北京大学学报(自然科学版)

恒山高压麻粒岩对其构造环境和出露过程探讨

张志强, 李江海, 黄雄南, 牛向龙   

  1. 北京大学地球与空间科学学院地质学系,北京,100871
  • 收稿日期:2003-04-01 出版日期:2004-03-20 发布日期:2004-03-20

Analysis on Tectonic Setting and Exhumation of Hengshan HP-Granulites

ZHANG Zhiqiang, LI Jianghai, HUANG Xiongnan, NIU Xianglong   

  1. Department of Geology, School of Earth and Space Sciences, Peking University, Beijing, 100871
  • Received:2003-04-01 Online:2004-03-20 Published:2004-03-20

摘要: 研究高压麻粒岩对于认识地壳深层次构造作用、陆壳底部物质组成有重要意义。通过研究恒山高压麻粒岩构造环境和出露过程,阐明恒山与五台变质岩区之间的相互关系,探讨华北克拉通新太古代构造格架。恒山高压麻粒岩的 p-T-t 变质作用、构造变形研究表明高压麻粒岩经历陆壳俯冲的升温升压过程后,又经近等温减压过程(ITD)抬升,之后在中部地壳长期近等压冷却(IBC),最终出露地表。恒山高压麻粒岩形成与“安第斯型”俯冲-碰撞模式有关。恒山和五台变质岩区地质年代学、变质程度以及构造关系的对比研究表明两者在构造热事件存在耦合关系,它们在构造上连续,恒山属岛弧根部,而五台山区代表中浅层次地壳。同位素年龄及构造分析表明东西陆块在2.5Ga发生碰撞,形成中部造山带以及五台前陆盆地,华北在新太古代存在板块运动。

关键词: 高压麻粒岩, 新太古代, 恒山, 五台, 碰撞, 前陆盆地

Abstract: HP(high pressure)-granulites are very important for understanding compositions of lower continental crust and tectonism. A neoarchean tectonic model of the North China is built by analysing on setting and exhumation of Hengshan HP-granulites, correlation between Hengshan metamorphic terrain and Wutai metamorphic terrain. The studies of p-T-t path the HP granulites show that it experienced p and T increasing during the subduction of the continental crust at first, and then, uplift in a way of clockwise ITD and cooling in a way of IBC, and finally exhumed. The studies of geological relations between Hengshan metamorphic terrain and Wutai metamorphic terrain confirm that they were actually the coupled and represented the island-arc root zone and shallow crust respectively. There are many kinds of conglomerates in Wutai foreland basin. Many evidences show age of Wutai foreland basin is 2.5 Ga. It is suggested that HP-granulites and Wutai foreland basin were formed during a "Andes type" subduction-collision. The western block collision with the eastern block occurred at 2.5Ga.

Key words: HP-granulite, Neoachean, Hengshan, Wutaishan, collision, foreland basin

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