摘要
在总结大洋板块俯冲形成加积楔的基础上,对大别—苏鲁造山带内部及北缘浅变质岩进行了系统的研究,指出它们是扬子大陆板块俯冲的构造加积楔。这些浅变质岩既有产出在造山带北缘,也有少量出露在超高压变质带的内部,它们均形成于前印支期扬子板块北缘,主体为低绿片岩相变质的复理石相沉积岩和少量侵入岩,并遭受了与造山带超高压变质岩相同的加里东—印支期构造热事件的改造,具有板块俯冲过程中被刮削下来的构造残片——加积楔的形成机制和特征。垂向剖面上,这些浅变质岩原岩主要由表层浅海复理石相沉积岩系和下伏陆壳基底岩石(花岗质侵入体—变质中基性杂岩—大理岩组合)两部分组成,而超高压变质岩原岩主要为扬子板块北缘的俯冲陆壳基底岩石。将构造加积楔形成理论纳入到印支期扬子板块俯冲过程,通过对部分浅变质岩与超高压变质岩在地质特征上的对比,综合探讨了扬子板块俯冲与超高压变质岩及构造加积楔形成过程的时空耦合关系,确定了扬子板块俯冲加积楔不同构造部位浅变质岩的构造组合特点,探讨了扬子板块俯冲过程中构造加积楔形成的动力学过程。
It is well established that the accretionary wedge is a large wedge-shaped mass of sediments that has accumulated in subduction zones and accreted to overriding crustal blocks. A great deal of studies have been devoted to the accretionary wedge of oceanic plate subduction in last two decades. Its general characteristics and occurrence are summarized at first in this paper in order to identify the accretionary wedge of continental plate subduction. A number of controversial low-grade metamorphic rocks in the interior and the northern margin of the Dabie - Sulu orogen are investigated in this study, which are ascribed to a portion of the accretionary wedge due to the subduction of the Yangtze plate. The low-grade metamorphic rocks are mostly at greenschist facies and consist of two parts. One occurs in the interior of the ultrahigh pressure belt and is composed of metaclastics, phyllite and marbles, while the other occurs on the northern margin of the belt and is composed of slates, schists, phyllites, metasandsones and marble as well as strongly deformed intrusions. Palaeotological, petrologi-cal and geochronological evidence shows that most of the metasedimentary rocks were deposited at the northern passive continental margin of the Yangtze plate as a flysch facies prior to Triassic, and suffered dynamic meta-morphism of greenschist-facies due to plate subduction. Both Caledonian and Indonisian events were dated, being concordant with tectonic events experienced by the ultrahigh pressure rocks in the Dabie-Sulu orogen. Obviously, the low-grade metamorphic rocks were scraped off from the subducting Yangtze continental plate and thus correspond to a part of the accretionary complexes of the Yangtze plate subduction. Within the framework of the accretionary wedge of continental plate subduction, the low-grade metamorphic rocks in the interior and northen margin of the Dabie-Sulu orogen can be unified as a whole in comparison with the ultrahigh pressure metamorphic rocks. Relationship in time and space between the lo
出处
《地质学报》
EI
CAS
CSCD
北大核心
2001年第3期338-352,共15页
Acta Geologica Sinica
基金
中国科学院知识创新工程项目(KZCX2-107)资助的成果
关键词
加积楔
板块构造
扬子板块
浅变质岩
大别-苏鲁造山带
accretionary -wedge
plate tectonics
continental subduction
low-grade metamorphic rock
Dabie-Sulu orogen
