Yasuhito Osanai

Verified

Yasuhito verified their affiliation via an institutional email.

Learn more

Verified

Yasuhito verified their affiliation via an institutional email.

Learn more

• PhD
• Professor Emeritus at Kyushu University

This paper reports laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) zircon U–Pb ages of a suite of high-grade metamorphic rocks collected from Sinnan Rocks, Akebono Rock, Niban Rock, Gobanme Rock, Tenmondai Rock, Akarui Point, Cape Omega, and Oku-iwa Rock along the Prince Olav Coast, in the Lützow-Holm Complex (LHC), East Ant...

The metamorphic and plutonic rocks within a serpentinite mélange in the Nagato Tectonic Zone, Yamaguchi prefecture, southwest Japan have been known as a part of the early Paleozoic rock record in Japan. Thus, they play an important role in deciphering the tectonic evolution of proto-Japan. This study determined their U–Pb zircon ages to deduce the...

Granitic and gabbroic xenoliths have been found within dacitic lavas in the Hime-shima volcanic group (HVG) of northeastern Kyushu, Japan. The HVG is located near the boundary between the Ryoke and Sangun belts, suggesting that the HVG and associated crustal xenoliths may provide insights into the subsurface distribution of the Ryoke and Sangun bel...

We have found corundum in direct contact with quartz and biotite and as inclusions in garnet in the pelitic gneisses of northern Austkampane in the Northeastern (NE) Terrane of the Sør Rondane Mountains (SRM), East Antarctica. Our samples, which include corundum–bearing gneisses, show petrographic features such as staurolite inclusions in garnet, c...

The Dai Loc Complex, located in the southern Truong Son Belt, is separated from the northern Kontum Massif by the early Paleozoic Tam Ky–Phuoc Son suture zone. This study presents new zircon U–Pb ages and petrographic observations of the migmatitic pelitic gneisses and mylonitized granite intrusions from the Dai Loc Complex in order to constrain th...

To further constrain the tectonic evolution of the convergent margin of the West Mongolian segment in the Paleo–Asian Ocean, we have investigated coarse-grained kyanite metapelites associated with quartz veins in the Gobi Altai Mountains, Mongolia, where the metamorphic belt is in a thrust contact with a Paleozoic accretionary complex. The metapeli...

The Kirigamine area is one of the major obsidian sources in the Chubu-kanto region of central Japan, and is regarded as an important archaeological study area for improving the understanding of historical changes in human–environment interactions related to obsidian procurement activities during the Upper Paleolithic. Previous studies have presente...

This study reported the U-Pb ages and Hf isotopes of the zircons of Triassic and Silurian metamorphic rocks in the Kontum Massif, central Vietnam to understand the origin and evolution of the Indochina Block. The detrital zircon signature of the Triassic metasedimentary rocks corresponds to the Neoproterozoic sequence in the Indochina Block and tha...

The Oshima metamorphic complex, which is located on Oshima Island, western Ehime, Shikoku Island, is a rare high-temperature metamorphic complex in the outer belt of Southwest Japan. The complex and accompanying granitic mylonites were subjected to zircon U-Pb age dating by LA-ICP-MS and monazite U-Th-Pb chemical age dating by FE-EPMA. The complex...

Granitoid magmatism is widespread in the Mongolian Altai, and it provides critical information to understand the crustal formation, evolution, and growth. This study reports newly investigated petrography, whole–rock geochemistry, and zircon U–Pb geochronology of granites and quartz syenites emplaced in the Mongolian Altai to investigate their sour...

Felsite inclusions (FIs) in granulite garnets from continental collision orogens are supercooled felsic melt inclusions. Not only do these represent non-equilibrium textures , such as dendritic and spherulitic crystals of quartz and other minerals, but the porphyritic texture is that of hypabyssal and volcanic rocks. This paper presents representat...

DOI:10.17014/ijog.7.3.225-239Garnet amphibolites, which suggest medium-pressure/high-temperature (MP/HT), are widely recognized in Luk Ulo Complex, Central Java. Their occurrences associated with high-pressure/low-temperature (HP/LT; eclogite, blueschist) metamorphic rocks in the Luk Ulo Complex will provide important constraint on the geodynamic m...

