吉林省松嫩-张广才岭地块榆木川辉绿玢岩年代学及其地质意义

Zircon U-Pb age and geological significance of the diabase porphyrite from the Yumuchuan area in the Songnen-Zhangguangcailing Block,Jilin,China

为探讨位于兴蒙造山带松嫩-张广才岭地块南部的榆木川辉绿玢岩的成岩时代、构造背景及地质意义，对其进行了LA-ICP-MS 锆石U-Pb定年和Sr-Nd同位素测试。结果显示，榆木川辉绿玢岩的成岩时代为399±1.8Ma，而非前人所指的二叠纪。Sr-Nd同位素测试结果显示，该套辉绿玢岩具有相对较低的（87Sr／86Sr）i值（0.704439～0.705518）和正的εNd（t）值（6.8～7.9）。结合前人对该区构造背景的认识，进一步将松嫩-张广才岭地块与佳木斯地块伸展拉张环境的时间限定为早泥盆世。另外，东北地区显生宙地壳增生显著，榆木川辉绿玢岩本身就为地壳增生的产物，其形成暗示晚古生代早期松嫩-张广才岭地块可能存在一期重要的地壳垂向增生事件。

In order to comprehensively discuss the petrogenic age,tectonic setting and geological significance of the Yumu-chuan diabase porphyrites in the southern part of the Songnen-Zhangguangcailingblock of the Xingmeng orogenic belt,the zircon LA-ICP-MS U-Pbdating and Sr-Nd isotope measurement of the diabase porphyrites have been carried out in this paper. Results show that thezircon LA-ICP-MS U-Pb age of 399±1.8Ma for the Yumuchuan diabase porphyrites is different from the previously reported K-Ar age（Permian）.In addition,these diabase porphyrites have relatively low（87Sr/86Sr）i ratios （0.704439-0.70551 8）and positive εNd（t）values（6.8-7.9）.With the combination of results of previous studies,we have suggested that the timing of the extension of the Songnan-Zhangguangcailing and Jiamusi blocks is furtherly constrain-ed to the early Devonian.In addition,as there was significant crustal growth in the NE China in phanerozoic,the forma-tion of the Yumuchuandiabase porphyrites,which was the direct product of the crustal growth,means that there could be an important event of the vertical crustal growth in the Songnan-Zhangguangcailingblock in early stage of the LatePaleozoic.