SRD41-01

Room:106

Time:May 25 09:00-09:25

Chemical analysis of individual fluid inclusion by SXRF: application to hydrothermal ore
deposits
HAYASHI, Ken-ichiro1∗
1

Faculty of Life and Environmental Sciences, University of Tsukuba

Information on chemical composition of ore-forming fluid is significant when discuss the origin and evolution of ore-forming
fluid, dissolution and transportation mechanisms of heavy metals and precipitation mechanisms of ore minerals. Salinity of fluidinclusion has been extensively reported, however data of heavy metals is scarce. Chemical compositions of individual fluidinclusion are measured recently with a development of micro-analytical techniques. Examples of SXRF analysis of individual
fluid inclusion are described.
Chemical compositions of ore-forming fluid responsible for vein-type W deposit at the Takatori mine was measured. Four mineralization stages are distinguished at the deposit, such as early wolframite-fluorite-topaz-muscovite-lepidolite, middle sulfidefluorite, late carbonate-cassiterite and final carbonate-clay mineral stages. Quartz is accompanied in all these stages. Pseudosecondary fluid inclusions hosted in quartz are selected for chemical analyses. Temporal relation of these inclusions is determinedfrom cross-cut nature of trails that accompany fluid inclusions. SXRF analyses suggest compositions of ore-forming fluid asfollows. Metal concentrations in early stage fluid are very high as 1400-3700 ppm W, 4100-6200 ppm Fe, 1000-1800 ppm Mn,
1500-3000 ppm Cu and 1800-2900 ppm Zn. Middle to late stage fluids contains 300-600 ppm Fe, 100-300 ppm Mn, 50-100 ppm
Cu and 50-100 ppm Zn with less than detection limit of W. Concentrations of ore-forming metals in fluid decreased remarkably
with mineralization.
Vapor-liquid partitioning coefficients for Cu and Zn in aqueous fluid were determined under boiling conditions at 500-650℃ and 35-100 MPa in sulfur-bearing and sulfur-free systems. A synthetic fluid inclusion technique was used to sample theexperimental system coexisting vapor-rich and liquid-rich fluid inclusions, with the Cu and Zn concentrations in individual fluidinclusions then analyzed by SXRF. The vapor-liquid distribution constant of Cu (KD = mCu(vapor) /mCu(liquid) ) is found to bestrongly dependent on the sulfur content in the experimental solutions. In sulfur-bearing systems, Cu preferentially partitions
into the vapor phase, whereas Zn preferentially fractionates into the hypersaline liquid. The KD values for Cu and Zn obtainedin this study correspond well with those obtained from natural fluid inclusions in hydrothermal ore deposits. The results suggestthat differential volatility of metals is an important factor affecting the enrichment of certain metals in different hydrothermal ore
deposits.

Keywords: fluid inclusion, SXRF, chemical analysis, ore-forming fluid

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SRD41-02

Room:106

Time:May 25 09:25-09:40

Characteristics of Magmatic Hydrothermal System at Southeastern Martabe High Sulfidation Epithermal Deposit, Indonesia
SAING, Stephanie1∗ ; TAKAHASHI, Ryohei1 ; IMAI, Akira1
1

