LA-ICP-MS Zircon U-Pb Dating of the Haladala Basic Pluton in Tekesi County,Western Tianshan and Its Geological Implication

The Haladala basic pluton, consists of troctolite, olivine gabbro, hornblende gabbro, and gabbro, intruded into Late Carboniferous rocks in the Northeastern Tekesi County, Western Tianshan.As the largest basic-ultrabasic intrusive complex of western Tianshan orogenic belt, the formation age and tectonic environment of the Haladala pluton have always been the focus problem for the evolution of Tianshan orogenic belt.In the process of magma evolution, after the fractional crystallization of olivine and plagioclase, the residual magma intruded and formed gabbro.LA-ICP-MS zircon U-Pb chronology indicates that the age of gabbro is (304.5 ±2.6)Ma (MSWD=0.59, n=25).The Haladala gabbro belongs to calc-alkaline series, with the enrichment of large ion lithophile elements and the depletion of high strength field elements.The geochemical characteristics suggest that the Haladala basic pluton was produced by mantle-based magmatic invasion and crustal contamination, and it was affected by the fluid at the same time.Based on the regional geological data, it is concluded that the Western Tianshan was in the extentional setting during the Late Carboniferous, which may be related to the post collision rift evolution of the Tianshan orogenic belt.