Abukuma and Sanbagawa metamorphic belts in the Kanto district

'29th IGC field trip guide book' vol.5, C08: [Editors] Hirokazu Kato, Harufumi Noro「IGC巡検ガイドブック」 第5巻: [編者] 加藤 碵一, 野呂 春

Geochemistry of syenite of the Phalaborwa Carbonatite Complex, South Africa

We surveyed the Spitskop syenite pipe,one of the satellite bodies of the Phalaborwa Carbonatite Complex located in northeastern Transvaal,South Africa. This pipe is composed of the inner cumulus syenite and outer ring syenite.The brecciation zone between these syenites includes many blocks of syenite,pyroxenite, melanocratic rock,biotite gneiss and granitic rocks.Dolerite dykes intruded into the plug and brecciation zone.Fine-and coarse-grained syenites,melanocratic rock, alkali-feldspar granite and dolerite were collected from the brecciation zone of this pipe.The whole-rock and mineral chemistry suggests that syenites and melanocratic rocks of the brecciation zone were derived from the inner cumulus syenite magma. These rocks do not indicate any clear isochron.It may be a result of mixing of various rocks at the brecciation stage

Geology of the eastern Dronning Maud Land, East Antarctica: Missing link to Sri Lanka

The Tenth Symposium on Polar Science/Ordinary sessions: [OG] Polar Geosciences, Wed. 4 Dec. / Entrance Hall (1st floor), National Institute of Polar Researc

中圧型広域変成岩の比較研究‐日本列島と東南極大陸

金沢大学教育学部研究課題/領域番号:58540522, 研究期間(年度):1983出典：研究課題「中圧型広域変成岩の比較研究‐日本列島と東南極大陸」課題番号58540522（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-58540522/）を加工して作

黒部川下流地域に分布する飛騨変成岩類の形成史

金沢大学教育学部研究課題/領域番号:X00210----374263研究期間(年度):1978出典：「黒部川下流地域に分布する飛騨変成岩類の形成史」研究成果報告書　課題番号X00210----374263（KAKEN：科学研究費助成事業データベース（国立情報学研究所）） （https://kaken.nii.ac.jp/ja/grant/KAKENHI-PROJECT-X00210----374263/）を加工して作

Calc-silicate rocks and marbles from Lutzow-Holm Complex,East Antarctica, with special reference to the mineralogy and geochemical characteristics of calc-silicate mega-boudins from Rundvagshetta

We report here the mode of occurrence of calc-silicate rocks and marbles from the Lutzow-Holm Complex, East Antarctica, and a worked example from Rundvagshetta. Calc-silicate boudins were observed in Cape Hinode, Akarui Point, Byobu Rock, Skarvsnes, Skallevikshalsen and Rundvagshetta, whereas they were reported earlier from Sinnan Rock, Cape Ryugu, Akebono Rock, Cape Hinode, Niban Rock, Kasumi Rock, Daruma Rock, Cape Omega, Langhovde, Ytrehovdeholmen and Skarvsnes. They vary in size from decimeters to few meters and are commonly enclosed within pelitic or psammitic gneisses. In addition, extensive layers of marbles and calc-silicate rocks are distributed in Skallevikshalsen. The calc-silicate mega-boudins within the layered pyroxene-gneiss from Rundvagshetta, up to 5m long and 2m thick, comprises of coarse to medium grained assemblage of scapolite+anorthite+garnet+clinopyroxene+calcite+quartz+titanite±wollastonite. Co-existing scapolite and plagioclase suggest a "minimum" estimate of peak metamorphic temperature of ～830°C . Peak metamorphic mineral assemblages equilibrated at moderate to high X_(CO2) conditions (0.3-0.7) and temperatures between 850 and 1000°C , consistent with the ultrahigh temperature metamorphic conditions reported in the region. Multistage garnet corona formation preserved in the calc-silicate assemblage suggests a local increase in hydrous fluid activity during retrogression. Preliminary bulk rock geochemistry of different mineralogical zones in the boudin shows chemical potential gradients in some major elements, especially SiO_2, Al_2O_3 and CaO, possibly controlled by the compositional variations in the protolith. Altogether, these results suggest that calc-silicate rocks preserve information on the metamorphic evolution and help us in deducing the geodynamic evolution of high-grade terrains

Charnockitization of khondalite in the vicinity of calc-silicate \u27dykes\u27

第2回極域科学シンポジウム/第31回極域地学シンポジウム 11月17日（木） 国立極地研究所　2階大会議

Geochemistry of mafic metamorphic rocks in the Lutzow-Holm Complex, East Antarctica: Implications for tectonic evolution

Mafic metamorphic rocks are widely distributed through the Lutzow-Holm Complex (LHC) of East Antarctica, as layers between or enclaves within metasedimentary and metaigneous lithologies. It has been inferred that the peak metamorphic grade of the LHC progressively increases in a southwestern direction from amphibolite-facies to granulite-facies conditions, with mineral assemblages in the mafic metamorphic rocks changing from hornblende (magnesiohornblende)±biotite+plagioclase to orthopyroxene+clinopyroxene±hornblende (pargasite, magnesiohasting-site and tschermakite)±biotite±garnet+plagioclase. Field relationships suggest that amphibolite-grade mafic metamorphic rocks derive from mafic magma intruded into metasedimentary units, whereas granulite-facies mafic metamorphic rocks are a mixture of detrital blocks and mafic sill or intrusions. Major and trace element compositions of mafic metamorphic rocks are similar to those of igneous rocks of tholeiite affinity, and can be divided into volcanic-arc basalt (VAB)-type or mid-ocean ridge basalt (MORB)-type compositions. On a regional scale, VAB-type lithologies are predominant in amphibolite-facies areas, and MORB-type lithologies predominate in granulite-facies areas. On the basis of HFSE concentrations and Nb/Y ratios, MORB-type lithologies have T-type and E-type MORB compositions with oceanic plateau basalt and back-arc basin basalt affinities, and are occasionally found in the field intercalated with metasedimentary layers, characteristic of magmatism and sedimentation cycles in a marginal sea basin setting. Such field relationships provide information on the tectonic environment of protolith formation in the LHC. Various crustal components have been amalgamated into a relatively narrow mobile belt, which was subjected to high-grade metamorphism during the final closure of oceanic basins as a result of continent-continent collision

Granulites from Cape Hinode in the amphibolite-facies eastern part of Prince Olav Coast, East Antarctica: New evidence for allochthonous block in the Lutzow-Holm Complex

High-grade metamorphic rocks occurring along the Prince Harald, Soya, and Prince Olav Coasts make up the Latest Proterozoic-Early Paleozoic Lutzow-Holm Complex, which is the youngest orogenic belt in the East Antarctic Shield. A systematic increase in metamorphic grade from east to west, ranging from upper amphibolite facies on the eastern Prince Olav Coast to upper granulite facies at the head of Lutzow-Holm Bay, has been well-established in the complex. However, granulites are newly found to occur as blocks sitting within meta-tonalites at Cape Hinode located on the amphibolite-facies eastern Prince Olav Coast. In addition, it is newly revealed that kyanite occurs rather commonly in meta-tonalites which contain hornblende with or without clinopyroxene. The modes of occurrence in the field, petrographical features, and major element bulk rock compositions of the granulites and related rocks are given in some detail in this study. These, along with the previously presented geochronological, geochemical and petrographical data, would indicate that the rocks in the Cape Hinode area as a whole make up a Mesoproterozoic allochthonous block in the Latest Proterozoic-Early Paleozoic Lutzow-Holm Complex