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Sedimentology and Geochemistry of the REE-bearing placer
deposits in the Kualakurun area, Central Kalimantan
Billy G. Adhiperdana, ST., M.Si. NIP: 197111301999031002
Faculty of Geology UNIVERSITAS PADJADJARAN
November 2018
Summary
This report contains an outline of preliminary exploration results on mineral-bearing alluvial in Kualakurun area, Central Kalimantan, Indonesia. The results from core drilling, geological fieldwork and geochemical-laboratory examination will be describe in this report. Local mining and abandoned tailing became an important issue in this exploration activity. Distribution of local mining has been roughly delineated during alluvial and bedrock mapping. From total IUP area (18.127 km2), 23% of them are local mining areas (± 4.165 km2). The other 44% (±8.12 km2) in the western portion are covered by bedrocks and weathered bedrocks (Appendix E). Samples were analyzed to standard laboratory procedures at the PT Intertek Laboratory in Jakarta. Sample testing in the laboratory to include several methods of inductive-coupled plasma analysis (ICP-MS, ICP-OES), and fire assay technique. On average, the borehole reached measured total depth of 5.1 m on average. The alluvial-terrace deposits can be divided into two major facies associations, from the bottom to top: 1) Facies B, gravel and coarsed-sand deposits; and 2) Facies A, fine-grained-sand/sand-dominated deposits. In this investigation, Au (ppm) is a proxy for gold, Zr (ppm) is a proxy for zircon mineral, whereas the abundance of REE (REE) is a proxy for REE-bearing minerals such as monazite and xenotime. Detrital composition of the alluvial consists largely of various types of quartz grains, fine-grained feldspar in very small quantity, and heavy minerals. Rutile, ilmenite, zircon, garnet, iron-oxide (hematite), and opaque minerals were evidently observed by using a hand lens. A total of 61 elements were obtained from the laboratory test. These elements can be grouped into seven groups, arranged in decreasing order: 1) Transition metal, 2) Rare-earth elements/REE, 3) Alkaline-earth metal, 4) Alkali metal, 5) Metaloid/semi metal s, 6) Non-metal, and 7) Actinide-transition metal. Test result from laboratory indicate that Au (ppm) in the sample was found in very small quantities (maximum Au 0.305 ppm, g/ton). In total, concentration of Au (ppm) which was obtained from seven drill-core locations is varied in the range between 0.015–0.225 ppm (g/ton). The verage concentration of Au (ppm) is 0.042 ppm (g/ton). It can be concluded that the gold in the exploration area has low economic potential to be developed. The maximum concentration of Zr which was obtained from the Kualakurun samples is less than 100 ppm (g/ton). It can be concluded the Zr concentration in the alluvial deposits of Kualakurun has low economic potential to be developed. The REE concentration found in the samples taken at the Kualakurun are lower than the values determined for the known high-grade REE deposits, thus are considered to be low potential REE deposit. In conclusion, the grade of gold (Au), zircon (Zr) and REE in alluvial placer of the Kualakurun area are too small and low to be developed in today's economic condition. So it is not recommended for further investigation at this time.
