柴北缘托莫尔日特地区变基性火山岩年代学、地球化学特征及地质意义  

Geochronology, geochemistry and significance of the metabasic volcanic rocks in Tuomoerrite area, North Qaidam

作　　者：王振强 张照伟[3] 丁培超 冯建之 薛志强 吕达鑫 WANG Zhen-qiang;ZHANG Zhao-wei;DING Pei-chao;FENG Jian-zhi;XUE Zhi-qiang;LU Da-xin(No.1 Institute of Geological&Mineral Resources Survey of Henan,Luoyang 471023,China;Key Laboratory of Gold and Silver Polymetallic Mineralization Series and Deep Prediction of Henan,Luoyang 471023,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits,MLR Xi'an Institute of Geology and Mineral Resources,Xi'an 710054,China)

机构地区：[1]河南省地质矿产勘查开发局第一地质矿产调查院,河南洛阳471023 [2]河南省金银多金属成矿系列与深部预测重点实验室,河南洛阳471023 [3]自然资源部岩浆作用成矿与找矿重点实验室西安地质矿产研究所,陕西西安710054

出　　处：《岩石矿物学杂志》2022年第3期491-503,共13页Acta Petrologica et Mineralogica

基　　金：中国地质调查局项目(12120114018216,121201011000150005-12)。

摘　　要：托莫尔日特-赛坝沟蛇绿混杂岩带位于柴北缘结合带东段,对该蛇绿混杂岩带中的变火山岩进行了系统的年代学及岩石地球化学研究。结果表明,变基性火山岩SiO_(2)含量为47.78%~50.01%,MgO含量为4.52%~9.36%,TFeO含量为8.00%~14.94%,K_(2)O含量为0.04%~0.80%,Na_(2)O含量为1.02%~4.20%,具典型的拉斑玄武质岩浆特征。微量元素上表现出轻稀土元素弱亏损,富集大离子亲石元素,亏损Nb、Ta等高场强元素特征,表明该基性岩很可能形成于弧后盆地环境。LA-ICP-MS锆石U-Pb测年结果显示,变基性火山岩年龄为480.1±1.8 Ma。综合区域地质资料,认为原特提斯洋在早奥陶世已经开始了俯冲消减作用。Tuomoerrite ophiolitic mélange is located in the eastern segment of the northern margin of Qaidam terrane.This paper presents a systematic geochronological and petrogeochemical study of the meta-basaltic rocks in the ophiolite mélange.The metabasalts have whole-rock SiO_(2) contents of 47.78%~50.01%,MgO contents of 4.52%~9.36%,^(T)FeO contents of 8.00%~14.94%,K_(2)O contents of 0.04%~0.80%,and Na_(2)O contents of 1.02%~4.20%,resembling those features of tholeiitic magma.They show slightly depletion in LREE,enrichment in LILE and LREE,and depletion in HFSE,similar to the patterns of arc-related volcanic rocks.These features collectively suggest a back-arc setting for the meta-basalts.The zircon U-Pb age of these metabasalts determined by LA-ICP-MS is 480.1±1.8 Ma,suggesting that the expansion time of the back-arc basin in this area should be around 480 Ma,and the oceanic slab subduction occurred in Early Ordovician.

关 键 词：变基性火山岩 SSZ型蛇绿岩 锆石U-PB测年 地球化学 柴北缘 

分 类 号：P588.41[天文地球—岩石学] P597[天文地球—地质学]