Graduate School of Engineering and Resource Science Akita University

The Martabe Au-Ag deposit, North Sumatra Province, Indonesia is a high sulfidation epithermal deposit, which is hosted by
Neogene sandstone, siltstone, volcanic breccia, and andesite to basaltic andesite of Angkola Formation. The deposit has six
ore bodies that occur as silicified massive ore (enargite-luzonite-pyrite-tetrahedrite), quartz veins (tetrahedrite-galena-sphaleritechalcopyrite), banded sulfide veins (pyrite-tetrahedrite-sphalerite-galena) and cavity filling. All ore bodies were controlled by
N-S and NW-SE trending structures. The Barani and Horas ore bodies are located in the southeast of the Purnama ore body. Fluid
inclusion microthermometry and alunite-pyrite pairs sulfur isotopic geothermometry show slightly different forming temperature
among the ore bodies. Formation temperature of the Purnama ore body ranges from 215 to 260o C and salinity from 5 to 8 wt%
NaCl equivalent. Formation temperature of the Barani ore body ranges from 200 to 240o C and salinity from 0 to 2.5 wt% NaClequivalent and those of the Horas ore body ranges from 240 to 260o C and from 2 to 3 wt% NaCl equivalent, respectively. The
general sequences of mineralization at Martabe are divided into the early stage as main high sulfidation mineralization stage andthe late stage of oxidation and brecciation, which were followed by weathering. Sulfides (enargite-luzonite-pyrite-tetrahedrite)that were associated to gold and silver are abundant at the Purnama ore body. The Barani and Horas ore bodies are less silicified
and sulfide abundance is less than the Purnama ore body. The salinity and sulfur isotopic values indicate a mixing trend among
different fluids. Salinity of fluid inclusion decrease from higher salinity (› 5 wt% NaCl equivalent) in the Purnama ore bodyto lower salinity (‹ 3 wt% NaCl equivalent) in the Barani ore body which is directly located in southeast of the Purnama ore
body. The sulfur isotope ratio values of sulfide and sulfate in Purnama range from -4.2 to +5.5 ‰ and from +1.2 to +26.7 ‰, and those in the Barani range from -4.3 to +26.4 ‰ and from +3.9 to +18.5 ‰, respectively. The Horas ore body shows low
salinity but higher formation temperature compared to Barani which possibly indicate different mixing condition unrelated with
Purnama and Barani ore bodies. The sulfur isotope ratio values of sulfide and sulfate in the Horas ore body range from -11.8 to+3.5 ‰ and from +1.37 to +25.7 ‰. At the Purnama and Barani ore bodies, alteration assemblages consist of quartz-kaolinitedickite - alunite - illite - pyrophillite and ore mineral assemblages are mostly composed of enargite-luzonite-pyrite-tetrahedrite.
In contrast, mineralization style at the Horas ore body including the alteration assemblages (quartz - alunite - illite - dickite muscovite) and ore forming temperature is different from the Purnama and Barani ore bodies.
Keywords: epithermal high sulfidation, sulfur isotope, fluid inclusion microthermometry

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SRD41-03

Room:106

Time:May 25 09:40-10:00

Lithium isotope index as powerful research tool for earth resource
NISHIO, Yoshiro1∗
1

JAMSTEC

Lithium (Li) is one of important natural resources, because Li is used for secondary battery of electric and/or hybrid vehicles.
The lightest alkali element, Li, is one of fluid-mobile elements. The leaching of Li from sediments into fluids is dramaticallyelevated together with increasing temperature, and the fact that subsequent re-uptake of the leached Li from the fluid by sediments(which occurs as the fluid cools) takes a considerable time. Li is relatively unaffected by surface water contamination because
the Li contents of deep-rooted fluid samples are much greater than the surface water content. The two stable isotopes of Li are6
Li and 7 Li, and their relative abundances are about 7.5% and 92.5%, respectively. Furthermore, the difference in the 7 Li/6 Li
ratio between fluid and solid phases varies with the reaction temperature. As a result, the Li isotope ratio is a potentially usefulgeothermometer because the Li cation is monovalent and hence not redox sensitive, and it is not a nutrient, so it does notparticipate in biologically mediated reactions.
In this presentation, I’ll talk about fundamental feature of Li isotope tool at first, and after then I show the potential of Li
isotope tool for earth resource science.

Keywords: lithium isotope, deep crustal fluid, geochemical thermometer, fluid inclusion

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SRD41-04

Room:106

Time:May 25 10:00-10:15

Li isotopic composition of submarine vent fluids from arc and back-arc hydrothermal systems in the western Pacific
ARAOKA, Daisuke1∗ ; NISHIO, Yoshiro2 ; GAMO, Toshitaka3 ; YAMAOKA, Kyoko4 ; KAWAHATA, Hodaka3
1

