We performed impact experiments of cratering using a two-stage light gas gun at Kobe University. We used a dunite block (10 x 10 x 3 cm) as a target and a Nylon projectile (1.6 mm in diameter).  Small fragments of the ejecta (~100 μm) were captured by silica aerogel (110 mg/cc). Their 3D shape distribution were measured in-situ using a high resolution X-rays CT machine. We also measured 3D shape distribution of fragments which were not penetrated into the aerogel with low ejection velocities, using SR-based micro-tomography at SPring-8. We compared these results with Itokawa particles.

View full abstract

Various materials and impact craters of the Solar System bodies, are obtained by progress steps of three states circulation at global and/or local system, which can be applied to formation of life organic molecules. Various impact craters are formed at fine-grained irregular target-rocks, though typical craters are found hard rocks (Earth) or icy surfaces (some satellites) on the Solar System.

View full abstract

NWA 6704 is a unique achondrite. We performed a detailed petrological and mineralogical study of this meteorite based on optical microscopy, secondary electron microscopy, micro-Raman spectroscopy, and electron microprobe analysis. We identified olivine, low-Ca pyroxene, high-Ca pyroxene, plagioclase, chromite, awaruite, pentlandite, and heazlewoodite. These minerals are almost identical to those in NWA 6693, which has been thought as one of paired meteorites of NWA 6704 although K-rich plagioclase was not identified in NWA 6704. However, the major crystal structure of low-Ca pyroxene is different between NWA 6693 and NWA 6704. In the former, the major phase is low-Ca pigeonite.

View full abstract

We examined the petrological/mineralogical characteristics of Allende CAI to study its crystallization process.

View full abstract

The canonical solar nebula pressure has been estimated to be 0.01-100 Pa.  The chondrules have been reproduced under the atmospheric pressure.  The textures of reproduced chondrules are similar to those under the atmospheric pressure rather than under the nebula condition (~1 Pa).  Chondrules might have formed under the atmospheric condition.  However, partial pressures relating volatile species (Fe, Si, Mn) have not been into consideration.  Using the newly developed furnace under the quasi-closed system, chondrules may be reproduced under the canonical nebula pressures.  The preliminary experimental results may show the decrease of the iron content.

View full abstract

The present study shows detailed petrographic and mineralogical features of the unique CO chondrite,Yamato(Y)-82094.As a result,Y-82094 seems to have been formed under reduced condition because of the presence of abundant metallic phases.Additionally,chemical composition of kamacite indicates anomalous metamorphic history inconsistent with other typical COs.

View full abstract

Early Cretaceous igneous rocks in the Kitakami Mountains are diveided into volcanic rocks, dike rocks, and plutonic rocks. Plutonic rocks are composed mainly of adakitic granites in central part of zoned plutonic bodies surrounding by adakitic to non-adakitic granites in marginal part. The exposure of the adakitic plutons is divided into two zones: from the eastern part of the north Kitakami belt to the eastern margin of the south Kitakami belt (E zone), and the inner part of the South Kitakami belt (W zone). Zircon U-Pb age of the adakitic granites in W zone are younger than those in E zone, they are considered to be derived from higher pressure and vapor-present condition.

View full abstract

Cretaceous Grt-Ms-Bt-granite intrusion is distributed in the Kanamaru district of the northern Niigata. Although the granite has a similar geochemical feature to that of A-type granitoid, this feature was the cause of the highly-fractionation of its magma.

View full abstract

Two granitoid samples from Vladivostok of southern part of the Voznesenka Belt yield 427.0 ± 3.1 Ma and 254 ± 3.4 Ma. Five granitoid samples from the Maizuru Belt yield 259.0 ± 3.0 Ma, 291.6 ± 4.3 Ma, 294.0 ± 4.5 Ma, 279.7 ± 2.4 Ma and 441.9 ± 2.8 Ma. The uncertainties in the ages are 95 % confidence interval (1.96 σ). Reffering to the coexistence of Triassic sequence and Silurian and Permo-Triassic granitoids, it seems that there are strong relations between the Maizuru Belt and southern part of the Voznesenka Belt.

