【摘要】 对新疆东北部地区二叠纪构造动力学背景的研究,前人已经做过很多工作,但争议较大。本文通过对位于新疆东北部边缘的三塘湖盆地二叠纪火山岩常量、微量元素的分析测试及讨论,为恢复二叠纪盆地性质与古构造环境提供岩石地球化学约束。研究区内火山岩主要岩石类型为玄武岩、安山玄武岩、辉绿岩、安山岩以及少量英安岩和流纹岩,显示亚碱性系列特征。玄武岩常量元素总体显示高Ti的特征,轻、重稀土元素分馏明显,含量比值(LREE/HREE)在3．8和8．35之间变化,不同岩石类型均具有LREE富集的特征,玄武岩和玄武安山岩Eu异常不明显(δEu=0．92～1．13)；微量元素LILE富集,Nb、Ta相对于La强烈亏损,具有较明显“TNT”负异常,不相容元素丰度并不很高,判别图解投入板内玄武岩及火山弧玄武岩区域,总体上既显示板内的构造环境,又携带俯冲带地球化学信息,与“滞后弧火山岩”特征类似,但是缺少CFB端元,综合区域地质特征及前人的研究结果,新疆北部地区晚石炭世至二叠纪处于造山后期伸展裂陷的构造背景。更多还原

【Abstract】 The study on the Permian dynamic background of northeast Xinjiang has gained more consideration.Based on analyses of major and trace elements of Permian volcanic rocks in Santanghu basin,this paper attempts to clarify the palaeo-tectonic setting more objectively and also provides independent evidence for understanding the nature of the basin.The volcanic rocks are dominated by basalts,diabases,andesite-basalts and with minor dacites and rhyolites,which are fallen into sub-alkaline series.Major elements show the characteristics with higher titanium(Ti=1.54～2.68).LREE/HREE ratio are varying range from 3.8 to 10.40.Different volcanic rocks are all enriched in LREE without obviously Eu anomaly(δEu=0.92～1.13).LILE are enriched in the basahs.Nb and Ta relative to La deplete strongly and show“TNT”negative anomaly.This type of volcanic rocks shows not only the signature of within-plate setting,but also that of subduction zone,which are similar to the some characteristics of“lagged arc volcanic rocks”,but lack CFB element.Combining with the regional geological data,we conclude that the Permian magmatic activity of the study area generated in an extensional setting of the late stage of orogenesis.更多还原