GSJ, AIST, 2 JAMSTEC, 3 AORI, The Univ. of Tokyo, 4 GSJ, AIST

Submarine hydrothermal systems significant contribute to heat and elemental fluxes to the ocean. Vent fluid geochemistry in
mid-ocean-ridge (MOR) hydrothermal systems were well-studied, while studies on vent fluid geochemistry in arc and back-arc
systems with various geological characteristics were insufficient, especially in terms of lithium. To reveal control factors onlithium in arc and back-arc hydrothermal systems and lithium isotopic behavior in water-rock interaction at high temperature,
we determined Li contents and its isotopic compositions of 11 vent fluids collected from 5 submarine arc/back-arc hydrothermal
systems in the western Pacific.
Based on mass balance calculation, Li in vent fluids are dominated by seawater-rock (seawater-sediment) interaction in
sediment-starved (sediment-hosted) hydrothermal systems in arc and back-arc basins at equilibrium. Li contents in vent fluids is also influenced by phase-separated processes, by temperature-related portioning of rock Li into fluid phase, and by hostrocks and sediments. In contrast, Li isotopic composition in vent fluids is affected by host rocks and sediments, but not by phaseseparated processes. These results demonstrate that lithium is a useful tracer for investigating geological processes occurredunderground such as a phase separation process and water-rock/water-sediment interaction at high temperature.
Keywords: submarine hydrothermal system, lithium isotope ratio, vent fluid, arc, back-arc basin

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SRD41-05

Room:106

Time:May 25 10:15-10:30

Salinity of pore waters in sedimentary basins under geothermal gradients
YOSHIMURA, Shumpei1∗1Dept. Earth Environ. Sci., Yamagata Univ.

The pore waters in sedimentary basins are crucial in the control of diagenesis, sediment-hosted ore formation, and generationand transport of hydrocarbons. The chemical and hydrological properties of the pore waters are therefore of importance in theunderstanding of these geological phenomena. An increasing number of studies reported that the pore waters often have higher
salinity than seawater, and the salinity generally increases with the increase of the depth (e.g., Kharaka and Hanor, 2003). Suchsalinity distribution has been often attributed to infiltration of brines from underlying halite beds. However, the downward salinity increase is observed also in basins that are lacking halite beds (e.g., Xie et al., 2003). Therefore, more general mechanisms
may exist for the formation of the salinity distribution.
In this study, I demonstrate on the basis of thermodynamics that the chemical equilibrium of the saline water in a sediment column under gravity and the pressure and geothermal gradients results in the downward salinity increase. The chemical potential ofsolute is the function of pressure, temperature, concentration, and gravity potential. The pressure term increases with increasing
the depth, whereas the temperature term and the gravity potential decrease. The sum of these terms generally decreases with theincrease of the depth. In the final equilibrium state, the chemical potential should be constant along the column. Therefore, we
consider that the concentration term increases to keep the chemical potential constant, leading to the downward salinity increase.
Assuming that the pore water is the NaCl-H2O mixture, I calculated the concentration of NaCl in the solution using the modelof Pitzer et al. (1984) and Rogers and Pitzer (1982). The calculations showed that the salinity increased from 32 to 208 g/L in
the 2000 m-thick sediment column under the geothermal gradient of 0.05 K/m. Such a salinity increase is in the same order tothose observed in many sedimentary basins. In an isothermal case, the salinity increased only weakly, and it reached 36 g/L. This
result is consistent with the conclusion of Mangelsdorf et al. (1970) that gravity alone does not explain the observed enrichmentof salinity. If we set the salinity at the top of the column at 1 g/L, it increased to 24 g/L under the identical condition. Therefore,
the high-salinity waters are generated in fresh to brackish environments.
This study showed that the simple chemical equilibrium along the sediment column resulted in the downward salinity increase.
The method proposed here may be applicable to studies of fluids in other geological systems, such as in mantle, crustal rocks,
hydrothermal environments, and magmatic systems.
Keywords: pore waters, salinity, sedimentary basins

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SRD41-06

Room:106

Time:May 25 10:30-10:45

Distribution of rare earth elements between deep granitic groundwater and fracture fillingcarbonate
MUNEMOTO, Takashi1∗ ; OHMORI, Kazuaki1 ; IWATSUKI, Teruki1
1