View full abstract

Many greenstone-chert bodies occur in the Devonian accretionary complex in the Hangay Mountains, Central Mongolia. Previous studies concluded that they are mostly alkali basalt of seamount origin. Our research in the Uyanga Village, however, reveals that the greenstones are mostly tholeiitic, ferrobasalt is also abundant, and alkali basalt does not occur. We also find ferropicrite. These facts indicate their origin in an oceanic LIP. The high-Mg andesite occurs as sills and resembles sanukite in respect to high Cr# of spinel and distinct negative anomaly of Nb. These HMA sills may represent forearc magmatism related to subduction of a young oceanic plate or a spreading axis after the formation of the accretionary complex. 

View full abstract

Hawaiian shield volcanoes produce olivine tholeiite magma. On the other hand, most ocean island produce alikali basalt magma (OIBs).  Origin of the tholeiite magma in Hawaii plume was studied based on hjgh-pressure melting experiments with eclogite-peridotite hybrid system.

View full abstract

We here propose a new calculation method for estimation of primary basalt magmas from mid ocean ridges (MOR) and island arcs (tholeiite to mildly alkalic basalt with various H₂O). The calculation model uses a thermodynamic crystallization model of COMAGMAT 3.72 (COM3) which runs with an Excel spreadsheet calculator PRIMACALC 2.00 (PMC2) for mantle equilibrium and trace element back calculations of primary basalt.

View full abstract

Stratigraphy of northern Kita-Hakkoda volcano, consisting of Mae-dake, Tamoyachi-dake, Narusawa-daichicones, was established. Combined with the stratigraphy, differentiation process was investigated from whole-rock chemistry and mineralogy. The activity initiated with the effusion of differentiated tholeiitic basaltic magma around 0.4Ma. After a dormancy, the activity resumed around 0.2Ma with effusion of andesitic magma, followed by a series of lavas with a successive decrease in SiO₂ from andesite to basalt. Then, the magma composition jumped to high silica andesite. Disequilibrium mineral assemblages in calc-alkaline rocks imply open system processes. As indicated by linear trends between basalt and the high-silica andesite, magma mixing is a plausible process to produce the series. Stratigraphic chemical variation might be caused by temporal variation in mixing ratios.

View full abstract

During mingling of magmas, thermal equilibration induces resorption in felsic magma and crystallization in mafic magma. Crystals can also experience chemical fluctuation of surrounding magmas during mechanical mixing and hybridization These processes are well recorded as intracrystalline textures of phenocrysts in a mixed rock from Chokai volcano. Behaviors of crystals are well preserved as oscillatory and normally zoned margins surrounding felsic-derived rounded cores. Varieties in thickness and in compositions of the margins imply that after the thermal equilibrium the resorbed crystals are incorporated with the crystallizing mafic magma at different times during mingling.

View full abstract

Between AD 871 and 1801, magmatic activities in Chokai volcano occurred at least three times. Based on petrologic data of the historical lavas, previous studies revealed the erupted products were formed by magma mixing. Bulk compositions of lavas are depicted on same linear trends in silica variation diagrams. Here, we report the estimated time intervals between mixing and eruption, based on compositional zoning of mafic minerals in the Chokai historical lavas. Zoning patterns of olivine show that the time intervals were almost one month to four years.

View full abstract

During the 2004 eruption of Asama volcano, sulfur-rich basaltic magma repeatedly intruded into a felsic reservoir beneath the summit. Olivine phenocryst includes sulfur-rich mafic melt (S ≤ 2600 ppm) before the mixing. Olivine phenocryst also includes Cu and Ni-bearing heterogeneous sulfide globules and homogeneous Ni-rich pyrrhotite. In contrast, the major phenocrysts (ortho- and clinopyroxene, and plagioclase) include only homogeneous Cu,Ni-poor pyrrhotite. And these sulfides are also found to be scattered in the glassy groundmass. The melt inclusion and sulfide mineral data reveal that basaltic magma provides a large amounts of sulfur to the frontal volcanoes in central-northeastern Japan.

