Geochemistry and geochronology of the troodos ophiolite: An ssz ophiolite generated by subduction initiation and an extended episode of ridge subduction

Soichi Osozawa, Ryuichi Shinjo, Ching Hua Lo, Bor Ming Jahn, Nguyen Hoang, Minoru Sasaki, Ken'ichi Ishikawa, Harumasa Kano, Hiroyuki Hoshi, Costas Xenophontos, John Wakabayashi

Research output: Contribution to journalArticlepeer-review

49 Citations (Scopus)

Abstract

New trace-element, radiogenic isotopic, and geochronologic data from the Troodos ophiolite, considered in concert with the large body of previously published data, give new insight into the tectonic history of this storied ophiolite, as well as demonstrating the variability of suprasubduction-zone ophiolites, and differences between them and commonly used modern analogs. Similar to earlier studies, we fi nd that island-arc tholeiite of the lower pillow lava sequence erupted fi rst, followed by boninite. We further divide boninitic rocks into boninite making up the upper pillow lava sequence, and depleted boninites that we consider late infi ll lavas. We obtained an Ar-Ar age from arc tholeiite of 90.6 ± 1.2 Ma, comparable to U-Pb ages from ophiolite plagiogranites. New biostratigraphic data indicate that most of the basal pelagic sedimentary rocks that conformably overlie the boninitic rocks are ca. 75 Ma. This suggests that voluminous eruption of boninitic rocks persisted until ca. 75 Ma. Limited eruption of boninitic lavas may have continued until 55.5 ± 0.9 Ma, based on the Ar-Ar age we obtained. The duration of arc magmatism at Troodos (at least 16 m.y., with some activity perhaps extending 35 m.y.) without the development of a mature arc edifi ce greatly exceeds that of other well-studied suprasubduction-zone ophiolites. We propose that Troodos was formed over a newly formed subduction zone, similar to many proposed models, but that the extended period of magmatism (boninitic) resulted from a prolonged period of ridge subduction.

Original languageEnglish
Pages (from-to)497-510
Number of pages14
JournalLithosphere
Volume4
Issue number6
DOIs
Publication statusPublished - 2012 Dec

ASJC Scopus subject areas

  • Geology

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