In the present study, we conducted reducing gas-levitation and laser heating experiments in order to reproduce micro-textures of chondrules, and constrain their formation conditions. We used natural carbonaceous chondrites as stating materials, and recovered samples were analyzed by XCT and SEM. Recovered samples consists of iron nodule and barred-olivine like texture. The technique in the present study may give us new insight for elucidating formation process of chondrules/chondrites.

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NWA1232 is a CO3 chondrite consisting of three lithologies (A, B, C) of different metamorphic grades. We have undertaken an extensive survey of NWA1232, and found that olivine phenocrysts in chondrules vary widely in Fe/Mg composition in lithology A suggesting that the chondrules have different thermal histories. We also found that many chondrules in lithology A have fine grained rims that show different mineralogical characteristics according to the metamorphic grades of their host chondrules. These results suggest that lithology A is composed of many clasts that underwent various degrees of thermal metamorphism in different locations of the CO parent body.

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We found the fine grained, heavily-hydrated microclasts in a CO chondrite (Y-81020) and CM chondrites (Murchison and Cold Bokkeveld). SR-XRD analyses and high resolution TEM observations revealed that the clasts in Y-81020 consists mainly olivine and magnetite, with small amounts of smectite and serpentine. The clasts in Murchison and Cold Bokkeveld consists mainly magnetite and serpentine in which crystalline olivine were not observed. Most of clasts in three meteorites contain framboidal or platelet magnetite, which are typical morphology in CI chondrite. These results suggest that the clasts had been altered by aqueous alteration under a condition similar to CI chondrites.

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In this study, we use silica gel and glycine complex as a model material of comet and investigated the structural change of this model material by shock compression with X-ray diffraction, IR and Raman spectroscopy. Obtained results may indicate glycine molecule remain even after shock compression of 18 GPa. This may indicate a possibility of extraterrestrial origin of biomaterial on the Earth.

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Fine-grained rims surrounding chondrules and inclusions in the VigaranoCV3 carbonaceous chondrite can be divided into phyllosilicate-rich and olivine-rich types. We present a petrographic and electron microscopic study of the olivine-rich rims and their host objects (referred to as chondrules/olivine-rich rims). The olivine-rich rims consist mainly of Fe-rich olivine and very minor phyllosilicate (saponite). Their host chondrules contain minor saponite and phlogopite, which resulted from aqueous alteration of anhydrous silicates. The results suggest that the chondrules/olivine-rich rims experienced extensive replacement reactions in an environment in which aqueous fluids existed but only in minor amounts.

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We performed mineralogical study on 7 Itokawa particles returned by the Hayabusa spacecraft. The analyzed particles constitute of olivine and plagioclase with minor shock metamorphism (shock stage: S2). Olivine is Fo_70-73, consistent with the cell dimensions obtained by SR-XRD and close to LL chondrites. Plagioclase is An_13-10Or_5-7 and its equilibration temperature is ~800^oC. Fe SR-XANES of plagioclase suggests high fO2 and affinities with LL chondrites. Their petrologic type is ≥4 based upon plagioclase sizes and homogeneous olivine compositions. Thus, this study demonstrates that analyzed particles could be equilibrated LL chondrites with minor shock metamorphism, reconfirming the preliminary examination study.

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The surface of a platy carbon grain is observed by SEM. In some areas, individual diamond crystals show triangular faces parallel to the surface of the grain surrounded by triangular pits. The Raman spectrum obtained at a triangular pit shows very broad Raman band at 1580 cm^-1 which does not associated with D-band at 1350 cm^-1. Like this characteristic pattern is observed distinctively for tetrahedral amorphous carbon (ta-C). The presence of ta-C in the pit suggests that the triangular pit has been formed by melting of carbon followed by quenching at a high pressure.

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We investigated one of eucrites Béréba to clarify a dynamic event occurring on 4 Vesta. Coesite and stishovite were identified in and around the shock-melt veins of Béréba. Considering radio-isotope ages, the expected age of the dynamic event that formed coesite and stishovite is ca 4.1 Ga ago, which is inconsistent with the predicted formation age (ca 1.0 Ga) of the impact basins on 4 Vesta.