View full abstract

Ioto is an active volcanic island (8.5 km long in NE-SW and 4.5 km wide) located about 1250 km south of Tokyo. Since early February 2012, small explosive eruptions have repeatedly occurred at the Old Crater (Million Dollar Hole) in the western part of the island (JMA, 2013). Ejected mud materials collected in the vicinity of the crater consist of free crystals (plagioclase, clinopyroxene, olivine, Fe-Ti oxides), relatively fresh volcanic glass, altered volcanic glass, lithic fragment, altered lithic fragment and pyrite aggregate. No juvenile materials existed in the samples, suggesting these explosive events were phreatic eruption (Ikehata and Tamura, 2013).

View full abstract

The Cretaceous to Paleogene plutonic rocks are widely distributed as a basement rock of the NE Japan Arc. In this report, newly obtained Sr, Nd, Pb, and Hf isotopic composition are reported, and comparison and verification with a geotectonic division and isotope zone division are performed. The epsilon Nd-Sr (0Ma) diagram, the domain of the Abukuma Belt and the Ashio Belt is distinguished clearly. The epsilon Hf-Nd diagram shows the narrow extent, and the Abukuma and the Ashio Belts are distinguished more clearly. Re-classification of isotope zone by Hf isotope may possibly.

View full abstract

We investigated distributions of whole-rock chemical compositions in the Haki Granodiorite, Cretaceous granitic rocks in northern Kyusyu. The Haki Granidiorite mainly consists of medium-grained porphyritic hornblende biotite tonalite to granodiorite. The Haki Granidiorite indicates normal laterally compositional zonation.

View full abstract

The Zao volcano is one of epresentative stratovolcanoes in northeast Japan, situated in the central part of the Quaternary volcanic front. The most recent stage of the Zao volcano began at about 30 ka, and numerous small to medium-sized explosive eruptions of calc-alkaline basaltic andesite magmas have occurred since then. The eruption products of this stage are divided into Komakusadaira agglutinate (ca. 32 to 13 ka), Umanose agglutinate (ca. 7.5 to 4.1 ka), and Goshikidake pyroclastic rock (ca. 2.0 ka to present). We will show the stratigrapy and temporal change in chemical compositions of eruption products in Umanose agglutinate activity.

View full abstract

During c. 300 to 100 ka activity of the Zao volcano, several middle sized edifices were formed. The Kumanodake edifice is one of them. The eruption products of Kumanodake edifice can be divided into four units. All of the rocks belong to medium-K calc-alkaline series. The SiO₂ contents of first two units are c. 58-60%, while those of third and fourth are 55.5-57.5% and c. 53%, respectively. All units are plotted on same general trends in most of the SiO₂ variation diagrams. But, some of the units are not plotted on the general trends in some of the diagrams.

View full abstract

Black-colored olivine has been found in some dunites (or wehrlites) from Horoman, Iwanai-dake and Oman ophiolite. It is characteristically coarse, and not found from associated harzburgites. The black olivine contains minute (< 10µ) rod-shaped black inclusions, which are magnetite associated with diopside determined with laser Raman spectroscopy. Olivine is free of the black inclusions around a primary chromite. TEM observations show various textures indicating exsolution of the inclusions from host olivine. The black inclusions show homogeneous distribution, which precludes an oxidation origin due to oxygen supply from the outside. They possibly formed by dehydrogenation from a primary OH-bearing olivine.

View full abstract

There are many ultramafic complexes and chromitites in the Sangun zone (Oeyama-ophiolite), Central to Northern Kinki district, southwest Japan. We are clarifing the chemical compotition of chromian spinel from chromitite. And we are discuss about relationships between size of chromitite and chemical composition of spinel.   

View full abstract

We described petrological and geochemical characteristics of basal peridotites of Oman ophiolite overlying metamorphic sole as an analogue of slab-mantle interface in the mantle wedge. The basal peridotites are slightly serpentinized lherzolite, commonly containing amphiboles (hornblende and tremolite). Clinopyroxene and hornblendes in peridotites close to the boundary have LREE and LILE-enriched characters. The basal peridotites were surely hydrated at relatively high temperatures, and LREE and some LILE are added to them during the hydration.

View full abstract

Dunites and olivine-clinopyroxenites can be formed by simple crystal cumulation from melts, but wehrlites cannot be formed by the same way. The olivine-clinopyroxene rocks from the Takashima xenolith suite show gradual modal variations from dunite to clinopyroxenite. They show recrystallization textures formed at subsolidus conditions, leading to change of Mg# of olivine and clinopyroxene. The igneous Mg#s of olivine and clinopyroxene are recalculated. The mineral chemistry indicates that the order of formation is dunites through clinopyroxenites to wehrlites. We will discuss the formation process.

