摘要
通过对福建沿海平潭－东山变质带中夕线石榴云母片岩的岩相学和变质作用特征的研究，讨论了该区变质作用的演化历史，为地质学家建立该区乃至整个东南部的构造演化模式提供科学的依据。研究表明，石榴夕线云母片岩实际上是两期变质作用叠加的产物，其中的石榴石、夕线石和黑云母等是第一期变质作用的产物，代表古老变质基底（泥质）的残余，而白云母和大部分石英（白云母石英片岩）则是在第二期变质作用（中生代区域变质）期间由前述变质基底改造而成。也就是说，在人们熟知的绿片岩相－低角闪岩相区域变质作用之前，还曾发生一期更高级的变质作用。第一期变质作用的条件为Ｐ＝０．５５～０．６２ＧＰａ，Ｔ＝６９２℃～７１７℃，达高角闪岩相；第二期变质作用在本区影响最大，并形成递增变质带，变质作用的温度和压力范围分别是Ｐ＝０．２～０．５ＧＰａ，Ｔ＝４００℃～５６０℃，属中低级变质。早期高级变质残余的发现使我们不得不重新考虑福建沿海变质带的变质演化与构造演化的过程。
Based on the research of petrography and metamorphism of garnet and sillimanite bearing mica schists of Pintan Dongshan metamorphic belt in eastern Fujian, SE China, the paper discusses the metamorphic evolution of the area, which will probably serve as evidence for the reconstruction of tectonic evolution process of the area, and even of the whole SE China. The research indicates that (1) the garnet and sillimanite bearing mica schists were virtually products of overprints of two different stages of metamorphism.In these schists, garnet, sillimanite and biotite are relicts of first stage of the metamorphism (M 1), while muscovite quartz schists, as well as hornblende bearing plagioclase leptite were products of the second stage of metamorphism(M 2). In other words, a higher grade of metamorphism occurred before the generally recognized regional metamorphism with greenschist facies to low amphibolite facies grade, which had never been reported before. (2)The P T conditions of the M 1 metamorphism are estimated as in the range of 0 55￣0 62GPa and 692℃￣717℃, respectively, reaching high amphibolite facies garde. The metamorphic conditions estimated for the M 2 metamorphism are P =0.2￣0.5 GPa, T =400℃￣560℃, typical of mid low grade metamorphism. Therefore , considering the discovery of evidences of the previous high grade M 1 metamorphism we have to reconsider the metamorphic and tectonic evolution history of the area.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1997年第3期380-394,共15页
Acta Petrologica Sinica
基金
国家自然科学基金
关键词
变质岩
夕线石
石榴石
云母片岩
变质作用
岩相
Relics of high amphibolite facies metamorphism, Garnet and sillimanite bearing mica schists, eastern Fujian metamorphic terrain
