宣化西望山高压麻粒岩的岩相学特征及变质P-T轨迹  

The Petrographic Feature and P-T Path of High-Pressure Granulites in Xiwang Mountain of Xuanhua

作　　者：吴伟哲 李宾 WU Wei⁃zhe;LI Bin(Hebei GEO University,Shijiazhuang 050031,China;Hebei Geological Survey Institute,Shijiazhuang 050031,China)

机构地区：[1]河北地质大学资源学院,河北石家庄050031 [2]河北省地质调查院,河北石家庄050031

出　　处：《河北地质大学学报》2020年第2期9-16,共8页Journal of Hebei Geo University

基　　金：河北地质大学太行山实习基地建设项目。

摘　　要：宣化西望山的高压麻粒岩主要由单斜辉石、斜方辉石、斜长石、石榴子石、磁铁矿、钛铁矿组成。它经历了三个变质作用期次:峰前进变质阶段,标志性矿物是石榴石+被石榴石包裹的单斜辉石+斜长石+石英;峰期高压麻粒岩相阶段,典型矿物组合是石榴石+单斜辉石(基质)+斜长石(基质);峰后中压麻粒岩相阶段,矿物组合为斜长石+斜方辉石。运用传统的地质温压计算出,三个变质作用期次的温度和压力分别为:627~669℃,8. 2~8. 7 kbar;728~878℃,10~15 kbar;771~849℃,7~9 kbar。指示了一个近等温减压的P-T轨迹,结合相关资料,说明高压麻粒岩形成于陆-陆碰撞的造山作用过程,而后的减压阶段经历快速的地壳抬升过程。The High-pressure Granulites get in Xiwang Mountain is mainly composed of garnet,plagioclase,clinopyroxene,orthopyroxene,magnetite and ilmenite. It underwent three metamorphic stages: pre-peak metamorphism granulites facies mineral assemblage consists of garnet+ plagioclase+ quartz+ clinopyroxene;high-pressure granulite facies mineral assemblage comprises garnet,clinopyroxene and plagioclase;medium-pressure granulite facies mineral assemblage contains plagioclase and orthopyroxene. Geological temperature-pressure indicator showed that the temperature-pressure conditions of different metamorphic stages are calculated roughly to be 627 ~ 669℃,8. 2 ~ 8. 7 kbar;728 ~ 878℃,10 ~ 15 kbar;771 ~ 849℃,7 ~ 9 kbar,respectively,indicating a clockwise P-T evolutional path of isothermal decompression. Combined with information available,the essay proposes that the high-pressure granulites are formed from continental collision orogenics and undergo a rapid crustal uplift during the pressure decrease history.

关 键 词：西望山 高压麻粒岩 P T轨迹 华北克拉通 碰撞造山 

分 类 号：P581[天文地球—岩石学]