In this study, we investigated the level of contamination of agricultural soil near an old recycling lead smelter in Vietnam and proposed an effective treatment for the remediation of the soil. The analysis of soil samples using an ICP-MS method revealed that the soil in the area was heavily contaminated by heavy metals, especially lead (Pb) with c...

The Central Asian Orogenic Belt had been formed by amalgamation of voluminous subduction–accretionary complexes during the Late Neoproterozoic to the Mesozoic period. Mongolia is situated in the center of this belt. This study presents new zircon U–Pb geochronological, whole-rock major and trace element data for granitoids within central Mongolia a...

A narrow zone of migmatitic rocks forms part of the metamorphic complex associated with the Boroujerd plutonic complex in the north-western part of the Sanandaj-Sirjan zone, Iran. It includes stromatic, dyktionitic, schollen and massive migmatite, metatexites and diatexites. Leucosome (alkali-feldspar granitic and trondhjemitic) and mesosome are we...

FeAlO3a) was synthesized under ultrahigh–temperature metamorphic conditions. The assemblage of FeAlO3, SiO2–rich melt and vapor was obtained from a mixture of Rundvågshetta sillimanite and reagent–grade Fe2O3 (weight ratio of 95:5) in Pt capsules at pressures of 5 and 9 kbar and a temperature of 1050 °C under hydrous conditions. No hematite was fou...

In this paper, we describe the metamorphic conditions of Fe-rich granulite and variations in rare earth elements (REE) between peak garnet porphyroblasts and secondary garnet coronae. The Fe-rich granulites were collected from Vesthaugen, Sør-Rondane Mountains, East Antarctica, and consist mainly of cordierite, garnet, spinel, perthite, K-feldspar,...

Detailed geochronological and petrological investigations of metamorphic and igneous rocks can significantly improve our understanding of the tectonic processes that occur in orogenic belts. The Kon Tum Massif, central Vietnam, includes various types of magmatic and metamorphic rocks, the latter including ultrahigh- to high-temperature units. The L...

Metamorphic rocks in the Kontum Massif, including the Kannak, Ngoc Linh and Kham Duc Complexes are characterized by amphibolite- to granulite-facies metamorphism and their mono- versus poly-metamorphic evolution is a matter of debate. In this study, we constrained on the timing of high-grade metamorphism in this massif by combining laser ablation i...

The Khatsavch porphyry Cu-Au (Mo) deposit is located in the Gurvansayhan island arc terrane of South Mongolia, approximately 45 km southwest of the Oyu Tolgoi Cu-Au district, one of the largest porphyry-type Cu-Au deposits in the world. The mineralization of the Khatsavch deposit is spatially and temporally associated with the second stage of the B...

The Higo metamorphic terrane in west–central Kyushu, southwest Japan, consists of a sequence of greenschist– to granulite–facies metamorphic rocks. This study reports the U–Pb Zrn ages and rare earth elements (REE) characteristics of Zrns and Grts from pelitic gneisses in the Higo metamorphic terrane to constrain its timing of high–temperature meta...

Soil quality, especially its toxic elements content, plays an important part in clarifying the sustainability of an estuarine ecosystem. In this study, six toxic elements (As, Pb, Cd, Zn, Cr, Cu) in soils and sediments of the Ba Lat estuary, northern Vietnam, were assessed using the ICP-MS technique. Soil properties, such as major minerals, soil pa...

Ultrahigh–temperature (UHT) granulites characterized by the parageneses of sapphirine + quartz and orthopyroxene + sillimanite + garnet + quartz are found in Rundvågshetta, Lützow–Holm Complex (LHC), East Antarctica. In this study, we report previously undocumented features of the UHT pelitic granulites, including the presence of felsite–nanogranit...

Gem-quality zircon megacrysts occur in placer deposits in the Central Highlands, Vietnam, and have euhedral to anhedral crystal shapes with dimensions of ~3 cm in length. These zircons have primary inclusions of calcite, olivine, and corundum. Secondary quartz, baddeleyite, hematite, and CO2 fluid inclusions were found in close proximity to cracks...

