 2.99, 1.11

and 0.46, respectively (Figure 4.B and 5.B). The

strong enrichment of K2O may related to the

presence of illite and sericite in the samples

(Table 1). The addition of Rb and Ba indicates

that the elements are probably absorbed in altered

plagioclase and sericite (Idrus et al., 2009); this

may also explains the addition of Cr in the

samples. MgO is slightly enriched in sample

WBC.2B, with enrichment factor of 0.29 (Figure

5.B), which may related to the presence of

clinochlore in the sample; result of semi-

quantitative XRD indicates proporsion of 25.28

wt.% (Nur et al., 2011c,d). The depletions of

Na2O and Sr reflect destruction of plagioclase

during the alteration. The moderate to strong

gains of Zn, As, Ag and Pb are respectively

indicate a high abundance of early zinc-, arsenic-,

silver- and lead-bearing sulphides in this inner

zone of alteration. Cu and Bi are depleted in

sample WBC.2C, but are then enriched in the

more proximal sample, WBC.2B, which may

explains that copper- and bismuth-bearing

sulphides are more developed in the more

proximal zone (to the vein). Other elements such

as MnO, V, Ni, Y, Zr, Sb, Cs, Ce and U are

enriched, whereas In and Sn are depleted (Figure

4 and 5).

Table 2. Whole-rock Geochemical Data of the Four

Samples

Sample code BCFW.1 WBC.2B WBC.2C WBC.2D

Sample type Andesite Andesite Andesite Basalt

Alteration zone Least-altered Quartz-carbonate Quartz-carbonate Epidote-chlorite-calcite

(vein-related propylitic)

Major elements (%)

SiO2 49.14 44.67 47.33 48.51

TiO2 1.04 0.86 0.90 1.05

Al2O3 15.28 13.28 13.63 15.35

FeO 9.50 9.13 9.13 9.35

MnO 0.20 0.36 0.25 0.26

MgO 6.54 6.97 6.08 8.26

CaO 8.07 8.53 7.33 7.18

Na2O 3.15 1.85 2.46 2.21

K2O 2.45 4.20 5.01 3.77

P2O5 0.40 0.37 0.39 0.37

H2O 3.66 9.47 7.23 3.00

Total 99.43 99.69 99.74 99.31

Trace elements (ppm)

V 254 237 229 246

Cr 70 130 120 70

Co 32 28 26 32

Ni 20 40 30 20

Cu 100 130 50 190

Zn 80 200 160 90

Ga 17 16 15 16

Ge 1.3 1 1 1.3

As < 5 11 < 5 < 5

Rb 57 112 129 92

Sr 729 407 554 679

Y 22.2 21 22 21.7

Zr 104 96 98 99

Nb 5.5 4.8 4.4 5

Mo < 2 < 2 < 2 < 2

Ag < 0.5 0.6 < 0.5 < 0.5

In 0.1 < 0.1 < 0.1 < 0.1

Sn 3 2 2 2

Sb < 0.2 33.4 4.7 < 0.2

Cs 0.5 4.7 3.3 1.4

Ba 540 592 748 583

La 17.7 16.7 17.8 17

Ce 36.1 34.9 37 35.5

Pr 4.78 4.64 4.89 4.64

Nd 20.2 19.4 20.5 19.5

Sm 4.82 4.86 5.07 4.77

Eu 1.45 1.45 1.46 1.47

Gd 4.55 4.43 4.75 4.52

Tb 0.73 0.69 0.73 0.72

Dy 4.09 3.88 4.13 4

Ho 0.78 0.73 0.79 0.76

Er 2.17 2.06 2.23 2.15

Tm 0.32 0.302 0.326 0.322

Yb 2.09 1.99 2.05 2.05

Lu 0.362 0.319 0.311 0.318

Hf 2.4 2.2 2.2 2.3

Ta 0.55 0.5 0.46 0.45

W < 0.5 < 0.5 < 0.5 < 0.5

Tl 0.42 0.51 0.55 0.4

Pb 21 29 42 13

Bi 0.2 0.2 0.1 0.1

Th 4.65 4.84 5.22 4.52

U 1.74 2.16 2.27 1.71

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Figure 3. A. Isocon diagram of sample BCFW.1 (least-altered rock) vs WBC.2D (vein-related

propylitic altered rock); major oxides in wt.% and elements in ppm. B. Enrichment-depletion

diagram of the sample pair.

