东昆仑石头坑德镁铁-超镁铁质岩体矿物学特征及成矿指示

发布时间：2018-07-09 16:42

本文选题：矿物学特征 + 镁铁-超镁铁质岩　；参考：《地质与勘探》2017年05期

【摘要】：石头坑德镁铁-超镁铁质岩体位于东昆仑造山带东段五龙沟地区,邻近昆中大断裂,主要岩性为辉石岩、橄辉岩、橄榄岩、辉长岩等,铜镍矿体主要赋存于Ⅰ号岩体的辉石岩、橄辉岩和橄榄岩中。岩石地球化学特征表明,其镁铁比值(m/f)变化范围在2.77~6.01之间,属铁质系列的镁铁-超镁铁岩,有利于成铜镍矿。稀土总量总体较低,轻稀土元素之间分馏强,重稀土元素之间分馏弱。岩石总体富集LILE(Rb、Ba、Th、U),贫HFSE(Nb、Ta、Zr、Y),具有明显的Rb、U正异常及Nb、Ta的负异常。超镁铁岩类橄榄石中的Ni普遍亏损,指示深部存在硫化物的熔离作用,在橄榄石结晶之前,大量的Ni进入到硫化物中,极有利于形成富矿岩浆或矿浆。可见,伴随同化混染作用的发生,岩浆中S达到过饱和,进而硫化物发生不混溶作用,富含硫化物的岩浆运移至东昆仑造山带邻近昆中断裂构造薄弱的部位成岩成矿。铜镍矿体多赋存在含橄榄石的超镁铁质岩体内,指示石头坑德岩体深部存在高度富集铜镍的部位,是下一步的找矿方向。
[Abstract]:The Shikunde Magnesium-ultramafic rock body is located in the Wulonggou area of the eastern part of the East Kunlun orogenic belt, and is adjacent to the Kun mid-large fault. The main lithology is pyroxenite, olivine, peridotite, gabbro, etc. The copper-nickel orebody is mainly located in the pyroxenite of the No. 1 rock mass. In olivine and peridotite. The petrogeochemical characteristics show that the ratio of mg / f (m / f) varies from 2.77 to 6.01, which is a series of magnesia-ultramafic rocks, which is favorable for Cu-Ni ore formation. The total amount of rare earth is low, the fractionation of light rare earth elements is strong and the fractionation of heavy rare earth elements is weak. The rocks are generally enriched in Lile (RbPU) and poor in HFSE (NbTa-Ta-Zr-Y), with obvious positive RbTU anomalies and negative NbTa-Ta anomalies. The general depletion of Ni in ultramafic olivine indicates that there is a melting process of sulfides in the deep part. Before olivine crystallization, a large amount of Ni enters into sulfides, which is beneficial to the formation of ore-rich magma or magma. It can be seen that with the occurrence of assimilation and contamination, S in magma is supersaturated, and the sulfide-rich magma is immiscible, and the sulphide rich magma migrates to the diagenetic and metallogenic position near the middle Kunlun fault structure of East Kunlun orogenic belt. The copper-nickel orebodies mostly occur in ultramafic rocks containing olivine, indicating that there are highly enriched copper-nickel deposits in the deep part of the Shikunde rock mass, which is the next prospecting direction.
【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;青海省地质调查局;四川省地质矿产勘查开发局一八地质队;
【基金】：国土资源部公益性行业科研专项“拉陵灶火镍成矿赋矿机理及勘查技术研究示范”(201511020) 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)共同资助
【分类号】：P584;P612

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