新疆博格达造山带东段二叠纪流纹岩地球化学特征及地质意义  

Geological significance and geochemical characteristics of permian rhyolite from the eastern section of Bogeda orogenic belt,Xinjiang

作　　者：第鹏飞[1] 李泰德 王金荣[1] 王晓伟[1,3] 欧阳京[1] 王怀涛[1] 赵志雄[1] 于漫[1] 

机构地区：[1]兰州大学资源环境学院,兰州730000 [2]新疆有色地质勘查局物探大队,乌鲁木齐830011 [3]甘肃省地矿局第三地质矿产勘查院,兰州730050

出　　处：《兰州大学学报（自然科学版）》2010年第3期8-13,19,共7页Journal of Lanzhou University(Natural Sciences)

基　　金：中国地质调查局地质勘查基金项目(QD200509)

摘　　要：二叠纪火山岩主要由酸性火山岩及其火山碎屑岩组成,其中流纹岩Rb-Sr同位素等时线年龄为278±2 Ma;具有高Si低Al,富K贫Na,强不相容元素和LREE相对富集,Nb-Ta呈负异常,特别是Sr,P,Ti为强烈的负异常,以及δEu负异常明显等特点.流纹岩(w(^(87)Sr)/w(^(86)Sr))_I=0.7068～0.707 1,δ^(18)O_(SNOW)=11.97‰.因此,总体地球化学特征揭示了二叠纪酸性火山岩是中基性物质发生部分熔融的结果,斜长石可能是源区的主要残留相或在岩浆作用过程中经历过低压分离结晶作用,形成于后造山隆升的伸展构造背景下.Permian volcanic rocks consist of acidic volcanics and pyroclastic rocks,and the Rb-Sr isochronal age of rhyolite is 278±2 Ma.Rhyolite has the characteristics of high Si and low Al,enriched K and deleted Na,and enriched strong incompatible elements and LREE,and relatively Nb-Ta negative anomaly,especially strong Sr,P and Ti negative anomaly,and significantlyδEu negative anomalies.In addition, （w（^（87）Sr）/w（^（86）Sr））_I of rhyolite is 0.7068～0.7071,andδ^（18） O_（SNOW） is 11.97‰.Therefore,these geochemical characteristics reveal that permian acidic volcanic rocks are the results of the partial melting of the intermediate-basic substance,that plagioclase may serve as a major residual phase in the process of partial melting,or that experienced significant low-pressure fractional crystallization in shallow crust in the process of intrusion formed under extensional tectonics of the post-orogenic uplift.

关 键 词：流纹岩 地球化学 二叠纪 博格达造山带 新疆 

分 类 号：P588.14[天文地球—岩石学] P534.46[天文地球—地质学]