Heat transport by fluid migration is potentially faster than heat conduction through solid rock, because of rate of fluid migration is independent from temperature gradient and thermal conductivity of solid rock. Fluid in crust should be melt when pressure and temperature are appropriate. Water-rich fluid may assist to decrease solidus temperature of rocks and viscosity of melt. Melts release a large amount of latent heat when solidification occurs. Therefore, melt migration coupled with release of latent heat is the most efficient mechanism for heat transport. In addition to this, melt migration and solidification cause modification of crustal composition. Therefore, it is expected that melt migration should be important role in evolution of the earths crust. I present results of evaluation of role of melt migration in Cretaceous high-T metamorphic belts in the inner zone of the southwest Japan.

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In the N.Qaidam UHP terrane, quartzo-feldspathic gneisses contain minor amount of mantle-derived garnet peridotite, and the Shenglikou peridotite massif is the largest peridotite body among them, which are mostly composed of garnet lherzolite and garnet pyroxene rocks. Previous study proposed that saline-rich fluid activity took place in the Shenglikou peridotite prior to the UHP metamorphism. In this study, we carefully examine the chlorine concentration of the hydrosilicate that were formed during the prograde stage of metamorphism to test the hypothesis of prograde saline-rich fluid activity. In the Shenglikou peridotite, large garnet porphyroblasts with several mm diameters are commonly observed, and they contain numerous prograde amphibole crystals. Furthermore, such porphyroblast are replaced by secondary amphibole at the rims. Analyses of these prograde- and retrograde-amphibole crystals demonstrated that prograde ones contain systematically higher chlorine. This result indicates supports the view that the peridotite was altered by saline-rich fluid during the prograde stage prior to UHP metamorphism.

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Fluid–rock interaction and deformation in ultramafic melange were studied using the isocon method. In ultramafic melange in the Nishisonogi metamorphic rocks, pelitic-schist blocks have albitized rims. The isocon analysis indicates losses of H₂O and C, decoupling of LILE from HFSE and REE, and solid-volume change of about -20 % during albitization. The decrease in solid volume could reduce pore-fluid pressure and promote influx of fluid and deformation of rocks. Similarly, jadeitite blocks have albitite rinds. The isocon analysis indicates gains of K₂O, H₂O, Sr and Ba, losses of SiO₂, Na₂O and Fe₂O₃, and solid-volume change of about +10 % during albitization. The albitite rinds could protect the jadeitite cores from retrogression, because the increase in solid volume reduces permeability.

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To help identification of K-cymrite (KAlSi3O8*H2O) and its anhydrous form (kokchetavite) in UHP metamorphic rocks, K-cymrite and kokchetavite are studied by Raman spectroscopy. K-cymrite is produced at 5 GPa and 800 C. Kokchetavite is made by dehydration of K-cymrite heating up to 800 C. In-situ high pressure Raman spectra of two phases are obtained using diamond anvil cell. Raman shifts of the main peak for K-cymrite and kokchetavite are 380 and 390 cm-1, respectively. Our result reveals that the previously reported K-cymrite from China (Zhang et al., AM, 2008) would be kokchetavite rather than K-cymrite. Pressure dependences of Raman shifts for main peaks for K-cymrite and kokchetavite are 4.9 and 5.6 cm-1/GPa, respectively.

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Whiteschist is a metamorphic rock type characterized by the occurrence of kyanite-talc assemblage, and extremely high MgO and Al2O3 bulk composition (Schreyer, 1977). Alpine geologists suggested two main genetic hypotheses; metasomatic or sedimentary. The metasomatic interpretation was mainly derived from the close field association of orthogneiss and whiteschist (Bearth, 1952).According to the sedimentary hypothesis, the whiteschist protolith is a highly magnesian meta-evaporite or an Mg-rich metapelite (Schreyer, 1977).We present recently obtained several lines of evidence suggesting the metasomatic origin of the whiteschist, which was formed by the influx of Mg-rich fluid into shear zones developed in granitoids under Alpine HP conditions.

