Petrology of Alkali Wehrlite Sills in the Oman Mountains

S. J. Lippard
Earth Science Department, Open University, Milton Keynes, MK7 6AA, UK

Abstract: Alkaline mafic sills of Jurassic to Cretaceous age in the Oman Mountains have coarse-grained wehrlite centres composed of olivine and zoned diopside-titanaugite with large interstitial poikilitic titanian hornblendes and titanian barian phlogopites and biotites which appear to have crystallized from a trapped, intergranular, volatile-rich liquid. The fine-grained chilled margins of the sills are olivine-poor and composed largely of titanaugite, kaersutite, sphene, and interstitial altered plagioclase. The rocks have high contents of incompatible elements (Ti, P, Sr, Ba, Zr, Nb, and others) and steeply inclined, light element enriched, REE patterns. The parent magma is estimated to have been a hydrous alkali picrite with c. 12% MgO from which the wehrlite formed by olivine accumulation. The unusual tectonic setting of the sills, in a Mesozoic continental margin sequence emplaced in an Alpine thrust belt, is noted.

Mineralogical Magazine; March 1984 v. 48; no. 346; p. 13-20; DOI: 10.1180/minmag.1984.048.346.02
© 1984, The Mineralogical Society
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