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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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Irzal Nur
Universitas Hasanuddin
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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: [email protected]
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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Hal | 39
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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Hal | 40
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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Hal | 41
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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Hal | 42
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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