大别山超高压变质带中牛凸岭地区低温-高压榴辉岩的发现及其意义  

The discovery of low-temperature and high-pressure eclogites across Niutuling area in the ultrahigh pressure eclogite Unit and its significance.

作　　者：石永红[1] 林伟[2] 王清晨[2] 

机构地区：[1]合肥工业大学资源和环境工程学院,合肥230009 [2]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029

出　　处：《岩石学报》2008年第6期1288-1296,共9页Acta Petrologica Sinica

基　　金：国家自然科学基金(40772039)项目资助

摘　　要：依据对南大别超高压带腹地的榴辉岩野外地质调查、岩相学和热力学的研究表明,南大别腹地——牛凸岭地区榴辉岩属于低温高压榴辉岩,并未经历超高压变质作用。该地区榴辉岩的共生围岩主要为片岩、片麻岩和斜长角闪岩,石榴石多为自形-半自形,内含大量的早期矿物包体,峰期变质温压条件分别为:T=360～520℃;P=1.3～2.4GPa。对比南大别超高压榴辉岩形成的变质条件,两者压力差可达0.7GPa,约20km 厚的地壳深度缺失。结合构造分析牛凸岭单元更类似于桐城-源潭铺高压块体,推测其属于构造上层部位岩片。On the basis of the field investigation, petrology and thermodynamic estimates for eclogites in the middle of the South Dahie Terrane （ SDT）, the eclogites across Niutuling area in the the middle of SDT belong to low-temperature and high-pressure eclogites, and no underwent ultrahigh pressure metamorphism. The country rocks for the ecolgites are schists, gneisses and plagioclase amphibolite. Garnet display enhedral or subhedral crystal with inclusions in earlier stage, the peak metamorphic temperature and pressure are T = 360 - 520℃ and P = 1.3 - 2.4GPa respectively. Compared with the metamorphic conditions for ultrahigh pressure eclogites in the SDT, 0. 7GPa pressure gap exist between two units, which imply the loss of 20km thickness crust. Combined with the analysis of structure, Niutuling unit is similar to the Tongcheng--Yuantanpu, and guessed as the upper tectonic slice.

关 键 词：榴辉岩 峰期变质P—T条件 牛凸岭单元 压力差 

分 类 号：P588.348[天文地球—岩石学]