We observed volcanic ash of phreatic eruptions from Ontake, Tokachi, Kurikoma, and Azuma volcanoes. Various alteration conditions are interpreted from the alteration mineral assemblages. The difference in the alteration mineralogy is related to the frequency of magma eruptions. The volcanoes with high frequencies of magma extrusions tend to discharge the ash with the monotonous mineral assemblages of the low-T advanced argillic alteration, whereas those with low frequencies are related to the assemblages from porphyry-type hydrothermal systems.

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Holness (2014) proposed the average aspect ratio of plagioclase can be used as a speedometer of magma cooling. However, in this paper the influence of magma composition on the aspect ratio is not discussed in detail. Therefore, we investigated the vertical variation of average aspect ratio of plagioclase in alkaline dolerite (Atsumi dolerite; Kushiro 1964). As a result, average aspect ratios in our study are larger than those in Holness (2014). This may be because of the influence of magma viscosity on diffusion coefficient.

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Many ultramafic dykes intrude peridotite of mantle section in the Oman ophiolite, especially pyroxenitic dykes account for around 50% (Python and Ceulenner, 2003). Result of our investigation in the Miskin massif, almost all dykes consist of pyroxenite. Classifying these forms of intrusion, we define a layer as concordant dyke and having gradual boundary with host rocks. Result of polarizing microscopes observations, orthopyroxene shows partial melting and crystallizes olivine in layer. In terms of mineral chemical composition, layer equilibrate with harzburgite.

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Boninites in the western Pacific extruded during the early stage of the subduction zone development. We discuss the genetic relationships of boninite and antecedent protoarc basalt magmas based on the T-P conditions and Pb-Hf-Nd isotopic modeling. Yb-Os isotopic modeling demonstrates that the high-Si boninite source formed by18−30 wt% melting of the primitive upper mantle at 1.5−1.7 Ga, whereas the source mantle of the protoarc basalt experienced only 3.5−4.0 wt% melt depletion at 3.6−3.1 Ga.

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Izu calderas that have produced only rhyolite have no mantle roots beneath the crust, but dikes from adjacent basalt volcanoes might provide the heat source to partially melt the surrounding middle crust (Tamura et al., 2009). The middle crust is deemed to be andesitic in composition, which have been produced when the crust was thin (Tamura et al., 2016) and, thus, only in the early stage of arc crust evolution. In the later stage of the Izu arc, we suggest that only basalt magmas are produced in the mantle wedge, which could be the heat source to melt the andesitic middle crust.

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B concentrations of three of four representative volcanic glass samples (Sheep Track, Laki, and Old Crow tephras) obtained by 193 nm excimer LA differ from those obtained by 260 nm femtosecond LA, apart from the Lipari obsidian. The rarity of microcrysts in the Lipari obsidian, and the different ablation depths of the two types of LA analyses, suggest that microcrysts affected the B concentrations. XRD analysis of the Sheep Track and Laki tephras identified peaks of B-bearing minerals. The Old Crow tephra showed no significant XRD peaks, but may contain B-bearing nanolites.

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We will present about the petrogenesis and geological significance of Cretaceous Dogo Minamidani granit, Oki islands, SW Japan.

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The Cretaceous granodiorite is widely exposed on the northern half of Kyusyu where the bouguer anomaly is definitely high. The granodiorite coexists with coeval fine-grained diorite as stocks and include coarse-grained gabbro as blocks. Considering geological, geophysical and geochemical signatures, the Cretaceous volcanic arc curst was formed by voluminous magma activity with differentiation of felsic upper to middle curst due to partial melting of mafic lower crust.

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We report results of Sr and Nd isotopic measurements of standard apatites and apatite grains separated from natural granitoids.

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The partial melting of depleted peridotite plus slab melt at 1.5 GPa was studied for H2O saturated conditions. The quenched glasses obtained at 1000℃ are dacitic in composition, and glasses obtained at 1050℃ are andesitic in composition. This suggests that calk-alkaline dacites to andesites can be generated by the reaction of slab melts with mantle peridotite. Moreover, this suggests that calk-alkaline dacites to andesites can be formed by direct partial melting of the hydrous upper mantle contaminated with slab melts.

