西南天山下二叠统小提坎立克组火山岩地球化学特征

小提坎里克组火山岩分布于西南天山南缘的塔里木微板块之塔里木北缘古生代活动陆缘,主要由中酸性陆相火山岩组成.地球化学特征显示:该岩石富碱、富钾,其中酸性火山岩稀土总量高,轻重稀土分异不明显,负Eu异常明显,稀土分布曲线呈显著"V"字形态,明显富集Rb,Th,K亏损Ba,相对富集Ce,Sm,而相对亏损Ta.地球化学特征表明该火山岩形成于板内伸展环境.通过锆石U-Pb测年获得(296.2±6.1)Ma的年龄数据,时代为早二叠世.综合南天山已有研究成果,小提坎里克组火山岩与分布于托什干河上游一带的早二叠世高钾钙碱性的巴雷公花岗岩属同源岩浆的产物,在早二叠世时,西南天山已演变为一个统一的区域伸展背景.由此可以推断,南天山晚古生代碰撞造山的峰期在早二叠世之前已结束,南天山古洋盆在早二叠世之前已经闭合.

GEOCHEMICAL CHARACTERISTICS OF THE LOWER PERMIAN XIAOTIKANLIKE FORMATION VOLCANIC ROCKS IN SOUTHWESTERN TIANSHAN

Xiaotikanlike Formation volcanic rocks mainly composed of the acid to mid acid continental volcanic rock occur in Tarim micro-plate.Geochemical studies indicate that those rocks are enriched in alkali and k.Acid volcanic rocks are enriched in rare earth,flat REE normalized patterns and a distinctly positive Eu anomaly,the rare earth partifion line assumes obviously "V" the character shape,with high content of Rb,Th,k and strongly depleted Ba,relativel enrichment Ce、Sm and relatively depleted Ta.its geochemistry characteristic indicated that this volcanic rock forms in the extensional environment.Through zircon U-Pb measured that the year obtains(296.2±6.1) the Ma age data,the time for the early permian.Based on the data of south Tianshan,demonstrate that both Xiaotikanlike Formation volcanic rocks and early permian Baleigong granite in the Upstream of Tuoshengan river are form co-magmatism source.When early permian world,southwest Tianshan the evolution was already a unified region extension background,from this may infer,south Tianshan late Paleozoic Era collision mountain building peak time before early permian world already finished,south Tianshan ancient ocean basin before early permian world already closed.