Petrologic characteristics and geologic age of green rocks including chert xenoliths in the Pippu area, central Hokkaido, Japan

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Authors:Sakakibara, Masayuki; Hori, Rie S.; Ikeda, Michiharu; Umeki, Misa
Author Affiliations:Primary:
Ehime University, Department of Earth Sciences, Matsuyama, Japan
Volume Title:Chishitsugaku Zasshi Journal of the Geological Society of Japan
Source:Chishitsugaku Zasshi = Journal of the Geological Society of Japan, 103(10), p.953-963. Publisher: Nippon Chishitsugaku Gakkai, Tokyo, Japan. ISSN: 0016-7630
Publication Date:1997
Note:In Japanese with English summary. 45 refs.; illus., incl. 2 plates, 2 tables, geol. sketch map
Summary:Green rock including chert xenoliths has been found in an outcrop of the Pippu area, central Hokkaido, Japan. It is petrologically divided into two types; massive hornblende basalt and picritic basaltic hyaloclastite. The former structurally overlies the latter. The hornblende basalt includes a large amount of chert xenoliths and was subjected to the high-P/T Kamuikotan metamorphism. Radiolarian fossils indicating late Callovian have been obtained from xenoliths of red chert in the hornblende basalt. The picritic basaltic hyaloclastite displays mineral assemblages corresponding to the prehnite-pumpellyite facies. The hornblende basalt is alkalic and rich in TiO2 and P2O5, being similar to oceanic island basalt, whereas picritic basalt is tholeiitic, but very poorer in TiO2 and P2O5 than oceanic ridge basalt. These data suggest that the hornblende basalt belongs to the Kamuikotan complex, whereas the picritic basaltic hyaloclastite is correlative with the Sorachi Group. The Kamuikotan green rocks is inferred to have been generated as intra-plate volcanism after late Callovian.
Sections:Petrology
Subsections:Metamorphism: regional, dynamic
Subjects:Basalts; Callovian; Chemical composition; Chemically precipitated rocks; Chert; Facies; Greenstone; Igneous rocks; Inclusions; Jurassic; Major elements; Mesozoic; Metamorphic rocks; Microfossils; Middle Jurassic; Mineral assemblages; Petrography; Prehnite-pumpellyite facies; Radiolaria; Schists; Sedimentary rocks; Trace elements; Volcanic rocks; Volcanism; Xenoliths; Asia; Far East; Hokkaido; Japan; Kamuikotan Belt; Invertebrata; Pippu area; Protista; Sorachi Group
Abstract Numbers:03M/3378
Record ID:1998027732
Copyright Information:GeoRef, Copyright 2020 American Geosciences Institute.
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