i
Table of Contents
Page
Amendment
Summary
Table of contents ......................................................................................................... i
Introduction ................................................................................................................. 1
Methods ........................................................................................................................ 2
Geological setting ........................................................................................................ 3
Alluvial-terrace deposits ............................................................................................. 4
Elemental variation (test result) ................................................................................. 5
Gold (Au) deposit ........................................................................................................ 5
Zircon (Zr) deposit ...................................................................................................... 7
Rare earth (REE) deposit ........................................................................................... 7
Conclusions and recommendations ........................................................................... 8
References .................................................................................................................... 28
Figures
Figure 1. Simplified geographical map shows the exploration area. .......................... 10
Figure 2. Physiographic outline of the Kalimantan. ................................................... 11
Figure 3. Simplified geological map, modified after several authors. ....................... 12
Figure 4. Deposits analogue for Quaternary-alluvial exploration. ............................. 13
Figure 5. Variation diagram of the seven elemental groupes. .................................... 15
Figure 6. Variation plot of the gold signature elements. ............................................ 16
Figure 7. Bivariate plot of indicator elements for gold Au vs. Cu. ............................ 17
Figure 8. Zr/Hf plot and Plot of Th/Sc vs. Zr/Sc (McLennan, 1993). ........................ 18
Figure 9. Zr and associative elements plot in the variation diagram. ......................... 19
Figure 10. The REE concentration of the Kualakurun alluvial. ................................... 22
Figure 11. REE chondrite-normalized plot (Floyd, 1991). .......................................... 23
Figure 12. Facies-based REE chondrite-normalized plot (Floyd, 1991). ..................... 24
Figure 13. REE (ppm) comparison diagram from the Kualakurun. ............................. 25
ii
Figure 14. REE (UCC-normalized) comparison diagram (McLennan, 2001). ............ 26
Figure 15. La/Th vs. Th/Yb plot for igneous discrimination. ...................................... 27
Tables
Table 1. Summarized elemental concentration. ........................................................ 14
Table 2. REE (ppm) comparison diagram from the Kualakurun. ............................. 20
Table 3. Summarized grades of gold (Au), zircon (Zr) and total REE. .................... 21
Appendices (Enclosure)
Appendix A. Geographic-accessibility map of the exploration area.
Appendix B. Topographic map of the exploration area, generated from Digital Grid
Elevation map.
Appendix C. Regional geology of the exploration area, adapted after the Indonesian
GRDC map of 1;250,000.
Appendix D. Proposed and actual drill hole location, and channel sampling location.
Appendix E. Thickness distribution of the alluvial deposits in the Kualakurun area.
Appendix F. Lithologic log of the drill core and channel samples.
Appendix G. Intertek's Laboratory-test result.
Appendix H. Photographs of exploration activities, outcrops, and abandoned local
mines.
Appendix I. Photographs of drilling equipments.
1
Preliminary Exploration Results for Gold, Zircon and REE-Bearing Placer at the Kualakurun Area,
Central Kalimantan Indonesia
Introduction
This report contains an outline of preliminary exploration results on mineral-bearing
alluvial in Kualakurun area, Central Kalimantan, Indonesia. The results from core
drilling, geological fieldwork and geochemical-laboratory examination will be describe
in this report (see Appendix A–I). Data analysis which have relevance to the potential of
mineral deposits in the alluvial sediments which have been investigated will be
summarized as well.
This preliminary exploration in the Kualakurun IUP area is intended to: 1) describe the
mineral-bearing placer, alluvial-terrace deposits at the Kualakurun, Kahayan sub-basin,
2) summarize the provenance and stratigraphy of these deposits, and 3) summarize the
economic mineral potential (gold, zircon and REE) of the Kualakurun area (IUP
exploration area).
Some parts of the Kalimantan areas, for example, Barito basin, Kahayan basin,
Mahakam dan Kapuas basins have been known for a long time as regions of the
Quaternary-alluvial pacers which produce important economic mineral resources, gold,
diamond and rare-earth minerals (e.g. Watters et al., 1991; de Keyser and Noya-Sinay,
1992; Seeley and Sendedn, 1994; Abidin, 1998; Herman, 2007; Lolon and Rahman,
2015).
The Kualakurun areas which is situated in western portion of the Kahayan basin (Figure
1 and 3), thus is likely has the same potential for gold and other economic minerals
which are associated with the Quaternary-alluvial placer.
The exploration area at Kualakurun area is classified into lowland-morphologic setting
under the perhumid climatic condition in equator which is also occupied by the tropical-
lowland rain-forest area (Thorp et al., 1990; Thorp and Thomas, 1992). This climate
condition provide important effects on rock weathering in these regions. Topographic
2
elevation in the exploration area ranges between 34–112 m above mean sea level
(Appendix B).
Local mining, excavation and abandoned tailing materials became an important issue in
this exploration activity (Appendix E and H). Illegal mining are common and obvious in
the Kualakurun. Abandoned and active local mining are very extensive within the IUP
exploration area. This illegal mining have been operated by local people or locals who
cooperate with domestic investors since early 1990's (anonymous, pers. comm.).
Distribution of local mining has been roughly delineated during alluvial and bedrock
mapping. From total IUP area (18.127 km2), 23% of them are local mining areas (±
4.165 km2). The other 44% (±8.12 km2) in the western portion are covered by bedrocks
and weathered bedrocks (Appendix E).
