信阳-舒城断裂带西段石榴云母片岩中石榴石的矿物学特征及其构造意义  

Mineralogy feature and tectonic significance of garnet from garnet-mica schist at the west section of Xinyang-Shucheng fault belt

作　　者：任升莲[1] 宋传中[1] Lin Shoufa 张浩然[1] 李加好[1] 涂文传[1] 张欢[1] 章俊杰[1] 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009 [2]加拿大滑铁卢大学,Ont.,Canada N2L 3G1

出　　处：《地质科学》2011年第2期350-363,共14页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目(编号:40372097,40772131,4107216);中石化基础研究项目(编号:09-02)资助

摘　　要：桐柏山地区信阳—舒城断裂带西段石榴云母片岩中石榴石变斑晶保留了较多岩石形成过程中的变形—变质信息,它真实地反映了中国南北两大板块缝合带的形成条件和演化历史。石榴石探针成分分析结果表明其属于铁铝榴石,反映出经受中级区域变质作用的特征。在Nadi石榴石成分与变质带的关系图上主要投影在略偏石榴石带的蓝晶石带内,显示岩石遭受了绿帘角闪岩相一角闪岩相的变质作用。石榴石环带成分特征显示该岩石经历的是递进变质作用,变质环境先是持续地升温升压,中期有两次不同步的短暂降温压过程,最后又经历了热松驰环境的增温减压过程,没有遭受到明显的退变质作用。透射电镜观察石榴石的位错主要是自由位错和位错壁,自由位错密度p=6.14×10~8/cm^2,位错特征反映的是中温偏高条件下的塑性变形。石榴云母片岩的形成条件估算为562℃～617℃,压力为(0.77～1.02)GPa。At the western part of the Xinyang-Shucheng fault of Tongbai Mountain, garnet porphyroblast in garnet-mica schist retained many deformation and metamorphic information during the process of rock formation. It is a true reflection of formation conditions and evolution history of plate suture zone of China＇s two major plates. Garnet microprobe analysis shows that it belongs to almandine,and reflects it had experienced mid-level regional metamorphism. In Nadi garnet composition and metamorphic belt diagram, it majorly falls in kyanite belt with clients tends to garnet belt,showing that the rock had suffered epidote amphibolite facies-amphibolite facies metamorphism. Compositional zoning of garnet shows that the rocks had experienced progressive metamorphism. First metamorphic environment was continuous temperaturepressure, and in mid-term there were two non-synchronous transient cooling and decompression process, and finally underwent decompression and warming process of the thermal relaxation environment, not subjected to significant retrograde metamorphism. Dislocations of garnet observed through TEM are mainly edge dislocations and dislocation walls. Free dislocation density p = 6. 14×10^8/cm2 , these dislocation features show a plastic deformation in medium temperature conditions. Formation conditions of garnet-mica schist is estimated： temperature is 562 ℃ -617 ℃ ,and the pressure is （0.77 - 1.02） GPa.

关 键 词：桐柏山 信阳-舒城断裂带 变质作用 石榴石成分环带 位错 

分 类 号：P541[天文地球—构造地质学] P542[天文地球—地质学]