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.