藏北美多锑矿带地质地球化学特征及其地球动力学背景探讨  

Geology and Geochemistry of the Meiduo Antimony Ore Belt in Northern Tibet: Its Origin and Geodynamic Setting

作　　者：闫升好[1] 余金杰[1] 赵以辛[2] 徐志忠 王安建[4] 滕荣丽[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]吉林大学地球科学学院,吉林长春130026 [3]西藏自治区地质矿产局第六地质队,西藏拉萨850000 [4]中国地质科学院,北京100037

出　　处：《地球学报》2004年第5期541-548,共8页Acta Geoscientica Sinica

基　　金：国家重点基础研究规划 973项目 (编号 :2 0 0 1CB40 980 7);国土资源部定向基金资助。

摘　　要：藏北美多锑矿带位于小唐古拉山南麓 ,东西长 2 0 0km、南北宽 4 0km ,已发现锑矿床 (点 ) 10多处 ,其中以美多矿床规模最大。锑矿产于上三叠统土门格拉群的硅质岩组 ,受NW向和NE向断裂联合控制。矿石矿物主要为辉锑矿 ,脉石矿物有石英、蛋白石和方解石等。矿石类型有浸染状硅质岩型、辉锑矿 石英脉型、角砾状硅质岩型、辉锑矿 方解石脉型等 4种。矿石硫、铅、氦、氩同位素研究表明 ,成矿流体为大气降水 ,成矿物质不可能主要由围岩地层提供 ,地幔物质参入成矿明显。成矿年龄为 2 0Ma ,处于青藏高原新生代大陆碰撞造山带形成演化的后碰撞构造阶段。成矿作用在时间与空间上与藏北大规模富碱中性熔岩所对应的构造热事件 (30～ 10Ma)相耦合以及地幔物质参入成矿的事实表明 ,藏北锑矿带的形成可能与中新世以来造山带增厚岩石圈底部拆沉作用引起的软流圈上升和地幔底辟作用有关。The EW-trending Meiduo antimony ore-forming belt,200 km in length and 40 km in width, is distributed along the sou- thern edge of the TanggulaMountains in the northern part of Tibet. More than ten deposits have been founded in this area, of which Meiduo is the largest one. The antimony orebody is hosted in the siliceous rocks of the Tumengela Group and controlled jointly by the NW-andNE-striking faults. The antimony ores are mainly composed of such minerals as stibnite, quartz, opal and calcite. Four types of ores could be identified, namelydisseminated siliceous rocks, stibnite-quartz veins, brecciated siliceous rocks, and stibnite-calcite veins. Isotopic compositions of the sulfur, lead, heliumand argon indicate that the ore-forming fluids were mainly meteoric water, theore metals seemed unlikely to be provided mainly by the wall rocks, and some mantle-derived materials obviously participated in the ore-forming process. The metallogenic age is about 20.2 m.y., suggesting the post-collision stage of the Qinghai-Tibet Cenozoic continent collision orogen. The time-space coupling of theore-forming event with the tectonic-thermal event corresponding to the extensivealkali-rich lavas (30～10 m.y.) and the obvious participation of the mantle-derived materials in the ore-forming process suggest that the formation of the Meiduoantimony ore belt was most probably connected with the upwelling of the rheosphere or mantle diapir and the delaminating of the bottom part of the thickened lithosphere within the orogen since Miocene.

关 键 词：锑矿 氦氩同位素 碰撞造山带 地幔 

分 类 号：TD864[矿业工程—金属矿开采]