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Architecture of the Oman-UAE ophiolite : evidence for a multi-phase magmatic history

By K.M. Goodenough, M.T. Styles, D. Schofield, R.J. Thomas, Q.C. Crowley, R.M. Lilly, J. McKervey, D. Stephenson and J.N. Carney

Abstract

The Oman–United Arab Emirates ophiolite is the\ud world’s largest ophiolite. It is divided into 12 separate faultbounded\ud blocks, of which the northern three lie wholly or\ud partly in the United Arab Emirates. Extensive mapping has\ud shown that the United Arab Emirates blocks contain mantle\ud and crustal sections which correspond to the classic\ud ‘Penrose conference’ ophiolite definition but which are\ud cut by a voluminous later magmatic sequence including\ud ultramafic, mafic and felsic components. Samples from the\ud later magmatic sequence are dated at 96.4±0.3, 95.74±0.3\ud and 95.2±0.3 Ma; the early crustal section, which has not\ud been dated directly, is thus constrained to be older than c.\ud 96.4 Ma. Petrological evidence shows that the early crustal\ud section formed at a spreading ridge, but the later magmatic\ud sequence was formed from hydrous magmas that produced\ud different mineral crystallisation sequences to normal midocean\ud ridge basalt (MORB). Mineral and whole-rock\ud geochemical analyses show that the early crustal rocks are\ud chemically similar to MORB, but the later magmatic\ud sequence has chemical features typically found in suprasubduction\ud zone (SSZ) settings. The ophiolite in the United\ud Arab Emirates thus preserves clear evidence for two stages\ud of magmatism, an early episode formed at a spreading\ud centre and a later episode associated with the onset of\ud subduction. Similar two-stage magmatism has been recognised\ud in the Oman sector, but the United Arab Emirates\ud contains the most voluminous SSZ magmatism yet described\ud from this ophiolite

Topics: Earth Sciences
Publisher: Springer
Year: 2010
DOI identifier: 10.1007/s12517-010-0177-3
OAI identifier: oai:nora.nerc.ac.uk:11347

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