Petrogenesis of Early Carboniferous Alkaline Basalt from the Wusun Mountain: Implications for Tectonic Evolution of the Western Yining Block, NW China,Acta Geologica Sinica-English Edition

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Petrogenesis of Early Carboniferous Alkaline Basalt from the Wusun Mountain: Implications for Tectonic Evolution of the Western Yining Block, NW China
Acta Geologica Sinica-English Edition ( IF 3.5 ) Pub Date : 2019-10-04 , DOI: 10.1111/1755-6724.14382
Zuopeng WANG ₁ , Yongjun LI ₁ , Hongqi CHEN ₂ , Yanlong ZHOU ₁ , Gaoxue YANG ₁ , Ganyu LI ₃ , Philemon LINDAGATO ₁ , Lili TONG ₁

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Late Paleozoic volcanic rocks are well exposed in the Yining Block, NW China, and are predominately composed of andesites, rhyolites and volcaniclastics as well as minor basalts. Study of the petrology, whole-rock geochemistry and zircon U-Pb dating for the Early Carboniferous alkaline basalts from Wusun Mountain, western Yining Block, constrains their petrogenesis and tectonic evolution. The alkaline basalts consist mainly of plagioclases, mostly albite and labradorite, as well as clinopyroxenes and olivines; zircon U-Pb dating indicates their formation at ca. 350 Ma. Geochemically, the basaltic samples have low SiO₂ contents, and high TiO₂, Al₂O₃ and alkaline contents, coupled with high Na₂O/K₂O ratios, displaying an alkaline basalt affinity. They show remarkable LILE enrichment and HFSE depletion. Meantime, these samples have relatively high TFe₂O₃, MgO, and Mg^# values as well as Ni and Cr, relatively high Sm/Yb and U/Th, suggesting origination from a mantle source metasomatized by slab fluids. They formed in a transitional tectonic setting from arc to intraplate, showing a typical affinity of back-arc basin basalts. The alkaline basalts were likely generated in a nascent back-arc extension setting resulting from slab rollback of the southern Tianshan oceanic lithosphere. A bi-directional subduction model seems more reasonable for the evolution of the southern Tianshan Ocean. These new data will provide a new tectonic model for Late Paleozoic tectonic evolution of the western Yining Block.

更新日期：2019-10-04

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