桐柏山地区大阜山岩体辉长岩-榴辉岩相转变研究

The troctolites, metamorphic gabbros and (omphacite-bearing) garnet amphibolites of the Dafushan mafic-ultramafic intrusion and the adjacent eclogites and gneisses in southern eclogite belt of the Tongbai orogen are chosen to be the research objects. Based on detailed petrographic observation, we try to distinguish different metamorphic mineral assemblages and structures of metamorphic stages. Combined with the results of electron microprobe analysis and whole rock major elements analysis, the method of THERMOCALC phase equilibrium calculation will be used to get the P-T stability fields of eclogite facies and P-T paths of the different rock types. Especially, we will use the above method to quantitatively trace the effects of different compositions of the protolith on gabbro-eclogite phase transition. In addition, ion microprobe zircon and rutile U-Pb dating on different rock types of the Dafushan intrusion will be carried out to obtain metamorphic ages. The aim of this research is to reveal the time and the main controlling factors of gabbro-eclogite phase transition of the Dafushan intrusion and comprehensively discuss the relationships between the Dafushan intrusion and the high pressure eclogite belt.

选择桐柏造山带南部榴辉岩带内的大阜山镁铁质-超镁铁质岩体中橄长岩、变质辉长岩、（含绿辉石）石榴角闪岩以及岩体外榴辉岩和片麻岩为研究对象，通过详细的岩相学观察确定不同变质演化阶段的变质反应矿物组合和结构，再结合电子探针和全岩化学分析结果，利用THERMOCALC相平衡计算方法来确定不同类型岩石的榴辉岩相P-T稳定区域和演化轨迹，定量地示踪原岩成分的变化对辉长岩-榴辉岩相转变的影响，同时利用离子探针对不同岩石中的锆石和金红石进行变质年代测定，揭示大阜山岩体中辉长岩-榴辉岩相转变的时间，综合探讨大阜山岩体与所处高压榴辉岩带的关系。