地质通报2012，Vol.31Issue(1)：50-62,13.
西天山乌孙山地区大哈拉军山组火山岩LA-ICP-MS锆石U-Pb年龄及其构造环境
LA-ICP-MS zircon U-Pb age and tectonic background of the Dahalajunshan Formation volcanic rocks in Wusunshan area, West Tianshan Mountains.
摘要
Abstract
Volcanic rocks in the Dahalajunshan Formation of Wusunshan area in West Tianshan Mountains are composed of basalt, an-desite, dacite, rhyolite and relevant volcaniclastic rocks, with andesite and rhyolite being dominant. The LA-ICP-MS zircon dating results show that adesite and andestic tuff lava in the Dahalajunshan Formation from Wusunshan area yield concordant 206Pb/238U ages of 353.9 ±6.5Ma and 356.3 ±4.4Ma, implying that they were erupted at the early stage of Early Carboniferous. Regional correlation shows that the volcanic magmatism gradually became younger from the north and the south edge of Yili-Central Tianshan plate to Yili basin, and the eruption time span is small (about 40Ma). Therefore, the age of Dahalajunshan Formation at the south edge of Yili block should be confined between 363Ma and 326Ma, namely Late Devonian to Early Carboniferous and mainly in Early Carboniferous Tournaisian period-Visean period. The geochemical characteristics show that the volcanic rocks belong to the calc-alkaline series, enriched in LREE and depleted in HREE relatively. The primitive mantle -normalized trace element patterns show that intermediate volcanic rocks are slightly enriched in large-ion-lithophile elements(LILE) such as Cs, Rb, Th and U and relatively depleted in HFSE and have obvious negative Nb, Ta, Ti anomalies, and that acid rocks are characterized by Rb, Th, U, Ta enrichment and Ba, Sr, P,Eu,Ti depletion. In combination with the south edge of Central Tianshan tectonic evolution, the characteristics of volcanic rocks inDahalajunshan Formation suggest that they were probably formed in an active continental margin environment.关键词
LA-ICP-MS锆石U-Pb定年/构造环境/大哈拉军山组/西天山Key words
LA-ICP-MS zircon U-Pb dating/ tectonic background/ Dahalajunshan Formation/ West Tianshan Mountains分类
天文与地球科学引用本文复制引用
茹艳娇,徐学义,李智佩,陈隽璐,白建科,李婷..西天山乌孙山地区大哈拉军山组火山岩LA-ICP-MS锆石U-Pb年龄及其构造环境[J].地质通报,2012,31(1):50-62,13.基金项目
国家自然科学基金项目《西天山西南缘那拉提段古生代花岗岩成因对天山洋陆转换的制约》(批准号:40872061)和中国地质调查局项目《天山-兴蒙成矿带火山岩浆作用对成矿制约的综合研究》(编号:1212010050503)、《西北地区重要成矿带基础地质综合研究》(编号:1212010610319)、《天山成矿带基础地质综合研究》(编号:1212010010200) （批准号:40872061）