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Early to middle Miocene basalt are distributed in Kanuma, southern margin of NE Japan arc. These volcanic rocks are divided into two types, Hinata basalt (Hn-type) and high Sr isotopic basalt (HSr-type) based on their petrological, and Sr-Nd isotopic characteristics.
The Hn-type basalt show Sr-Nd isotopic ratios close to the mantle, suggesting that the Hn-type was originated from the mantle.
The HSr-type basalt show has extremely high Sr isotopic ratios and low Nd isotopic ratios. Therefore, the HSr-type cannot be produced by partial melting of mantle added to the slab-fluid.

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Hime-shima Volcano Group are Quaternary small volcanoes located offing of Kunisaki Peninsula, western Inland Sea. It is thought that the volcano rocks of the Hime-shima volcanic groups were formed of magma mixing of dacite magma and rhyolitic magma. However, generation condition of Hime-shima magmas are estimated qualitative temperature condition at phenocryst-garnet (Itoh, 1990), it is not made a general study of magma genesis and magmatic explosion.

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We investigated the pressure and temperature conditions of the magmas of Yufu volcano using by the amphibole geothermobarometer. From the result, at least three magma chambers with different depth are required beneath the volcanoe.

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We investigated the magma genesis of Sakurajima volcano from the trace and Sr-Nd-Pb isotopic compositions. The Nb depletion show the typical island arc magma characters. The Sr, Nd, and Pb isotopic compositions plot close to a mixing curve between MORB-type mantle and sediments of the Philippine Sea Plate, (PSP) but displaced a bit towards more radiogenic compositions. These observations indicate that mixing of andesitic and dacitic magmas and that multiple dacitic magma chambers with different geochemical characteristics.

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The Zao volcano is located in the central part of Abukuma Belt, and basement rocks is composed of Hbl-Bt granodiorite. Results of petrography and geochemical data indicate fractional crystallization of Pl and Hbl. Zircon U-Pb age is 97.8 +/- 1.3 Ma and initial Sr ratios are 0.7070~0.7072. Generally, initial Sr ratios of granitic rocks of Abukuma Belt are 0.705-0.706. Therefore, forming process of Zao basement rocks are different from other areas, and it can explain by the AFC model with pelitic gneiss.

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The Tsukuba Mountains is mainly composed of granitic and gabbroic rocks intruded into the Yamizo Group. About the age of these plutonic rocks, the granitic and the gabbroic rocks are assumed to be 63 to 58 Ma and 75 Ma. Granitic rocks are divided into Inada, Kabasan and Tsukuba granites. We tried to revalidate the formation age of these plutonic rocks.
In this study, we select the zircon particles from 12 samples, and the U-Pb ages were measured. As a result, the magma activity of 81 ~ 78 Ma and 66 ~ 61 Ma was observed and it is considered necessary to reexamine the history of magma activity.

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Cretaceous to Paleogene intrusive rocks are widely distributed in San'in district, SW Japan. The rocks are divided into three types based on their lithofacies, whole rock and mineral chemistry, and magnetic susceptibility. They are important in understanding the igneous activity and transition of the tectonic setting in the Eastern margin of Asian continent during Cretaceous to Paleogene. This study aims to investigate the igneous activities of and to discuss the primary igneous stage of the large batholith in volcanic arc.

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Post metamorphic mafic dyke was found on Skallevikshalsen, LHC. The dyke cut host gneissosity obliquely, and contains small pieces of gneiss as xenoliths. The dykes are holocrystaline. Some constituent minerals, especially biotite flakes are commonly aligned to parallel to the trend of the dyke intrusion. Grain size of the minerals is ranging 0.5 to 3 mm, and some kind of minerals were coarsened from margin to center in the dyke. The dyke rocks have much incompatible elements, especially LIL elements. The dyke rocks are finally regarded as minette.