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The Godzilla Megamullion, the largest oceanic core complex, is located at the extinct Parece Vela Basin spreading ridge in the Philippine Sea. Fault rocks are common on the surface of the Godzilla Megamullion, indicating the presence of a detachment fault exposed on the seafloor (Harigane et al., 2011a). Based on a study of deformed gabbroic rocks at the breakaway region, Harigane et al. (2008) showed that the hydrothermal metamorphism occurred retrogressively, associated with deformation in the lower crust related to the detachment fault. But the origins of fluids and the fluid/rock ratio during deformation are still unsolved. Here, we present trace element geochemical analyses of amphibole and clinopyroxene of the gabbroic rocks sampled from the medial area of the Godzilla Megamullion.

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Metamorphic rock is a unique substance that directly records physco-chemical conditions of subduction zone processes such as pressure, temperature, deformation and mass transfer. In this study, pressure-temperature-time path and associated mass transfer were simultaneously acquired from the same sample, same mineral zoning, which provides quantitative mass transfer with time resolution.

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It is well known that there is difference in partial melting degree between forearc and mid ocean ridge peridotite. However, those data of forearc peridotite are almost from the Izu-Bonin-Mariana region. In this study, we tried to reveal the melting processes and the origin of the mabtle peridotite in the Ust'-Belaya ophiolite and state the above problem.

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Diopsidites and anorthite diopsidites are dykes of hydrothermal origin present in the mantle section of the Oman ophiolite. Their textural, mineralogical and chemical characteristics are compatible with a genesis process by high Ca-metasomatism at high to very high temperature. They show variation in their mineralogical assemblages ranging from diopside with more or less tremolite and antigorite to anorthite+diopside and compatible with a crystallisation temperature varying from 650 to 850°C or more.

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The distribution of elements between coexisting immiscible silicate liquids could be useful for an understanding of the evolution of lunar crust, and/or of the process of fluid inclusions in rocks because such liquids might correlate with the transportation of elements from upper mantle to crust, and crystallization differentiation. In the present study, partitioning of major, trace and rare earth elements (REEs) between immiscible liquids coexisting with liquidus zircon was determined at the atmospheric pressure and 1300 degree-C. Our analytical result for the run product at 1300 degree-C revealed that Si, Al, K, Rb, Cs and Hf are enriched in the Si-rich liquid, as compared to the Si-poor liquid.

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The metamorphic rocks formed in the plate boundary have common banding structures which composed of albite and quartz and chlorite layers. Their banding interface shows wavy having unique dominant wavelength. The available model for this phenomenon is based on the coupling of metasomatic instability proposed by the author and shear instability along on the banding surface. The characteristic wavelength is controlled by boundary migration velocity and diffusion rate of ionic components in interstitial solution.

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Under middle-upper crustal conditions, there is the system that solution-precipitation creep of minerals can be dominant in addition to dislocation creep of quartz. Feldspar is the major constituent in the crust as well as quartz, and its solution-precipitation creep has recently been focused. However, there are a lot of points to be considered for solution-precipitation creep of feldspar, and in this study we discuss: (1) microstructures of K-feldspar involved in solution-precipitation process by mapping measurements of electron-backscatter-diffraction, (2) water distribution by mapping measurements of infrared spectroscopy, and (3) quantitative estimation of diffusivity at intergranular regions by using an analogue by high temperature in-situ infrared spectroscopy.

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We have detected that injected fluid in link thrust would cause fault propagation and fault lubrication due to vapor-separation from the fluid from the great link-thrust, Lishan fault, in Taiwan orogenic belt. In order to measure fluid chemistry, PIXI analysis was done. The result is summarized as follows. 1) Br/Cr ratio is lower than seawater, 2) Ti, Cr, Ni content is signifantly high, suggesting that fluid is related to magma activity beneath, and 3) Vapor-phase inclusion contains considerable amount of metal elements (Ti, Zn, Ge, Mn, Ca, Fe, Pb, Rb, Cu) as well as K, and Br.

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In order to estimate water content in the low velocity anomalies of the crusts, it is important to understand the influence of geofluids on the elasticity of crustal materials. Here we examined the effect of fluid on compressional wave velocities (Vp) and shear wave velocities (Vs) for gabbronorite at pressures to 1.0 GPa and temperatures to 1073 K corresponding to lower crusts of island arcs.

