MISC

2005年6月

Geochemistry of adakitic quartz diorite in the Yamizo Mountains, central Japan: Implications for Early Cretaceous adakitic magmatism in the inner zone of southwest Japan

ISLAND ARC
  • Y Takahashi
  • ,
  • SI Kagashima
  • ,
  • MU Mikoshiba

14
2
開始ページ
150
終了ページ
164
記述言語
英語
掲載種別
DOI
10.1111/j.1440-1738.2005.00465.x
出版者・発行元
BLACKWELL PUBLISHING ASIA

Small-volume plutons of Early to Late Cretaceous ages are widely distributed in the Yamizo Mountains, central Japan. These plutons consist predominantly of granitoids, classified into hornblende gabbro, quartz diorite, hornblende-biotite granodiorite and coarse-grained biotite granite. The quartz diorite (52-64 wt% of SiO2) is characterized by a high Sr content (606-769 p.p.m.) associated with a low Y (13-27 p.p.m.) and heavy rare earth element content (Yb content of 1.19-2.13 p.p.m.). On the Sr/Y versus Y diagram, this rock type mainly plots in the adakite and Archean high-Al tonalite, trondhjemite and granodiorite (TTG) field. Together with its initial Sr isotopic ratios, which range from 0.7038 to 0.7046, these data suggest that quartz diorite originated as slab melts. However, geochemical calculations assuming either eclogite or garnet amphibolite as the source material do not support this suggestion. Instead, the chemical compositions of quartz diorite are better explained by the fractional crystallization of hornblende, plagioclase and biotite from a primitive, basaltic melt in a magma chamber. In this case, the formation of the associated hornblende gabbro can also be explained by the accumulation of hornblende and plagioclase. Adakitic rocks of Early Cretaceous ages have also been reported in the Tamba Belt of the inner zone of southwest Japan, located ca 500 km west of the Yamizo Mountains. These rocks can be correlated to the adakitic rocks in the Yamizo Mountains based on the geology, petrography, geochemistry and radiometric ages. Therefore, we propose the possibility that the Early Cretaceous adakitic rocks in the inner zone of southwest Japan were produced by fractional crystallization from basaltic arc magmas generated by a partial melting of metasomatized wedge mantle peridotite.

リンク情報
DOI
https://doi.org/10.1111/j.1440-1738.2005.00465.x
CiNii Articles
http://ci.nii.ac.jp/naid/10020373891
Web of Science
https://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=JSTA_CEL&SrcApp=J_Gate_JST&DestLinkType=FullRecord&KeyUT=WOS:000229190500006&DestApp=WOS_CPL
ID情報
  • DOI : 10.1111/j.1440-1738.2005.00465.x
  • ISSN : 1038-4871
  • CiNii Articles ID : 10020373891
  • Web of Science ID : WOS:000229190500006

エクスポート
BibTeX RIS