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晚石炭纪—早二叠纪,在准噶尔盆地西北缘,发育区域性的火山岩建造,岩性以酸性英安岩和流纹岩为主,同时发育少量中性玄武安山岩和安山岩,多属于中-低钾的钙碱性系列。样品全碱(Na_2O+K_2O)含量为0.99%～8.12%,K_2O的含量较低,为3.01%～0.05%,稀土元素总量(∑REE)较低。稀土元素轻重分异,轻稀土元素(LREE)相对于重稀土元素(HREE)富集:(La/Yb)_N=0.76～5.18,且部分样品显示轻微的Eu负异常和Ce正异常:δEu=0.533～1.148,δCe=0.979～1.224。微量元素中大离子亲石元素(LILE)富集,高场强元素Nb、Ta亏损。分析认为石炭系末期—二叠系早期,研究区所处构造环境为洋内弧附近的前弧盆地,发育的火山岩是母源岩浆经历了一定程度分异作用后的产物,以岛弧环境为主,兼具有部分板内大陆环境特征。
Late Carboniferous - Early Permian, in the northwestern margin of the Junggar Basin, the development of regional volcanic rock, acidic rock and rhyolite rock-based, while the development of a small amount of neutral basaltic andesite and andesite, mostly belong to the - Low potassium calcium alkaline series. The content of Na 2 O + K 2 O in the sample was 0.99% -8.12%, while the content of K 2 O was 3.01% ~ 0.05%. The content of rare earth elements (ΣREE) was lower. The LREEs are enriched with respect to heavy rare earth elements (HREE): (La / Yb) _N = 0.76 ~ 5.18, and some samples show slight Eu anomaly and Ce positive anomaly: δEu = 0.533 to 1.148, and δCe = 0.979 to 1.224. LILE enrichment of trace elements, high field strength elements Nb, Ta loss. It is concluded that the tectonic environment in the study area is the forearc basin near the arc in the study period. The developed volcanic rocks are the products of the mafic magma undergoing a certain degree of differentiation. Taking the island arc environment as Lord, and part of the continent with the environmental characteristics.