Methods
Samples were collected from channel sampling at the surface and from drill cores
(Appendix F and H). Cores and channel samples were prepared and analyzed to
standard laboratory procedures at the PT Intertek Laboratory in Jakarta. Examination
methods and limitations were enclosed in this report on appendix (Appendix G). Sample
testing in the laboratory to include several methods of inductive-coupled plasma
analysis (ICP-MS, ICP-OES), and fire assay technique.
The total number of drilled boreholes are 18 drill holes. On average, the borehole
reached measured total depth of 5.1 m on average (below the surface). In most cases,
the drill pipes were stuck in more than 5 m depths, and it took a long time to remove the
pipes. The drilling machine (Appendix I) might not be suitable for full-core drilling in
loose and unlithified sediments.
Technical-drilling problems were some times encountered during core drilling in loose
and unconsolidated alluvial deposits, it was almost impossible to obtain 100% core
recovery (Appendix F and H). The average core percentage recovery is 54%. One bore
hole (DH-GMO-005) experienced a total loss (CR = 0%). For this reason, it was
decided to conduct channel sampling (e.g. Halloran, 2013; Haldar, 2013) to complement
borehole which have poor core recovery. In such case, a borehole was located above the
preserved alluvial behind the face of open cut exposure (Appendix H).
3
In addition to drilling, surface mapping was also conducted to delineate the distribution
of alluvial-terrace deposits. On the regional-scale geological map (Sumartadipura and
Margono, 1996) of Tewah (Kualakurun) which has been published by the GRDC, 90%
of the exploration area are covered by bedrock of the Mid-Miocene Warukin Formation.
More detail delineation of bedrock exposure and alluvial terrace were needed to get the
actual distribution of bedrock and surficial deposits in the exploration area (Appendix
E).
In general, potential of the economic-sand minerals are reported in percentage and
estimated based on the proportion of detrital compositon (Haldar, 2013; McLemore et
al., 2016). In this investigation, the laboratory examination of mineral concentration
were not based on the detrital analysis of mineral species, but based on chemical
(elemental) analysis of bulk-sediment samples. In this investigation, Au (ppm) is a
proxy for gold, Zr (ppm) is a proxy for zircon mineral, whereas the abundance of REE
(REE) is a proxy for REE-bearing minerals such as monazite and xenotime.
Since ppm means parts per million (1/106), and ton (metric) equal to 106 grams, then 1
ppm equal to 1 g/ton. Therefore, grade unit g/ton is put together beside the ppm unit
when it is needed in the report.
Geological setting
According to the regional stratigraphic framework, the Kualakurun area is characterized
by the presence of the two bedrock units and widely distributed surficial deposits of
alluvial origin (Sumartadipura and Margono, 1996). The bedrock units are classified
into the Mid-Miocene Warukin Formation and the Miocene─Pliocene Dahor Formation.
In some locations, an outcrop of the Mid-Miocene Warukin Formation have been found.
These bedrock exposures were outcropped at in the roadcut at the western part of the
exploration area (photographs on Appendix H). Bedrocks of the Warukin and Dahor
Formation were also exposed as outcrop windows in several shallow local mining's
excavation. Most of the western part of the exploration area are covered by the
podzolized deposits, which are the product of extensive bedrock weathering. Alluvial
terrace deposits are commonly absent in these area. Podzols from weathered bedrock
are mainly consist of angular-quartz sands, fine to medium sized-sand with typical
4
thick-oxidized whitish-yellow and brownish–reddish clay covers. Extensive
podzolisation are very common in the perhumid climate such in Kalimantan which is
situated in equator under the tropical-climate condition (Thorp et al., 1990; Thorp and
Thomas, 1992).
Sedimentary-alluvial terraces have been widely identified in the areas of Kalimantan.
Many previous workes have divided this terraces into Old and Young Alluvium. Many
economic-mineral deposits were commonly associated with these various facies types of
the Young-alluvium deposits (Figure 4). These sediments were deposited during low sea
level in response to the last major glacial period (Thorp et al., 1990; Thorp and Thomas,
1992, Seeley and Senden, 1994).
