The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex be...The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex belongs to calc alkaline series. Geochemical characteristics of major and trace elements show that the complex was derived from the fractional crystallization of co source magma. It is suggested that the complex was formed in island arc tectonic environment and was closely related to the northward subduction of the Erlangping back arc basin. Thus, the subduction of the back arc basin can induce the island arc type magmatism similar to the one formed in the setting of ocean plate subduction.展开更多
文摘The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex belongs to calc alkaline series. Geochemical characteristics of major and trace elements show that the complex was derived from the fractional crystallization of co source magma. It is suggested that the complex was formed in island arc tectonic environment and was closely related to the northward subduction of the Erlangping back arc basin. Thus, the subduction of the back arc basin can induce the island arc type magmatism similar to the one formed in the setting of ocean plate subduction.
文摘桐柏造山带中秦岭群中出露有志留纪麻粒岩,然而其原岩形成时代和变质年龄却没有得到有效的约束.本文对北桐柏秦岭群中长英质麻粒岩中锆石开展了详细的形貌学、阴极发光图像、微量元素以及U-Pb 年代学研究.LA-ICP-MS锆石U-Pb 定年结果表明继承碎屑锆石给出了2.7 - 0.55 Ga 的年龄,岩浆锆石给出了478± 7 Ma（MSWD=0.73）的206Pb/238U 加权平均年龄,代表了桐柏长英质麻粒岩原岩的形成年龄.变质锆石区域获得了437± 7 Ma（MSWD=1.3,n=10）的206Pb/238U加权平均年龄.结合锆石微量元素特征和前人研究结果表明437± 7 Ma 可能代表了前进变质阶段的年龄.而最外层的增生边给出了406± 8 Ma（MSWD=0.72,n=4）的206Pb/238U加权平均年龄,代表了退变质年龄.我们认为在480 Ma 时,商丹洋已开始向北俯冲,导致480 Ma 左右的岩浆作用,由于持续的俯冲消减,在440 - 420 Ma 时,洋中脊与弧交汇,发生洋脊俯冲导致志留纪麻粒岩相变质作用以及岩浆作用的发生.
