Mineral chemistry of ultramafic rocks associated with the Asaji metamorphic rocks, eastern Kyushu

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Authors:Soda, Yusuke; Takagi, Hideo
Author Affiliations:Primary:
Waseda University, Division of Geology, Tokyo, Japan
Volume Title:Chishitsugaku Zasshi Journal of the Geological Society of Japan
Source:Chishitsugaku Zasshi = Journal of the Geological Society of Japan, 110(11), p.698-714. Publisher: Nippon Chishitsugaku Gakkai, Tokyo, Japan. ISSN: 0016-7630
Publication Date:2004
Note:In Japanese with English summary. 77 refs.; illus., incl. 1 plate, 1 table, geol. sketch maps
Summary:The Asaji metamorphic rocks have previously been considered as a member of the Ryoke belt. However, the occurrence of ultramafic bodies interlayered in the Chokai Unit and the Hikata Unit has led to an alternative suggestion for the correlation of the Asaji metamorphic rocks with other terranes, such as the Sambagawa terrane or the Kurosegawa terrane. To discuss these possibilities, we examined the petrological characteristics of the ultramafic rocks and chemical compositions of chromian spinel. The ultramafic body is composed mainly of pyroxenites and serpentinite. Spinel in the serpentinite has high Cr# (Cr/(Cr+Al) atomic ratio) of 0.7-0.9 and very low TiO2 content (<0.5 wt%). Although the ultramafic body suffered weak contact metamorphism, chemical composition of chromian spinel has preserved those in the peridotite stage. The spinel chemistry suggests that the original peridotite is a refractory residue after the extraction of basaltic magma. The pyroxenites are subdivided into clinopyroxenite, olivine-clinopyroxenite and olivine-websterite. Compositions of clinopyroxene from the pyroxenites are similar to those of arc cumulates. It suggests that the peridotites (now completely serpentinitized) and pyroxenites were formed in a subduction zone. Chemical compositions of spinel in the serpentinites from the Saganoseki area (the Sambagawa metamorphic belt), the Sashu Fault on the southern margin of the Sambagawa metamorphic belt, and the Miemachi and Usuki area (the Kurosegawa belt) exposed near the Asaji metamorphic rocks were analyzed for comparison. Spinels from the Saganoseki area are clearly different in Cr# and TiO2 content from those from the Asaji area and also from the Sashu Fault. On the other hand, the chemical compositions of spinels from the Miemachi and Usuki area (the Kurosegawa belt) resemble to those from the Asaji area, suggesting a similar tectonic setting for the formation of those ultramafic rocks.
Sections:Geochemistry; Petrology
Subsections:Metamorphism: regional, dynamic; Minerals and ores
Subjects:Absolute age; Cenozoic; Chemical composition; Chemical ratios; Chromium; Cretaceous; Crystal chemistry; Dates; Geochemistry; Granites; Igneous rocks; Ion probe data; K/Ar; Lineaments; Lithostratigraphy; Magmatism; Major elements; Mass spectra; Mesozoic; Metaigneous rocks; Metals; Metamorphic belts; Metamorphic rocks; Metasomatic rocks; Mineral composition; Nesosilicates; Orthosilicates; Oxides; Paleozoic; Permian; Petrography; Plate tectonics; Plutonic rocks; Pyroxenite; Rb/Sr; Serpentinite; Shimanto Group; SHRIMP data; Silicates; Spectra; Spinel; Structural analysis; Subduction; Subduction zones; Tectonics; Terranes; Textures; Trace elements; U/Pb; Ultramafic composition; Ultramafics; Zircon; Zircon group; Asia; Far East; Honshu; Japan; Kurosegawa Zone; Kyushu; Ryoke Belt; Sambagawa Belt; Shikoku; Usuki Japan; Asaji Japan; Chichibu Group; Chokai Unit; Hikata Unit; Kabunoki Fault; Miemachi Japan; Nishikawauchi Formation; Onogawa Group; Saganoseki Japan; Sashu Fault; Tano Group; Usukigawa quartz diorite
Coordinates:N330000 N333000 E1320000 E1311500
Abstract Numbers:06M/2031
Record ID:2005053926
Copyright Information:GeoRef, Copyright 2020 American Geosciences Institute.
