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    青藏高原东北缘岩浆型铜镍钴硫化物矿床勘查模型与研究进展

    Exploration and research progress of magmatic copper−nickel−cobalt sulfide deposits in the north−eastern margin of the Qinghai−Xizang Plateau

    • 摘要:
      研究目的 为提升我国Cu−Ni−Co资源供应安全,有必要梳理青藏高原东北缘东昆仑造山带的岩浆型铜镍钴硫化物矿床的的成矿规律与找矿标志。
      研究方法 为建立矿床勘查模型,本文剖析了代表性岩浆铜镍硫化物矿床的地质特征与成因,并系统总结了东昆仑地区晚奥陶世—早志留世、中晚志留世—早中泥盆世、早石炭世、中二叠世—早三叠世、中—晚三叠世5期基性−超基性侵入杂岩体的矿物学、岩石学、年代学、地球化学和地球物理特征。
      研究结果 东昆仑在显生宙存在2期岛弧基性或基性—超基性岩体:(1)原特提斯洋向北俯冲背景下形成的晚奥陶世—早志留世的基性岩体;(2)中二叠世—早三叠世的古特提斯洋俯冲形成的基性—超基性岩体;与之对应,存在2期碰撞后伸展基性—超基性岩体,分别为中晚志留世—早中泥盆世和中晚三叠世。辉石岩地幔可能是东昆仑部分岩浆型镍矿床的源区,板块断离−折返模型可较好解释岩浆铜镍钴硫化物矿床成矿年龄与高压—超高压退变质年龄一致的现象。针对幔源岩浆硫化物饱和机制,大体识别了有利地壳混染与有害地壳混染的种类,并深入分析结晶分异对硫化物饱和影响,提出了矿体优选赋存的位置,对比了成矿岩体与非成矿岩体在构造、岩石类型、矿物学、时代、蚀变、围岩种类代表性差异。
      结论 建立了东昆仑造山带岩浆铜镍钴硫化物矿床的地质−地球化学−地球物理综合信息勘查模型。

       

      Abstract:
      This paper is the result of mineral exploration engineering.
      Objective To improve the supply security of Cu−Ni−Co resources in China, it is necessary to sort out the mineralization regularity and prospecting indicators of the magmatic copper−nickel−cobalt sulfide deposit in the Phanerozoic in the Eastern Kunlun orogenic belt on the northern margin of the Qinghai−Xizang Plateau.
      Methods To establish the exploration model, this paper analyzed the geological characteristics and genesis of representative magmatic copper-nickel sulfide deposits, and the geological, geochronology, geochemistry, and geophysical characteristics of five stages mafic−ultramafic complexes including the Late Ordovician−Early Silurian, the Middle Silurian−Middle Devonian, the Early Carboniferous, the Middle Permian−Early Triassic, and the Middle−Late Triassic are summarized.
      Results There are two stages of island arc mafic or basic−ultramafic rocks in the East Kunlun during the Phanerozoic: (1) Mafic rocks formed in the Late Ordovician−Early Silurian during the northward subduction of the Proto−Tethys Ocean; (2) Mafic−ultramafic rocks formed due to the subduction of the Paleo−Tethys Ocean in the Middle Permian−Early Triassic. Correspondingly, there are two stages of post−collision extensional mafic−ultramafic rocks: From Middle−Late Silurian to Early−Middle Devonian and Middle−Late Triassic. The pyroxenite mantle may be the source of some magmatic nickel deposits in the East Kunlun, and the plate break−off model can explain the phenomenon that the mineralization age of magmatic copper−nickel−cobalt sulfide deposits is nearly same to the high−pressure−ultrahigh−pressure retrograde metamorphism age. Regarding the sulfide saturation mechanism of mantle−derived magma, the types of favorable crustal contamination and harmful crustal contamination were roughly identified, and the influence of crystal differentiation on sulfide saturation was analyzed. The preferred location of ore bodies was proposed, and the representative differences between ore−forming and non−ore−forming rock bodies in geological structure, rock type, mineralogy, age, alteration type, and surrounding rock types were compared.
      Conclusions Finally, this paper established a geological−geochemical−geophysical comprehensive information exploration model for magmatic copper−nickel−cobalt sulfide deposits in the East Kunlun orogenic belt.

       

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