Trace-element of Tuoyun clinopyroxene: Implication for the deep processes of lithospheric mantle beneath the southwest Tianshan, West China

Abstract

Based on the LAM-ICPMS analytic results on the trace elements of clinopyroxenes in peridotitic xenoliths occurring in early-Cretaceous basalts from western Xinjiang, the properties and the deep processes, including partial melting and mantle metasomatism, of the subcontinental lithospheric mantle beneath the Tuoyun Basin are analyzed. In the northern edge of the Tarim Basin (southwest Tianshan), the Mesozoic subcontinental lithosphere which has experienced the effect of partial melting (<10%) and intricate mantle metasomatism is characterized by Phanerozoic ‘ocean-type’ mantle. The superposed influence of SiO2-unsaturated silicate melt and carbonate melt probably results in the metasomatic medium which resembles the hydrous silicated carbonate melt in some aspects. By comparing Tuoyun mantle with Cenozoic main mantle beneath eastern China, the properties are similar, while the former shows finer grain and higher diopside content of the peridotites and more conspicuous modal metasomatism.