柴达木北缘东段呼德生镁铁-超镁铁质岩体锆石U-Pb年代学、地球化学及成岩成矿分析

发布时间：2018-05-31 18:51

  本文选题：结晶分异作用 + 同化混染作用　； 参考：《地质与勘探》2017年05期

【摘要】：呼德生岩体位于柴北缘造山带欧龙布鲁克微陆块东南缘,侵位于古元古代金水口变质岩群中。该岩体从中心到边缘依次出现橄榄岩→辉石岩→辉长岩的岩相分带特征,岩石主要类型有纯橄岩、橄榄二辉岩和辉长岩,各岩石之间多为过渡接触关系,镍铜矿化主要赋存于辉石岩中。锆石LAICP-MS U-Pb年代学研究表明,岩体形成年龄为425.2±5.8Ma,为柴北缘晚志留世-晚泥盆世后造山伸展阶段岩浆作用的产物。岩石镁铁比值(m/f)为2.51~5.37,属于铁质系列基性-超基性岩。各类岩石富集轻稀土元素(LREE)和大离子亲石元素(Ba、Sr、Rb),而亏损高场强元素(Zr、Hf、Nb、Ta)。岩相学、矿物学及岩石地球化学研究表明岩浆在演化过程中发生了一定程度的结晶分异作用和同化混染作用。结合岩体形成年代及区域地质资料,呼德生岩体应形成于大陆边缘伸展阶段,原始岩浆在演化过程中经历了地幔流体的交代作用。通过对岩浆结晶分异程度及同化混染情况等方面的综合评价,认为呼德生岩体具有良好的铜镍硫化物矿床形成条件。
[Abstract]:The Hudesheng rock body is located in the southeastern margin of the Oulong Brook micro-continental block in the northern Qaidam orogenic belt and in the Gu Yuan ancient gold-water mouth metamorphic rock group. The lithofacies zonation of peridotite pyroxenite gabbro appears from the center to the margin. The main types of rock are pure olivine, peridotite and gabbro, and most of them are transitional contact relationship. Nickel copper mineralization occurs mainly in pyroxenite. The zircon LAICP-MS U-Pb chronological study shows that the formation age of the rock mass is 425.2 卤5.8 Ma, which is the product of magmatism during the late Silurian and post-Devonian orogenic extensional stages in the northern margin of Qaidam. The ratio of mg / f is 2.51 ~ 5.37, which belongs to the basic-ultrabasic rocks of iron series. Various types of rocks are enriched with LREE) and large ion lithophile elements BaSrsrbn, while the high field strength elements are depleted. Petrographic, mineralogical and petrogeochemical studies indicate that the magma experienced a certain degree of crystallization differentiation and assimilation mixing during the evolution of magma. Based on the age and regional geological data of the formation of the rocks, the Hudesheng rock body should be formed in the continental margin extension stage, and the primitive magma experienced mantle fluid metasomatism during the evolution process. Based on the comprehensive evaluation of the degree of crystallization differentiation and assimilation of magma, it is considered that the Hudesheng rock body has good conditions for the formation of Cu-Ni sulfide deposits.
【作者单位】： 国土资源部岩浆作用成矿与找矿重点实验室中国地质调查局西安地质调查中心;青海省核工业地质局;
【基金】：国土资源部公益性行业科研专项项目(201511020) 国家自然科学基金青年基金项目(41603050;41602094) 中国地质调查局“东昆仑铜镍多金属资源基地调查”二级项目(DD20160013)联合资助
【分类号】：P587;P597.3;P611
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本文编号：1960912