新疆东准噶尔碰撞后成矿响应:来自松喀尔苏铜金矿床地质特征及花岗斑岩地球化学证据

    Post-collisional metallogenic response in Eastern Junggar, Xinjiang: geological characteristics of the Songkalsu copper-gold deposit and geochemical evidence of granite porphyry

    • 摘要: 本文对松喀尔苏斑岩型铜金矿床的地质特征,以及与矿化关系密切的花岗斑岩开展了岩石地球化学特征研究,同时结合区域构造演化特点及岩浆活动与成矿响应等,分析矿床形成的成矿专属性。微量元素特征显示出明显的亏损Sr、Nb、Ti、P等大离子亲石元素,富集Rb、Th、Zr、Hf等高场强元素。钾长花岗岩稀土元素特征显示稀土配分模式为“海鸥式”,δEu介于0.41~0.49之间,表现为强烈亏损型,暗示源区存在斜长石的分离结晶。花岗斑岩样品稀土元素REE介于30×10−6~50.6×10−6之间,变化范围窄且含量稍低,所有样品配分模式一致,δEu介于0.80~1.17之间,表明岩浆在演化过程中没有发生明显的斜长石分离结晶作用。这些特征表明松喀尔苏钾长花岗岩形成于浅部的长英质年轻地壳,花岗斑岩可能起源于新元古代新生地壳的部分熔融,但在形成过程中混入了不同比例的幔源组分。本文研究为理解东准噶尔地区的成矿机制提供了地球化学证据,以期为下一步在该地区开展找矿勘查及预测提供理论依据。

       

      Abstract: In this paper, the geological characteristics of Songkalsu porphyry copper-gold deposit and the geochemical characteristics of granite porphyry closely related to mineralization are studied. At the same time, combined with the characteristics of regional tectonic evolution, magmatic activity and metallogenic response, the metallogenic specificity of the deposit formation is analyzed. The trace element characteristics show obvious depletion of Sr, Nb, Ti, P and other large ion lithophile elements, and enrichment of Rb, Th, Zr, Hf and other high field strength elements. The characteristics of rare earth elements of K-feldspar granite show that the rare earth distribution mode is “seagull type”, and the δEu is between 0.41 and 0.49, which shows a strong depletion type, suggesting that there is separation and crystallization of plagioclase in the source area. The rare earth elements REE of the granite porphyry samples are 30×10−6-50.6×10−6, with a narrow range of variation and a slightly lower content. The distribution patterns of all samples are consistent, and the δEu is 0.80-1.17, indicating that there is no obvious plagioclase separation and crystallization during the evolution of the magma. These characteristics indicate that the Songkalsu K-feldspar granite is formed in the shallow felsic young crust, and the granite porphyry may have originated from the partial melting of the Neoproterozoic newborn crust, but during the formation process, different proportions of mantle-derived components are mixed. This study provides geochemical evidence for understanding the metallogenic mechanism of the Eastern Junggar Area, with a view to providing a theoretical basis for further prospecting and prediction in the area.

       

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