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Numerous minerals of the Earth's variety were formed by continuous marine sediments with larger lands, which are studied by nano-observation of remained volatile (carbon)-bearing-materials from the marine sediments to land-minerals. High-pressure minerals can be formed from surface activity.

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We report a new set of electrical conductivity data for the gabbro sample of Oman ophiolite, under high-pressures, high-temperatures and dry conditions. Compared with the electrical conductivity values of lower oceanic crust derived by field surveys, the measured electrical conductivity of the gabbro is considerably lower in the temperature ranges expected for lower oceanic crust. The discrepancy can be explained by the presence of conductive pore-fluids in the gabbroic lower crustal rocks.

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The presence of solid inclusions in chromite is one the characteristics of all types of chromitites. They are globular in form, 100 microns across, and mainly composed of pargasite, aspidolite and pyroxenes. They are evenly distributed in the chromite grains and have been interpreted to be of primary origin. In this talk we will present another possibility, the secondary metasomatic origin of the solid inclusions in chromites.

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The Mineoka peridotites are sometimes intruded by gabbro and orthopyroxenite dikes. Mineral compositions in the gabbro dikes are more depleted in light rare earth element than those of the orthopyroxenite. This is consistent with the relationship in the whole-rock compositions between gabbro and diorite-tonalite in the Mineoka belt. Our recent study suggested that the Mineoka plutonic rocks are fragments of the middle to lower crust beneath the IBM arc. The orthopyroxenite and gabbro dikes in the residual mantle are derived from the IBM basaltic and felsic melts, respectively.

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Nepheline-olivine (Ne-Ol) basalt is distributed at the east area of the Bolaven plateau in Southern Laos. The Ne-Ol basalt is massive and dark blue gray in color. Olivine, Ti-pyroxene, Ti-Fe oxide, spinel, are occurred as microphenocryst in the Ne-Ol basalt. Especially, nepheline occurs as three modes; 1) euhedral microphenocryst, 2) anhedral interstitial mineral, and 3) inclusions in Ti-pyroxene and Ti-Fe oxide. By these observations, an order of crystallization is considered as follows; Ol+Nep+Px+Sp+Opq -> Nep+Px+Opq.

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To understand the frictional property of slickenside, we conducted the frictional experiments of Carrara marbel using a high velocity and a biaxial frictional apparatuses. The important result is that the formation of slickenside influences strongly the property of fault slip.

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Oxygen isotopic compositions of skarn minerals were analyzed. Garnet and scheelite have variable δ¹⁸O, 4.6-8.2 per mil and 0.8-2.9 per mil, respectively. Temperature of skarn formation was calculated using oxygen isotope fractionation factor between quartz and scheelite, and T= 277°C was obtained. δ¹⁸O of skarn-forming solution was calculated. Early stage solution had δ¹⁸O values of 6-8 per mil and most garnet precipitated from this solution. While later stage solution had δ¹⁸O values 1-5 per mil, and this solution was responsible for precipitation of scheelite and quartz.

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The western part of Itoigawa in Niigata Prefecture contains serpentinite mélange.
In early June 2017, the Kotakigawa River developed turbidity. This report focuses on the mineralogical investigation into the cause of this phenomenon. The cause of the turbidity was minute particles of chlorite, talc, chrysotile and tremolite. The chrysotile and tremolite were determined to be asbestos.
If the river runs through a serpentinite belt, further mineralogical investigations should be done about asbestos.

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Amakusa pottery stone deposits are distributed in the Amakusa-Shimojima island, Kumamoto prefecture. Teikado-Toseki means pottery stone having lower refractoriness than the Seger Cone of SK20. XRD measurement indicates the existence of albite in it, but, albite has not been identified in the thin section until now. In order to observe the definite structure, we tried a new polishing technique; dry method. It revealed that albite has 50 micro meters in the mean size. This method is very effective for the observation on the clay rich samples.

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We investigate zircon U-Pb age of the gneissose quartz diorite in Futagojima Island. There are two types of zircon; clear fine grains and dusty coarse grains. The former indicate weighted mean age of 103.7 ± 1.6 Ma which is interpreted as protolith age whereas the latter indicate scattered younger ages which is considered to be rejuvenation by a later thermal effect. The metamorphism which formed gneissose texture of the rock is considered not to be Higo but a younger one.

