极端条件下的变质作用——变质地质学研究的前沿

在简单回顾变质地质学形成和发展的不同历程的基础上,扼要地总结了近年来有关极端条件下的超高压变质作用、超高温变质作用和很低温变质作用研究的现状和存在的问题。根据峰期变质温度的不同,结合其矿物组合和地质产状特征,进一步提出将超高压变质作用划分为低温超高压变质作用(峰期变质温度低于600℃)、中温超高压变质作用(峰期变质温度介于600~900℃)和高温超高压变质作用(峰期变质温度大于900℃)。低温超高压变质作用与大洋板块的冷俯冲作用有关,其研究对于探讨俯冲带水流体的循环和地幔水流体的成因具有重要意义;中、高温超高压变质作用与大陆深俯冲作用相关,是目前超高压变质作用研究的热点领域;高温超高压变质作用的研究与探讨地球内(深)部组成和结构相关,一直是地质学家关注的前沿问题。超高温变质作用研究正在向深入发展,中国有关超高温变质作用的研究才刚刚起步;很低温变质作用的研究长期以来没有得到应有的重视,随着研究手段和方法的不断完善和提高,将会有大的发展。极端条件下的变质作用是近年来固体地球科学研究取得的重要进展,是目前变质地质学研究的前沿领域。

Extreme metamorphism: the frontier of metamorphic geology

The progress and some problems in the study of extreme metamorphism are summarized in this paper. The metamorphism under extreme conditions includes ultrahigh pressure (UHP) metamorphism, ultrahigh temperature (UHT) metamorphism and very low temperature (VLT) metamorphism. Based on peak metamorphic temperatures, mineral associations and geological occurrence, we further divide the UHP metamorphism into three types: (1) low temperature UHP metamorphism (<600 ℃), (2) medium temperature UHP metamorphism (600-900 ℃) and (3) high temperature UHP metamorphism (>900 ℃). Because the low temperature UHP metamorphism was caused by cold oceanic plate subduction, studies of the low temperature UHP metamorphism is of great significance for the understanding of the H_2O cycle in subduction zones and the origin of fluids in the mantle. Medium and high temperature UHP metamorphism is associated with continental subduction, and this will probably be an important topic in the future. The high temperature UHP metamorphism or metamorphism in the Earth deep interior is related to the study of mantle structure and materials, which will continue to be a frontier of the solid earth sciences. Much recent progress has been made in the study of UHT metamorphism, but we are just at the beginnings of the research on UHT metamorphism in China. Little attention was paid to VLT metamorphism in recent years. With the development of new methodology and technology, a great progress in VLT metamorphism research in the future is expected. Extreme metamorphism is a frontier of metamorphic geology.