Meta-pelitic rocks with interlayers of meta-psammites within the inner thermal aureole of the Alvand plutonic complex (Sanandaj-Sirjan Zone (SaSZ), western Iran) underwent partial melting; generating various types of migmatites. The mesosome of the Hamedan migmatites is classified into two groups: (1) cordierite-rich and Al-silicate-poor mesosomes...

The oxidation states of Fe within olivine, orthopyroxene, clinopyroxene, and spinel in a spinel lherzolite xenolith from the Tariat Depression, Mongolia were investigated using ⁵⁷Fe Mössbauer spectroscopy to evaluate the redox condition of the upper mantle from which the Tariat spinel lherzolite xenolith was derived. The purity of separated mineral...

The high-grade metamorphic rocks of Sri Lanka place valuable constraints on the assembly of central parts of the Gondwana supercontinent. They are subdivided into the Wanni Complex (WC), Highland Complex (HC) and Vijayan Complex (VC), but their correlation with neighbouring Gondwana terranes is hindered by a poor understanding of the contact betwee...

We have investigated the geological processes recorded in aluminous granulites from the Red River shear zone in northern Vietnam using mineral and whole-rock chemistries, fluid inclusions, metamorphic pressure–temperature paths, and geochronology. The granulites are extremely rich in Al2O3 (36.3–50.9 wt%), TiO2, and total Fe2O3, and poor in SiO2 (7...

Ultrahigh-temperature (UHT) and ultrahigh-pressure metamorphism indicate extreme metamorphic conditions in regional metamorphic settings. In particular, the metamorphic temperature of UHT metamorphism is the highest limit of crustal metamorphism, exceeding 900°C and is equivalent to the temperature of basaltic magma. Typical UHT metamorphic rocks h...

A series of arsenic remediation tests were conducted using a washing method with biodegradable organic acids, including oxalic, citric and ascorbic acids. Approximately 80% of the arsenic in one sample was removed under the effect of the ascorbic and oxalic acid combination, which was roughly twice higher than the effectiveness of the ascorbic and...

We investigated the stability of Fe3+- and Fe2+-rich armalcolite at pressures 6–10 kbar and temperatures 900–1080 °C under the high oxygen fugacity. Armalcolite was synthesised in the bulk Mg/(Mg+Fetotal) of 0.2 from the mineral mixture of ilmenite, rutile and titanomagnetite (or ulvöspinel) within a platinum capsule at all experimental P–T conditi...

Here we report the occurrence of garnet porphyroblasts that have overgrown alternating silica-saturated and silica deficient microdomains via different mineral reactions. The samples were collected from ultrahigh-temperature (UHT) metapelites in the Highland Complex, Sri Lanka. In some of the metapelites, garnet crystals have cores formed via a deh...

We report first finding of low–temperature eclogite–facies metamorphism from the Red River shear zone in northern Vietnam that has been known as the Paleogene high–temperature metamorphic belt. The rock is extremely aluminous (50.13 wt% Al2O3) and oxidized [Fe3+/(Fe3+ + Fe2+) = 0.89] emery–type rock. Its composition is also characterized by very lo...

Chemically precipitated carbonate sediments directly record seawater composition that helps to decode the Earth’s paleo–environment, the existence of paleo–oceans, and provide valuable clues on the paleo–tectonic position of continents through Earth’s history. In addition, the geochemical and isotopic composition of carbonate rocks have a strong de...

The Kontum Massif is situated in the southern part of Trans Vietnam Orogenic Belt (TVOB), central Vietnam, and contains various types of magmatic and metamorphic rocks, the latter including both ultrahigh–pressure and ultrahigh–temperature units. While geochronological data indicate the existence of two main tectonothermal events at 480–420 Ma and...

The regional ultrahigh-temperature (UHT) metamorphism of the Highland Complex, Sri Lanka is well established and has an important role in our understanding of the tectonic history of the Gondwana supercontinent. U-Pb zircon dating of sapphirine-bearing Mg-Al granulites yielded two major metamorphic age populations at approximately 620-590 and 563-5...

The ultrahigh-temperature (UHT) regional metamorphism of Sri Lanka has a significant role in understanding the tectonics and formation of the Gondwana supercontinent. Sri Lanka is specifically important because of its central position in Gondwana, located between southern India, Madagascar and eastern Antarctica. In particular, the Highland Complex...

