西藏仁布地区上三叠统重矿物组合与物源分析  

Heavy mineral assemblages and provenance analysis of the Upper Triassic in Renbu area,southern Tibet,China

作　　者：曾庆高[1,2] 李祥辉[3] 夏斌[1] 徐文礼 尼玛次仁[2] 普琼[2] 李君[5] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640 [2]成都理工大学沉积地质研究院,四川成都610059 [3]南京大学地球科学系,江苏南京210093 [4]西藏自治区地质调查院一分院,西藏堆龙德庆850000 [5]长江大学地球科学学院,湖北荆州434023

出　　处：《地质通报》2009年第1期38-44,共7页Geological Bulletin of China

基　　金：西藏仁布地区4幅联测1∶5万地质调查项目(编号:1212010610210);国家重点基础研究发展计划项目(编号:2006CB701401)联合资助

摘　　要：采用重矿物组合和指数方法对西藏南部仁布地区上三叠统朗杰学群和涅如组的物源进行了分析。结果显示:该区上三叠统常见的重矿物主要为锆石、磷灰石、金红石、锐钛矿和电气石;重矿物组合ZTR和ATi指数均高,MZi指数较低但多见,GZi指数低且多为零;郎杰学群的ZTR和ATi指数成反比关系,涅如组的ZTR增加时ATi基本不受影响。仁布地区上三叠统的物源主要来自火山岩,次为中酸性岩浆岩,少量来自变质岩和超基性侵入岩;涅如组的物源可能来自南边;朗杰学群的物源则可能来自北边,向郎杰学群提供物源的可能是拉萨地块。涅如组和郎杰学群在重矿物组合及其指数上的异同的成因有待进一步工作。Provenance of the Upper Triassic Langjiexue Group and Nieru Formation in Renbu area, southern Tibet was analyzed by heavy mineral association and index methods. Results indicate that common heavy minerals found in the Upper Triassic are mainly zircon, apatite, rutile, anatase, and tourmalin, both of the ZTP,. and ATi indexes from the mineral association are high, the MZi index is low but can be observed frequently, and the GZi index is low and sometimes zero; for Langjiexue Group, ZTR is inversely proportional to ATi indexes, but it is independent from the Nieru Formatin sandstones. It is herein proposed that most of the heavy minerals came from volcanic rocks, secondary intermediate to acidy magmatic rocks, very few from metamorphic and nltra-basic magmatic sources; by provenance analysis of heavy mineral ZRT index, clastic composition of the Langjiexue Group could be derived form the north where the Lhasa block could be the alternative, and those of the Nieru Formation could be from the south （perhaps Indian Shield）. However, there are some contradictions among the indexes of heavy mineral associations to be distinguished in future although the feature of heavy minerals of the Upper Triassic can provide us a good clue to explore the source and tectonic setting of the flysch strata in northern Tethyan Himalays.

关 键 词：物源分析 重矿物指数 上三叠统 西藏仁布地区 

分 类 号：P534.51[天文地球—古生物学与地层学] P57[天文地球—地质学]