南秦岭西乡群锆石SHRIMP U—Pb年龄及其构造地质意义

2009年陕西省地质志修编项目组,重点对出露于西乡县城东孙家河附近,南秦岭西乡群孙家河组英安质火山熔岩进行了锆石SHRIMP U-Pb同位素年代学和岩石化学、稀土元素、微量元素等方面的研究,获得了新的同位素年龄为814.8±5.2 Ma。认为该岛弧火山系的形成时代为青白口纪晚期,属晋宁期古扬子板块西缘与青康滇古板块汇聚的产物,为研究南秦岭扬子陆块过渡基底的形成时代,提供了有力的佐证。对进一步详细研究扬子陆块Rodinia超大陆汇聚时限及秦岭造山带的构造演化提供了新的时代证据,具有重要的地质构造意义。

ZIRCON SHRIMP U-PB DATING AND THE TECTONIC SIGNIFICANCE OF THE XIXIANG GROUP IN SOUTHERN QINLING

Systematic researches on zircon SHRIMP U-Pb isotope chronology,lanthanon and trace elements of dacite volcanic lava in the Sunjiahe Formation of the Xixiang Group in Southern Qinling come out a new isotopic age 814.8±5.2Ma.The isotopic age has indicated that the formation time of the island-arc volcanic system should be in the late of the Qinbaikou period,belonging to convergent products between the west margin of the ancient Yangtze Plate and the Qing-Kang-Dian ancient plate in the Jinningian period,providing evidences for research on the formation time of the transitional basement of the Yangtze Landmass in Southern Qinling,the tectonic evolution of Qinling orogenic zone and the convergent period of the Rodinia supercontinent of the Yangtze landmass.