This contribution reports the metamorphic evolution of the high-pressure metamorphic rocks from the Bantimala Complex, South Sulawesi, Indonesia. Barroisite-bearing and barroisite-free eclogites were examined to assess their metamorphic evolutions, which have implications regarding the tectonic conditions in this region. The eclogites mainly consis...

The Sør Rondane Mountains in East Antarctica consist of the various metamorphic rocks and several plutonic rocks, which are related to formation of Gondwana supercontinent. In order to understand the detrital provenances, LA–ICP–MS zircon U–Pb dating were conducted from metamorphosed sedimentary rocks in southern Sør Rondane Mountains. Detrital cor...

This paper presents metamorphic evolution of metamorphic rocks from the Meratus Complex in South Kalimantan, Indonesia. Eight varieties of metamorphic rocks samples from this location, which are garnet-bearing epidote-barroisite schist, epidote-barroisite schist, glaucophane-quartz schist, garnet-muscovite schist, actinolite-talc schist, epidote sc...

We investigated the stability of Fe3+- and Fe2+-rich armalcolite at pressures 6--10 kbar and temperatures 900--1080 C under the high oxygen fugacity. Armalcolite was synthesised in the bulk Mg/(Mg+Fetotal) of 0.2 from the mineral mixture of ilmenite, rutile and titanomagnetite (or ulvöspinel) within a platinum capsule at all experimental P-T condit...

We investigated the stability of Fe 3+-and Fe 2+-rich armalcolite at pressures 6–10 kbar and temperatures 900–1080 °C under the high oxygen fugacity. Armalcolite was synthesised in the bulk Mg/(Mg+Fe total) of 0.2 from the mineral mixture of ilmenite, rutile and titanomagnetite (or ul-vöspinel) within a platinum capsule at all experimental P–T cond...

We investigated the stability of Fe3+- and Fe2+-rich armalcolite at pressures 6–10 kbar and temperatures 900–1080 °C under the high oxygen fugacity. Armalcolite was synthesised in the bulk Mg/(Mg+Fetotal) of 0.2 from the mineral mixture of ilmenite, rutile and titanomagnetite (or ulvöspinel) within a platinum capsule at all experimental P–T conditi...

Four amphibolite-faciespelitic gneisses from the western Mongolian Altai Range exhibit multistage aluminosilicate formation and variouschemical zoning patterns in garnet. Two of themcontain kyanite in the matrix and sillimanite inclusions in garnet, and the others have kyanite inclusions in garnet with sillimanite or kyanite in the matrix. The Ca z...

Early Cretaceous igneous rocks in the Kitakami Mountains consist of volcanic rocks, dike rocks, and plutonic rocks, from older to younger. Plutonic rocks are composed mainly of adakitic granites in central part of zoned plutonic bodies surrounded by adakitic to non-adakitic granites in marginal part. These adakitic plutons is divided into E and W z...

We have experimentally confirmed that the solubility of SiO2 in clinopyroxene at ultrahigh-pressure metamorphic conditions is buffered by coesite and kyanite. The present findings were derived from high-pressure experiments on metapelite glass, powdered andesite and eclogite glass under anhydrous conditions. The metapelite glass and powdered andesi...

We have experimentally confirmed that the solubility of SiO2 in clinopyroxene at ultrahigh-pressure etamorphic conditions is buffered by coesite and kyanite. The present findings were derived from high-pressure xperiments on metapelite glass, powdered andesite and eclogite glass under anhydrous conditions. The metapelite glass and powdered andesite...

The southern part of Okushiri Island in the present-day back-arc margin of the NE Japan arc is one of the rare convergent plate boundaries where similar magma types (high-magnesian adakitic andesite (HMAA) and high-TiO2 basalt (HTB)) have been erupted concurrently at more than one time. Oligocene HMAA can be divided into two types: HMAA-I is charac...