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008 190110e200411 ja a 0 0 jpn d
034 0 |a a  |d E1311500  |e E1320000  |f N333000  |g N330000 
040 |a ViAlAGI  |c ViAlAGI 
041 |a jpn  |b eng 
072 7 |a 05A  |2 georeft 
072 7 |a 02C  |2 georeft 
100 1 |a Soda, Yusuke  |e analytic author  |u Waseda University, Division of Geology, Tokyo 
245 1 0 |a Mineral chemistry of ultramafic rocks associated with the Asaji metamorphic rocks, eastern Kyushu 
300 |a p. 698-714 
500 |a In Japanese with English summary. 77 refs. 
500 |a Abstract number: 06M/2031 
500 |a Category Section: Geochemistry 
500 |a Category Section: Petrology 
500 |a Category Subsection: Metamorphism: regional, dynamic 
500 |a Category Subsection: Minerals and ores 
500 |a Affiliation: Waseda University, Division of Geology; Tokyo; JPN; Japan 
500 |a Key title: Chishitsugaku Zasshi = Journal of the Geological Society of Japan 
500 |a Source note: Chishitsugaku Zasshi = Journal of the Geological Society of Japan, 110(11), p.698-714. Publisher: Nippon Chishitsugaku Gakkai, Tokyo, Japan. ISSN: 0016-7630 
500 |a Publication type: journal article 
504 |b 77 refs. 
506 0 |a Open access 
510 3 |a GeoRef, Copyright 2020 American Geosciences Institute. 
520 |a The Asaji metamorphic rocks have previously been considered as a member of the Ryoke belt. However, the occurrence of ultramafic bodies interlayered in the Chokai Unit and the Hikata Unit has led to an alternative suggestion for the correlation of the Asaji metamorphic rocks with other terranes, such as the Sambagawa terrane or the Kurosegawa terrane. To discuss these possibilities, we examined the petrological characteristics of the ultramafic rocks and chemical compositions of chromian spinel. The ultramafic body is composed mainly of pyroxenites and serpentinite. Spinel in the serpentinite has high Cr# (Cr/(Cr+Al) atomic ratio) of 0.7-0.9 and very low TiO<2` content (#LT0.5 wt%). Although the ultramafic body suffered weak contact metamorphism, chemical composition of chromian spinel has preserved those in the peridotite stage. The spinel chemistry suggests that the original peridotite is a refractory residue after the extraction of basaltic magma. The pyroxenites are subdivided into clinopyroxenite, olivine-clinopyroxenite and olivine-websterite. Compositions of clinopyroxene from the pyroxenites are similar to those of arc cumulates. It suggests that the peridotites (now completely serpentinitized) and pyroxenites were formed in a subduction zone. Chemical compositions of spinel in the serpentinites from the Saganoseki area (the Sambagawa metamorphic belt), the Sashu Fault on the southern margin of the Sambagawa metamorphic belt, and the Miemachi and Usuki area (the Kurosegawa belt) exposed near the Asaji metamorphic rocks were analyzed for comparison. Spinels from the Saganoseki area are clearly different in Cr# and TiO<2` content from those from the Asaji area and also from the Sashu Fault. On the other hand, the chemical compositions of spinels from the Miemachi and Usuki area (the Kurosegawa belt) resemble to those from the Asaji area, suggesting a similar tectonic setting for the formation of those ultramafic rocks. 
