藏北羌塘中部日湾茶卡地区堆晶岩LA-ICP-MS锆石U-Pb年龄、地球化学特征及其构造意义  

LA-ICP-MS zircon U-Pb ages and geochemical characteristics of cumulates in the Riwanchaka area, middle Qiangtang, the Tibetan Plateau

作　　者：张天羽[1] 李才[1] 苏犁[2] 解超明[1] 吴彦旺[1] 王明[1] 

机构地区：[1]吉林大学地球科学学院,吉林长春130061 [2]中国地质大学(北京)地学实验中心,北京100083

出　　处：《地质通报》2014年第11期1662-1672,共11页Geological Bulletin of China

基　　金：国家自然科学基金项目(批准号:41272240;41072166);中国地质调查局项目(编号:1212011221093;12120113036700)

摘　　要：在藏北羌塘中部日湾茶卡地区发现蛇绿混杂岩,岩石单元包括堆晶辉长岩、辉长岩岩墙、玄武岩等。通过对该蛇绿岩中堆晶辉长岩的地球化学研究发现,它们属于E-MORB型,与桃形湖和果干加年山地区的蛇绿岩比较相似。堆晶辉长岩(R12T11)中用于LA-ICP-MS定年的锆石具有明显的Ce正异常和Eu负异常,属于典型的岩浆成因锆石;12个测试点的年龄加权平均值为442.7Ma±3.4Ma,表明日湾茶卡蛇绿岩形成于早志留世。日湾茶卡蛇绿岩是龙木错—双湖—澜沧江缝合带内一处新的早古生代洋壳残片,将为进一步揭示龙木错—双湖—澜沧江洋的构造演化提供新依据。A set of ophiolite melanges, which are composed of cumulate gabbros, gabbro dykes, basalts and some other kinds of rocks, were first found in the Riwancaka area, middle Qiangtang. Geochemical characteristics of cumulutes in Chaka area show that gabbros within the Riwanchaka ophiolite belong to the E-MORB type, similar to features of ophiolites in Taoxinghu and Guoganjiashan areas. LA-ICP-MS U-Pb analyses of twelve zircon samples from this cumulate gabbro are similar to data of magmatic zircon in the chondrite-normalized REE patterns, with an average weighted age of 442.7Ma ± 3.4Ma, suggesting that the cumulate gabbros were formed in the Early Silurian. The Riwanchaka ophiolite is a new oceanic crust fragment of Early Palaeozoic in the Lungmu Co-Shuanghu-Lancang River suture zone. The results achieved by the authors will provide new evidence for the tectonic evolution of the Lungmu Co-Shuanghu-Lancang River Ocean.

关 键 词：龙木错-双湖-澜沧江缝合带 羌塘中部 日湾茶卡 堆晶辉长岩 LA-ICP-MS锆石U-PB年龄 

分 类 号：P595[天文地球—地球化学] P597.3[天文地球—地质学]