新疆北部哈纳斯盆地火山岩地球化学特征、锆石U-Pb年龄及其构造意义

The Hanasi volcanic basin is located in the northern part of the Altai orogenic belt, Xinjiang, China. There is a calc-alkaline volcanic suite consisting of andesite-dacite-rhyolite in the basin. These volcanic rocks are generally enriched in LILE (Rb, Sr, Th and La) and depleted in HFSEs (Zr, Y, Ti, Nb and Ta). REE distribution patterns are characterized by a moderate enrichment of LREE. These trace element and REE characteristics are typical of arc volcanic rocks. The content of major elements, such as Fe, Mg, Ca and Al, and trace elements, such as Ti, Sr, Ni, Cr and Co, is linearly correlated to that of SiO2, which suggests that the different volcanic rocks in the basin should be the product of fractional crystallization of congenetic magmas. The parental magma may be generated by the partial melting of an enriched mantle wedge formed by the metasomatism of slab-derived fluids in an active continental margin tectonic setting. U-Pb single-grain zircon age of the dacite is (474.5±4.7) Ma, which agrees with stratigraphic chronology. During this period, the Paleo-Asia Ocean in North Xinjiang subducted northward under the Siberia plate, which resulted in a series of continental volcanic arcs. The Hanasi volcano-sedimentary basin is representative of the typical early Paleozoic lateral continental accretion arc in the Central Asian orogenic belt.