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NWA 5480 is a crystalline stone, but shows a heterogeneous texture. Olivine aggregates and grains of olivine and chromite show resorption textures and set in a crystalline pyroxene matrix. Flow textures are observed near olivine aggregates. Olivine, chromite, and pyroxene show minor chemical zoning, implying relatively rapid cooling. NWA 5480 contains a significant amount of platinum group elements with chondritic relative proportions. All these evidence support that NWA 5480 is an impact melt rock from a target composed olivine and pyroxene-rich lithologies. Such impact melt would have formed by melting crustal materials.  

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Most Martian meteorites underwent severe shock metamorphism and contain dark olivine. Though the olivine darkening appears related to the presence of iron nano-particles in olivine, their detailed formation conditions and processes are not well understood. Since dark olivine is exclusively found in Martian meteorites, they may have characteristic information about the Martian shock events. To constrain its formation conditions, we compare 5 Martian and 1 chondritic meteorites. Our observations revealed that high-pressure minerals are rarely found in meteorites with dark olivine, suggesting that post shock heating prevented preservation of high-pressure minerals. More detail discussions will be presented at the meeting.

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Asteroid and meteorite collisions contribute to revolution of the Moon and Earth. Recently, Ohtani et al. (2011) and Miyahara et al. (2013) discovered high-pressure silica polymorphs (coesite, stishovite and seifertite) in lunar meteorites, Asuka-881757 and NWA4734 and their existences give us valuable information on impact history on the Moon. In this study, we newly found moganite coexisted with coesite in lunar meteorite NWA2727 and provide constraints on the shock pressure and temperature during impact event, based on transition processes clarified by high-pressure experiments using diamond anvil cell for terrestrial moganite.

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The study of ungrouped achondrites is important to understand the degree of asteroidal diversity and igneous differentiation in the early solar system. NWA 7325 is such an ungrouped achondrite and has drawn attention as the first meteorite sample possibly from the planet Mercury. In this study, we analyzed NWA 7325 using FEG-SEM with EDS and EPMA, and subseqently measured its noble gases. We suggest that the parent body of NWA 7325 has experienced a break-up event to partially melt and quench the mantle rock by shock in the early solar system while ¹²⁹I was still present.

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The local structure of K-T boundary clays was studied by Zr K-edge XAFS in order to provide quantitative data on bonding distance and coordination numbers. The zirconium XANES spectra in K-T boundary clays are similar to rhyolitic volcanic glasses (obsidian and pitch stone) and tektite. It suggested that local structures of Zr in K-T clays remain the thermal quenching history at meteorite impact. The Zr-O distance in K-T boundary clays is 2.164 Å and the coordination number is 6.3. The data suggested that Zr local structure in K-T boundary clays are formed relatively under the condition of higher temperature and lower oxidation state than volcanic glasses and total electric charge of Zr ions is less than 4 and estimated as 3.8.

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We performed a petrological/mineralogical study of alteration texture in the Allende by using a TEM.

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Our purpose is to clarify the genetic relationship between chondrules, rims and matrix in Yamato-82094. By detailed SEM and EPMA analysis, we found chondrule rims. Chondrules with rims show evidence of thermal metamorphism. It is commonly that enstatite has reacted with nearby opaque nodules to form Fe-rich olivine. The resultant materials are similar to rims. And alteration textures are found in some chondrules all over Y-82094. Therefore, we suggest that chondrules/rims are actually clasts produced in a different place, but the same condition, where the host was produced. They separately experienced thermal metamorphism and then mixed by brecciation and transportation.

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DaG999 polymict ureilite is composed of a large clast of about 1cm and an aggregate of fine grained clasts. The coarse clast is composed of olivine and pyroxene. It contains C-grains, 7.0vol%, with blade like shapes. The fine-grained clasts are composed of olivine, pyroxene and plagioclase. Fine-grained C is present also in the aggregate in 1.5vol%. In the large clast, there are fine mineral veins composed of pyroxene and plagioclase.

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NWA2092 LL6/7 chondrite was examined using a polarizing microscope and EPMA. It consists mainly of olivine, pyroxene, and plagioclase. Fa contents of olivine and Fs contents of pyroxene are in the ranges of the LL group. The estimated temperatures are 840 (40) °C and 810 (50)  °C  by clinopyroxene and orthopyroxene compositions, respectively. These two temperatures are very similar and reveal that chemical compositions of these pyroxene and equilibrated.

