Magnesian igneous enclave in the Ohmine granitic rocks of Kii Peninsula

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Authors:Shinjoe, Hironao; Shimoda, Gen; Fukuoka, Takaaki; Sumii, Tomoaki
Author Affiliations:Primary:
Tokyo Keizai University, Tokyo, Japan
Geological Survey of Japan, Japan
Rissho University, Japan
Volume Title:Ganseki Kobutsu Kagaku Japanese Magazine of Mineralogical and Petrological Sciences
Source:Ganseki Kobutsu Kagaku = Japanese Magazine of Mineralogical and Petrological Sciences, 34(1), p.15-23. Publisher: The Mineralogical Society of Japan and The Japanese Association of Mineralogists, Petrologists and Economic Geologists, Tokyo, Japan. ISSN: 1345-630X
Publication Date:2005
Note:In Japanese with English summary. 30 refs.; illus., incl. 3 tables, sketch maps
Summary:Magnesian igneous enclaves showing sub-angular shape and up to 2 m in the maximum dimension were found from granodiorite in the Dorogawa pluton, the northernmost pluton of the Ohmine granitic rocks in Kii peninsula, southwest Japan. Igneous enclaves are composed mainly of plagioclase and hornblende, as phenocrysts, and of plagioclase, hornblende, quartz, and biotite as groundmass minerals. They also contain hydrous mafic mineral aggregates consisting of chlorite, actinolite, and biotite with rare chromian spinel microcrystals. Their whole rock compositions were characterized by high MgO content (5.8-7.0 wt%), low Fe*/MgO ratio (0.80-0.92), high Cr (256-346 ppm), and Ni (81-138 ppm) contents. Patterns of trace element abundances are close to those of the high-Mg andesite (HMA) of the Setouchi volcanic rocks. The compositional range of microcrystals of chromian spinel within hydrous mafic mineral aggregates is similar to those of included in olivine or orthopyroxene phenocrysts of the Setouchi HMA. These geochemical and mineralogical characteristics of the igneous enclaves suggest the activity of HMA magma closely in space-time with the intrusion of the Dorogawa pluton.
Sections:Geochemistry; Petrology
Subsections:Igneous petrology; Igneous rocks
Subjects:Alkaline earth metals; Andesites; Cenozoic; Chemical composition; Geochemistry; Granitic composition; Granodiorites; Igneous rocks; Inclusions; Lithogeochemistry; Magnesium; Metals; Middle Miocene; Mineral inclusions; Miocene; Neogene; Plutonic rocks; Tertiary; Trace elements; Volcanic rocks; Asia; Far East; Honshu; Japan; Kii Peninsula; Dorogawa Pluton; Ohmine granitic rocks
Coordinates:N333000 N340000 E1360000 E1353000
Abstract Numbers:07M/2533
Record ID:2005076094
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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