Japan Atomic Energy Agency

The chemical properties of rare earth elements (REEs) and yttrium (YREE) have been widely studied as geochemical tracer
in aqueous environments. The YREE abundances in groundwater are mainly regulated by mineral-water interaction. The YREE
variability in natural groundwater system is very complex and dependent upon geologies, water flow-path, mixing and chemical
condition of groundwater. We investigated distribution of rare earth elements (YREE) between deep granitic groundwater withdiverse geochemical character and fracture filling calcite in order to understand YREE behavior in natural groundwater systems.
In Tono area, central Japan, the chemical types of groundwater varied with depth; Na-HCO3 type of groundwater in sedimentary rock, Na-Cl type in upper part of base rock granite and Ca-Cl type in deeper granite. The Na-Cl type groundwater
was collected using boreholes from 200, 300 and 400 m, the Ca-Cl type from 650 and 1150 m below ground surface. The
concentrations of YREE were measured by ICP-MS. The fracture filling calcite was obtained from drill core of boreholes similar
to the groundwater sampling. The collected samples were dissolved into 1M NH4 -acetate buffer solution (pH = 4.8) and theconcentrations of YREE in the leached solutions were measured by ICP-MS. Furthermore, in order to assess the precipitation
condition, we measured isotopic composition of O and C for calcite.
Chondrite-normalized YREE patterns of Na-Cl type groundwater exhibited enrichment in heavy REEs relative to light REE,
which was well explained by the predominance of YREE carbonate aqueous complex in the groundwater. On the other hand,
YREE patterns of Ca-Cl type groundwater were enriched in middle REEs (MREEs). In addition, Y/Ho of the Ca-Cl typegroundwater was significantly lower than that of chondrite. MREE-enrichment in natural water occurs from dissolution of
MREE-enriched Fe-oxyhydroxide [1], and lower Y/Ho than chondrite is common in distribution patterns of Fe-oxyhydroxide[2]. The concentration of Fe in the groundwater increased with depth and the Eh measurement of the groundwater showedstrongly reducing condition. Consequently, YREE in the Ca-Cl type groundwater can be explained by dissolution of MREE-rich
Fe-oxyhydroxide with sub-chondritic Y/Ho.
Oxygen isotopic composition of fracture filling calcite varied regardless of depth. The correlation between precipitation temperature and depth was not observed. On the other hand, carbon isotopic composition became heavier with depth. This result
indicates the fracture filling calcite precipitated from mixture of seawater and freshwater. For YREE patterns of fracture filling
calcite collected from 200˜400 m depth exhibited negative Eu anomaly, while the samples from 670˜1294 m along borehole
showed positive Eu anomaly when the YREE contents were normalized by granite. For the fracture filling calcite from 200˜400
m depth were precipitated from groundwater with YREE eluted from granite, because the negative Eu anomaly has been observedin mother rock granite [3]. Therefore, the positive Eu anomaly in calcite indicates that the groundwater precipitated calcite wasenriched in Eu.
[1] Johannesson and Zhou, 1999, Geochim. Cosmochim. Acta 63, 153-165.
[2] Bau, 1999, Geochim. Cosmochim. Acta 63, 67-77.
[3] Takahashi et al., 2002, Chem. Geol. 184, 311-335.

Keywords: rare earth elements, granite, groundwater

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SRD41-07

Room:106

Time:May 25 11:00-11:15

Fractionation between LREE and HREE in hydrothermal fluids associated with felsicmagmatism
SANEMATSU, Kenzo1∗ ; HOSHINO, Mihoko1
1