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This study was conducted to quantitatively understand element mobilization during hydrothermal alteration. Oyasu Gorge is located in the south of Akita Prefecture, which is an active hydrothermal area. We collected samples with measuring the distance from hydrothermal vent and analyzed their major and trace elements. The proximal rocks indicate increase of Na, Si and decrease of Ca, Sr, Rb and Mg on isocon diagram. On the other hand, the distal samples show Na, Si decrease, while Mg, Ca increase. Black parts in proximal rocks show Ni, Cr and Zn increase.

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Coal fly ash is produced in thermal power plants but contains significant amounts of useful elements including rare earth elements (REE). Although the minerals and chemical composition of coals and coal fly ashes are different between Baganuur and Shivee-Ovoo, chemical compositions of glassy particles in their coal fly ashes are similar. Especially REE contents of colorless particles in both coal fly ashes showed greater than those of coal fly ashes. If the method to extract colorless particles from coal fly ash is developed, it represents a significant economic opportunity.

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The unique reaction texture was found in the albitite specimen collected from Ohya-district, Hyogo Prefecture. This albitite specimen was composed of Na-rich plagioclase (Ab₉₂), but albitization of these plagioclase was partly occurred into pure albite (Ab₁₀₀), near the contact boundary with jadeitite directly crystallized from the hydrous fluid.

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Current study deals with the evolution of microstructures in shallow crustal active fault within Himalayas, India. The outcrops portray an increase in fracture density, with consequent development of gouge, due to stress accumulations towards the core of thrust. The petrographic analysis, shows corresponding evolution of microstructures, suggesting pressure solution and cataclastic deformation as primary deformation mechanisms, with low deformation temperature.

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An association of eclogite and granitic orthogneiss, with 2×8 km in size, occurs at the Chandmani village, W. Mongolia. We have shown that amphibole-poor eclogite at the northern part of the body records UHP condition (2.8 GPa at 580 ºC) whereas amphibole-rich ones at the southern part experienced HP condition (<2.5 GPa and <550 ºC). Our result and previous K-Ar geochronology data suggest that the UHP metamorphism at 600 Ma might take place prior to the HP one at 550 Ma.

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The studied sample is a paragneiss from the Tromso Nappe in the Scandinavian Caledonides. Geothermobarometries gave P-T conditions of 640-700℃ and 1.5-1.7GPa for garnet core. Zircon geochronology suggested zircon core and mantle (2800-950Ma) were magmatic origin and the rim (480-430Ma) was recrystallized during metamorphism. The detrital zircon age spectra are similar to those of each side of the Caledonides. This metamorphic zircon ages are consistent with those of the previous study.

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Sri Lanka is a key area to reveal the Gondwana amalgamation. This study conducted the bulk chemistry and zircon U-Pb age dating for 45 high temperature metamorphic rocks from the Highland and Wanni Complexes. On the basis of these results we establish the tectonic evolution model for Sri Lankan metamorphic complexes.

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The present study highlights the deformation microstructure and chemical zoning in cataclastic garnet porphyroclasts in a quartzofeldspathic gneiss, Ranipathar Shear Zone of Phulbani Domain, Eastern Ghats Belt, India. The rocks contain cm- to mm-thick ultramylonite to pseudotachylite veins. Contrasting conditions of such vein formations and that of garnet zoning will be investigated from the data.

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Myanmar has been geologically divided into the Eastern and Western provinces separating by the 1200 km long and N-S trending Sagaing dextral strike-slip fault. The Mogok metamorphic belt, which extends along the western margin of the Eastern province, comprises marbles, calc-silicate rocks, and paragneisses of granulite facies. Evolution of metamorphic fluid during the peak granulite facies stage and subsequent retrograde stage recorded in these rocks is discussed.

