【摘要】 新疆阿尔泰地区科克辉长岩位于额尔齐斯断裂和可可托海-二台断裂交汇部位的东南侧,为探矿过程中发现的隐伏岩体。本次工作对科克辉长岩体地质、年代学和地球化学进行了系统研究,结果显示科克辉长岩体锆石SIMS U-Pb同位素年龄为291Ma左右,对应于早二叠世,岩体具有较低SiO₂（46.14%～52.53%）和MgO（3.00%～7.68%）含量,较低La/Sm（2.56～4.10）和较高的（Gd/Yb）_N（1.12～1.61）比值,微量元素具富集大离子亲石元素（K,Rb,Pb等）、亏损高场强元素（Nb与Ta等）等地球化学特征,指示科克辉长岩的岩浆起源于氧化的俯冲交代地幔源区的部分熔融,在上升侵位过程中受外来物质混染作用较弱的特点。综合地质和地球化学特征显示,新疆阿尔泰地区二叠纪科克辉长岩形成于伸展构造背景,岩浆侵位受额尔齐斯断裂走滑作用控制,该岩浆岩是北疆地区广泛发育的二叠纪基性岩浆岩的组成部分。更多还原

【Abstract】 The Keke gabbro, located in the southeast side at the intersection of Ertix and Koktokay and Ertai faults, South Altay, is one concealed intrusion discovered in recent exploration. In this study, we performed detailed analysis of geological characteristics, geochronology and geochemistry of the Keke gabbro. The results show that the SIMS U-Pb age of zircons from the Keke gabbro is ca 291 Ma, suggesting an age of Early Permian. The Keke gabbro exhibits low SiO₂（46.14%～52.53%） and MgO（3%～7.68%） contents, with low La/Sm（2.56～4.10） and high（Gd/Yb）_N ratios（1.12～1.61）, as well as enrichment of LILE（K, Rb and Pb）, and depletion of HFSE（Nb and Ta）. Those geochemical characteristics indicate that the magma of the Keke gabbro resulted from partial melting of the oxidized replacement mantle due to subduction, weakly contaminated by crustal materials during its emplacement. Combined with geological and geochemical features, the Permian Keke gabbro in the Altay region formed in extensional tectonic setting, with emplacement of magma controlled by the Ertix strike slipping. Therefore, the gabbro is the important component of the Permian mafic magmatic rocks widely developed in the northern Xinjiang region.更多还原