In the regional physiographic setting (Figure 2–3), the exploration area is situated in
transitional area between southern boundaries of the Mueler mountains and northern
boundaries of the foothills and lowland of South Kalimantan (Darman, 2014). This
transition represent the proximal alluvial setting in terms of sedimentary provenance.
Alluvial-terrace deposits
The alluvial-terrace deposits can be divided into two major facies associations (Figure
4; Appendix F and H), from the bottom to top: 1) Facies B (gravel and coarsed-sand
deposits), and 2) Facies A (fine-grained-sand/sand-dominated deposits).
Facies B consists mainly of interbed gravel and very-coarsed sands with common
humicrete intercalation, plant remains, lenticular-thin clay and organic clay layers.
Facies B is unconformably underlain by bedrocks and/or residual weathering of
bedrocks. This basal gravels commonly pass upwards into sands with occasional silty
and clay lenses of the Facies A. Cut and fill-erosional structures were evidently
observed.
Facies A consists mainly of sand-dominated deposits, fine–medium sized sand grains,
gravels, organic clay and plant remains are observed locally. This facies is characterized
by gradual basal interval. However, sharp extensive humicrete were also found overlain
the Facies B.
Detrital composition of the Kualakurun-alluvials consists largely of various types of
quartz grains, range between sand to cobble, rock fragments, fine-grained feldspar in
5
very small quantity, and heavy minerals. Rutile, ilmenite, zircon, garnet, Iron-oxide
(hematite), and opaque minerals were evidently observed by using a hand lens.
Elemental variation (test result)
A total of 61 elements were obtained from the laboratory test (see Table 1; Figure 5;
Appendix G.). These elements can be grouped into seven groups, arranged in decreasing
order: 1) Transition metal, such as Au, Ti, Sn, and Zr (27 elements), 2) Rare-earth
elements/REE (14 elements, divided into LREE, and HREE; 5 and 9 elements
respectively), 3) Alkaline-earth metal such as Ba, Be and Sr (5 elements), 4) Alkali
metal such as K and Na (5 elements), 5) Metaloid/semi metal such as Ge and Sb (4
elements), 6) Non-metal (P, S and Se), 7) Actinide-transition metal (Th and U).
Relative elemental variation and abundances can be seen in the table and variation
diagram (Table 1 and Figure 5). This diagram indicates that transition metal is the group
with the highest concentration in the Kualakurun alluvial deposits (1–10%). Alkali
metal and Alkaline-earth metal are the group with the second highest concentration. The
most important elements in transition metal are Al, Ti, Fe, Mn and Zr (1–10%). The
most important REE are Ce, La and Nd (<0.01%), all of which are Light REE.
This diagram does not show particular concentration trend or association of elemental
groups with particular samples. They show an overall similar patterns with some
overlapping patterns.
Gold (Au) deposit
Although now, local people operates small-scale mining and excavation for gold in the
southern and eastern part of the Kualakurun IUP areas (Appendix H), but they get only
very small and erratic gold placer. The excavation and small-scale mining in search of
gold and zircon which were operated by local people have existed in Kualakurun area,
particularly around the river valley of Kahayan since the late eighties (local residents,
pers. comm.). At that time, such traditional mining were able to collect about 5–20 g of
fine gold for several days work in one location. According to them, gold has been more
difficult to discover in recent years, and its existence is very irregular.
6
Panning tryout for gold on preserved sediments which were taken from abandoned
opencut near drilling locations, was only produced concentrate of heavy minerals
without showing any indications of gold. The panning results only medium-sand
concentrate containing heavy minerals such as rutile, ilmenite, zircon, garnet and
tourmaline medium sized sand.
Test result from laboratory (fire assay method) indicate that Au (ppm) in the sample is
found in very small quantities (maximum Au 0.305 ppm, recovered in the second run
fire assay). In total, concentration of Au (ppm) which was obtained from seven drill-
core locations is varied in the range between 0.015–0.225 ppm (g/ton). The verage
concentration of Au (ppm) which was obtained from seven drill cores is 0.042 ppm
(g/ton) (Table 3; Appendix G).
