新疆新源县巴音居里克一带下—中二叠统乌郎组火山岩特征及地质意义

新源县巴音居里克一带的下—中二叠统乌郎组陆相火山岩呈面状分布.乌郎组分为上段(P1w2)和下段(P1w1),其中乌郎组上段(P1w2)为巴音居里克乌郎组主体火山岩建造,为一套基性火山岩→酸性火山岩的双峰式火山岩组合.对主量元素分析,表明该组火山岩为碱性系列.微量元素的分布特点呈“双隆”型式,表现为Ba、Th、Ta的强烈富集,但又有Ce、Hf、Zr、Sm的富集,与板内碱性玄武岩的地球化学型式基本一致.稀土元素配分曲线向右倾斜,轻稀土明显富集,重稀土在流纹岩中略有富集,而在玄武岩中相对亏损.地球化学图解也显示该组火山岩形成于板内构造环境.综合对比分析,表明巴音居里克乌郎组火山岩的形成时代为早—中二叠世.

Geological Significance and Volcanic Features of Wulang Formation of Lower-Middle Permian in Bayinjulike Area,Xinyuan County,Xinjiang

The continental volcanic rocks of Wulang formation of Lower-Middle Permian displayed a planar spatial distribution in the Bayinjulike area. Wulang formation is divided into upper unit (P1w2) and lower unit (P1w1), where the upper formation is a bimodal volcanic combination of basic volcanic rocks and acid volcanic rocks, constructed by the main body volcanic rocks of Wulang formation. The major elements show that the volcanic rocks of Wulang formation are alkaline series. Characterized by strong enrichment of Ba, Th, Ta, and other enrichment of Ce, Hf, Zr and Sm, the distribution feature of trace elements is double uplift, which is basically identical with geochemical pattern of within plate alkaline basalts. Rare earth elements distribution curve inclines to the right, the LREE concentrated obviously, while HREE slightly enriched in the rhyolite, and relatively depleted in the basalt. Discrimination diagrams in further clarifies that the group volcanic rock formed in the intraplate evolution environment. The comparative study on the formation inferred that volcanic rocks of Wulang formation in Bayinjulike area formed in the early-middle Permian.