Felsic volcanic rocks from northern Tarim, NW China: Zircon U-Pb dating and geochemical characteristics
Felsic volcanic rocks from northern Tarim, NW China: Zircon U-Pb dating and geochemical characteristics
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发表时间：
2011
影响因子：
1.8
通讯作者：
Yung-Chul Jun
中科院分区：
文献类型：
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作者：
Yung-Chul Jun
塔里木盆地早二叠世岩浆活动分布广泛，面积约25万平方公里，被认为是一个新的大型火成岩省（LIP）。塔里木盆地长英质火山岩研究为认识塔里木二叠纪岩浆作用提供了新途径。我们报告了塔里木隆起北部长英质火山岩的锆石 U-Pb 定年、主量和微量元素组成以及 Sr-Nd 同位素数据。所有样品均从深度约5公里的钻孔中采集。这些样品的锆石U-Pb测年显示，喷发年龄跨度为274Ma至282Ma，这被认为是塔里木唇部大喷发后的岩浆活动。这些样品富含钾，K2O+Na2O=7.29%~8.34%，K2O/Na2O1，属于高钾钙碱性系列和过铝质（A/CNK=1.32~1.53）。大部分样品富含轻稀土元素、锆、铪、钇，而锶、磷、钛、铌和钽含量较低。原始地幔归一化不相容元素蛛网图与大陆地壳相似，具有右倾型球粒陨石归一化稀土元素模式，并伴有少量负Eu异常。 Sr-Nd-Pb同位素研究表明，塔里木北部长英质岩的成因可能受到了大陆岩石的污染。与地壳亲和力较高的 Th、U、Nb/La、Nb/U 和 Th/Ta 比率也支持了这一点。根据上述资料，我们推测塔里木隆起北部的长英质火山岩是与地幔柱活动有关的大陆地壳深熔作用的产物。
The widely distributed Early Permian magmatism in Tarim Basin, extending about 250,000km2, is considered to be a new large igneous province (LIP). The research about the felsic volcanic rocks in Tarim basin provides a new way to understand the Permian magmatism of Tarim. We report zircon U-Pb dating, major and trace element composition and Sr-Nd isotopic data for felsic volcanic rocks from northern Tarim uplift. All the samples were collected from the drill holes which have depths about 5km. Zircon U-Pb dating of these samples revealed an eruption age span of 274Ma to 282Ma, which is supposed to be post major eruption magmatism of Tarim LIP. These samples are enriched in potassium, K2O+Na2O=7.29%~8.34%, K2O/Na2O1, and belong to high-K calc-alkaline series and peraluminous (A/CNK=1.32~1.53). Most of the samples are enriched in LREE, Zr, Hf, Y, with low Sr, P, Ti, Nb and Ta. The primitive-mantle normalized incompatible element spidergrams are similar to those of continental crust and they have right-dipping type chondrite-normalized REE patterns with minor negative Eu anomalies. The study of Sr-Nd-Pb isotope shows that the origin of the northern Tarim felsic rocks may suffer contamination by continental rocks. This is also supported by the high Th, U, Nb/La, Nb/U and Th/Ta ratios which are affinity with the crust. Based on the data indicated above we suppose that the felsic volcanic rocks from northern Tarim uplift are the products of anatexis of the continental crust associated with the mantle plume activity.