| 内蒙古嘎仙镍钴矿区岩浆作用与成矿 |
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| 引用本文： | 李德东,王玉往,石煜,黄行凯,陈伟民,王福.内蒙古嘎仙镍钴矿区岩浆作用与成矿[J].矿床地质,2018,37(5):893-916. |
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| 作者姓名： | 李德东 王玉往 石煜 黄行凯 陈伟民 王福 |
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| 作者单位： | 北京矿产地质研究院;有色金属矿产地质调查中心 |
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| 基金项目： | 本文得到北方增生造山成矿系统的深部结构与成矿过程（编号：2017YFC0601204）和中国地质调查局项目（编号：12120113086300）资助 |
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| 摘 要： | 内蒙古嘎仙矿床为大兴安岭北段与岩浆作用有关的大型低品位镍钴硫化物矿床,成矿作用主要与花岗质岩浆作用有关。文章主要对矿区内矿体下盘的花岗岩类(花岗斑岩、长石斑岩、伟晶状花岗岩、黑云母花岗岩)进行了锆石LA-ICP-MS U-Pb定年,获得花岗斑岩的谐和线年龄(125.3±1.1)Ma～(127.5±4.5)Ma,长石斑岩的谐和线年龄为(128.1±2.2)Ma,伟晶状花岗岩的谐和线年龄为(127.9±2.3)Ma,黑云母花岗岩的谐和线年龄为(127.9±1.4)Ma,说明这些花岗岩类主要形成于中生代早白垩世。通过对矿化超镁铁岩、科马提岩、镁铁岩(辉绿岩、玄武岩)、长英质岩(闪长岩、长石斑岩、斜长花岗岩、花岗斑岩、伟晶状花岗岩、黑云母花岗岩)及围岩(大理岩)的主量、微量元素地球化学测试分析,结果表明,与吉峰科马提岩成分相比较,矿化超镁铁岩具有较高的w(SiO_2)(40.53%～54.96%)、w(TiO_2)(0.24%～0.86%)、w(Al_2O_3)(3.58%～10.47%)、w(FeO)(5.30%～8.80%)、w(CaO)(7.35%～13.66%)、w(Na_2O)(0.01%～0.76%)、w(K_2O)(0.02%～0.66%)和w(P_2O_5)(0.06%～0.61%);镁铁岩(包括辉绿辉长岩、玄武岩)铝含量较高,w(Al_2O_3)=16.34%～17.74%;长英质岩类也富铝质(Al_2O_3/(CaO+Na_2O+K_2O)=1.34～1.63),多数岩石属于钙碱性系列。闪长岩与镁铁岩相比,具有较高的硅、铝、钾、钠,较低的铁、镁和钙,微量元素具有大离子亲石元素富集,高场强元素相对亏损的右倾模式;稀土元素具有轻稀土元素富集,重稀土元素相对亏损特征,超镁铁岩类成分点位于N-MORB与OIB范围之间,而镁铁岩和长英质岩类成分点位于E-MORB和OIB之间。镁铁岩落入火山弧玄武岩范围,长英质岩落入火山弧花岗岩+同碰撞花岗岩范围,同属于造山后花岗岩的范围,因此镁铁质岩的形成应属于俯冲-碰撞环境,而长英质岩的形成应属于造山后伸展环境。根据各岩类所含成矿元素和亲流体元素分析,认为含矿热液来自矿区西部的深部,并且构建了嘎仙矿床的成矿模型,即超镁铁岩先期侵位,后期经历了区域的变质变形,最后发生燕山期大规模花岗质岩浆活动及成矿流体的蚀变矿化。
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| 关 键 词： | 地质学 镍钴矿床 含矿热液流体 岩浆作用 嘎仙 内蒙古 |
| 收稿时间： | 2017/7/20 0:00:00 |
| 修稿时间： | 2018/6/4 0:00:00 |
Magmatism and ore-forming process of Gaxian nickel cobalt deposit, Inner Mongolia |
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| LI DeDong,WANG YuWang,SHI Yu,HUANG XingKai,CHEN WeiMin and WANG Fu.Magmatism and ore-forming process of Gaxian nickel cobalt deposit, Inner Mongolia[J].Mineral Deposits,2018,37(5):893-916. |
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| Authors: | LI DeDong WANG YuWang SHI Yu HUANG XingKai CHEN WeiMin and WANG Fu |
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| Institution: | Beijing Institute of Geology for Mineral Resources, Beijing 100012, China,Beijing Institute of Geology for Mineral Resources, Beijing 100012, China,Beijing Institute of Geology for Mineral Resources, Beijing 100012, China,Beijing Institute of Geology for Mineral Resources, Beijing 100012, China,Non-ferrous Metals Resource Geological Survey, Beijing 100012, China and Non-ferrous Metals Resource Geological Survey, Beijing 100012, China |
