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C retaceous granitoids and their zircon U – P b ages across the south‐central part of the A bukuma H ighland, J apan
Author(s) -
Ishihara Shunso,
Orihashi Yuji
Publication year - 2015
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1111/iar.12105
Subject(s) - geology , zircon , batholith , geochemistry , metamorphic rock , biotite , diorite , greenschist , terrane , cretaceous , quartz , plutonism , pluton , paleontology , tectonics
Zircons separated from C retaceous granitoids are dated from a south‐central transect of the A bukuma metamorphic and granitic terrane. The zircon ages do not follow ‘older’ and ‘younger’ granitoid ages that are used conventionally. In the western part of the study area ( Z ones I , II and III ) where the T akanuki and G osaisho metamorphic rocks are exposed, the I ritono quartz dioritic stock intruding the greenschist facies rocks in Z one III exhibits the oldest age of 121 Ma in the studied region. Quartz diorite located northward shows 112 Ma, but the other four granitoids intruding into the T akanuki and G osaisho metamorphic rocks are younger and 103–99 Ma. Two‐mica and biotite granites belong to the youngest age group of 99 Ma. The granitic activities of both the A bukuma and R yoke belts were initiated by intrusion of quartz dioritic magmas and were ended by two‐mica granite activity. The ages of the eastern two batholiths vary from 110 to 106 Ma (four samples), and show no age common to the K itakami granitoids farther to the north. Throughout the J apanese I slands arc, C retaceous granitic activities became younger toward the marginal sea side from the K itakami M ountains, to the A bukuma H ighland, and the R yoke B elt, then to the S anin belt of the I nner Z one of S outhwest J apan.