阿尔泰南缘冲乎尔盆地康布铁堡组变质酸性火山岩年龄及岩石成因  

Geochronology and Genesis of Meta-felsic Volcanic Rocks from the Kangbutiebao Formation in Chonghuer Basin on Southern Margin of Altay, Xinjiang

作　　者：柴凤梅[1] 杨富全[2] 刘锋[2] 耿新霞[2] 姜丽萍[1] 吕书君[3] 郭旭吉 陈斌[1] 

机构地区：[1]新疆大学新疆中亚造山带大陆动力学与成矿预测实验室,乌鲁木齐830049 [2]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [3]中国地质大学(北京),北京100083 [4]新疆维吾尔自治区有色地勘局706地质队,新疆阿勒泰836500

出　　处：《地质论评》2012年第6期1023-1037,共15页Geological Review

基　　金：国土资源部公益性行业科研专项经费项目(编号200911007-06);国家科技支撑计划项目(编号2011BAB06B03-02);新疆大学"天山学者"特聘教授启动经费联合资助成果

摘　　要：冲乎尔盆地是阿尔泰南缘等间斜列的火山沉积盆地之一,盆地内出露有重要的康布铁堡组赋矿地层。本文对该组一个凝灰岩和两个变质流纹岩样品进行了LA-ICP-MS锆石U-Pb年龄测定,获得了385.3±1.2Ma、398.1±1.8Ma和405.6±2.2Ma的结果。变质流纹岩的岩石地球化学分析结果表明,与克朗和麦兹盆地内的酸性火山岩的特征相同,即变质流纹岩属钙碱性低Ti流纹岩;在原始地幔标准化图上显示出Ti、P、Sr、Ba明显负异常,Th、U、Pb的正异常,LREE相对HREE略富集的特征,并显示强的Eu负异常(δEu=0.25～0.54)。结合其区域地质特征,认为本区变质酸性火山岩形成于活动大陆边缘环境,是下地壳发生了部分熔融后演化的产物。阿尔泰南缘的火山沉积盆地是早—中泥盆世时期在挤压环境中形成的断陷盆地。The Chonghuer basin is one of the fault-bounded volcano-sedimentary basins on the southern margin of the Altay orogenic belt, where the Kangbutiebao Formation （Fm.） stratigraphic unithosted many economic deposits outcrops. LA-ICP-MS U-Pb zircon analyses from two meta-rhyolites and one meta-tuff of the Kangbutiebao Fm. in the Chonghuer Basin yield weighted mean ^206pb/^238U ages of 385.3 ± 1.2Ma,398.1 ±1.8Ma and 405.6 ±2.2Ma, respectively, which can be interpreted as the eruption age of the Kangbutiebao silicic volcanic rocks in the Chonghuer Basin. The meta-rhyolites have similar geochemical features to meta-rhyolites in Kelang Basin and Maizi Basin, which are low-Ti rhyolite with obvious negative anomaly of Ti, P, Sr, Ba, Nb, Ta and Eu （δEu = 0.25 - 0.54）, obvious enrichment of Th, U, Pb, Zr, Hf and LREE. These features, together with the regional geological characteristics, indicate that these felsic volcanic rocks were generated by partial melting of lower crust on an active continental margin. These volcano-sedimentary basins are down-faulted Basin formed in compression tectonic environment of Early--Middle Devonian period.

关 键 词：变质酸性火山岩 地球化学 LA-ICP-MS锆石U-PB定年 新疆阿尔泰南缘 

分 类 号：P597.3[天文地球—地球化学] P588.14[天文地球—地质学]