Bivariate plot (Figure 7) of indicator elements for gold between Au (ppm) and Cu (ppm)
does not show a distinct positive correlation (Kravtsova et al., 2016). The correlation
coefficient between Au (ppm) and Cu (ppm) only gives the small value (r = 0.47), this
represent a weak association. The existence of Au (ppm) is generally associated with
gravel and coarsed-grain sediments of Facies B.
Together with the Au-Cu plot, another interpretation of the gold signature elements
(Figure 6) were also conducted with other associative elements such as Ag, Fe, Mn, S,
As, Pb, Ni, Zn, and Bi (Kravtsova et al., 2016). The element data was normalized to the
average upper-continental crust concentration (McLennan, 2001). The results do not
show any anomalous patterns of the samples that should be higher when there are
anomalies. Gold (Au) value indicates 64 times higher than the average crust
concentration. However, this concentration is not indication of an anomalous
concentration since the average gold concentration in the upper continental crust-value
of about 0.0018 ppm (g/ton) (McLennan, 2001). Moreover, the value of other elements
associated with Au do not indicate any anomalies, and most of them are much smaller
than the average concentration of upper-continental crust (UCC). It can be concluded
based on the Au concentration and the above associated-element analysis, that the gold
in the exploration area has low economic potential to be developed.
7
Zircon (Zr) deposit
Zr (ppm) is a proxy for zircon mineral, because Zr is mostly concentrated in zircon
mineral. Occurrence of zircon in the studied sediments is confirmed by Zr from
laboratory test and also was suggested by the Zr/Hf plot (Figure 8A) which indicates
linear positive correlation (r=0.97). Positively correlated Zr and Hf concentrations are
due to the presence of heavy minerals in the sediments, such as zircon (ZrSiO4),
ilmenite (TiO2, FeO, Fe2O3), or rutile (TiO2).
Zircon is generally occurred as small crystals, commonly associated with the later-
formed minerals, granite and in syenite (Belousova et al., 2002). For this reason, to see
the relative importance of zircon in the samples, thus Zr was plotted in the variation
diagram (UCC-normalized samples) together with its associated trace elements such as
Ti, Nb and Y which are commonly important in granite and syenite (Figure 9). This
diagram indicates there is no Zr anomaly in the samples, that the concentration of Zr is
much lower than the average upper-continental crust (<1 UCC normalized samples). It
may suggests that the provenance of the alluvial deposits in Kualakurun were not
exclusively derived from typical felsic-igneous rocks that rich in zircon (Figure 15). A
typical first-cycle sediment which are derived from granitoid provenance that contain
zircon will have concentration of Zr greater than 500 ppm (Belousova et al., 2002). The
maximum concentration of Zr which was obtained from the Kualakurun samples is less
than 100 ppm (g/ton). It can be concluded based on the Zr concentration in the alluvial
deposits of Kualakurun, that the detrital zircon in the exploration area has low economic
potential to be developed (Table 3).
Rare earth (REE) deposit
In general, the REE-bearing placers which have economic potential are characterized by
a large concentration of REE. Its element anomalies can be several times larger than the
average upper-continental crust (Castor and Hedrick, 2006; Atwood, 2012; Hellman and
Duncan, 2014; McLemore et al., 2016). For example, REE data from the Kualakurun
were compared (Table 2; Figure 10–11) with some known high-grade REE-bearing
placer deposits (e.g. JICA, 1993; Zech et al., 1994; Orris and Grauch, 2002; Shuterland
et al., 2013; Budiharyanto et al., 2015; McLemore et al., 2016), such as Bangka Island,
8
Mesaverde-USA, Bald Mountain-USA and alluvial-placer deposits in Thailand (Khlong
Nam Khao).
Compared to the fine samples of clay and silt which were originated from bedrock
weathering, the coarser sand and gravels of Facies A and Facies B (Figure 12–13) have
slightly lower REE concentrations (in both normalized to chondrite and to upper
continental crust/UCC). However, in chondrite-normalized plot (Floyd, 1991), the REE
concentrations shows an overall similar patterns with some overlapping patterns. This
may be due to the secondary accumulation processes during weathering and surface
processes. REEs are commonly in the form of positive hydrated ions, adsorbed on the
surface of clay minerals like kaolinite, halloysite and illite (e.g. Castor and Hedrick,
2006; Atwood, 2012).
