Trace element characteristics of partial melts produced by melting of metabasalts at high pressures: Constraints on the formation condition of adakitic melts

Xiaolin Xiong*, J. Adam, T. H. Green, Hecai Niu, Jinhua Wu, Zhiyong Cai

*Corresponding author for this work

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    51 Citations (Scopus)

    Abstract

    Experiments were conducted on a natural basalt (with 5 wt.% added H2O) at 1.0-2.5 GPa and 900-1100°C. Experimental products include partial melts (quenched glasses) + residual mineral assemblages of amphibolite or eclogite. Electron microprobe and LAM-ICP-MS were used to determine major and trace element compositions of these quenched melts, respectively. Major element compositions of all the melts are tonalitic-trondhjemitic, similar to adakite. Their trace element characteristics are controlled by coexisting residual minerals. Signatures of adakite such as high Sr/Y, low HREE and negative Nb-Ta anomaly, etc. are present only in the melts coexisting with residual assemblages containing rutile and garnet (rutile-bearing eclogite or rutile-bearing amphibole-eclogite). Garnet leads to HREE depletion in melts, whereas rutile controls Nb and Ta partitioning during the partial melting and causes negative Nb-Ta anomaly in melts. Therefore, in addition to garnet, rutile is also a necessary residual phase during the generation of adakite or TTG magmas to account for the negative Nb-Ta anomaly of the magmas. The depth for the generation of adakite/TTG magmas via melting of metabasalt must be more than about 50 km based on the approximate 1.5 GPa minimum-pressure for rutile stability in the partial melting field of hydrous basalt.

    Original languageEnglish
    Pages (from-to)915-925
    Number of pages11
    JournalScience in China, Series D: Earth Sciences
    Volume49
    Issue number9
    DOIs
    Publication statusPublished - Sep 2006

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