四川攀西地区层状基性-超基性岩体SHRIMP锆石U-Pb年龄及其地质意义

    Zircon SHRIMP U-Pb age of the layered mafic rock mass in Panxi area, Sichuan Province, and its geological significance

    • 摘要: 应用SHRIMP锆石U-Pb测年,对攀西地区白马和太和含矿层状基性-超基性岩体的年龄进行研究,获得白马层状辉长岩体锆石U-Pb年龄为258±2Ma(95%可信度),太和层状辉长岩体锆石U-Pb年龄为262±2Ma(95%可信度)。结果表明,攀西地区的白马和太和含矿层状辉长岩体均形成于二叠纪晚期。该年龄信息显示了从层状辉长岩体的侵入到峨眉山玄武岩的喷发高峰期(250Ma)仅距5~10Ma,二者应属于同期不同阶段岩浆活动的产物。鉴于空间上层状辉长岩体与峨眉山玄武岩密切相关,基性-超基性岩体和玄武岩的形成均与晚古生代末期峨眉地幔柱活动有关。

       

      Abstract: In this paper, based on the application of SHRIMP zircon U-Pb dating method, the authors studied the age of the orecontaining layered basic-ultrabasic rocks in western Panzhihua area, with the U-Pb ages of zircons from the Baima layered gabbro body being 258±2Ma (95% confidence) and those of zircons from the Taihe layered gabbro body being 262±2Ma (95% confidence).These data show that both Baima and Taihe ore-bearing gabbros in western Panzihua metallognetic belt were formed in Late Perm-ian.The age information also suggests that the time gap between the intrusion of the layered gabbro body and the eruption of the Emeishan basalt (peak at 250Ma) was only about 5~10Ma, and both the intrusive rocks and the basalts should have resulted from mag-matic activities at different stages.Considering the spatial relationship between the layered gabbro body and the Emeishan basalt and consulting the above age dating results, it is suggested that both the mafic ultramafic rocks and the basalts were formed at the end of the late Paleozoic period and associated with the Emei mantle plume activity.

       

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