摘要
【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SiO_(2)含量31.52%~53.31%,MgO含量7.5%~39.03%,Al_(2)O_(3)含量0.1%~16.01%,CaO含量0.23%~13.85%,MgO与SiO_(2)、Al_(2)O_(3)、Na_(2)O、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δ^(34)S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。
[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 SiO_(2),MgO,Al_(2)O_(3),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 SiO_(2),Al_(2)O_(3),Na_(2)O,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.Theδ^(34)S 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.
作者
张照伟
钱兵
王亚磊
李文渊
ZHANG Zhaowei;QIAN Bing;WANG Yalei;LI Wenyuan(Xi'an Center of Geological Survey,China Geological Survey,Xi'an 710054,Shaanxi,China;MNR Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,Xi'an 710054,Shaanxi,China)
出处
《中国地质》
CAS
CSCD
北大核心
2024年第2期371-384,共14页
Geology in China
基金
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)
中国地质调查局项目(DD20240128)联合资助。
关键词
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 intrusions
tectonic settings
Paleox Tethys Ocean
magmatic nickel-cobalt sulfide deposit
eastern Kunlun orogenic belt
mineral exploration engineering
