南祁连亚曲含镍铜矿基性杂岩体形成年龄及机制探讨

The Formation Age of the Yaqu Ni-Cu Bearing Basic Complex in Southern Qilian Mountain and a Discussion on Its Mechanism

通过亚曲岩体的实地调查和研究,利用ID-TIMS方法对岩体定年,获得(440.74±0.33)Ma成岩年龄,为加里东期。岩石地球化学特征分析及区域对比研究表明,亚曲基性杂岩体以低Ti、亏损Nb和Ta、富集轻稀土元素和大离子亲石元素为特征。结合其同位素特征,提出该岩体的形成与祁连山及其邻区460～440Ma时期俯冲向碰撞转换的作用有关,可能是岛弧岩浆作用的结果。这对于南祁连化隆一带区域铜镍找矿具有重要意义,亦对丰富完善早古生代岩浆铜镍硫化物矿床的研究和形成机制具有借鉴作用。

This paper reports partial achievements in potential evaluation of magmatic type copper-nickel ore resources in Hualong County, Qinghai Province, mainly by field survey and investigation of Yaqu intrusive rocks, and obtained the zircon U-Pb age of rock formation （442.4±1.6） Ma by ID-TIMS. Geochemical studies of the basic complex closely associated with the deposit show that it is characterized by low Ti, depletion of Nb or Ta and enrichment of LREE and large lithosphile elements. These features, combined with the isotope geochemistry, have led the authors to believe that the magma occurred under the condition of the conversion of subduction to collision in 460-440 Ma in the Qilian Mountain and its adjacent areas, and might have resulted from arc magmatism. The results not only have great significance for regional prospecting of Ni-Cu ore resources in Hualong area but also have reference value for enrichment of the knowledge of early Paleozoic magmatic Ni-Cu sulfide deposits and their formation mechanism.