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Petrochemical studies of the plutonic rocks in the Abukuma Mountains are carried out. The leucocratic members (biotite granite – granodiorite) in the northern Abukuma Mountains have typical chemical characteristics of evolved granitic rocks. Granitic rocks in the southern Abukuma Mountains show chemical characteristics slightly different from those of granitic rocks in the northern areas.

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The Central Asian Orogenic Belt resulted from amalgamation of voluminous subduction – accretionary complexes of Late Neoproterozic to Mesozoic time. Considering geology and geochemistry of the intrusive rocks, the subduction - zone and collision - zone magmatism occurred in the Hangay batholith and the Lake zone, respectively. In other words, the landmass of south - central Mongolia would have been resulted by the specific geotectonics through the formation of volcanic arc due to the oceanic crust subduction and the microcontinent collision during the Paleozoic.

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The Oman ophiolite is a sliver of the Neo-Tethys oceanic lithosphere obducted onto the Arabian plate during the late Cretaceous time. Felsic to intermediate rocks in ophiolite suites are classified into three stages; high-level intrusive rocks of axis stage, late stage intrusive rocks, and granitic rocks associated with obduction stage. We investigate petrochemistry and U-Pb zircon ages of granitic rocks associated with obduction stage. These granitic rocks are considered to be generated from partial melting of metamorphic sole (basal metamorphic rocks).

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In this presentation, we will discuss petrography and petrogenesis of Cambrian high-K adakitic granite in the Sør Rondane Mountains, East Antarctica.

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In this study, we discuss the magma evolution process of calc-alkaline rocks from the Northern Kita-Hakkoda based on topographic analysis, geological survey, bulk rock chemical composition and petrography. Compositional trends of compatible elements of calc-alkaline series are liner on the Harker’s diagrams, in contrast with those tholeiitic series. Some calc-alkaline rocks contain disequilibrium mineral assemblages and disequilibrium textures in the phenocryst. From the chemical variation of trace elements and from the disequilibrium textures, we conclude that the calc-alkaline series magma were formed by magma mixing.  

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Two types of Miocene volcanic rocks are distributed in Utsunomiya, central Japan. Andesite and rhyolite are intercalated with Kazamiyamada Formation, in the lower, and Oya Formation, in the upper, respectively. The Kazamiyamada andesite was subdivided into Kasamatsu andesite and Hanzo andesite, on the basis of geochemical characteristics. Rhyolites are divided to Oya and Haguro types. The Haguro rhyolite differs from the Oya rhyolite in REE pattern.
In addition, magma genesis of these volcanic rocks will be discussed by the Sr and Nd isotope ratios.

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In andesitic rocks from back-arc volcanoes in central Japan, observations of small-scale heterogeneities of groundmass and microprobe analyses of melt inclusions reveal that F and Cl-rich high-K₂O mafic magma batches are often injected into the crystal-rich reservoirs of these volcanoes. These data likely suggest that the F and Cl-rich high-K₂O magma batches are generated in a metasomatized deep mantle wedge (above the subduction slab of 150-220 km depth), probably veined by phlogopite and/or apatite-bearing dykes, and are repeatedly input into crustal reservoirs to contribute for producing the medium to high-K₂O andesitic rocks in the back-arc region of central Japan.

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We analyzed trace element and Sr-Nd isotopic compositions of the magmas from pre-Komitake volcano. From the Sr-Nd isotopic compositions, magmas of pre-Komitake volcano can be generated from the same source of Fuji volcano, and the crustal materials contributed to the magma genesis. Geochemical signatures, especially Eu^* values, Al₂O₃ contents and Sr/Y ratios, plagioclase was accumulated in the primary magma of pre-Komitake volcano, and it was removed from the magma with the proceeding of the fractional crystallization contributed the magma genesis of pre-Komitake volcano.

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We present the genetic conditions of the Eocene magmas from the Ogasawara (Bonin) Ridge and discuss the thermo-chemical structure of the mantle wedge beneath the Ogasawara region during the incipient stages of the IBM arc. After the FAB (forearc basalt) activity, depleted harzburgite upwelled from deeper asthenosphere to <1 GPa, suffering flux melting to generate the high-Si boninite magma (48-46 Ma). By 45 Ma, asthenosphere began circulating in the wedge. As a result, magma composition changed from high-Si boninite through low-Si boninite to arc tholeiite and calc-alkaline magmas.

