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Trace-Element Geochemistry of Volcanic Rocks from Site 786: The Izu-Bonin Forearc
Conference proceeding   Open access

Trace-Element Geochemistry of Volcanic Rocks from Site 786: The Izu-Bonin Forearc

Bramley J Murton, David W Peate, Richard J Arculus, Julian A Pearce and Sieger van der Laan
Proceedings of the Ocean Drilling Program, Scientific Results,, Vol.125, pp.211-235
1992
DOI: 10.2973/odp.proc.sr.125.133.1992
url
https://doi.org/10.2973/odp.proc.sr.125.133.1992View
Published (Version of record) Open Access

Abstract

Eocene-Oligocene volcanic rocks drilled at Site 786 in the Izu-Bonin forearc cover a wide range of compositions from primitive boninites to highly evolved rhyolites. K-Ar dating reveals at least two distinct episodes of magmatism; one at 41 Ma and a later one at 35 Ma. The early episode produced low-Ca boninites and bronzite andesites that form an oceanic basement of pillow lavas and composite intrusive sheets, overlain by flows and intrusive sheets of intermediate-Ca boninites and bronzite-andesites and a fractionated series of andesites, dacites, and rhyolites. The later episode produced high-Ca boninites and intermediate-Ca boninites, exclusively as intrusive sheets.

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