View full abstract

Petrographical and geochemical approaches were adopted by samples of the Inagawa Granite and Naegi-Agematsu Granite, distributed along upper river basin of Toki River. And gravel from upper layer of these rock bodies were investigated for identification of granitic rock bodies. Petrographic feature of these rock bodies are distinguished by hornblende or muscovite contents. Major element analyses of biotites by EPMA showed the samples from the Naegi-Agematsu Granite were rich in Fe relative to those from the Inagawa Granite. By using this method, the gravel from upper layer of these rock bodies is suggested to be from the Naegi-Agematsu Granite area.

View full abstract

Post-collisional layered syenite complex is exposed in the Sør Rondane Mountains, eastern DML. The syenite complex has been derived from the high-K alkaline magma, and fractional crystallization and accumulation play an important role of formation of the layered structure. The present result demonstrate that the Sør Rondane Mountains underwent the extensional collapse similar to that observed in other part of DML.

View full abstract

The purpose of this research is to confirm whether Fe concentration on dislocation core occurs in deformed mantle olivine, due to Cottrell atmosphere. The samples we observed are alpine type peridotites and mantle xenoliths in basalt. The present result is that Fe concentration is observed in the former, not in the latter samples. The microstructural observations suggest that the result of the mantle xenoliths is caused by static annealing or higher additional stress applied to the sample after steady state creep, or that the Cottrell atmosphere does not occur in the upper mantle.

View full abstract

Isochemical kelyphite was successfully synthesized from a natural garnet using a piston cylinder apparatus and the run product was compared with natural examples of such kelyphite.

View full abstract

In order to clarify generation process of slickenside, we observed the microstructures of slickenside developed in chert, limestone and greenstone. The present result is the following. The slickenside is generated during faulting due to slip concentration only within 50 nm – 100 nm in width from slip surface. This layer is composed of very tiny flattened grains with 50 nm-100 nm in diameter and ca. 10 nm in height. These grains is probably formed by crashing the fault fragment. This generation process of slickenside is similar to that of tribofilm. Now we study those of serpentinite and coal seam.

View full abstract

All mineral identification by X-ray and electron beam methods should be applied from macroscopic to microscopic nano-scales, which is originally at water planet Earth. extraterrestrial materials of the Moon, Asteroids and Mars are different system with non-active one or two states and without global circulation. Mineral identification can be applied to extraterrestrial materials, but no direct indication of formation condition, because of dynamic unstable formation of main impact process. In short, mineral combinations on the extraterrestrial materials are limited to apply from Earth’s formation which is considered to be specificity of the Earth in the Solar System.

View full abstract

Unwanted multiple difrrection by analyzing crystal of wavelength-dispersive spectrometer (WDS) causes a sharp “negative” X-ray peak, know as “background hole”. PET (002) crystal has 33 possible hole positions and 10 of them are observed using electron probe microanalyzer (EPMA).

View full abstract

According to geology, petrology and fluid inclusion analysis, two main gold mineralization events are proposed in the Boroo deposit. Early stage disseminated and stockwork mineralization caused by granite emplacement, and later stage quartz vein type mineralization due to hydrothermal activity related to structural fault.

View full abstract

Ore minerals of Kuki mine, Onan district, Shimane Prefecture, Japan, were investigated to identify silver-bearing minerals and characterize mineralization. Kuki mine is a vein-type deposit occurring in quartz porphyry. Samples were collected from dump of Oyokodani-Mabu and Mizunuki-Mabu. Wall rocks are serisitized, chloritiized and silicified. Main ore minerals are pyrite, galena, sphalerite, chalcopyrite and arsenopyrite. Silver minerals with less than 1 micron occur around galena grains in pyrite, and those with less than 2 microns occur in fissures in sphalerite. Crystallization sequence is pyrite+arsenopyrite -> sphalerite -> galena -> chalcopyrite -> pyrite -> silver minerals.

