Palaeozoic multiphase magmatism at Barleik Mountain, southern West Junggar, Northwest China: implications for tectonic evolution of the West Junggar

摘要

The West Junggar lies in the southwest part of the Central Asian Orogenic Belt (CAOB) and consists of Palaeozoic ophiolitic melanges, island arcs, and accretionary complexes. The Barleik ophiolitic melange comprises several serpen-tinite-matrix strips along a NE-striking fault at Barleik Mountain in the southern West Junggar. Several small late Cambrian (509-503 Ma) diorite-trondhjemite plutons cross-cut the ophiolitic melange. These igneous bodies are deformed and display island arc calc-alkaline affinities. Both the melange and island arc plutons are uncomfortably covered by Devonian shallow-marine and terrestrial volcano-sedimentary rocks and Carboniferous volcano-sedimentary rocks. Detrital zircons (n = 04) from the Devonian sandstone yield a single age population of 452—517 million years, with a peak age of 474 million years. The Devonian-Carboniferous strata are invaded by an early Carboniferous (327 Ma) granodiorite, late Carboniferous (315-311 Ma) granodiorites, and an early Permian (277 Ma) K-feldspar granite. The early Carboniferous pluton is coeval with subduction-related volcano-sedimentary strata in the central West Junggar, whereas the late Carboniferous-early Permian intrusives are contemporary with widespread post-collisional magmatism in the West Junggar and adjacent regions. They are typically undeformed or only slightly deformed.