Geochemistry of metasomatized peridotites above subduing slab
Geochemistry of metasomatized peridotites above subduing slab: a case study of hydrous metaperidotites from
Happo-O’ne complex, central Japan
Mohamed Zaki Khedr and Shoji ArAi
Department of Earth Sciences, Kanazawa University, Kanazawa 920-1192, Japan
Hydrous peridotites from the Happo O’ne area in central Japan, which form a serpentinite mélange in the high P/T Renge metamorphic belt, vary from depleted lherzolites to harzburgites with subordinate dunite that contains primary chromian spinel with Cr# = 0.72 on average. Systematic variations of major and trace ele- ments of bulk rock compositions possibly resulted from various degrees of partial melting experienced by their protoliths (15% to <30% fractional melting). Some hydrous peridotites from the tremolite zone are representa- tives of the mantle peridotite facies with Ti rich chromian spinel (up to 5.7 wt% TiO2), and these peridotites have the same compositions as other peridotites except for enrichment in Na2O, Ba, and Ti. Their bulk rocks show U shaped PM (primitive mantle) normalized REE (rare earth elements) patterns (0.050.5 times PM) and are enriched with Cs, Pb, Sr, Ba, and Rb (0.220 times PM), indicating metasomatism by fluids derived from the subducting slab. The hydrous peridotites contain low amounts of Zr, Hf, Ta, and Nb (HFSEs), which possi- bly indicate that metasomatizing melts are not involved. These results are confirmed by in-situ analysis of trem- olites that show U-shaped REE patterns (0.1-3 times PM) and are highly enriched with fluid mobile elements (B, Li, Cs, Sr, an Pb; 1-100 times PM) and Sc relative to HFSEs
Keywords: Bulk-rock compositions, Hydrous metaperidotites, Tremolites, Happo-O’ne, Japan
:to download the paper click here
Geochemistry of metasomatized peridotites above subduing slab
Reviewed by Dr. Mohamed Zaki Khedr
on
سبتمبر 23, 2017
Rating:
ليست هناك تعليقات: