大别——苏鲁高压变质带中榴辉岩的多样性及其成因

THE DIVERSITY AND ORIGION OF ECLOGITES FROM THE DABIE--SULU HIGH--PRESSURE METAMORPHIC BELT

最近的研究表明,大别—苏鲁高压变质带中的榴辉岩是多种多样的。与蓝片岩共生的C类榴辉岩可能由俯冲洋壳经低温高压变质作用(t=523℃,p=1.2—1.5GPa)形成;与片麻岩共生的B类榴辉岩则可能是在陆-陆碰撞过程中由俯冲陆壳中的基性成分岩石经原地高温(超)高压变质作用(t=651—828℃,p=1.2—3.8GPa)形成;侵入于B类柯石英榴辉岩中的脉状榴辉岩(A类)可能是在相对高温高压条件下(t=769℃,p>1.8GPa)由偏超基性岩浆直接结晶出来的。这些不同类型的榴辉岩不是一次简单高压变质事件的产物,表明华北—扬子板块边界经历了漫长而多期次的演化历史。

The eclogites in the Dabie-Sulu high-pressure metamorphic belt are very di-verse based on a recent study. The C-type eclogites coexisting with blueschist pro-bably formed by low-temperature and high-pressure metamorphism (t=523℃, p=1.2—1.5 GPa) of the subducted oceanic crust. The B-type eclogites coexisting withgneiss are supposed to be derivod by high-temperature and (ultra) high-pressuremetamorphism (t=651—828℃, p=1.2—3.8 GPa) of basic rocks in the subductedcontinental crust during continent-continent collision. The A-type eclogite veinsintruding into the B-type coexsite eclogites might directly crystallize from theapproximate ultrbasic magma under relatively high-temperature and high-pres-sure conditions (t=769℃, p>1.8 GPa). These different types of eclogite are not theproduct of a simple high-pressure metamorphic event. This suggests that the bound-ary of the North China and Yangtze plates underwent very long and multiphase-evolutionary history.