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Franciscan eclogite/blueschist blocks from Jenner beach, California were formed at ∼17 kbar and ∼490 degree Celsius. These blocks suffered retrogressive hydration and equilibration at 7-9 kbar, <280 degree Celsius under fluid absent conditions.

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Serpentinization in subduction zone affects physical and chemical properties of mantle rocks, and the circulation of water and mantle dynamics. In this study, serpentinization processes of Iwanai-dake peridotite, Kamuikotan belt, Hokkaido, have been investigated with petrological observations, chemical analyses, measurement of density and magnetic susceptibility. The results demonstrate that the peridotite body experienced two-stage serpentinization.

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we investigated the P-T conditions and paths of the Kamuikotan metamorphic rocks. The rocks in the Kamuikotan gorge area was characterized by mineral assemblages of the greenshist facies, the range of P and T of which is constrained by the Pseudosection method, as P = 3.4-4.7 kbar and T = 275-300°C. In addition, we estimated conditions for trapping of fluid inclusions in quartz as P = 2.5 kbar and T = 300°C. And, we have inferred that the metamorphism of greenshist facies was the retrogressive metamorphism caused by fluid infiltration in the rocks, because in the rocks Na-amphiboles are surrounded by fine-grained actinolite and many mineral veins exist. On the other hand, for the rocks in the vicinity of the Etanbetsu Pass, compositional analysis of the zonal structure of amphibole and epidote revealed at least two types of P-T paths in this area.

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Calc-silicate rocks develop at the lithological boundaries between khondalite and dolomitic marble (Yoshida et al., 1976; Matsueda et al., 1983) in the Skallevikshalsen, Lützow-Holm Complex, East Antarctica. These calc-silicate rocks also occur as discordant dykes in the khondalite layer. Khondalite progressively changes to Grt-Spl-Bt gneiss (GSB), Grt-Opx-Bt gneiss (GO) and charnockite (CH) toward the calc-silicate dykes. Based on the Isocon analysis (Grant, 1986) of the GS-CH, we consider that (1) partial melting and subsequent melt-segregation occured in the GSB, triggered off by the infiltration of the H2O-rich fluids from the calc-silicate dykes, (2) GO were formed by the mixing of GS and calc-silicate dykes (or melt), (3) CH were formed by the mixing of granitic melt and calc-silicate dykes.

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Felsic gneisses were affected by at least two fluid-rock interaction events during granulite-facies metamorphism. The charnockitization-related fluid event and an additional Ca-Fe metasomatic event could be identified in metasomatized felsic gmeisses in Madagascar. At this locality, the metasomatised part display a distinct change in mineral assemblage. The results were achieved by petrographic analysis and point counting in selected thin sections. The results suggests that Ca-Fe metasomatism was occured late during the fluid infiltration history.

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Sr and Nd isotope compositions of migmatites and leucogranites in the highest grade zone of the Higo low-P /high-T (andalusite-sillimanite type) metamorphic terrane, central Kyushu, Japan, suggest that the nebulitic migmatites (diatexite) formed by melt infiltration into the pelitic gneisses, and the stromatic migmatites (metatexite) by in situ partial melting of the pelitic gneisses. The nebulitic migmatites preserve a record of large magnitude Sr and Nd isotope disequilibrium with the pelitic gneisses, which show the isotope equilibrium with the stromatic migmatites.

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We examined fluid-rock interactions and their scales in the Finero mafic-ultramafic complex, Italy.

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We described petrological and geochemical characteristics of bottom peridotites of Oman ophiolite overlying metamorphic sole, garnet amphibolite, in northwestern Fizh block as an analogue of slab-mantle interface in mantle wedge. The bottom peridotites are slightly serpentinized lherzolite and harzburgite, and commonly include amphiboles (hornblende and tremolite). Modal proportions of amphiboles systematically decrease with increase of the distance from the garnet amphibolite-peridotite boundary. Clinopyroxene and hornblendes in peridotites close to the boundary have LREE-enriched characters, and the degree of LREE enrichment decrease with increase of the distance from the boundary. In addition, hornblendes in the peridotite close to the boundary are extremely rich in Rb and Ba (20 times higher than chondrite). The bottom peridotites are surely hydrated, and LREE and some LILE are added to them during the hydration.

