东天山维南地区下石炭统火山岩地球化学特征及地质意义

新疆东天山维南地区下石炭统雅满苏组第三岩性段火山岩由基性-中、酸性岩类组成,其中SiO2、K2O、Na2O含量范围分别为48.9%~81.0%、0.2%~5.7%、1.6%~7.9%,该套火山岩属低钾-高钾钙碱性系列;对微量和稀土元素分析,表明稀土元素分配型式均为略向右倾的平滑型曲线,LREE有一定富集,具明显的δEu负异常,中、酸性岩类具有明显的Nb、Sr、P、Ti负异常。综合研究表明,研究区火山岩具有成熟岛弧-陆缘弧的岩石地球化学特征。该套火山岩是研究区铜锌矿富集层位,对其开展地质和地球化学研究,对于区域找矿具有重要意义。从东天山觉罗塔格区域地球化学与成矿的关系分析看,区域矿化受到火山-沉积建造与断裂带的控制,该中、酸性岩石成矿物质富集明显,说明中酸性岩浆与构造活动在矿床的形成过程中起到了重要的作用。

Geochemical Characteristics and Geological Significance of the Lower Carboniferous Series Volcanic Rocks in Weinan Area,Eastern Tianshan

The volcanic rock of 3rd lithologic section in the Lower Carboniferous Series Yamansu Formation in Weinan area of Eastern Tianshan is consisted of the basic, neutral and acidic rocks, and is defined as the calc-alkaline volcanic rock series, with SiO2 content of 48.9%-81.0%, K2O content of 0.2%-5.7%, and Na2O content of 1.6%-7.9%. Analysis on trace and rare earth elements suggests that, the distribution patterns of rare earth elements are all smooth curves rightward, with enrichment of LREE and obvious δEu negative anomaly. There is also obvious negative anomaly of Nb, Sr, P and Ti in neutral and acidic rocks. Comprehensive analysis demonstrates that volcanic rocks in the study area have geochemical characteristics of island arc-epicontinental arc rocks. The volcanic rock series is found abundant in Cu-Zn deposits, thus it is significant in geological and geochemical research as well as prospecting of Cu-Zn deposits. The relationship between geochemistry and mineralization of Jueluotage region of East Tianshan indicates that regional mineralization is controlled by volcano-sediment formation and fault. Rich mineralization material in these neutral and acidic rocks illustrates that intermediate-acidic magma and tectonic activity play important roles in the deposit formation.