(B) 1.0

0.5

0

-0.5

-1.0 SiO2 FeO MgO CaO Na2O K2O V Cr Co Cu Zn As Rb Sr Y Zr Mo Ag Sn Ba Pb Bi

BCFW.1 vs WBC.2D

Concentr

ation c

ha

ng

e (

∆C

)

Isocon gradient: 0.92 Mass change: -0.95% Volume change: -8.75%

Vein

-rela

ted p

ropylit

ic a

ltere

d r

ock (

WB

C.2

D)

Cu

K2O

Rb Zn

SiO2

Zr

Sr

Ba

V

Tl

P2O5 Y

Cr

Lu

Na2O

Sn

Pb

Ni

Nd Tm As

La Hf MnO

Al2O3 Co

W

Yb

U

Bi

Eu

FeO Ge

Cs

MgO TiO2

CaO Mo

Sm Nb

Ag Dy

Ta H2O

In

Er Ga

Ce

Tb

Th Ho

Sb

Pr

0 30 Least-altered rock (BCFW.1)

0

30 (A)

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Figure 4. A. Isocon diagram of sample BCFW.1 (least-altered rock) vs WBC.2C (quartz-

carbonate altered rock); major oxides in wt.% and elements in ppm. B. Enrichment-depletion

diagram of the sample pair.

Quart

z-c

arb

onate

altere

d r

ock (

WB

C.2

C)

Ce SiO2 Zr

V

Sr

P2O5

Ba

Y

Lu

Na2O

Sn

Cu

Nd Tm

La As

Hf

Ga

Rb Zn

Cr Cs

Pb

Ni U MnO

Er W Yb

Al2O3 Co

Bi

Eu FeO

Ge CaO Mo

TiO2

MgO

In

Nb

Ho Th Gd

Dy

Ta

Tl

K2O

H2O

Sb

Tb

Least-altered rock (BCFW.1) 0 30 0

30

Isocon gradient: 0.92 Mass change:+15.56% Volume change: +6.09%

(A)

(B)

SiO2 FeO MgO CaO Na2O K2O V Cr Co Cu Zn As Rb Sr Y Zr Mo Sn Ba Pb Bi Ag

2.0

1.5

1.0

0.5

0

-0.5

-1.0

BCFW.1 vs WBC.2C

Concentr

ation c

ha

ng

e (

∆C

)

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Figure 5. A. Isocon diagram of sample BCFW.1 (least-altered rock) vs WBC.2B (quartz-

carbonate altered rock); major oxides in wt.% and elements in ppm. B. Enrichment-depletion

diagram of the sample pair.

(B)

SiO2 FeO MgO CaO Na2O K2O V Cr Co Cu Zn As Rb Sr Y Zr Mo Sn Ba Pb Bi Ag

5.0

4.0

3.0

2.0

1.0

0

-1.0

BCFW.1 vs WBC.2B

Concentr

ation c

ha

ng

e (

∆C

)

(A)

Quart

z-c

arb

onate

altere

d r

ock (

WB

C.2

B)

Zr SiO2

Ba

V

Sr

P2O5

Pb K2O

Cu

Y

Lu Nd

Sn Na2O

Tm

La Ga

Hf

Ce W

Er Co

Al2O3

Yb

Zn

Cr Rb

MnO

Ni

U

Bi

Sb

As

H2O

Cs Ag

Tl

Th Ho

In

Ge

Eu FeO

CaO

TiO2

Mo MgO

Gd

Ta Dy Tb

Nb Isocon gradient:1.11 Mass change:+20.93% Volume change: +33.87%

Least-altered rock (BCFW.1) 0 30 0

30

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VI. Conclusion

Mass balance calculation indicates that in the

vein-related propylitic altered zone there is a little

decrease in bulk composition of the altered rock

with respect to the least-altered rock; the mass and

volume changes is -0.95% and -8.75%,

respectively. In contrast, the quartz-carbonate

altered rocks show an increasing in bulk

composition with respect to the least-altered

rocks, which expressed by the positive values of

their mass and volume changes, +15.56% to

+20.93% and +6.09% to +33.87%, respectively.

The gains and losses of the major oxides and trace

elements in the both alteration zones are generally

consistent either with the hydrothermal alteration

mineral assemblages of each alteration zone,

indications of the hydrothermal alteration

processes such as destruction of primary minerals

and absorption of certain elements in altered

minerals, and the behaviours of early metal-

bearing sulphides.

Acknowledgments

This paper is a section of the first author’s

dissertation completed at the Graduate Program of

Geological Engineering, Faculty of Engineering,

Gadjah Mada University, Yogyakarta, Indonesia.

The authors are very thankful to the management

of PT. Sungai Berlian Bhakti Mining for the

permission to collect field data for the study. The

authors also wish to express honest gratitude to

Dr. Ryohei Takahashi and Mr. Naohiro Goto,

respectively for the guidance and assistance in

conducting XRF analysis at Kyushu University.

Sincere gratitude also directed to the Directorate

of Higher Education, Department of National

Education, Indonesia for the grant of Hibah

Disertasi Doktor 2010 that made possible for the

authors to send samples to be analyzed by ICP-

MS method at the Actlabs, Canada. This study

was made possible through the long-term

scholarship of the Fellowship Doctoral Degree

Program, Hasanuddin University Engineering

Faculty Development Project under JBIC (Japan

Bank International Cooperation) Loan No.IP-541.

The manuscript improvements from reviewers are

gratefully acknowledged.

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