In order to understand the age and tectonic framework of Eastern to Peninsular Thailand from the viewpoint of basement (metamorphic and plutonic) geology, the LA-ICP-MS U-Pb zircon dating and the chemical Th–U-total Pb isochron method (CHIME) monazite dating were performed in the Khao Chao, Hub-Kapong to Pran Buri, and Khanom areas in Eastern to Pe...

This paper explains the first report in metamor-phic evolution of pelitic schist from Barru Complex in South Sulawesi, Indonesia. Garnet-biotite-muscovite schist was examined petrologically to assess the metamorphic evolution history, which has implications on tectonic condition of this region. The rock mainly composed of garnet, biotite, muscovite...

The ‘Wariyama Sheared Granodiorite’ occurs along the east side of the Futaba Fault with the Wariyama uplift zone, Miyagi, Japan. Rocks from the ‘Wariyama Sheared Granodiorite’ can be geochemically classified as typical adakite, and further subdivided into medium-grained and K2O- and Sr-poorer rocks, and coarse-grained and K2O- and Sr-richer rocks....

The Yatsushiro area in Kyushu Island, southwest Japan, forms the western tip of the Kurosegawa tectonic belt. This area is underlain by a serpentinite melange with complicated tectonic block assemblage of granitic rocks, high-temperature (HT)-type metagabbro (Grt-Cpx granulite, Grt-amphibolite and Cpx-bearing amphibolite), and high-pressure (HP)-ty...

High-Mg, high-Al metasedimentary gneisses from the Altai Mountains, Mongolia, belonging to a subduction-accretion complex within the Central Asian Orogenic Belt can be divided into five rock types on the basis of mineral assemblages. Most rock types have high MgO and Al2O3 content and low CaO, Na2O, Rb, and Sr content. All rock types experienced a...

Various metamorphic rocks are exposed in the central part of Indonesia, including the islands of Java, Kalimantan and Sulawesi. Metamorphic complexes, regarded as products of Cretaceous subduction of Indonesia outcrop in Central Java, South Kalimantan, and South Sulawesi. The lithology in these locations is predominantly composed of high-pressure m...

Here we report on the unexpected occurrence of felsic (granitic) inclusions with quench textures such as spherulite and dendrite (hereafter referred to as “felsite inclusions”), similar to some volcanic rocks, within garnet in presumably “slowly cooled” lower-crustal granulites of various geologic ages ranging from Early Proterozoic to Middle Paleo...

Jiwo Hills is an isolated hill with approximately occupied 30 km 2 in Bayat area of Central Java. The Jiwo Hills has been considered to be composed of very low-grade metamorphic rocks. This contribution explains a preliminary view of the metamorphic rocks from collected rocks sample in the Jiwo Hills. Common metamorphic rocks found in this area are...

A possible armalcolite pseudomorph has been identified in garnet–sillimanite gneiss from Skallevikshalsen, located c. 30 km NE of Rundvågshetta, in a terrane with the highest metamorphic grade in the Lützow-Holm Complex, East Antarctica. It occurs as an Fe–Mg–Ti compositional domain consisting of ilmenite, rutile and pseudorutile, partially mantled...

Metamorphic rocks in the central part of Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica, are classified into three types based on petrological characteristics. (i) The Austkampane area preserves c. 800 °C and 0.5–0.6 GPa peak metamorphic conditions followed by decompression and subsequent isobaric cooling and later hydration (A-...

A possible armalcolite pseudomorph has been identified in garnet–sillimanite gneiss from Skallevikshalsen, located c. 30 km NE of Rundvågshetta, in a terrane with the highest metamorphic grade in the Lützow-Holm Complex, East Antarctica. It occurs as an Fe–Mg–Ti compositional domain consisting of ilmenite, rutile and pseudorutile, partially mantled...

The Ryozen Formation, which crops out on the trench side of the NE Japan arc, contains middle Miocene rhyodacite with adakite-like trace element geochemical characteristics (Ryozen adakitic rhyodacite) and spatially and temporally related basalt (Ryozen basalt) and andesite (Ryozen andesite). K-Ar age data for the basalt and a zircon U-Pb age for t...

In this paper we clarify the history of deformation in the Sor Rondane Mountains (SRMs), eastern Dronning Maud Land (DML), East Antarctica, and construct a form-line contour map of the metamorphic and plutonic rocks in order to comprehend their structural features and provide constraints on the collisional tectonics of East and West Gondwana. We di...

