西天山大哈拉军山组火山岩SHRIMP锆石U-Pb年龄及其构造意义  

SHRIMP zircon U-Pb geochronological and geochemical data of the Early Carboniferous Dahalajunshan Formation: Evidence for the subduction processes in Western Tianshan

作　　者：周翔[1,2] 余心起[1] 王宗秀[3] 肖伟峰[3] 李春麟[3] 李鹏举[1] 童继初 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国地质大学(武汉)地球科学学院,湖北武汉430074 [3]中国地质科学院地质力学研究所,北京100081

出　　处：《地质通报》2015年第5期845-860,共16页Geological Bulletin of China

基　　金：中国地质调查局项目(编号:1212011120335)

摘　　要：新疆早石炭世大哈拉军山组火山岩由西向东表现出由早到晚的演化规律。伊宁县博尔博松河孟玛热勒林场附近大哈拉军山组底部的英安质晶屑岩屑凝灰岩的SHRIMP锆石U-Pb年龄为359±2Ma,表明西天山西段该组底界时代为晚泥盆世末期—早石炭世之间。岩石地球化学数据统计表明,大哈拉军山组火山岩主要受岩浆结晶分异作用控制,是泥盆纪末期—石炭纪时期洋壳消减、壳幔混熔的产物。其岩石组成、时空分布的变化与天山洋由西向东的俯冲―碰撞过程相对应,不需要对其进行解体。From east of Xinyuan County through Duku Highway to Yuximolegai area in the middle of the west Tianshan Mountains, the regional unconformity of Carboniferous Akeshake Group upon Lower Carboniferous Dahalajunshan Formation can be easily founded. This paper reports SHRIMP zircon U-Pb age of 359±2Ma from Dahalajunshan dacitic tuff near the Boerbosong River in Yining County, which constrains the age of the lower boundary of the west part of Dahalajunshan Formation. In combination with previously published results, the authors hold that Dahalajunshan Formation was formed at about 40Ma, with the characteristic that the early deposition appeared in the west and the later deposition occurred in the east. Taking into account all available chronological data published in the past ten years, petrological features, and major and trace elements data of these Carboniferous volcanic rocks, the authors consider that the basic lavas were most plausibly formed by mixing between enriched mantle sources and ocean floor sediments （melt） and modified by subduction zone fluids. Changes in volcanic rock composition, spatial distribution and temporal evolution of Dahalajunshan Formation correspond to features of the Tianshan oceanic subduction-collision process （from west to east）, and therefore its disintegration is not necessary.

关 键 词：大哈拉军山组 早石炭世 安山质底砾岩 SHRIMP锆石U-PB年龄 西天山 

分 类 号：P588.14[天文地球—岩石学]