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We have analyzed element migration in drill core penetrating the Median Tectonic Line, southwest Japan with X-ray fluorescence analysis. It has been found out that the amount of SiO2 increased accompanied by the mass increase with increasing cataclasis at first, which is followed by decrease in the amount of SiO2 accompanied by the mass decrease with further increasing cataclasis (i.e. two-stage development of cataclasite).

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In order to clarify the generation mechanism of slickenside, we observe the microstructures of faulted chert, which is composed of the Jurassic accretionary complex in eastern Yamaguchi Prefecture. The chert is a pale blue to white color itself, but the surface of slickenside shows up as black. The observation by a stereo microscope indicates the surface of slickenside is covered by transparent-Si-material. On the thin section parallel and perpendicular to striation and slickenside, respectively, the elongated quartz grains containing many inclusions are oriented obliquely to the slickenside with 20-30 degree. These quartz grains show strong undulose extinction and bulging-recrystallization. TEM observation indicates the amorphous layer with several ten nanometers in width distributes along the slickenside. These results suggest the slickenside was generated by the frictional melting of quartz grains on slip plane.

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Based on the helium isotopic composition and the systematics of oxygen and hydrogen isotopes, the Arima brine is deduced to be originated from a subducted slab. Beneath the Arima area,the Philippine sea and the Pacific plates are subducting 50~70km and 450km depth ,respectively. In this study,we first establish the methods to determine the composition of trace element of hotspring containing highly alkaline chloride, and aim to detect the contribution of slab-derived fluid.

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The results of fluid-flow experiments revealed a significant permeability anisotropy in highly sheared serpentinite. Fluid flow parallel to the serpentinite foliation is an order of magnitude or more higher than that normal to the foliation at confining pressures as high as ~50 MPa. Although buoyancy is the driving force of upward fluid flow in the mantle, the strong anisotropy in permeability results in preferential fluid migration along the subducting plate interface, where extensive plastic deformation and a strong crystal-preferred orientation are expected to occur. The development of a relatively thin hydrous layer in the mantle wedge is consistent with the occurrence of highly anisotropic fluid migration rather than vertical flow.

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Low P-wave velocity in the shallower part of the backarc mantle has been observed throughout eastern Asia. Elucidation of the origin of the local seismic anomaly offers a clue to clarification of the mantle dynamics in the backarc. The depth provenances of mantle xenoliths in far eastern Russia are correlated with equilibrium temperatures. Assuming that the correlation reflects the geotherm in this region, it corresponds to heat flow of ∼100 mW/m2. Such high heat flow in the backarc is consistent with the geothermal gradient supposed in the Big Mantle Wedge (BMW) model. We report noble gas isotopic compositions of BMW-derived xenoliths to reveal the occurrence of the subduction related fluid in BMW. The results can be interpreted as contribution of deep seawater with addition of radiogenic components. It is most likely that the atmospheric signature were originated from the subducting oceanic plate.

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Partition coefficients between high Mg andesite and aqueous fluids with and without (Na, K)Cl under high-pressure and high-temperature conditions suggest slab fluids can be saline solutions.

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After being found in the adak island of Aleutian Arc, the adakite had been thought to be caused by the melting of subducting slab. For the last decade, the distinct composition has been detected in many various arcs (e.g., Defant & Kepenzhinskas, 2001). In this study, we newly report the adakite in cold tectonic setting beneath central Japan where the double plates subduct, and discuss its generation and thermal condition of mantle wedge.

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We found the graphite-bearing orthopyroxene vein from Tallante peridotite xenolith (SE Spain). We did the pertological study of the vein and revealed that the vein was derived from slab-derived melt with sediment signature and such a melt converted to the reduced condition in the wall mantle peridotite.

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Active volcanoes are the primary source for CO2 emission from the Earth's interior to the atmosphere. CO2 fluxing may be an elementary process of CO2 transport in a magma, but its mechanism has not been understood yet. We modelled the CO2 fluxing as a reactive transport process and compared the calculation result to melt inclusion data of Mt.Etna from literature. We obtained a quantitative understanding for CO2 fluxing such that fluid velocity is > 10-4 m/s and flux is 32 g/m2 s.