This paper provides a detailed analysis of the geological evolution of the southern Austkampane region in the Sor Rondane Mountains, Antarctica, using geological and petrographical observations, geochemical, geochronological, radiogenic, and stable isotopic data, and metamorphic petrological techniques. The study area is dominated by felsic gneisse...

The Sor Rondane Mountains of eastern Dronning Maud Land, East Antarctica can be subdivided into two different crustal terranes: the NE-terrane and the SW-terrane. The former is underlain by basement rocks of amphibolite-facies (unit A) and granulite-facies (unit B), and the latter by granulite-facies (unit C) to greenschist-facies (units D and D')...

Several schools of thoughts exist on how and when exactly did the final assembly of East Gondwana occurred and this topic has been discussed over and again in the past few decades. Here we review the present status of our understanding of Neoproterozoic to Cambrian tectonic evolution of the southern sector of East Gondwana and by assembling this sp...

In this paper we provide evidence for a counterclockwise P–T path and isobaric cooling for metapelitic rocks from the Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica. The counterclockwise path was determined using the following mineral textures and relationships: (1) garnet coronae on sillimanite where the sillimanite is associat...

This study is a detailed investigation of the petrology and geochronology of the Late Proterozoic metatonalite in the Sør Rondane Mountains, eastern Dronning Maud Land, Antarctica. Metatonalite is dominant over roughly 100 × 20 km2 area in the southwestern end of the mountain range and is classified into five lithologies: gneissose Bt–Hbl metatonal...

In order to understand the tectonic evolution of the Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica, sensitive high resolution ion microprobe (SHRIMP) U–Pb zircon dating and electron probe micro analyzer (EPMA) U–Th–Pb monazite dating were carried out on igneous rocks and metamorphic rocks whose P–T conditions have been well-con...

The Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica, are situated within the Pan-African suture zone, between West and East Gondwana, and the timing of collision event is regarded as the late Neoproterozoic to early Cambrian. In order to understand the tectonothermal history and evolution of the continental lithosphere, geochemic...

The Sør Rondane Mountains in East Antarctica preserve two stages of tectonothermal events, at c. 650–600 Ma and c. 560–550 Ma, each of which is also widely preserved elsewhere in Gondwana within tectonic suture zones/orogens, although both ages of tectonothermal events are only rarely documented together in these other parts of Gondwana. A geochron...

Several metamorphic complexes in Southeast Asia have been interpreted as Precambrian basement, characterized by amphibolite to granulite facies metamorphism. In this paper, we re-evaluate the timing of this thermal event based on the large-scale geochronology and compositional variation of monazites from amphibolite to granulite facies metamorphic...

The Ediacaran sediments in the Yangtze Block preserve valuable records of biological evolution and drastic climate changes. However, most of the Ediacaran fossil occurrences have been reported from the shallow platformal facies, and few fossils have been described from the deep basinal facies in the Yangtze Block. Here, we report mineralized microf...

The Mogok Metamorphic Belt (MMB), situated in central Myanmar, contains an assemblage of high-grade metamorphic rocks believed to have been formed during a regional Early Eocene-Oligocene metamorphic event. We newly found Grt-Opx granulite in the Mogok area, which was formed under pressure-temperature (P-T ) conditions estimated as being 6.5-8.7 kb...

The Kurosegawa Tectonic Zone, which is one of the least geochronologically understood areas of the Japanese Islands, contains several rock types of contrasting ages in a serpentinite mélange. This paper presents the U-Pb ages of detrital zircons in pelitic schists and quartzite from the Kurosegawa Tectonic Zone, where high-pressure/low-temperature...

The Trans Vietnam Orogenic Belt (TVOB) of Southeast Asia is thought to have formed by a continent-continent collision between the South China and Indochina cratons in Permian-Triassic times. Here we focus on the nature and origin of metamorphosed mafic rocks that are widely distributed throughout the TVOB, including rocks from the Cangshan Mountain...

