房县石垭子花岗斑岩的形成时代及其地质意义

The Formation Age of the Granite-porphyry and Its Geological Significance in Shiyazi of Fang County

以南秦岭造山带南缘与扬子克拉通接壤区开展的1∶5万区域地质调查于房县石垭子发现的花岗斑岩侵入体,通过岩体野外地质学特征、岩石地球化学特征、同位素地球化学与年代学特征研究,对该岩体形成的岩浆成因与构造环境进行了探讨。采用锆石U-Pb同位素测试分析,取得其206Pb/238U加权平均年龄为(722.9±6)Ma,明确岩体形成于晋宁期;并根据岩石地球化学特征,提出该花岗斑岩形成为裂谷构造环境,深化了南秦岭造山带构造—岩浆—热事件研究程度。

In contiguous area of the south Qinling orogenic belt and Yangtze craton,the authors did the regional geological survey on the scale 1∶ 50 000 and then,the granitoid intrusion was discovered in Shiyazi of Fang County. By the way of the characters of the field geology of rock body,and the geochemical characters of the rock,and geochemical isotopic study with geochronological characters,the magmatic origin and tectonic environment of the rocks formation was discussed. By means of the zircon U-Pb isotopic method,the weighted mean206 Pb /238 U age is reported in this paper,which is722. 9 ± 6 Ma,it was indicated the rocks formed in the Jinningian movement. According to the geochemical characters of the rock,the granite porphyry might be formed in rift valley,which deepen the research tectonic-thermal event in the South Qinling orogenic belt.