【摘要】 在东天山地区中天山地块内发现了一套晚石炭世I型和A型的花岗岩组合,锆石SHRIM PU-Pb定年结果为(301.4±4.6)Ma,形成于晚石炭世,二者同期不同源。I型花岗岩组合为石英二长闪长岩、黑云母二长花岗岩、钾长花岗岩;A型花岗岩组合为石英二长岩、石英正长岩、石英正长斑岩、黑云母钾长花岗岩。岩石地球化学特征显示,A型花岗岩具板内花岗岩的特征,为经历过岛弧或碰撞岩浆事件后下地壳部分熔融的岩浆分离结晶产物;I型花岗岩具岛弧花岗岩的地球化学特征,岩浆来源于壳幔混合源区,可能是消减带洋壳和上部地幔楔滞后熔融的产物。研究结果表明,晚石炭世中天山应处于碰撞后的伸展构造环境。更多还原

【Abstract】 A series of Late Carboniferous I-type and A-type granites,formed in the same period with different origins,is discovered from middle Tianshan block,East Tianshan,NW China.11 zircons from biotite-Kf-spar granite were dated using SHRIMP U-Pb method,averaged at(301.4±4.6)Ma(206 Pb/ 238 U),which represents the intrusive age of the granites.The rock association of the I-type granites consists of quartz-monzodiorite,biotite-monzogranite,Kf-spar granite,while the A-type granites are composed of quartz-monzonite,syenite,quartz-syeniteporphyry,biotite-Kf-granite.The petrochemical and geochemical characteristics of the granites show that the A-type granites possess the characteristics of within-plate granites and could have been formed by the fractional crystallization of the magma formed by subduction or continent-continent collision.While the I-type granites bear the characteristics of volcanic arc granites,the product of magma from continental-mantle mixing origins,may be the post-dated melts of oceanic crust and upper mantle wedge at the subduction zone.Hence it is concluded that the Late Carboniferous Middle Tianshan should exist in postcollision within the plate extension tectonically.更多还原