The Central Asian Orogenic Belt consists of various terranes amalgamated in several periods from the Late Pre-cambrian/Early Paleozoic to the Late Mesozoic. Mongolia is situated in the center of this belt. Foliated garnet granite (Grt metagranite) and andalusite-bearing massive leucogranite (Leucogranite) are exposed in the Hanhohiyn region of nort...

Lasail plutonic complex (4.7 × 3.8 km), as a typical example of late stage intrusive rocks, is located to the south of Wadi Jizi, and intrudes into the base of V1 volcanic rocks and sheeted dike complex. The Lasail plutonic complex consists of various rock types ranging from ultramafic cumulates to tonalite, and is associated with minor amounts of...

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

抄録 脊振山地・浮嶽に産する泥質グラニュライトとその周囲の糸島花崗閃緑岩について，LA-ICP-MSジルコンU－Pb年代とFE-EPMAモナザイトU－Th－Pb年代を測定した．糸島花崗閃緑岩からはジルコンU－Pb法で102 ± 2 Maの火成年代が得られた．また，泥質グラニュライトのジルコンの縁辺部からは105 ± 2 MaのU－Pb年代が得られた．この年代は100－120 MaのモナザイトU－Th－Pb年代と調和的である．ジルコンの核部からは，400－510 Maに集中する砕屑性年代が得られ，最も若い年代は360 Maであった．この砕屑性ジルコンの年代分布は蓮華変成岩に類似するが，変成作用の時期や条件が異なる．浮嶽の泥質グラニュライトが示す変成年代は100－120 Maであり，肥後変成岩の...

This paper reports the first evidence of ultrahigh-temperature (UHT) metamorphism from the Sør Rondane Mountains, eastern Dronning Maud Land, East Antarctica, which is evident as orthopyroxene+spinel symplectite in an amphibolitized mafic granulite. The granulite consists of olivine, orthopyroxene, clinopyroxene, pargasitic amphibole, plagioclase,...

This is the first report of osumilite occurring as fine isolated inclusions within garnet porphyroblasts, as observed in garnet–sillimanite gneiss from Rundvågshetta, Lützow-Holm Complex, East Antarctica. The osumilite is characterized by high Si content (10.60 and 10.95 atoms based on 30 oxygens per formula unit), low Al content (2.99 and 3.82), a...

Ultrahigh-temperature (UHT) granulites of the central Highland Complex, Sri Lanka, underwent some of the highest known peak temperatures of crustal metamorphism. Zircon and monazite U-Pb systems in granulites near Kandy, the highest grade region (similar to 1050 degrees C; 0.9 GPa), preserve both a record of the timing of prograde and retrograde ph...

In this study, mafic granulite and related leucosomes from the Song Ma Suture zone in northern Vietnam were investigated. Euhedral garnet appears in both granulites and leucosomes, whereas the former is partly to mostly replaced by orthopyroxene + plagioclase symplectite. Most garnets occurring both in granulite and leucosome contain an Mg-rich and...

Granulite grade marble layers interlayered with metapelitic granulites from Lützow Holm Bay, East Antarctica, provide insight into fluid–rock interactions during burial to and exhumation from lower crustal levels. Sub-millimeter scale strontium, oxygen and carbon isotope variations along with LA-ICPMS trace element geochemistry and mineral chemistr...

In the central Sør Rondane Mountains, East Antarctica, orthopyroxene felsic gneiss (OPG) was converted to hornblende-biotite felsic gneiss (HBG) by hydration that accompanied the intrusion of pegmatite. The retrograde HBG contains exsolved rutile in quartz. The composition of orthopyroxene and clinopyroxene in OPG suggests a temperature of 840°C (i...

The Napier Complex in East Antarctica comprises some of the oldest rocks on earth (~3.8 billion years old), overprinted by an ultra-high temperature (UHT) metamorphic event near the Archean-Proterozoic boundary. Garnet, orthopyroxene, sapphirine, osumilite, rutile and a whole rock representing an equilibrated assemblage from this belt yield a Lu-Hf...

The first finding of low-temperature eclogites from the Indochina region is reported. The eclogites occur along the Song Ma Suture zone in northern Vietnam, which is widely regarded as the boundary between the South China and Indochina cratons. The major lithology of the area is pelitic schist that contains garnet and phengite with or without bioti...