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| Abstract: | The Gaxian deposit in Inner Mongolia, located in the northern part of the Da Hinggan Mountains, is a large low-grade nickel-cobalt sulfide deposit, and its genesis is related to granitic magmatism. In this paper, zircon LAICP-MS U-Pb dating of granitoids (granite porphyry, feldspar porphyry, pegmatic granite and biotite granite) on the footwall of the mining area was carried out. The concordant age of the granite-porphyry is (125.3±1.1) Ma~(127.5±4.5) Ma, that of the quartzite porphyry is (128.1±2.2) Ma, that of the pegmatic granite is (127.9±2.3) Ma and that of the biotite-granite is (127.9±1.4) Ma, which suggests that the granitic magma was mainly formed in Cretaceous period. Based on major and trace element analysis of mineralized-ultramafic rock, komatiite, mafic rocks (diabase, basalt), felsic rocks (diorite, feldspar porphyry, plagioclase granite, granite porphyry, pegmatic granite and biotite granite) and surrounding rock (marble), the authors revealed that mineralized-ultramafic rocks have higher w(SiO2) (40.53%~54.96%), w(TiO2) (0.24%~0.86%), w(Al2O3) (3.58%~10.47%), w(FeO) (5.30%~8.80%), w(CaO) (7.35%~13.66%), w(Na2O) (0.01%~0.76%), w(K2O) (0.02%~0.66%) and w(P2O5) (0.06%~0.61%), but lower w(MgO) (17.71%~25.07%), than the komatiite. However, mafic rocks are characterized by high w(Al2O3) (16.34%~17.74%), and felsic rocks have plenty of aluminum (Al2O3/(CaO+Na2O+K2O)=1.34~1.63). According to the geochemical discriminant diagrams, most rocks belong to the calc-alkaline series. Trace elements have the enrichment of large ion lithophile elements (LILE), depletion of high field strength elements (HFSE), whereas rare earth elements (REE) have higher concentrations of light rare earth elements (LREE) and lower concentrations of heavy rare earth elements (HREE). Trace elements of the ultramafic rocks lie between N-MORB and OIB, and those of mafic and felsic rocks are between E-MORB and OIB. The mafic rocks lie in the volcanic arc basalt area, but felsic rocks fall into the volcanic arc granite and syn-collisional granite area, belonging to the postorogeny setting, so mafic rocks'' tectonic setting should belong to subduction-collision and felsic rocks should belong to the post-orogeny environment. Based on the analysis of ore-forming and hydrophilic elements of these rocks, the authors hold that the ore-bearing hydrothermal fluid was derived from the deep part of the western area in the ore deposit. On such a basis, metallogenic model was constructed, which holds that ultramafic rocks were emplaced in the first period, and experienced regional metamorphic deformation later, and the large-scale granitic magmatism and hydrothermal fluid alteration mineralization occurred lastly in Yanshanian period. |
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| Keywords: | geology nickel cobalt deposit ore-forming hydrothermal fluid magmatism Gaxian Inner Mongolia |
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