Peridotite xenoliths from Grenada,Lesser Antilles Island Arc |
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| Authors: | I?J?Parkinson Email author" target="_blank">R?J?ArculusEmail author S?M?Eggins |
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| Institution: | (1) Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK;(2) Department of Geology, Australian National University, ACT 0200 Canberra, Australia;(3) Research School of Earth Sciences, Australian National University, ACT 0200 Canberra, Australia |
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| Abstract: | Ultramafic xenoliths comprising harzburgite, lherzolite (reacted harzburgite) and spinel-rich dunite, occur in alkali olivine basalts (M series) of Grenada in the Lesser Antilles island arc. Textures are protogranular, porphyroclastic and granular; the latter are restricted to dunites and areas of the harzburgites/lherzolites where interaction with host magma has occurred. Primary mineralogy comprises olivine, orthopyroxene, clinopyroxene, and spinel. Harzburgites are residual from a fractional partial melting event totaling ~ 22%. Infiltration of harzburgite by (and reaction with) basalt has produced: a wehrlite, with partial dissolution of primary spinel, an increase in the oxygen fugacity (ƒO2) from primary values 1–2 log ƒO2 units above the fayalite-magnetite-quartz (FMQ) buffer, to 2–2.5 log units above the buffer; reaction of orthopyroxene to form patches of intergrown olivine and clinopyroxene, and bronzite andesite glass (60 wt%, SiO2 18–20 wt% Al2O3 and 3–4 wt% Na2O) with flat to light rare earth element-depleted, chondrite-normalized abundances. Refertilisation of the mantle by reacting melts, producing a clinopyroxene-rich lithology, may form a source of ankaramitic (high-Ca) arc basalts.Editorial responsibility: T.L. Grove |
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