REE values which are largely derived from felsic rocks are typically represented by
highly elevated LREE together with distinct negative Eu anomaly (e.g. Floyd, 1991;
McLennan et al., 1993). In contrast, chondrite-normalized REE from the Kualakurun
shows only slightly elevated LREE together with indistinct negative Eu anomaly. It may
suggests that the provenance of the alluvial deposits in Kualakurun were not exclusively
derived from typical felsic-igneous rocks (Figure 12).
The REE concentration found in the samples taken at the Kualakurun are lower than the
values determined for the known high-grade REE deposits (e.g. JICA, 1993; Zech et al.,
1994; Orris and Grauch, 2002; Shuterland et al., 2013; McLemore et al., 2016), thus are
considered to be low potential REE deposit (Table 2–3; Figure 10–11).
Conclusions and recommendations
Test result from laboratory (fire assay method) indicate that Au (ppm) in the sample is
found in very small quantities (maximum Au 0.305 ppm, recovered in the second run
fire assay). In total, concentration of Au (ppm) which was obtained from seven drill-
core locations is varied in the range between 0.015–0.225 ppm (g/ton). The verage
concentration of Au (ppm) which was obtained from seven drill cores is 0.042 ppm
(g/ton). It can be concluded based on the Au concentration and the above associated-
element analysis, that the gold in the exploration area has low economic potential to be
developed.
9
A typical first-cycle sediment which are derived from granitoid provenance that contain
zircon will have concentration of Zr greater than 500 ppm (Belousova et al., 2002). The
maximum concentration of Zr which was obtained from the Kualakurun samples is less
than 100 ppm. It can be concluded based on the Zr concentration in the alluvial deposits
of Kualakurun, that the detrital zircon in the exploration area has low economic
potential to be developed.
The REE concentration found in the samples taken at the Kualakurun are lower than the
values determined for the known high-grade REE deposits (e.g. JICA, 1993; Zech et al.,
1994; Orris and Grauch, 2002; Shuterland et al., 2013; McLemore et al., 2016), thus are
considered to be low potential REE deposit.
Estimated abundance (grade in ppm) of gold (Au in ppm), zircon (Zr in ppm) and REE
from the samples of the Kualakurun give a values much lower than in the other places
that have been known to have potential for economic minerals, gold and REE, such as
Australia, USA and Thailand (e.g. JICA, 1993; Zech et al., 1994; Shuterland et al.,
2013; McLemore et al., 2016). In conclusion, the grade of gold (Au), zircon (Zr) and
REE in alluvial placer of the Kualakurun area are too small and low to be developed in
today's economic condition (Table 3). So it is not recommended for further investigation
at this time.
The following is a tentative interpretation to explain why the alluvial-terrace deposits in
the exploration area has low potential in economic mineral accumulations. From the
provenance point of view, the transitional situation in the proximal alluvial between
source area and alluvial entry point, can be disadvantage for economic placer
accumulation. This particular area is interpreted as bypassing zone during extensive last
glacial period when progressive alluvial terrace were developed. Thus, the economic
mineral accumulation might be concentrated at the more medial–distal part of the
alluvial system to the south and southeast. In addition, the geochemical signatures and
data interpretation indicates that the source rock of detritus for the Kualakurun alluvial
have compositional diversity (Figure 15). This means that they were not entirely derived
from the felsic-igneous rock which were enriched in economic mineral concentrations.
10
Figure 1. Simplified geographical map shows the exploration area, represented by black-empty square, to the north of Palangkaraya, the capital city of Central Kalimantan. The north–south oriented stream is the Kahayan River.
11
Figure 2. Physiographic outline of the Kalimantan, modified after Darman (2014). Exploration area indicated by filled-black square, which is approximately situated in the transition area between arcuate mountains to the north and the flank of South–Southeast Kalimantan alluvial plains.
12
Figure 3. Simplified geological map, modified after several authors. Exploration area indicated by small white square. This map illustrates basinal setting for mineral-bearing Quaternary alluvial. Wide range of felsic, mafic, volcanics and metamorphic rocks characterizing the source area to the north.
