柴北缘滩间山群火山岩岩石化学特征及构造环境  

CHEMICAL CHARACTERISTICS OF VOLCANIC ROCKS FROM THE TANJIANSHAN GROUP ON THE NORTHERN MARGIN OF THE QAIDAM BASIN AND ITS TECTONIC ENVIRONMENT

作　　者：张孝攀 王权锋[1,2] 惠洁[2] 常鑫[1,2] 童海奎 

机构地区：[1]成都理工大学数学地质四川省重点实验室,四川成都610059 [2]成都理工大学管理科学学院,四川成都610059 [3]青海省地质调查局,青海西宁810012

出　　处：《矿物岩石》2015年第1期18-26,共9页Mineralogy and Petrology

基　　金："十五"国家科技攻关计划项目(2003BA612A-07)

摘　　要：滩间山群海相火山-沉积岩广泛分布于柴北缘带,西起小赛什腾山,经过赛什腾山、绿梁山、锡铁山,一直延续到乌兰的赛坝沟,是一套活动型沉积,其中的火山岩构成了柴北缘地区早古生代火山弧。研究针对所采集的92件柴北缘滩间山火山岩样品进行主量元素,有49件属于钙碱系列、33件属于拉斑系列、10件属于碱性系列。再结合微量元素分析,结果主要有两种：1轻稀土中等富集,（La/Yb）N介于2~8之间,亏损Nb,Ta等高场强元素,以小赛什腾山和赛什腾山为例;2轻、重稀土分馏程度低,（La/Yb）N介于0.6~3之间,较弱或不亏损Nb,Ta等高场强元素,以绿梁山和双口山为例。最后结合年代学的系统综合分析认为,柴北缘滩间山群火山岩的稀土和微量元素标准化图型大体可以分为两种类型：第一种属拉斑系列,具有岛弧火山岩的大地构造属性,形成于晚寒武世的柴北缘洋盆俯冲消减;第二种与洋脊火山岩较为相似,具有弧后盆地的大地构造属性,形成于早奥陶世的弧后拉张。The marine volcano-sedimentary rocks of the Tanjianshan Group are widely distributed in the northern margin of the Qaidam Basin,it starts from the west of Xiaosaishitengshan,extends to Saishitengshan,Lvliangshan,Xitieshan,and Saigouba of Wulan.These active depositions of volcanic rocks belong to the volcanic arc in the northern margin of Qaidam basin in the early Paleozoic.The analysis of main elements from 92 petrochemical samples in Tanjianishan Group shows that 49 samples belong to calc-alkaline series,33 belong to the tholeiitic series and 10 belong to alkaline series.Analysis of trace elements shows that the LREE is secondary enrichment,the（La/Yb）Nis between 2and 8,deplete the high field strength elements,and that the degree of LREE and HREE fractionation is lower,the（La/Yb）Nis between 0.6and 3,the high field strength elements are slightly depleted.Through the system analysis of the geochemistry of volcanic rock and chronology on the northern margin of the Qaidam Basin Tanjianshan Group,it is showed that the REE and trace element normalized pattern can be divided into two types,the first type belongs to tholeiitic series of island arc volcanic rocks formed in the subduction of late Cambrian Period in northern margin of Qaidam Basin.The second type is similar to the ridge volcanic rocks of back arc basin formed in the extension condition in the early Ordovician Period.

关 键 词：柴北缘 滩间山群火山岩 岩石化学 岛弧 弧后盆地 

分 类 号：P584[天文地球—岩石学] P585.3[天文地球—地质学]