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How suboceanic mantle evolves into subarc mantle with the progress of a subduction zone is a fundamental question to understand the processes of subduction initiation and arc development. Primary arc magmas provide critical information to understand thermal and chemical structures of subarc mantle. We present geochemical characteristics of and genetic conditions of primary boninite magmas during the early stage of the Izu-Ogasawara-Mariana arc establishment (48-44 Ma), based on boninitic melt inclusions in chromian spinel from the Ogasawara Archipelago and Guam Island.

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We studied the precursory eruption products for Aso-4 and Aira eruptions in order to understand the changes in the magma supply system of large caldera-forming eruptions.  They include (1a) Omine pyroclastic cone and associated Takayubaru lava flow west of Aso caldera, (1b) tephra and minerals included in Hanafusa formation west of Aso caldera, (1c) Aso 3/4 pumice fall between Aso-4 pyroclastic flow deposit and Ata tephra found in the east of Aso caldera.  (2) A series of precursory volcanic products of Aira eruption.

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This report presents the biotite chloritization process with a focus on mass transfer in the Toki granitic pluton, Central Japan.   Singular value decomposition (SVD) analysis results in a chloritization reaction equation for each mineral assemblage, leading to the quantitative assessment of mass transfer between the reactant and product minerals, and inflow and outflow of components from and into the hydrothermal fluid.   The mass transfer provides the temporal variations in chemical characteristics of hydrothermal fluid associated with biotite chloritization during the sub-solidus cooling of the pluton.

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In the present study, whole-rock analyses, and Sr and Nd isotope analyses for granitoids (Ningyo Toge Granite, Tottori Granite, and Sangenya Granodiorite) from eastern Inbi Intrusives were carried out in order to discuss the plutonic magma history of the San-in Belt, Inner Zone of Southwest Japan. Whole-rock chemical characteristics categorize these granitoids as I-type. Rb-Sr isochron age for six samples of Ningyo Toge granites is given as 66.1 +/- 5.0 Ma (1 sigma). Relationship of epsilon NdI vs. epsilon SrI suggests that the parental magma of the Ningyo Toge Granite is probably not linked to that of the Tottori Granite.

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We try to understand the role of the so-called Older/Younger granitoids in the metamorphic history of the high temperature Ryoke Belt. We use field observations, geochemical data and zircon ages in order to constrain the mode and timing of emplacement of the different plutonic bodies exposed in the Iwakuni-Yanai area (Yamaguchi Pref., SW Japan).

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In this study, we investigate the magma processes of the granitoids from the Ryoke and Sanyo belts, the Yashiro district, eastern part of Yamaguchi prefecture, with respect to the Kfs-porphyritic granite, Rhoke belt, and the coarse-grained granite, Sanyo belt, in comparison with differentiation trends of these granitoids. Considering behavior of Nb and Y, and zircon saturation temperature, the coarse-grained granite would preserve a supra-solidus condition until 680˚C and was strongly influenced from fluid under the latest stage of its magma process.

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Using clinopyroxenes REE contents and the open system melting model of Ozawa (2001) we examined the process in which Oman peridotites with high Cr# spinel were formed by flux melting of harzburgite. Positive correlation was acquired between the Ce/Yb ratio of clinopyroxenes and the Cr# of spinels for peridotites from the Salahi mantle section. Flux melting of peridotite with low Cr# spinel by infiltration of fluid enriched in LREE can explain such signature. Peridotites with spinel Cr# less than 0.5 were distributed along a shear zone, and their clinopyroxenes are depleted in LREE as residues after lherzolite melting under mid-ocean-ridge.

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On Rundvågshetta in the LHC, intermediate to mafic dyke rocks were found in some places.  Relatively mafic rocks contain apatite with much fluorine; on the other hand, less mafic rocks have apatite with F-rich core and Cl-rich rim.  This suggests compositional progression from fluorine to chlorine in the less mafic condition during apatite crystallization. 

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Primitive modally-layered gabbros from the lowermost plutonic crust of a fast-spreading ridge exposed at the Hess Deep rift were firstly recovered by IODP Exp.345 on January 2013. Orthopyroxene amazingly occurs as an early crystallizing phase in the layered gabbros. Two main types of layered structures in the gabbros are simple modal layers and irregular bands. In this presentation, we will report petrographical and mineralogical characters of multitextured layered gabbros with the irregular bands (Opx-rich band, Melanocratic and leucocratic bands, etc.) and consider the origin of the bands. 

