Academic Thesis

Basic information

Name Satou Tomohiko
Belonging department
Occupation name
researchmap researcher code B000334895
researchmap agency Okayama University of Science

Title

Geochemistry of accreted metavolcanic rocks from the Neoproterozoic Gwna Group of Anglesey-Lleyn, NW Wales, UK: MORB and OIB in the Iapetus Ocean

Bibliography Type

 

Author

Takuya Saito
Masaoki Uno
Tomohiko Sato
Wataru Fujisaki
Satoru Haraguchi
Yi-Bing Li
Yusuke Sawaki
Shinji Yamamoto
Shigenori Maruyama

Summary

The Gwna Group in Anglesey-Lleyn, NW Wales, UK, is a Neoproterozoic accretionary complex that consists of basalt, bedded chert, red claystone, and trench turbidite that have been intercalated in coherent and incoherent melanges that are considered typical Ocean plate stratigraphy (OPS). The sediments in the OPS can be useful for constraining the geological environment in the Iapetus Ocean. Most basalts in this area have undergone hydrothermal alteration, greenschist facies regional metamorphism, and surface oxidation. This indicates that immobile elements such as Al2O3 and TiO2, Rare Earth Elements (REE) and High Field Strength Elements (HSFE) are appropriate for discriminating the origin of the basalts in the Gwna Group.
Most basalts showing light REE-enriched pattern in CI chondrite-normalized spider diagrams in within-plate basalt (WPB) fields, and some have flat patterns in spider diagrams in mid-oceanic ridge basalt (MORE) fields. In view of these relations, we conclude that the former erupted in an oceanic island. Oceanic island basalts (OIB) are common in Phanerozoic accretionary complexes, and this study presents the first evidence of OIB in a Neoproterozoic accretionary complex of the Gwna Group in Anglesey-Llyen and Llyen area. The OIB-like basalts are locally capped by red hematite-rich claystones. This indicates that a fully oxic pelagic condition was present around the oceanic island in the Iapetus Ocean in the Neoproterozoic, which is consistent with the redox condition estimated from contemporaneous shallow marine sediments. On the other hand, the presence of black mudstones on top of MORE-like meta-basalts suggests that deep-sea anoxia conditions were prevalent during the end-Proterozoic. (C) 2015 Elsevier B.V. All rights reserved.

Magazine(name)

TECTONOPHYSICS

Publisher

ELSEVIER SCIENCE BV

Volume

662

Number Of Pages

 

StartingPage

243

EndingPage

255

Date of Issue

2015-11

Referee

Exist

Invited

Not exist

Language

English

Thesis Type

Research papers (academic journals)

ISSN

 

DOI

10.1016/j.tecto.2015.08.015

NAID

 

PMID

 

J-GLOBAL ID

 

arXiv ID

 

ORCID Put Code

 

DBLP ID