Geological Survey of Japan, AISTAs crustal abundances of heavy rare earth elements (HREE) are generally smaller than those of light rare earth elements(LREE), HREE are more expensive than LREE in the market. HREE-rich deposits (e.g., Longnan in China, Nechalacho in
Canada) are associated with hydrothermally-altered felsic igneous rocks such as granite and syenite. This study aims to discuss
what caused the fractionation between LREE and HREE in such igneous rocks.
Alkaline rocks, formed by magma with a low degree of partial melting, are significantly enriched in LREE and are weakly
enriched in HREE because LREE are more incompatible than HREE in magma because of their larger ionic radii. Igneous rocks,
which can be HREE-rich deposits, are probably formed by either process of alkaline magmatism enriched in certain elements
and fractional crystallization. The former is represented by intercontinental alkaline rocks such as the Nechalacho deposit andis rich in REE, HFSE (high field strength elements), fluorine and carbonate. Previous experimental studies found that solubilityof zircon is high when magma is rich in alkali elements and/or fluorine and this causes the residual melt to contain more HREE
and Zr. On the other hand, calc-alkaline granite can be a source rock of HREE-rich deposits, as represented by the Longnan
deposit. The intensive magmatic differentiation and fractionation of LREE-bearing minerals may cause the residual melt to beenriched in HREE relative to LREE. For REE ore formation, however, such deposits require further processes including thedeuteric alteration, dissolution of REE-bearing minerals and adsorption of REE during weathering.
Fractionation between LREE and HREE by complexing with various ligands is likely to occur in hydrothermal fluids produced
from felsic igneous rocks. Different previous works have suggested that REE3+ ions are complexed with carbonate, bicarbonate,fluorine, chlorine and sulfate ions. A recent study indicates that REE-fluoride complexes do not have a significant role intransportation or fractionation of REE because of their lower stability than REE-chloride and sulfate complexes above 150 ℃(Migdisov et al., 2009). However, it appears that footprint of saline fluids or sulfate minerals are not very common compared toabundant carbonatite and fluorite in REE deposits.
The HREE-rich igneous rocks are commonly accompanied by alkali alteration and fluoritization in many ore deposits andprospects, however alkali igneous rocks containing high alkali or fluorine contents are not necessarily rich in HREE. REEfluoride complexes are not significant in hydrothermal fluids, however there are insufficient data to determine an importance ofchlorine or sulfate ions in complexing with REE. Fractionation between LREE and HREE in REE deposits still remains unclear
and further studies are expected to elucidate which is the more significant process for the REE fractionation, magmatism orhydrothermal alteration.
Reference
Migdisov, A.A., Williams-Jones, A.E. and Wagner, T. (2009) Geochimica et Cosmochimica Acta, 73, 7087-7109.
Keywords: HREE, LREE, hydrothermal fluids, fractionation, ore deposits, felsic igneous rocks

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SRD41-08

Room:106

Time:May 25 11:15-11:30

Petrogenesis of granitoids in northern Palawan (Philippines) and its implications on rareearth element mineralization
PADRONES, Jenielyn1∗ ; IMAI, Akira2 ; TAKAHASHI, Ryohei2 ; GABO, Jillian aira3 ; TANI, Kenichiro4
1

Graduate School of Engineering and Resource Sciences, Akita University, Japan, 2 Faculty of International Resource Sciences,
Akita University, Japan, 3 Department of Earth Resources Engineering, Kyushu University, Japan, 4 Department of Geology andPaleontology, National Museum of Nature and Science, Japan
Global attention brought about by the increasing demand of rare earth elements (REE) has paved the way for various exploration efforts worldwide. Areas with promising REE deposits were revisited. In the Philippines, explorations are now on-goingwith studies focused on several granitic intrusions. Some of these granitic bodies are distributed in northern Palawan, which is arifted fragment of the southeastern Eurasian margin during the opening of the South China Sea basin in the Oligocene.
The granitic bodies were investigated for possible concentration of REE during magmatic differentiation. The Kapoas granitoids include granites and granodiorites that are metaluminous, high-K calc-alkaline, and belong to the I-type and ilmenite-series.
The granitoids are mostly biotite-rich and contain xenoliths of schists and diorite, quartz xenocrysts, and mafic enclaves. Two
separate intrusive bodies are observed: the Mt. Kapoas which is 13.2 Ma in age; and the Bay Peak granite which is dated 14.1 Ma.
However, both intrusives have similar geochemical signature, which show LREE enrichment. These granitic rocks were more
evolved or highly differentiated I-type, probably generated in the middle to lower continental crust . The REE-bearing minerals
are allanite and monazite. The weathered crust also show LREE enrichment. Weathered crust profile shows Ce-anomaly in the
B-horizon portion where kaolinite, muscovite and illite act as absorptive materials.
This study also confirmed the presence of the Cretaceous Daroctan granitoids aside from the well-studied Middle Miocene
Kapoas granitoids. The Daroctan granitoids include granodiorites and granites which belong to ilmenite-series. The granodiorites contain xenoliths of metasedimentary rocks, quartz xenocrysts and mafic enclaves. It is also sporadically distributed in thenorthern part of the island but these different intrusive bodies have almost similar ages. The REE-bearing minerals are monazite.
Enrichment of LREE in the weathered crust is relatively higher than that of the Kapoas.
Allanite and monazites in the study areas are enriched in Ce, La, Nd, and Sm with associated radioactive element Th. Heavy
minerals concentrated in the beach in Erawan and Ombo, which is part of the Kapoas granitoids, contain up to >10,000 ppm of
La, Ce, and Sm.

Keywords: Palawan Continental Block, Kapoas granitoids, rare earth element mineralization, monazite, allanite

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