SHRIMP U-Pb ages of the Karasaki mylonites in western Shikoku, Japan

IR NDL Digital Collections Web Site 2 Citations 37 References Open Access

Bibliographic Information

Other Title
  • 四国西部唐崎マイロナイトのSHRIMP U-Pb年代
  • シコク セイブ カラサキ マイロナイト ノ SHRIMP U Pb ネンダイ

Search this article

Abstract

Zircon U-Pb isotope ages have been analyzed by the Sensitive High Resolution Ion MicroProbe (SHRIMP) in an leucocratic amphibolite mylonite from the Karasaki mylonites, western Shikoku, Japan which has been considered to belong to the "Paleo-Ryoke" belt. Eight zircon grains from the sample yielded U-Pb ages of Albian (Early Cretaceous) ranging from 114.2 ± 3.9 Ma to 102.3 ±4.5 Ma (± 1σ errors). The protolith of the mylonitized leucocratic amphibolite has been inferred to be basaltic volcanic sandstones, because the SiO_2 content is low (49 wt.%), and the leucocratic amphibolite (consisting of albite and epidote rich, and chlorite and epidote rich layers alternates with amphibole rich and chlorite rich layers on the order of a few mm, suggestive of original sedimentary layering. All the zircon grains can be inferred to be detrital based on both the facts that they were abraded possibly due to sedimentation processes, and that they show oscillatory zoning indicating igneous (primary) texture. The small range of U-Pb ages varying ca. 110 Ma suggests that the zircon grains in the volcanic sandstones were supplied only from the Oshima metamorphic rocks of the Maana belt and the Higo plutonic rocks of the Higo belt whose U-Pb zircon ages were dated as ca. 110 Ma. The fact clearly indicates that the metamorphic rocks (Karasaki mylonites) originated from post-Albian sediments also constitute as a new member of the "Paleo-Ryoke" belt.

Journal

Citations (2)*help

See more

References(37)*help

See more

Keywords

Details 詳細情報について

Report a problem

Back to top