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The Ohata Pumice Tuff, a sheet of andesitic and dacitic pyroclastic deposit that was deposited 2.6Ma-3.0Ma during the Yagen caldera(Middle-Shimokita Peninsula).In this work, we observed quartz of Ohata pumice tuff used Mini-CL. CL images of the quartz show oscillatory zonal structures.

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Zao volcano is one of representative active stratovolcanoes in NE Japan. The Goshikidake, the youngest cone in this volcano, started its activity at about ca. 2 ka. We examined geologic and petrologic features of the initial stage eruption products of this cone. Eruption products are divided into four units. All rocks are cpx-opx andesites, which belong to medium-K, calc-alkaline series. Many phenocrysts have dissolution textures. Bulk SiO₂ contents vary from 56 to 58%, and all samples are plotted in same variation trends in silica variation diagrams.    

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Trace element and isotopic micro-analyses were carried out for plagioclase crystals in Mafic Magmatic Enclave (MME) and granite in the Shodoshima Island, SW Japan. The results of the analyses suggest that the granite-derived plagioclase crystals were captured into basaltic melt and were partially melted. The process of the mixing between granite-derived crystals and basaltic magma can be a key to understand complex chemical evolution paths of the mixed rocks.

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Occurrence and chemical compositions of ore minerals and Ag-bearing minerals in Kuki mine, Onan, Shimane, have been investigated to clarify the mineralization process and to characterize silver mineralization. Three modes of occurrences of Ag mineral were observed: native silver and pyragyrite occur within minute cavities in the first generation pyrite; argentite and silver particles of sub-micron scale distribute around the minute cavities in pyrite; native silver occur within minute cavities in sphalerite. Au-mineralization is recognized only in pyrite and arsenopyrite. Two stages defined by the assemblage of pyrite and arsenopyrite, and by associated silver and gold mineralization are recognized.

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Diffusion processes recorded in sphalerite from some metamorphosed volcanogenic massive sulfide deposits, Abitibi greenstone belt, Canada were analyzed by EPMA.  The calculation of exsolution time in host sphalerite adjacent chalcopyrite and pyrrhotite inclusions were carried out by differential equation for diffusion fittind to the iron depletion profiles.

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The REE-F carbonate veins are distributed radially around the boundary of Lugiin Gol alkaline complex. This RE mineral bearing breccia vein is composed of broken fragments of fluorite and cemented by fluorite, quartz, RE minerals and small amount of very fine-grained pyrite. RE minerals are composed of synchysite and parasite in brecciate texture with quartz and fluorite.  Fluid inclusions occur in fluorite and are dominated by H2O–NaCl types. Based on mineral assemblage and texture of fluorite-REE veins, it is inferred that a fluorine-bearing hydrothermal activity was associated with REE mineralization.

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Gold occurrences and distributions in the orogenic type Boroo, Gatsuurt and Ulaanbulag deposits in the North Khentei gold belt of Mongolia were studied to recognize paragenetic relation between gold and sulfides. The result is concluded that gold continuously crystallized with ore-forming sulfides, but main gold deposition event took place after sulfide mineralization stage.

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I report a case that material segregation had occurred in a chemically closed system for a kelyphite after garnet from a garnet pyroxenite, Ronda peridotite, Spain. The kelyphite consists of Opx, Sp, Pl and Cpx. Opx-Sp symplectite patches in the kelyphite increases in both size and amount towards the outer side of the kelyphite away from the relict garnet. It was found out that, although the bulk composition of kelyphite differs between the inner and outer sides, overall bulk composition nearly coincides with the precurser garnet except sodium.

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In this study, 1) olivine phenocrysts and associated minerals in the black and red-brown scorias from Kami-Komesuka, Aso, Kumamoto Prefecture, Japan were described in detail, 2) their chemical compositions were determined, and 3) the oxidation state of Fe in olivine phenocrysts were examined using electron microbeam method to evaluate effect of high temperature oxidation on the scoria. The Kami-kometsuka scoria cone consists of black and reddish-brown scorias. The reddish-brown scoria is covered by the black scoria. In the olivine phenocrysts from the reddish-brown scoria, Fo content attains up to 99 mol%, and Fe-rich precipitate minerals, less than few mm in size, occur on the rims and along fractures. Such occurrence of the Kami-Kometsuka scoria cone consisting of the red-brown and black scorias, and the extremely Mg-rich olivine phenocrysts and Fe-rich precitates indicate that the Kami-Kometsuka scoria subjected to high temperature oxidation after the eruption.