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Based on petrologic and Raman spectroscopic approaches, we report the metamorphic evolution of newly discovered eclogite-facies pelitic schists, and present discussions of distributions of eclogite facies lithologies of the Sanbagawa belt in the Asemi-gawa region, central Shikoku, Japan.

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This study provides petrological data on a garnet glaucophane schist from the Kotsu area in the Sanbagawa belt. Pseudosection modeling reveals a decompression heating path during garnet growth, with the peak-P (2.2 GPa, 500 deg.C) and peak-T (1.8 GPa, 540 deg.C) conditions. The observed assemblage garnet + glaucophane + lawsonite + quartz + chlorite during garnet rim growth is consistent with the model predictions.

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One small block of eclogitic metabasite occurs within the serpentinite body, and it is a first discovery of eclogite evidence in the Gotsu area. Garnet, omphacite, glaucophane, and phengite are the constituents of the peak metamorphic stage, and these suggest eclogite facies metamorphic condition. The garnet-clinopyroxene exchange geothermometer and garnet-clinopyroxene-phengite geobarometer yielded 540-550 °C and 19 kbar for the peak metamorphic stage.

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Rate of kelyphitization of garnet was estimeted by applying a steady diffusion model accompanying a boundary migration and by the use of zoning width of the garnet adjacent to the kelyphite rim (for a Ronda garnet pyroxenite) and published diffuion data of garnet. The obtained rate is far greater than expected ascent rate of the peridotite body and therefore the termination of the kelyphitization cannot be ascribed to a cooling of the body but to a local stress development presumably occurred within the kelyphite rim due to the volume increase nature of the reaction.

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Ar-Ar analyses of biotites carried out for the samples collected systematically from the contact aureole revealed the ages older than the host rocks. This old biotite ages are due to that the biotites trapped the excess argon wave happened by the thermal heating. The excess argon waves also happen by the white mica decomposition in the high T metamorphic rocks and by the argon release from white micas during the deformation in the exhumations of the host schists. The author appeals to the audiences for the excess argon wave with reviewing the papers for the waves.

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We obtained the first evidence for regional ca. 1.8 Ga arc magmatism in the Lützow-Holm Complex (LHC) of East Antarctica. Based on the distribution of magmatic ages and lithologies, together with the geophysical data, the LHC can be divided into three units; the northern LHC (ca. 1.0 Ga juvenile arc), the central LHC (supracrustal unit), and the southern LHC (ca. 2.5 Ga microcontinent). We consider that the central LHC is a suture zone formed by the collision of the northern LHC and the southern LHC, and infer that the northern LHC and the Vijayan Complex in Sri Lanka were a single crustal unit.

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Garnet peridotites from Chijiadian in the Su-Lu region,China were reported to show UHP condition(>4GPa,>700°C) but kyanite-eclogites from the same area were reported to show about 3GPa and 800°C. Therefore we considered about the estimated pressure gap by applying new geothermobarometer. The kyanite-eclogites yielded about 4.0GPa at 700°C, and garnet peridotites yielded UHP condition of 5.0GPa,800°C.Thus, the pressure gap between eclogites and garnet peridotites was reduced.

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Metamorphic history of garnet amphibolite and pelitic schist from the Neldy Formation, Makbal district, Kyrgyz Northern Tien-Shan, Kyrgyzstan

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Garnet-glaucophane schist comprises mostly of garnet, amphibole (sodic, sodic-calcic and salcic: Gln, Wnc, Brs, Act, Mhb, Ed, Prg), epidote, albite, and chlorite, small amounts of omphacite, K-feldspar, rutile, titanite, hematite, and quartz. Garnet occurs as euhedral to subhedral porphyroblast and contains inclusions of amphibole (Gln, Wnc, Brs, Act), epidote, omphacite (X_Jd 0.29-0.41), chlorite, albite, K-feldspar, rutile, titanite, and quartz. The metamorphicconditions of garnet-glaucophane schists are estimated as 510 °C and 18.5 kbar in the eclogite facies.

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I would like to propose a thermodynamic model on the solubility of Fe and Ti in sillimanite coexisting with Fe-Ti oxide minerals.

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