View full abstract

Ca-rich plagioclase (An > 90 %) larger than 10 mm, which is called anorthite megacryst, occurs commonly from basalt – andesite in Japanese Island arc. We investigated plagioclase megacrysts from Mt. Fubou, Sado island and Fukue island and found sulfide inclusions in all of the specimens. Sulfide inclusions are 30 - 50 µm and droplet shaped. In particular, lineation of sulfide inclusions were observed in bytownite megacrysts from Sado island. Electron microprobe chemical analysis and texture observation of them indicate that these bytownite crystals grew through Ostwald Ripening during temperature cycling.

View full abstract

The Lace deposit located in the south part of Republic of Serbia is an epithermal Pb, Zn and Au vein type deposit.Three metallogenic provinces, Dinaric, Serbo Macedonian and Chpatho Balkan are known in Serbia. Many epithermal vein type and skarn type deposits are recognized in the Serbo Macedonian province. The Lece deposit located in Serbo Macedonian province, accompanies ore minerals such as pyrite, sphalerite, galena and quartz, amethyst and siderite as gangue minerals. In this study, we will report mineralogy of quartz vein and Pb, Zn ore 

View full abstract

Ore samples from the Akenobe mine are analyzed for the purpose to elucidate the detailed behaivior of Indium. Roquesite exists in the Chiemon, Ginsei and Ryusei vein. Cassiterite and/or stannite often exist in the part where roquesite co-exists with sphalerite. This means that mineralization of In and Sn has a close relationship. Indium contents are thought to be high with increasing of formation temperature. The Shirogane vein is the brittle deformation (Shoji, 1982), which means lower temperatures than others. This difference of temperature might be a main reason of difference in In occurrence.

View full abstract

 In order o elucidate provenance of the Eocene-Miocene sandstones, we obtained age of detrital monazite and compared with age distributions of present sand samples from major rivers in East Asia.  Studied areas are Sasebo (Early Eocene to Miocene), Tsushima (early Miocene), Goto Islands (early Miocene) and Nagato (Oligocene to Miocene), Yamaguchi Prefecture.   It is concluded that the detrital minerals in Eocene-Early Oligocene sandstones in Sasebo were derived from nearby terrane: Northern Kyushu. On the other hand, age distribution patterns in Late Oligocene to Early Miocene sandstones are similar to that of Yangtze River.

View full abstract

There are many ultramafic complexes in the Oeyama ophiolite, eastern Chugoku and northern Kinki districts, southwest Japan. We are clarified the chemical composition of detrital chromian spinel from the ultaramafic complexes. Cr# of chromian spinels are 0.43-0.56 of Sekinomiya complex, 0.36-0.78 of Izushi complex, 0.43-0.69 of Oeyama complex, 0.78-0.90 of Wakasa complex and 0.25-0.86 of Oshima complex. And Cr# of chromian spinels from chromitite of Sekinomiya and Oeyama complexes are 0.38-0.46. Above Cr# of spinels from chromitite of eastern Chugoku and northern Kinki district are higher than those of central Chugoku district.

View full abstract

Ophiolitic chromitites are classified into two types, concordant and discordant, in terms of structural attitude with surrounding mantle harzburgite. Spinel chemistry of discordant chromitites, dunite envelopes and surrounding harzburgites from Oman ophiolite, indicates that discordant chromitites were formed by arc-related magma. In a deeper mantle section along Wadi Hilti, two types of harzburgites, arc-type and oceanic-type, are exposed near the discordant and concordant chromitites in the same cliff, respectively. Contact of two types of harzburgites shows a gradual change in spinel chemistry. This indicates that pre-existing oceanic harzburgite was modified by arc magma.

View full abstract

Elemental mappings of felsic gneiss from Mt.Riiser-Larsen were obtained by using X-ray Fluorescence microscope and wave dispersive X-ray diffractometor, to reveal the heterogeneity chamical compositions of the gneiss and feldspars (Tfs) in the gneiss. In the results, the gneiss were clasified into 4 parts according to mineral assemblages; (a)oligoclase part (b)Tfs part, continuously-varied bulk chemical compositions (c)Or-rich Tfs part (d)myrmekite-like texture part that is composed of oligoclase and quartz. The occurrence of these 4 parts and heterogeneity of the gneiss are able to be explained reasonably by partial melting on ultra high temperature metamorphism and following crystal fractionation of feldspar.

