姜为佳+刘贻灿

摘要：不同造山带的榴辉岩和有关变质表壳岩石中柯石英及金刚石等标志性超高压变质矿物的发现，已证明陆壳岩石能俯冲到大于120 km的地幔深度并折返至地表。超高压变质带中榴辉岩和相关的榴辉岩相岩石常常与具有低级变质矿物组合的岩石（如变质花岗岩、花岗片麻岩、变玄武岩或斜长角闪岩等）密切伴生，然而它们之间的相互关系和成因联系却一直是地质学家长期争议的焦点。查明这两类岩石的变质演化历史以及相互联系，对理解大陆的深俯冲及折返过程具有重要意义。在总结、分析若干陆陆碰撞造山带中变质不均一性的研究成果及成因解释的基础上，讨论了影响岩石保存超高压变质记录的若干关键因素，包括原岩性质、变质流体、构造变形、退变质作用等。

关键词：超高压变质带；变质不均一性；大陆深俯冲；折返；碰撞造山带；榴辉岩；退变质作用

中图分类号：P588.3文献标志码：A

Metamorphic Heterogeneity Within a Single Ultrahighpressure Belt

JIANG Weijia1，2， LIU Yican1，2

（1. Key Laboratory of Crustmantle Materials and Environments， Chinese Academy of Sciences， Hefei 230026，

Anhui， China； 2. School of Earth and Space Sciences， University of Science and Technology of China， Hefei 230026， Anhui， China）

Abstract： Ultrahighpressure （UHP） index minerals， such as coesite and diamond in eclogites and related metamorphosed supracrustal rocks from various orogenic belts， suggest that continental crustal rocks can be subducted to mantle depths of more than 120 km and subsequently return to the surface. Furthermore， eclogites and related eclogitefacies rocks， and lowgrade mineral assemblagebearing rocks （i.e. metagranite， granitic gneiss， metabasalt and amphibolite） commonly coexist in UHP metamorphic belts. However， their relationship and petrogenetic links between highgrade and lower grade assemblagebearing rocks are often matter of debate. Hence， to clarify the metamorphic evolutionary histories and the correlation of the two groups of rocks plays a significant role in understanding the continental deep subduciton and exhumation processes. Some investigations on the metamorphic heterogeneity within a single UHP metamorphic belt were summarized. On this basis， several key factors such as protolith nature， metamorphic fluids， structural deformation and retrogression， which affect the preservation of UHP metamorphic records， were discussed.

Key words： UHP metamorphic belt； metamorphic heterogeneity； continental deep subduction； exhumation； collisional orogenic belt； eclogite； retrogression

0引言

板块构造理论自20世纪60年代以来已被地球科学研究领域所熟识，并成为认识岩石圈结构、组成及演化的基本理论。传统板块构造理论对大陆岩石圈的认识有所缺乏，认为大洋岩石圈密度大，可以俯冲进入地幔，而密度低的大陆地壳则不能进入地幔。然而，表壳岩石中柯石英[13]和金刚石[45]等超高压变质矿物的发现证明了陆壳物质可以俯冲到超过120 km地幔深度，然后折返至地表。

目前已发现的含柯石英和金刚石超高压变质带主要由片麻岩、榴辉岩、石榴橄榄岩、大理岩和片岩等组成。……