摘要
赤城地区退变榴辉岩的围岩以黑云斜长片麻岩为主,其原岩是元古代红旗营子群和古生代的表壳岩;退变榴辉岩原岩则为其中的基性侵入体。本文通过赤城地区退变质榴辉岩及围岩的锆石U-Pb年代学研究,对华北北缘古生代以来的地质演化提出了新的认识。峰期榴辉岩相变质作用发生于355Ma,代表俯冲作用发生的年龄,在320~300Ma的抬升过程中发生角闪岩相退变质,随后在280~290Ma期间存在一期大规模强烈的热事件,影响范围大,流体丰富,锆石发生了强烈的重结晶,因此使得之前记录的年代学信息难以保存。西四道沟的变质闪长岩记录了240Ma左右的一次变质事件。由此反映了赤城地区在古亚洲洋闭合的过程中陆壳发生俯冲,并遭受榴辉岩相变质作用,之后整个华北北缘处于伸展环境,并遭受大规模热事件影响,一直到晚古生代—早中生代转为挤压环境,在晚古生代—早中生代最终完成闭合。
The surrounding rock of retrograded eclogite from Chicheng, north Hebei is mainly composed of biotite-plagioclase gneiss, the protolith of which consists of Proterozoic Hongqiyingzi Group and Paleozoic supracrustal rock. The protolith of retrograded eclogite occurs as the mfaic intrusions in the supracrustal rock. This paper proposed a new interpretation for the geological evolution of the northern margin in North China since Paleozoic. The peak eclogite facies metamorphism occurred in 355Ma, which represented the age of subduction. The retrograde metamorphism in amphibolite facies occurred between 320Ma to 300Ma during the uplifting process. Then, a large scale thermal event in a broad range of influence occurred during 280~290Ma,with abundant fluid contributing to the intense recrystallization of the zircons,making it difficult to preserve the chronology information recorded before. The meta-diorite in West Sidaogou recorded a metamorphic event occurring in 240Ma. This is a significant reflection that the continental crust of Chicheng area had been in subduction during the close of Petro-Asian ocean and also experienced eclogite facies metamorphism. Soon afterwards the whole northern margin of North China was in extensional environment and influenced by the large scale thermal event until it was transferred into compressional tectonic setting and finally closed during Late Paleozoic to Early Mesozoic.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2013年第9期1233-1246,共14页
Acta Geologica Sinica
基金
国家青年自然科学基金项目(编号40902021)
中国地质大调查项目(编号1212010911005)资助的成果
关键词
红旗营子群
退变质榴辉岩
古生代
赤城
华北
Hongqiyingzi Group
retrograded eclogite
Paleozoic
Chicheng
North China
