Geochemistry of Lower Cretaceous sediments, Inner Zone of Southwest Japan: Constraints on provenance and tectonic environment

Daniel K. Asiedu, Shigeyuki Suzuki, Kenji Nogami, Tsugio Shibata

Research output: Contribution to journalArticlepeer-review

72 Citations (Scopus)

Abstract

A geochemical study was carried out on Lower Cretaceous sedimentary rocks of the Wakino Subgroup, Kenseki Formation, and Sasayama Group, distributed in the Inner Zone of Southwest Japan. The chemical characteristics of the Lower Cretaceous sediments indicate that these rocks are immature first-order sediments derived from igneous and/or meta-igneous rocks of predominantly felsic composition. The sediments from the Kenseki Formation and the Sasayama Group, however, show high Cr and Ni abundances, suggesting a significant contribution of detritus from ultramafic rocks. Weathering at the source areas was moderate. The high Th/U ratios (mostly >3.8), negative Eu anomalies (Eu/Eu(*) between 0.67 and 0.93) and Th/Sc ratios (mostly between 0.5 and 1) of the Lower Cretaceous sediments suggest their derivation dominantly from an old upper crust with minor amounts of young arc-derived detritus. The major, trace and rare earth element compositions imply that deposition took place in an active continental margin environment. The small amounts of young arc-derived material in the sediments support the inference by other workers that arc magmatism was not so prominent in Southwest Japan during the early Cretaceous.

Original languageEnglish
Pages (from-to)155-173
Number of pages19
JournalGEOCHEMICAL JOURNAL
Volume34
Issue number2
DOIs
Publication statusPublished - 2000

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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