华北中—新元古代的岩浆作用与多期裂谷事件  

Meso-Neoproterozoic magmatic events and multi-stage rifting in the NCC

作　　者：翟明国[1,2] 胡波[3] 彭澎[1,2] 赵太平[4] 

机构地区：[1]中国科学院矿产资源重点实验室 [2]中国科学院地质与地球物理研究所,北京100029 [3]长安大学地球科学与资源学院,陕西西安710054 [4]中国科学院广州地球化学研究所,广东广州510640

出　　处：《地学前缘》2014年第1期100-119,共20页Earth Science Frontiers

基　　金：国家重点基础研究发展计划'973'项目(2012CB4166006);国家自然科学基金重点项目(41030316)和重大国际合作项目(41210003)

摘　　要：经历了古元古代晚期的变质事件（吕梁运动或称中条运动）之后,华北开始进入地台演化阶段,即从此时起开始了裂谷系的发育与演化。裂谷系可大致分为南、北两个在地表没有完全连接的裂陷槽和北缘、东缘各一个裂谷带。在华北南部的裂陷槽称为熊耳裂陷槽。熊耳群双峰式火山岩最古老的岩浆年龄约为1 800～1 780Ma,向上的中—新元古代地层有汝阳群、洛峪群等。华北北部的裂陷槽称为燕辽裂陷槽,主要由长城系、蓟县系和青白口系组成。中—新元古代（1.8～5.4Ga）的岩浆作用可以分为4期：（1）火山岩分布在长城系的团山子组和大红峪组,锆石U-Pb年龄在1 680～1 620 Ma,是晚于熊耳群的火山岩;（2）非造山侵入岩（斜长岩-奥长环斑花岗岩-斑状花岗岩）的同位素年龄在约1 700～1 670Ma;（3）在原青白口系下马岭组的斑脱岩以及侵入下马岭组的基性岩席中,得到1 380～1 320Ma的锆石和斜锆石U-Pb同位素年龄,在东缘裂谷的沉积岩中也有1 400Ma和1 300～1 000Ma的碎屑锆石;（4）在华北以及朝鲜的中—新元古代地层中,已经识别出约900Ma的基性岩墙。此外,对华北北缘的白云鄂博群、狼山—渣尔泰群和化德群的研究,证实在华北北缘的裂谷系与燕辽裂陷槽具有相同的层序与沉积历史。其中在渣尔泰群中识别出约820 Ma的火山岩。盆地分析表明,华北克拉通与相邻大陆分离时间对应于大红峪组—高于庄组沉积时间,结束后开始蓟县系沉积,为1 600Ma或为古—中元古代接替时间,也大致对应于Columbia超大陆裂解的时间。值得注意的是,华北克拉通自古元古代末至新元古代,经历了多期裂谷事件,但是期间没有块体拼合的构造事件的记录,这对于理解华北中—新元古代的演化历史以及对于理解该时期全球的构造具有重要意义。During the Mesoproterozoic- Neoproterozoic, the North China Craton（NCC） was a stable platform or para-platform, on which vast and thick sedimentary sequences were deposited. The major sedimentary basins are the Xiong＇er ‘aulacogen＇ in the south central NCC, the Yanshan ~aulacogen＇ in the north-central NCC, the northern margin rifts in the northwestern NCC and the eastern margin-Korea rifts in the eastern NCC. Four stages of magmatic activities were recognized during the Late Paleoproterozoic- Neoproterozoic： （1） the ～1800 - 1780 Ma Xiong＇er Igneous Province （XIP）, （2） ～1720 - 1620 Ma anorogenic magnmtism, （3） ～1350 - 1320 Ma diabase sills, and （4） a ～900 Ma mafie dyke swarm. A ～1800 Ma Paleoproterozoic Large Igneous Province （LlP）-related to mantle plume has been suggested by Zhai and Liu and Peng et al. The XIP consists of 3 - 7 km of extrusive volcanics and some feeder dykes/sills distributing over an area 〉0.06 ×104 km2 along the southern margin of the NCC. The XIP is characterized by fractional crystallization from an EMI type mantle source. Mafic dyke swarms are widespread in the central NCC with an outcrop area 〉0. 1× 104 km2 , and are exposed at variable depths up to 20 km （deepest in the north）. Several studies have shown that the mafic dyke swarms recorded assimilation and fractional crystallization of an EMI type magma source, with a minor DM contribution in the younger magmas. Spatial and petrogenetic correlations suggested a cogenetic relationship between the dyke swarm and XIP, and that, together, they defined a Large Igneous Province. This LIP event is considered to have initiated the rifting of the Xiong＇er aulacogeN, The four magmatic events suggested that the NCC was situated in an extensional tectonic environment for an extended time during the Late Paleoproterozoic-Neoproterozoic, and witnessed multi-stage rifting activities.

关 键 词：华北 中—新元古代 岩浆作用 多期裂谷 地质意义 

分 类 号：P588.115[天文地球—岩石学]