内蒙古赵井沟大型铌钽矿床地质特征及成因  

Geological features and origin of Zhaojinggou Nb-Ta deposit in Wuchuan County,Inner Mongolia

作　　者：聂凤军[1] 王丰翔[1,2] 赵宇安[1,2] 孙艳[1] 柴华 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]石家庄经济学院,河北石家庄050031 [3]内蒙古第一地质勘查院,内蒙古察素齐010010

出　　处：《矿床地质》2013年第4期730-743,共14页Mineral Deposits

基　　金：国家重点自然科学基金项目(编号:41030421);地质调查项目(编号:1212010911029)资助

摘　　要：内蒙古武川县赵井沟矿床是近年来在内蒙古中部地区找到的一处大型铌钽矿床。铌钽氧化物储量为8000余吨(钽氧化物含量大于50%),其中,w(Nb2O5)和w(Ta2O5)的平均含量为0.011%和0.012%。铌钽矿化主要在早二叠世碱长花岗岩类侵入杂岩体内,呈浸染状和条带状产出,并且构成似层状、脉状和透镜状矿体。研究表明,碱长花岗岩、碱长花岗细晶岩和碱长花岗伟晶岩锆石U-Pb同位素年龄值分别为(277.14±0.82)Ma、(277.0±2.1)Ma和(276.6±2.1)Ma。鉴于铌钽矿化呈浸染状在含矿侵入杂岩体内产出,推测赵井沟矿床的成矿作用与海西期构造-岩浆活动有关。古大陆块体伸展构造条件下,富钠质钙-碱性岩浆作用为铌钽矿床的形成提供了动力和物质来源,而断裂构造为成矿物质沉淀聚集创造了空间条件。赵井沟矿床属富钠的过铝质花岗岩型铌钽矿床。Located in the central-eastern section of the Mongolian Axis of the Northern China craton Yinshan Precambrian uplift in the western segment of the Inner the newly discovered Zhaojinggou deposit is one of the largest Nb-Ta deposits in northern China. During the Hercynian orogeny, intense tectonic and igneous activities resul- tedin the large-scale granitoid magmatism in Zhaojinggou and its neighboring areas. The Zhaoiinggou alkaline feldspar granitoid （AFG） intrusive complex was emplaced in the meta-sedimentary sequence of the Middle Car- boniferous Shuanmazhuang Group, controlled by NE-, NNE- and NW-trending fault zones. The AGI complex has an outcrop area of 0.05 km2, and consists mainly of alkaline feldspar granite （AFG）, AFG pegmatite and AFG aplite that have no difference in mineral assemblage. Rock-forming minerals are mainly quartz, amazonite and albite associated with minor biotite, muscovite and sericite. Accessory minerals are rutile, apatite, zircon, topaz, fluorite, allanite and columbite. The AFG intrusive complex is petrochemically characterized by relatively high A1203, SiO2, Na20, Rb, Nb, Ta and Hf, obviously low CaO, Fe203, FeO, MgO, Sr, Ba, Zr and REE,belonging to silicon-high, sodium-rich rock of calc-alkaline series. Nb- and Tamineralization occurs entirely within the Zhaojinggou AFG intrusive complex as veinlets and disseminated blocks. Nb- and Ta- ores consist of parisite, columbotantalite, cassiterotantalite （ixiolite）, monazite, bismuthinite, chevkinite, laplandite, rutile, topaz, apatite, amazonite, Li-Rb-bearing biotite, Li-Rb-bearing muscovite, epidote, fluorspar, hornblende, zir- con, quarzt, barite, albite and calcite. As the most important economic Nb- and Taminerals, columbotantalite, cassiterotantalite （ixiolite） and parisite occur in the forms of impregnation, very fine grains, thin films, aggre- gated fine grains in the AFG intrusive complex. LA-ICP-MS U-Pb isotopic dating of the zircon separates from the AFG intrusive complex has given the ages varying from （277

关 键 词：地球化学 铌钽矿床 地质特征 矿床成因 碱长花岗岩类 赵井沟 武川县 内蒙古 

分 类 号：P618.79[天文地球—矿床学] P618.86[天文地球—地质学]