13
Figure 4. Deposits analogue for Quaternary-alluvial exploration. This stratigraphic scheme for gold and heavy mineral-bearing alluvial in the Ampalit river, is situated approximately 100 Km southwest of Kualakurun. Modified after Seeley and Senden (1994).
14
Tab
le 1
. Sum
mar
ized
ele
men
tal c
once
ntra
tion
obt
aine
d fr
om th
e la
bora
tory
test
.
15
Figure 5. Variation diagram of the seven elemental groupes which were obtained from the Kualakurun alluvial samples. This diagram shows Transition metal elements as the most important elements from the Kualakurun alluvial. Al, Ti, Fe, Mn and Zr are the highest concentrated elements (1–10%) among the transition metal group.
16
Fig
ure
6. V
aria
tion
plo
t of
the
gol
d si
gnat
ure
elem
ents
suc
h as
Ag,
Fe,
Mn,
S,
As,
Pb,
Ni,
Zn,
and
Bi
(Kra
vtso
va
et
al.,
2016
).
The
el
emen
t da
ta
was
no
rmal
ized
to
th
e av
erag
e up
per-
cont
inen
tal
crus
t co
ncen
trat
ion
(McL
enna
n, 2
001)
.
17
Figure 7. Bivariate plot of indicator elements for gold between Au (ppm) and Cu (ppm) does not show a distinct positive correlation (Kravtsova et al., 2016). The correlation coefficient between Au (ppm) and Cu (ppm) only gives the small value (r = 0.47), this represent a weak association.
18
Figure 8. A) Zr/Hf plot which indicates linear positive correlation (r=0.97). Positively correlated Zr and Hf concentrations are due to the presence of heavy minerals in the sediments, such as zircon (ZrSiO4), ilmenite (TiO2, FeO, Fe2O3), or rutile (TiO2). B) Plot of Th/Sc vs. Zr/Sc (McLennan, 1993) from various facies shows the high Zr/Sc ratio in sand-dominated facies resulting from sedimentary sorting and recycling. Other facies, were less affected by this sedimentary process, may be due to compositional variations of the provenance.
19
Fig
ure
9. Z
r w
as p
lott
ed i
n th
e va
riat
ion
diag
ram
(U
CC
-nor
mal
ized
sam
ples
) to
geth
er w
ith
its
asso
ciat
ed t
race
el
emen
ts s
uch
as T
i, N
b an
d Y
whi
ch a
re c
omm
only
im
port
ant
in g
rani
te a
nd s
yeni
te. T
his
diag
ram
ind
icat
es t
here
is
no
Zr
anom
aly
in t
he s
ampl
es,
that
the
con
cent
rati
on o
f Z
r is
muc
h lo
wer
tha
n th
e av
erag
e up
per-
cont
inen
tal
crus
t.
20
Tab
le 2
. R
EE
dat
a fr
om t
he K
uala
kuru
n w
ere
com
pare
d w
ith
som
e kn
own
high
-gra
de R
EE
-bea
ring
pla
cer
depo
sits
(e.
g.
JIC
A,
1993
; Z
ech
et a
l., 1
994;
Orr
is a
nd G
rauc
h, 2
002;
Shu
terl
and
et a
l., 2
013;
Bud
ihar
yant
o et
al.,
201
5; M
cLem
ore
et
al.,
2016
), s
uch
as B
angk
a Is
land
, Mes
aver
de-U
SA
, Bal
d M
ount
ain-
US
A a
nd a
lluv
ial-
plac
er d
epos
its
in T
hail
and
(Khl
ong
Nam
Kha
o).
21
Table 3. Summarized grades of gold (Au), zircon (Zr) and total REE for the Kualakurun alluvial deposits.
22
Fig
ure
10.
The
RE
E c
once
ntra
tion
fou
nd i
n th
e sa
mpl
es t
aken
at
the
Kua
laku
run
allu
vial
are
low
er t
han
the
aver
age
valu
es o
f th
e up
per-
cont
inen
tal c
rust
(M
cLen
nan,
200
1).