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The hydrogen in nominally anhydrous minerals (NAMs) can be a proxy of H2O in silicate melts if the partitioning behavior of hydrogen between NAMs and melts is known. We carried out hydrous melting experiments of basaltic magma at 350 MPa using an internally-heated pressure vessel to determine the partitioning of hydrogen between plagioclase and basaltic melt. A grain of plagioclase and powdered hydrous glass were sealed in a capsule and kept at temperature slightly above crystallization temperature of plagioclase. Oxygen fugacity was estimated to be 3 log unit above Ni-NiO buffer. Experiments were terminated after 24 hours. Concentration of H2O in melt and concentration of OH in plagioclase was analyzed using FT-IR. Obtained partition coefficient is about 0.006 in molar basis.

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To understand the water content in primary magmas beneath frontal-arc volcanoes, we have carried out a petrological study on Mg-rich basalts from Iwate Volcano, located on the volcanic front in NE Japan arc. The lavas contain ~5 vol.% olivine phenocryst and ~15 vol.% plagioclase phenocryst. The An content of plagioclase and the Mg# of olivine phenocrysts range from 85 to 92 and from 78 to 85, respectively. The An content of plagioclase phenocrysts correlate positively with the Mg# of coexisting olivine phenocrysts, and olivine phenocrysts with >Mg#82 do not coexist with plagioclase. These features are consistent with the variation in the mineralogical features that are expected from cooling of magma with olivine as the sole liquidus phase. Using multi-component thermodynamic models, water content of magma which can reproduce the observed variation in the mineral assemblage and the compositions was examined. The calculation shows that the magma contained about 5 wt.% water if the magma chamber was located at depth corresponding to 200 MPa pressure. This observation suggests that the primary Iwate magma may have been hydrous.

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The Hakone volcano is composed of island-arc type tholeiite magma, which is not dry but moderately hydrous. The moderately hydrous tholeiite magma can produce arc-tholeiite series and calc-alkali series through fractional crystallization in the magma reservoir under open-system condition and closed-system hydrous condition for water, respectively. The working hypothesis could be proposed by the change of magmatic temperature during fractionation. The magmatic temperature can be estimated by pyroxene-geothermometers.

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Thermal properties of crustal solutions are required to understand their migrations within geothermal systems or sedimentary basins. Those properties are also required for considering the temperature variations. Thermal properties of crustal solutions can be approximated to that of pure water in most cases. However, such an approximation is inapplicable to crustal solutions of high salt concentrations. Aqueous solutions of sodium chloride, which is the predominant salt in most of the crustal solutions, have been investigated with regards to the thermal properties. However, the thermal properties of aqueous calcium chloride solutions have often been overlooked. This study corrects the heat capacity equation of Holmes et al. (1994, 1997). The equation is applicable up to 523.15 K, 40 MPa, and 4 mol/kg.

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Gas transport in silicic magma is a mechanism controlling the degassing rate of magma and hence the explosivity and style of volcanic eruptions. The gas flow through fractures formed in sheared magma is thought to induce efficient degassing from silicic magma; however, the quantitative condition at which magma fractures remains poorly understood. In this study, we observed the formation of brittle fractures and the degassing through the fractures at high temperature and pressure. At a temperature of 850°C, vesicular rhyolite was fractured as well as rhyolitic melt without bubbles at a strain rate of 10^-2 s^-1. The fracturing induced the localization of deformation, and the degassing and compaction repeatedly occurred. The experimental result indicates that shear fracturing of silicic magma causes efficient degassing in a volcanic conduit.

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In general, fumarolic gas is the steam phase generated after the interaction of magmatic gas and groundwater. In this model, the CO2/H2O ratio of magmatic gas can be estimated by correlating the CO2/H2O ratio and isotope ratio of H2O (D/H and 18O/16O ratios). As the volcanoes with high CO2/H2O ratio, the recent Etna and Izu-Oshima after 1986 eruption can be exampled, the value of which is higher than 0.03. As the volcanoes with low CO2/H2O ratio, Kusatsu-Shirane, Atosanupuri and Hakone can be exampled, the value of which is less than 0.006. The fumarolic gas at Shinmoe volcano in 1994 contained the magmatic gas with 0.03 of CO2/H2O ratio, suggesting the volcano had been ready for the eruption in 2011.

