麻粒岩成因的反思  

PONDERATION OVER THE ORIGIN OF GRANULITES

作　　者：吴昌华[1] 

机构地区：[1]天津地质矿产研究所,天津300170

出　　处：《岩石学报》1992年第1期74-86,共13页Acta Petrologica Sinica

基　　金：国家自然科学基金"内蒙中部麻粒岩相带地质演化及深成作用研究"

摘　　要：通常麻粒岩被认为是火山岩进变质形成的。本文通过麻粒岩的产状、岩石组合、结构构造、共生矿物组合、温压条件、CO_2流体、PTt轨迹及同位素年龄等资料的讨论,对其成因提出了疑义,认为高级地体的麻粒岩可能主要是深成岩浆岩不同程度逆变质的产物。It has been ingrained in mind that regional metamorphism is generally thought today, in a rather loose way, as a progressive process, i. e. an endothermic and dehydration reaction. This concept deduced from the prograde metasedimentary rocks has automatically been extended to the origin of granulites in the high-grade terrains. It is undoubted that paragneisses and khondalite serives derived from metasedimentary rocks in granulite facies are formed under the progressive metamorphic conditions. But it is open to question that granulites in the high-grade terrains have been holden as the prograde metavolcanics, leucogranulite derived from acid volcanics and melanogranulite from intermediate-basic ones. There are indications that the concept of progressive metamorphism deduced from metasedimentary rocks may not universally be applicable to meta-magmatic rocks, especially granulites for which T-P conditions on the metamorphic facies diagram (Fig.1) lie in the field where the high-grade metamorphic facies and plutonic magmatism meet. In this paper, the origin of granulites which is traditionally considered as the products of prograde metamorphism of layer volcanics is pondered on in the other way round as the products of degeneration or converse metamorphism of gabbroid rocks. As we know, if a high-grade metamorphic rock either fails to survive post-metamorphic cooling or was remetamorphosed at lower temperature in some later metamorphic episode, and since theproduct is a lower-grade metamorphic assemblage the process is generally called retrogressive (retrograde)metamorphism or diaphthoresis. But the so-called degeneration or converse metamorphism by the author means a process from an original magmatic rock with an original high-temperatureigneous assemblage to a metamorphic rock with a metamorphic assemblage even if in granulite facies. So the term retrogressive metamorphism meaning the process from a (higher-grade)metamorphic to another (lower-grade) metamorphic cannot be used instead of the word de

关 键 词：麻粒岩 成因 变质作用 

分 类 号：P588.346[天文地球—岩石学]