650 7 |a Absolute age  |2 georeft 
650 7 |a Cenozoic  |2 georeft 
650 7 |a Chemical composition  |2 georeft 
650 7 |a Chemical ratios  |2 georeft 
650 7 |a Chromium  |2 georeft 
650 7 |a Cretaceous  |2 georeft 
650 7 |a Crystal chemistry  |2 georeft 
650 7 |a Dates  |2 georeft 
650 7 |a Geochemistry  |2 georeft 
650 7 |a Granites  |2 georeft 
650 7 |a Igneous rocks  |2 georeft 
650 7 |a Ion probe data  |2 georeft 
650 7 |a K/Ar  |2 georeft 
650 7 |a Lineaments  |2 georeft 
650 7 |a Lithostratigraphy  |2 georeft 
650 7 |a Magmatism  |2 georeft 
650 7 |a Major elements  |2 georeft 
650 7 |a Mass spectra  |2 georeft 
650 7 |a Mesozoic  |2 georeft 
650 7 |a Metaigneous rocks  |2 georeft 
650 7 |a Metals  |2 georeft 
650 7 |a Metamorphic belts  |2 georeft 
650 7 |a Metamorphic rocks  |2 georeft 
650 7 |a Metasomatic rocks  |2 georeft 
650 7 |a Mineral composition  |2 georeft 
650 7 |a Nesosilicates  |2 georeft 
650 7 |a Orthosilicates  |2 georeft 
650 7 |a Oxides  |2 georeft 
650 7 |a Paleozoic  |2 georeft 
650 7 |a Permian  |2 georeft 
650 7 |a Petrography  |2 georeft 
650 7 |a Plate tectonics  |2 georeft 
650 7 |a Plutonic rocks  |2 georeft 
650 7 |a Pyroxenite  |2 georeft 
650 7 |a Rb/Sr  |2 georeft 
650 7 |a Serpentinite  |2 georeft 
650 7 |a Shimanto Group  |2 georeft 
650 7 |a SHRIMP data  |2 georeft 
650 7 |a Silicates  |2 georeft 
650 7 |a Spectra  |2 georeft 
650 7 |a Spinel  |2 georeft 
650 7 |a Structural analysis  |2 georeft 
650 7 |a Subduction  |2 georeft 
650 7 |a Subduction zones  |2 georeft 
650 7 |a Tectonics  |2 georeft 
650 7 |a Terranes  |2 georeft 
650 7 |a Textures  |2 georeft 
650 7 |a Trace elements  |2 georeft 
650 7 |a U/Pb  |2 georeft 
650 7 |a Ultramafic composition  |2 georeft 
650 7 |a Ultramafics  |2 georeft 
650 7 |a Zircon  |2 georeft 
650 7 |a Zircon group  |2 georeft 
651 7 |a Asia  |2 georeft 
651 7 |a Far East  |2 georeft 
651 7 |a Honshu  |2 georeft 
651 7 |a Japan  |2 georeft 
651 7 |a Kurosegawa Zone  |2 georeft 
651 7 |a Kyushu  |2 georeft 
651 7 |a Ryoke Belt  |2 georeft 
651 7 |a Sambagawa Belt  |2 georeft 
651 7 |a Shikoku  |2 georeft 
651 7 |a Usuki Japan  |2 georeft 
653 |a Asaji Japan 
653 |a Chichibu Group 
653 |a Chokai Unit 
653 |a Hikata Unit 
653 |a Kabunoki Fault 
653 |a Miemachi Japan 
653 |a Nishikawauchi Formation 
653 |a Onogawa Group 
653 |a Saganoseki Japan 
653 |a Sashu Fault 
653 |a Tano Group 
653 |a Usukigawa quartz diorite 
700 1 |a Takagi, Hideo,  |e analytic author 
773 0 |t Chishitsugaku Zasshi Journal of the Geological Society of Japan  |d Tokyo : Nippon Chishitsugaku Gakkai, Nov. 2004  |x 0016-7630  |y CHTZA5  |n Chishitsugaku Zasshi = Journal of the Geological Society of Japan, 110(11), p.698-714. Publisher: Nippon Chishitsugaku Gakkai, Tokyo, Japan. ISSN: 0016-7630 Publication type: journal article  |g Vol. 110, no. 11  |h illus., incl. 1 plate, 1 table, geol. sketch maps