摘要
研究表明大别山朱家冲榴辉岩属于典型的高压榴辉岩,其具有复杂的变质演化历史。根据岩相学、矿物成份化学和热力学分析表明,该类榴辉岩记录了6期变质过程,具有"顺时针"的P-T演化轨迹。由Ⅰ-阶段、Ⅱ-阶段至Ⅲ-阶段显示了近于等温增压进变质特征,并在Ⅲ-阶段压力值最高达到P=2.53 GPa;Ⅳ-阶段和Ⅴ-阶段则表现为增温降压退变过程,温度在Ⅴ-阶段最高达到T=627℃;到Ⅵ-阶段则为降温降压过程。该过程暗示了高压板片在俯冲和折返过程中可能处于一个非匀速的状态。推测朱家冲榴辉岩后期增温退变的过程可能是源于受扰动的地温线恢复、超高压榴辉岩退变过程的"散热"以及该类榴辉岩对温度变化极为敏感所致。
This study show that the eclogites across Zhu Jiachong area belongs to the typical of highpressure eclogites and have the complex metamorphic evolution history. Based on the study of petrology, mineral chemistry and thermodynamic estimates, 6 metamorphic stages and the clockwise evolution path have been identified for the eclogites. The pattern of isothermic increasing pressure in prograde metamorphism has been displayed from the Ⅰ -stage, the Ⅱ- stage to the Ⅲ-stage, and the maxima pressure is obtained at the Ⅲ-stage： P = 2. 53 GPa; while in the Ⅳ-stage and the Ⅴ-stage it is identified by depressing pressure and increasing temperature,and the maxima temperature obtained in the Ⅴ-stage is 627 ℃ ; The Ⅵ-stage is characterized by depressing pressure and temperature. The P-T path implies that the high- pressure slab has a situation of different speed during subduction and exhumation. The increasing temperature during retrograde metamorphism may result from the recovery of the disturbed geothermal line, the ＂ lost heat＂ of ultrahigh-pressure eclogites in retrograde metamorphism and the sensitivity to temperature variation of the eclogites across Zhu Jiachong area.
出处
《地质科学》
CAS
CSCD
北大核心
2009年第3期983-1000,共18页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
国家自然科学基金项目(编号:40772039)资助
关键词
大别碰撞造山带
高压榴辉岩
朱家冲
P—T轨迹
增温退变
Dabie Mountains collision, High-pressure eclogites,Zhu Jiachong area,P-T path,Retrograde metamorphisim with increasing temperature.
作者简介
石永红，男，1968年12月，博士，副教授，变质岩石学专业。E-mail：yonghongshi3110@sohu．com