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In this study, syenite and monzonites from the mid Cretaceous Mount Dromedary were examined by combining new LA-ICP-MS analytical data and published whole rock data. This was done in order to discuss the distribution of trace elements and REEs in radioactive minerals and silicate minerals, and the crystallization differentiation between minerals. The igneous complex is a group of small plutons that occurs at the eastern edge of the mid Paleozoic Lachlan Fold Belt near the east coast between Narooma and Bermagui, New South Wales. The pluton is characterized by concentrically arranged sequence of compositionally and texturally distinct zones. There is a mafic (monzonitic) outer ring, intermediate, and felsic (syenitic) core zones. As well as monazite, allanite and zircon, we suggest that titanite and apatite also can have the potential for controlling Th-U distribution in bulk rock, because these are common accessory minerals.

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The first occurrence of eclogites in Mongolia has been described from the Chandman district in the Lake Zone, western Mongolia (Hanzl and Aichler, 2006; Takasu et al., 2008; Stipska et al., 2010). The Alag Khadny metamorphic complex consists of metamorphic rocks and ultramafic bodies which are exposed for about 10 km long and 4 km wide in the Lake Zone. Several lenticular-shaped bodies of eclogites and amphibolites (max. 2 km x 0.8 km) occur in the matrix of orthogneisses and minor metapelites. Eclogites consist mainly of garnet, omphacite, and amphibole with subordinate epidote, phengite, paragonite, plagioclase (An=1-17), biotite, K-feldspar, rutile, titanite, quartz, calcite, hematite, ilmenite, and zircon. Based on the texture and mineral chemistry, the eclogites experienced MT-LP condition of amphibolites-facies, and then suffered HP eclogite-facies metamorphism. Subsequently the eclogites exhumed to the shallow crustal level, and metamorphosed again in the MT-MP condition of epidote-amphibolite-facies.

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The Central Asian Orogenic Belt (CAOB) resulted from amalgamation of voluminous subduction – accretionary complexes of Late Neoproterozic to Mesozoic time. Mongolia is the heartland of the CAOB and geologically divided into four complexes; continental blocks, subduction complexes, sedimentary basins and Cenozoic cover sequences. The magma activity in the southern part of Lake zone would, therefore, be related to the continental collision event. Considering geochronology and geochemical features of the intrusive rocks, the subduction and collision events occurred in the Lake zone during Cambrian time. Finally, the North China craton collided to the Siberia craton, giving rise to collision-type metamorphism and S-type granite magmatism during Permian time in the Mongolian Altay region.

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The Jurassic accretionary terranes have been documented from the eastern margin of the Asian continent, including northeast and Far East Russia, NE China and SW Japan. The similarities of high-P/T blueschists from the Heilongjiang Complex, NE China, and the Suo metamorphic belt, SW Japan, suggest that both metamorphic belts were formed in the same subduction system, which is related to the Paleo-Pacific subduction, and this subduction event was instrumental in producing of voluminous Jurassic accretionary complexes along the eastern margin of the Asian Continent. Therefore, the appearance of Jurassic accretionary terranes plays an important role in reconstructing the geodynamic evolution of the eastern margin of the Asian Continent.

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Eclogites occur as lenses or layers in the Sambagawa schists, Besshi district, central Shikoku, Japan. Eclogite-bearing bodies are metamorphosed accretionary complexes (sediments, basaltic lavas and pyroclastic rocks), and mafic and ultramafic rocks derived from lower-crust and/or upper mantle (layered gabbros and peridotites). Three types of metamorphism occurred, i.e. relatively high T/P metamorphic event of amphibolite facies, eclogitic metamorphic event and epidote-amphibolite facies metamorphic event. The diverse metamorphic histories for these eclogite suggest that these masses reached different depths from the different route within the subduction zone. All of the eclogite-bearing bodies were eventually emplaced into the non-eclogitic Sambagawa schists during their initial stage of subduction in the shallow crustal level, and subsequently underwent later Sambagawa prograde metamorphism.

