西藏类乌齐地区含镍碳酸岩的发现与地质意义  

The discovery and geological significance of Ni-bearing carbonatites in the Leiwuqi area,Tibet,China

作　　者：周新 冯德新 樊炳良 余佳树 嘎桑顿珠 易金龙 ZHOU Xin;FENG De-xin;FAN Bing-liang;YU Jia-shu;GASANG Dun-zhu;YI Jin-ling(Geothermal Geological Survey Party,Tibet Bureau of Geology and Mineral Exploration and Development,Lhasa 850000,China)

机构地区：[1]西藏自治区地质矿产勘查开发局地热地质大队,西藏拉萨850000

出　　处：《矿物学报》2020年第2期109-115,共7页Acta Mineralogica Sinica

基　　金：中国地质调查局地质调查项目(编号:121201010000150007-15)。

摘　　要：野外调查发现西藏类乌齐地区分布着众多的含镍碳酸岩体,呈十几米至几百米不等的岩株出露。岩体与超基性岩之间具明显的港湾状、枝状侵入接触、岩石不具层理、岩石表现出细粒结晶等粒结构、岩体内见超基性岩捕掳体等特征均表明其为火成碳酸岩岩体。在成分上以菱镁矿为主,岩石中MgO的含量为27.16%~31.75%,为镁质碳酸岩。岩石稀土元素配分曲线呈平缓右倾的轻稀土富集型,轻重稀土元素分馏现象明显,具有明显的Eu正异常和弱的Ce负异常;微量元素显示Rb、Th、Nb、Hf元素相对富集,K、U、Ti元素相对亏损。含镍碳酸岩可能是富CO2的深部流体在中下地壳对超基性岩交代的结果,具备寻找硫化镍矿床的有利条件。On the basis of field investigation,many Ni-bearing carbonatites,which are exposed as stocks in sizes ranging from tens to hundreds of meters,have been discovered in the Leiwuqi area,Tibet,China.They are intruded into ultrabasic rocks with obviously embayed and dendritic intrusive contacts between them.They have xenoliths of ultrabasic rocks,with fine crystallized equigranular texture but no bedding,indicating that they are igneous carbonatites.They belong to magnesian carbonatite with main mineral component of magnesite and MgO contents of 27.16%-31.75%.They have gently right-declined REE distribution patterns with the obvious fractionation of LREE and HREE,obvious positive Eu anomalies,weak negative Ce anomalies,Relatively enriched Rb,Th,Nb,and Hf,but relatively depleted K,U,and Ti.The Ni-bearing carbonatite could be the product of metasomatism of ultrabasic rocks by deep-seated CO2-rich fluid in the middle and lower crusts.It has favorable potential for searching nickel sulfide deposits.

关 键 词：碳酸岩 元素地球化学 岩石成因 类乌齐 

分 类 号：P588.15[天文地球—岩石学] P612[天文地球—地质学]