View full abstract

In recent years, Ohi et al. (2008) found the stability fields of high-temoperature Opx (HT-Opx) in the system Mg2Si2O6-CaMgSi2O6. In present study, we revealed the stability field of HT-Opx in Mg2Si2O6- Fe2Si2O6 system by high-temperature X-ray diffraction (HT-XRD) experiments.

View full abstract

By introducing a chemical and internal textural classification of zircons, to Southwest Group of Sri Lanka, it may helps to identify the relationships between internal textural domains, and petrological evolution of the rock. The chemical analyses of major minerals were used to calculate the P-T conditions of the zircon bearing host rocks. According to the internal textures of zircon, three main events can be proposed as sediment deposition, first stage of metamorphism, and second stage of metamorphism. These different textural patterns in zircon are related to the metamorphic and temperature changes around the study area.

View full abstract

Here we report a wide spectrum of fluid chemistry during multiple events of fluid-rock interaction throughout the evolutionary history (~950 Ma to ~500 Ma) of lower crustal segment of the Eastern Ghats Belt. This study reveals entrapment of very high-density CO₂ fluid at the near-peak UHT metamorphic condition followed by at least two events of infiltration of carbonic fluids (mixed with vapor) at different crustal levels during reworking and eventual exhumation of this crustal segment up to the shallow depth. There is a possible resetting effect of fluids on the monazite and zircon dating.

View full abstract

The eclogite-bearing Alag Khadny metamorphic complex in the Lake Zone, SW Mongolia located in the central part of the Central Asian Orogenic Belt, consist mainly of orthogneisses which interleaving with marbles including lenses of garnet-chloritoid schists. Eclogites have two modes of occurrence, i.e. lenses and boudins in orthogneisses (eclogite 1) and those in marbles (eclogite 2).

View full abstract

We conducted geochronological study of the metamorphic rocks from east-central Madagascar. Ca. 3300 Ma, 2700 Ma, 820-760 Ma, 550 Ma, and 550-490 Ma are the significant ages for the crustal evolution process. The last age is the metamorphic age and the other ages are the igneous ages. Ca. 3300 Ma and 2700 Ma were independently recognized two of three domains, respectively. Ca. 820-760 Ma was recognized from both of these domains. Ca. 550-490 Ma was recognized from all three domains. Consequently, distinct Archean domains were juxtaposed by ca. 820-760 Ma and had experienced regional metamorphism at ca. 550-490 Ma.

View full abstract

Pelitic schists intercalated within Seba eclogitic basic schists in the Sambagawa metamorphic belt of the Besshi district preserve evidence of three distinct metamorphic events. These are a precursor metamorphic event, a first high-pressure metamorphic event, and a second high-pressure metamorphic event.

View full abstract

Mmetamorphism of the Eastern Iratsu mass in the Sambagawa metamorphic belt, Besshi district, central Shikoku, Japan is: 1)granulite facies metamorphism, 2)high-T eclogite facies metamorphism, 3)low-T eclogite facies metamorphism and 4)epidote amphibolite metamorphism. There are two events of eclogitefacies metamorphism distinguished in the Eastern Iratsu mass.

View full abstract

We reviewed the zonal structure of garnet and the paragenesis of inclusions in garnet from the Asemi-gawa region in the Sanbagawa belt. Residual pressure retained by quartz inclusions in garnet was also systematically determined. Based on these data, we discuss the petrological and mineralogical significance of an investigation of inferred eclogite facies metamorphism in the Asemi-gawa region.

View full abstract

Graphite-bearing pseudotachylyte was examined using micro-Raman spectroscopy and stable carbon isotope analysis to detect the activity of fluid during the coseismic slip. Stable carbon isotope analyses show a broad range of values between -27.8 and -45.6 ‰ for graphite. These data show the deposition of graphite in silicate melts. This process implicates that the frictional melting generates the COH fluids by dehydration of sheet silicate and oxidation of carbonaceous materials. These fluids have a potential for changing the dynamic properties of flash fluid pressure in the fault plane and may explain the anomalous discharge of carbon after large earthquakes.

View full abstract