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Mongolia has had a known significant geologic potential only for the last 50 years: about 4000 mineral deposits and occurrences of 40 different minerals have been discovered and explored. Today Mongolia is exporting copper, and molybdenum concentrates to Russia, Switzerland, Japan, Finland, USA, coal, fluorite, base metals to China and fluorite to Russia and some European countries. The non renewable nature of minerals makes it essential that the country's revenues from resources exploitation should be transformed into continuing productive industry, education, health care, in one word profit from mineral exploitation should continue to benefit the country.

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Mongolia has considerable reserves and resources of gold in both placer and primary deposits. Historical records and archaeological findings suggest that the gold mining on the territory of Mongolia begun in the ancient times. At present, in the territory of Mongolia 7 gold metallogenic belts: Mongolian Altai, Lake, North Mongolian, Central Mongolian, Khangai-Khentei, East Mongolian and South Mongolian belt consisting of 25 gold bearing zones and 70 ore belts. Gold mineralization is identified to be formed on various kinds of genesis during long history of geological and geodynamic evolution of Mongolia. According to genesis, gold mineralization can be divided into several types: volcanogenic massive sulfide; intrusion related quartz veins and stockworks; metamorphic quartz vein; epihermal; sedimentary and surficial.

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The Bayankhongor metallogenic belt, ∼700 km southwest of the capital city, Ulaanbaatar, is the second productive gold-field in Mongolia. Production of this gold-field is not well known, but is estimated at about 50 kg/yr. Most gold is recovered from alluvial deposits, however primary sources of alluvial gold in the district are not well understood. The Tsagaan Tsahir Uul (TTU) gold deposit is located at the southeastern part of the Bayankhongor metallogenic belt, and is possible source of alluvial gold. Based on the tectonic setting of the deposit, the TTU deposit possibly belongs to orogenic type gold deposit (Groves. 1998). The geological, mineralogical and geochemical features of TTU deposit are similar to those of worldwide orogenic gold deposits.

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This study is focused on the characterization of Gatsuurt gold mineralization, Mongolia. The ores mainly consist of intergrown fine-medium grained (0.05-0.5mm) pyrite and arsenopyrite aggregates, and sphalerite, chalcopyrite, galena, native gold and tetrahedrite occur in pyrite and arsenopyrite. Pyrite is the most abundant sulfide. Early stage pyrite occurs in later stage pyrite as small grains of 20 μm in diameter. Sphalerite, chalcopyrite, galena, tetrahedrite and native gold are observed as inclusions in subhedral pyrite grains. Arsenopyrite occurs not only as aggregates with pyrite but also as euhedral grains in thin quartz veinlets. Sphalerite, chalcopyrite and galena occur as inclusions in pyrite, and their grains are very fine. Tetrahedrite is anhedral in form and has grain sizes up to 0.2mm. It is usually infilled by fractures of pyrite and arsenopyrite, and observed as inclusions that rarely coexist with native gold. Native gold is fine grained (5-50 μm in diameter), and present as rarely dispersed and as visible grains along their fractures in pyrite and arsenopyrite.

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The author will introduce different styles of rare earth mineralization in Mongolia.

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Hanhohiyn Mountains is located in the northwestern part of Mongolia. The mountains are mainly composed of marble, meta-quartzite and pelitic gneisses intercalating with lenticular garnet-amphibolite, garnet-orthopyroxene gneiss and so on. Pelitic gneisses are classified into garnet-sillimanite-biotite gneiss, garnet-cordierite-biotite gneiss and garnet-biotite gneiss. These gneisses indicate the peak metamorphic condition of 600-700 degree and 5.5-6 kbar accompanied by decompression. The EPMA U-Th-Pb Monazite ages concentrate between 480-510 Ma which is interpreted as the timing of the peak metamorphism.

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We report results on geochemistry, geochronology, and P-T analyses of high-Al-Mg gneisses from the Mongolian Altay Mountains.

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Garnet and clinopyroxene megacrysts and spinel-garnet-bearing websterite from Quarternary alkali basalt erupted in the Tariat Depression of central Mongolia will be presented.

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