Ultrahigh-pressure corundum-rich garnetite in garnet peridotite,Sulu terrane,China |
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| Authors: | Zhang R Y Liou J G Zheng J P |
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| Institution: | (1) Department of Geological and Environmental Sciences, Stanford University, Stanford, CA 94305, USA;(2) Faculty of Earth Sciences, China University of Geosciences, 430074 Wuhan, China |
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| Abstract: | Corundum-rich garnetite occurs as an isolated lens in a garnet peridotite body in the Donghai area of the Sulu ultrahigh-pressure (UHP) terrane. This rock consists of garnet and corundum, along with minor crack-related zoisite, pargasite, Mg-staurolite, Mg-chloritoid, sapphirine and chlorite. Pyropic garnet (Prp54–63Grs26–36Alm10–12) exhibits a sinusoidal REE pattern, positive Ta, Pb, and negative Nb, Ti anomalies due to metasomatism. Reddish corundum contains 1.1–1.7 wt% Cr2O3, and shows three oriented sets of exsolved rutile needles. Both garnet and corundum contain inclusions of apatite, Mg-allanite (MgO>4 wt%), and Ni-Fe sulfides formed as trapped Ni-Fe-S melt. The protolith of the corundum-rich garnetite could have been spinel websterite formed in the upper mantle. Both the websterite and the host garnet peridotite were subjected to subduction-zone UHP metamorphism at  800 °C and >4 GPa. Crack-related hydrous phases were formed by fluid infiltration during exhumation.Editorial responsibility: T.L. Grove |
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