23
Figure 11. REE chondrite-normalized plot (Floyd, 1991), shows an overall similar patterns with some overlapping patterns. REE values which are largely derived from felsic rocks are typically represented by highly elevated LREE together with distinct negative Eu anomaly (e.g. Floyd, 1991; McLennan et al., 1993). In contrast, chondrite-normalized REE from the Kualakurun shows only slightly elevated LREE together with indistinct negative Eu anomaly.
24
Figure 12. Compared to the fine samples of clay and silt which were originated from bedrock weathering, the coarser sand and gravels of Facies A and Facies B have slightly lower REE concentrations (in both normalized to chondrite). However, the REE concentrations shows an overall similar patterns with some overlapping patterns. REEs are commonly in the form of positive hydrated ions, adsorbed on the surface of clay minerals like kaolinite, halloysite and illite (e.g. Castor and Hedrick, 2006; Atwood, 2012).
25
Fig
ure
13. R
EE
con
cent
rati
on (
ppm
) fr
om th
e K
uala
kuru
n w
ere
com
pare
d w
ith
som
e kn
own
high
-gra
de R
EE
-bea
ring
pla
cer
depo
sits
(e.
g. J
ICA
, 19
93;
Zec
h et
al.,
199
4; O
rris
and
Gra
uch,
200
2; S
hute
rlan
d et
al.,
201
3; B
udih
arya
nto
et a
l., 2
015;
M
cLem
ore
et a
l., 2
016)
, su
ch a
s B
angk
a Is
land
, M
esav
erde
-US
A,
Bal
d M
ount
ain-
US
A a
nd a
lluv
ial-
plac
er d
epos
its
in
Tha
ilan
d (K
hlon
g N
am K
hao)
.
26
Fig
ure
14. R
EE
con
cent
rati
on (
UC
C n
orm
aliz
ed d
ata)
fro
m th
e K
uala
kuru
n w
ere
com
pare
d w
ith
som
e kn
own
high
-gra
de
RE
E-b
eari
ng p
lace
r de
posi
ts (
e.g.
JIC
A,
1993
; Z
ech
et a
l., 1
994;
Orr
is a
nd G
rauc
h, 2
002;
Shu
terl
and
et a
l., 2
013;
B
udih
arya
nto
et a
l., 2
015;
McL
emor
e et
al.,
201
6),
such
as
Ban
gka
Isla
nd,
Mes
aver
de-U
SA
, B
ald
Mou
ntai
n-U
SA
and
al
luvi
al-p
lace
r de
posi
ts in
Tha
ilan
d (K
hlon
g N
am K
hao)
.
27
Figure 15. A) La/Th vs. Th/Yb plot showing felsic versus mafic character after McLennan et al. (1990). B) Th vs. Cr/Th for the samples. The samples indicate mixing of a continental source enriched in incompatible elements (Th) and a more mafic source enriched in compatible elements (Cr). Curves are mixing lines generated from the data points with the lowest and highest Th concentrations.
28
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TailingsTailings
Tailings
Preserved terrace deposits
Outcrop face of the Alluvial terrace deposits, exposed close to the DH-19 in local mining excavation. The succession is generally divided into two lithological associations: 1) interbedded gravel, gravelly-sand, coarse sand, humicrete and plant remains in the lowermost interval, and 2) interbedded sandy-clay, sand, clay, and organic clay in the uppermost interval.
Tailings
Preserved terrace deposits
Outcrop face of the Alluvial terrace deposits, exposed near DH-40 in local mining excavation. The succession is generally divided into two lithological associations: 1) interbedded gravel, gravelly-sand, coarse sand, humicrete and plant remains in the lowermost interval, and 2) interbedded sandy-clay, sand, clay, and organic clay in the uppermost interval.
Facies B
Facies A
A concentrated accumulation of mineral grains (zircon, ilmenite, etc.) in few cm’s impersistent layer which is typically associated with the lower-gravelly-terraces deposits. This example is taken at the outcrop face in front of DH-09
Gravel-bed as coarse lag deposits, heavy mineral accummulation are normally found in such deposits.
Facies B
Facies A
Perform additional channel sampling near the drilling site which has poor core-drilling recovery. (Ref. Halloran, 2013, Prospecting & Mining Journal, vol. 82, n. 11)