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We investigated anorthite magecrysts (grain size > 10 mm) occurring in mid-Miocene basaits from Ogi Peninsula, Sado Island, Niigata Prefecture, Japan, using elctron probe microanalyzer (EMPA) and scanning electron microscope (SEM). Some mineral and melt inclusions in the anorthite megacrysts were also analyzed in this study. EMP analyses showed that the anorthite megacrysts are chemically homogeneous (An 92 - 94 %) from core to rim and can be distinguished from the other plagioclase phenocrysts (grain size: 0.1 - 0.2 mm, An 79 - 84 %) by chemical composition. In addition, Fe-Cu-Ni sulfide globules and S, Cl-bearing mafic glass inclusions occur within the anorthite megacrysts. Many previous stuides on anorthite megacrysts occurring along the volcanic front (e.g., Kimata et al. 1995) reported that these anorthite megacrysts contains corroded olivine as mineral inclusion. These differences in inclusions suggests that the formation conditions of anorthite megacrysts between the volcanic front and back-arc are different each other.

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Basaltic to rhyolitic magmas in a subduction zone setting contain many types of plutonic xenoliths. Niijima volcano is predominantly composed of rhyolitic lava domes and pyroclastic units with minor basaltic to andesitic volcanic units. In this study, we conducted petrographical and geochemical studies on the gabbroic xenoliths contained within the volcanic rocks from the northern part of the volcano. We determined the mineral chemistry, whole-rock major and trace element and isotopic compositions of plutonic xenoliths from Niijima volcano in order to clarify their origin and formation process. 

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Deformed chromitites from the Golyamo Kamenyane serpentinized peridotite massif in SE Bulgaria have been studied as an example of chemical homogenization by deformation in monophase rock during metamorphism. Theses chromitites were affected by amphibolite-facies metamorphism and reacted with oxidizing Fe³⁺-rich fluids (∼ 1.0 GPa and 500-700ºC). Here, we describe the details of how the microstructure was produced in chromite, showing the important role of deformation due to metamorphism. deformation produces chemical homogenization of chromite, and also fluid-rock interaction leads to deformation of chromitites, which involves not only dynamic recrystallization but also nucleation of new grains.

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Neogene to Quaternary volcanic rocks distributed in the Fossa Magna region. They show geochemical and isotopic lateral variations suggesting deferent component of mantle sources. The low Nd isotopic group is distributed in marginal part of the Fossa Magna, while the high Nd isotopic group central part. The former group is lower in Zr/Nb and Hf/Nb ratios than the latter, which indicates E-MORB-like and MORB-like source. The volcanic rocks of high Nd isotopic group would be derived from the MORB like source which upwelled asthenospheric material were erupted.

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We conducted a field expedition to the Polar Ural ophiolites, Russia, in 2013. Ultrahigh-pressure chromitites containing diamond have been fround from one of them (Ray-Iz), and one of our targets was to observe their mode of occurrence. The peridotite (harzburgite) and chromitite have been strongly metamorphosed.  We are examining the relevance of the metamorphism to the ultrahigh-pressure minerals.

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Ultrahigh-pressure chromitites from Ray-Iz ophiolite, Polar Urals, and Luobusa ophiolite, Tibet, are examined and, to constrain the origin of ultrahigh-pressure chromitite. Ray-Iz chromitites are mostly concordant to the foliation of the surrounding meta harzburgite. Chromitites show disseminated, massive and nodular texture. Spinels from chromitite and surrounding dunite show high Cr# (0.75-0.85) and low TiO content (0.1 to 0.2 wt%). Chromian spinel grains of Ray-Iz chromitite contain thin lamellae of clinopyroxene and rutile. Spinels do not contain orbicular inclusions of primary hydrous minerals, such as pargasite and Na phlogopite. These characteristics of Ray-Iz chromitites are similar to that of Luobusa ophiolite, Tibet. 

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