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Closed-system geochemical recycling of crustal materials in alpine-type peridotite |
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| Authors: | Tomoaki Morishita Shoji Arai David H Green |
| Institution: | 1 Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia 2 Graduate School of Natural Science and Technology, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan 3 Department of Earth Sciences, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan 4 Instituto Andaluz de Ciencias de la Tierra, Universidad de Granada-CSIC, 18002 Granada, Spain |
| Abstract: | We examined aluminous mafic rock (with or without corundum or sapphirine) alternating with peridotite from the Ronda peridotite massif, southern Spain. On the basis of petrographic characteristics, these mafic rocks show a decompression history from high pressure (P > 1.5 GPa), but on the basis of their geochemical characteristics, they are crystal accumulates of plagioclase, clinopyroxene, and olivine formed within the lower crust (P < 1 GPa). A complex evolution history, including higher-pressure recrystallization after initial formation as cumulate gabbros at lower-pressure conditions, is proposed. The aluminous mafic rocks and their peridotite hosts are inferred to be recycled crustal materials now observed as centimeter-scale layered components in alpine-type peridotite. The rocks retained their original cumulate compositions; that is, their compositions were not affected by melting and metasomatic modifications during subduction, intense deformation within the upper mantle, and upwelling to the surface. |
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