东昆仑造山带岩浆镍钴硫化物矿床形成构造背景探讨OA北大核心CSTPCD
Tectonic settings discussion of magmatic nickel-cobalt sulfide deposits in the eastern Kunlun orogenic belt
[研究目的]青海省夏日哈木超大型岩浆镍钴硫化物矿床是世界范围内造山带背景发现的最大岩浆镍钴硫化物矿床.此外在东昆仑造山带夏日哈木外围还发现了石头坑德等岩浆镍钴硫化物矿床,初步显示东昆仑造山带良好的镍钴硫化物矿床形成条件和巨大的找矿潜力.[研究方法]通过野外地质调查,室内开展岩石学、矿相学、主微量元素分析、同位素地球化学等.[研究结果]精确锆石U-Pb测年发现,东昆仑造山带夏日哈木等含矿镁铁—超镁铁质岩体基本形成于 425～330 Ma,沿柴达木盆地南缘昆北断裂和昆中断裂自西向东依次展布.含矿岩体的岩性主要为辉石橄榄岩、辉石岩、二辉橄榄岩、纯橄岩等,其 SiO2 含量 31.52%～53.31%,MgO含量7.5%～39.03%,Al2O3 含量 0.1%～16.01%,CaO含量 0.23%～13.85%,MgO与SiO2、Al2O3、Na2O、K2O均呈负相关关系.稀土总量介于 6.36×10-6～81.5×10-6,平均为 29.92×10-6,LREE/HREE平均值为 5.34,(La/Sm)N、(La/Yb)N、(Sm/Nd)N、(Gd/Yb)N平均值分别为 2.58、5.99、0.76、1.78,轻重稀土分异程度较高.含矿超镁铁质岩普遍具有较为一致的微量元素分布曲线,且与镁铁质岩石表现特征类似,亏损高场强元素Ta、Nb、Ti、P等,而相对富集大离子亲石元素Rb、Th、U等.Sr、Nd同位素研究指示夏日哈木、石头坑德等岩体岩浆源区来源于软流圈地幔,同时δ34S均表现出较高的正值,揭示地壳物质同化混染是形成岩浆镍钴硫化物矿床的关键因素.[结论]结合区域最新构造演化认识,认为东昆仑夏日哈木等超大型岩浆镍钴硫化物矿床是伴随古特提斯裂解岩浆活动的成矿表现.该认识对丰富造山带内岩浆镍钴硫化物矿床成矿理论研究、拓展岩浆镍钴矿床找矿空间与潜力、支撑引领区域找矿实践实现新突破,均具有重要的研究价值和意义.
This paper is the result of mineral exploration engineering. [Objective]The Xiarihamu giant magmatic nickel-cobalt sulfide ore deposit in the eastern Kunlun orogenic belt,the largest magmatic nickel-cobalt sulfide deposit discovered in orogenic belt in the world,is the world's largest prospecting breakthrough in the magmatic sulfide deposits area in the past twenty years after the discovery of the Voisey's Bay deposit in Canada.In addition,several large-scale magmatic nickel-cobalt sulfide deposits,such as Shitoukengde,were discovered,indicating enormous prospecting potential in the eastern Kunlun orogenic belt.[Methods]Accurate zircon U-Pb dating found that the ore-bearing mafic-ultramafic rocks in the eastern Kunlun orogenic belt formed at 425-330 Ma.The ore-bearing mafic-ultramafic rocks are distributed along the north Kunlun fault and the central Kunlun fault.The ore-bearing mafic-ultramafic rocks reflected a large-scale magmatism event.[Results]The lithofacies of these ore-forming rocks are mainly dunite,pyroxene peridotite,and pyroxenite.The SiO2,MgO,Al2O3,and CaO content ranges from 31.52%to 53.31%,from 7.5%to 39.03%,from 0.1%to 16.01%,and from 0.23%to 13.85%,respectively.On the Harker diagram,the MgO content is negatively correlated with SiO2,Al2O3,Na2O,and K2O,respectively.The total amount of rare earth elements is between 6.36×10-6 and 81.5×10-6,with an average of 29.92×10-6.The average LREE/HREE,(La/Sm)N,(La/Yb)N,(Sm/Nd)N,(Gd/Yb)N value is 5.34,2.58,5.99,0.76,and 1.78,respectively,indicating the degree of differentiation between light and heavy rare earths is high.On the primitive mantle-normalized trace element spider diagram,the ore-bearing mafic and ultramafic rocks have a relatively uniform distribution curve,which are characterized by depletion of high field strength element(Ta,Nb,Ti,and P)and enrichment of large-ion lithophile elements(Rb,Th,and U).The Sr and Nd isotope data indicate that the magma source areas of the Xiarihamu ultramafic intrusion and the Shitongkengde ultramafic intrusions were derived from the asthenosphere mantle.The δ34S value shows a high positive value,revealing that crustal-sulfur contamination played a great role during sulfide saturation.[Conclusions]Based on the regional tectonic evolution,we believed that the magmatic nickel-cobalt sulfide deposits in the eastern Kunlun orogenic belt are associated with the break-up of the Paleo-Tethys Ocean.This opinion is significant to the ore-forming theory of magmatic nickel-cobalt sulfide deposits in the orogenic belt and could guide the regional exploration of the magmatic nickel-cobalt sulfide deposits.
张照伟;钱兵;王亚磊;李文渊
中国地质调查局西安地质调查中心,陕西 西安 710054||自然资源部岩浆作用成矿与找矿重点实验室,陕西 西安 710054
地质学
镁铁—超镁铁质岩构造背景岩浆成矿作用镍钴矿床东昆仑造山带矿产勘查工程
mafic-ultramafic intrusionstectonic settingsPaleox Tethys Oceanmagmatic nickel-cobalt sulfide depositeastern Kunlun orogenic beltmineral exploration engineering
《中国地质》 2024 (002)
371-384 / 14
国家自然科学基金地质联合基金项目"昆仑成矿带及西延镍钴锂矿产境内外对比与跨境成矿规律研究"(U2244204)、第二次青藏高原综合科学考察研究"稀贵金属(金、镍、钴、铬铁矿、铂族元素)科学考察与远景评估"(2019QZKK0801)及中国地质调查局项目(DD20240128)联合资助. Supported by the projects of the National Natural Science Foundation of China"Comparative study of across national border metallogeny of Ni-Co-Li deposits in the Kunlun orogenic belt and its western extension"(No.U2244204),the Second Comprehensive Scientific Investigation and Research Project of the Qinghai-Tibet Plateau(No.2019QZKK0801),and China Geological Survey(No.DD20240128).
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