Two Discrete UHP and HP Metamorphic Belts in the Central Orogenic Belt, China  

作　　者：索书田 钟增球 张利 周汉文 游振东 

机构地区：[1]Faculty of Earth Sciences, China University of Geosciences [2]School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China

出　　处：《Journal of China University of Geosciences》2006年第3期189-200,共12页中国地质大学学报（英文版）

基　　金：This paper is financially supported by the National Natural ScienceFoundation of China (Nos .40372094 and 49972067) .

摘　　要：An attempt is made to confirm the existence of the two discrete UHP and HP metamorphic belts in the central orogenic belt in China. Detailed geological mapping and structural and petrological analyses of the Kanfenggou （看丰沟 ） and Xiangfanggou （ 香坊沟 ） slices exposed in the eastern Qinling （秦岭） orogen indicate that they experienced ultrahigh pressure and high pressure metamorphism, respectively. The former, situated in northern Qinling, contains a large volume of fine-grained coesite and quartz pseudomorphs after coesite- and microdiamond-bearing eclogite lenses, whereas the latter, located in southern Qinling, preserves the relicts of a high pressure metamorphic mineral assemblage. Based on extensive fieldwork together with compilations at the scale of the orogenic belt, and a comparison of Pb isotopic compositions between the UHP metamorphic rocks from Kanfenggou slice and the Dabie UHP metamorphic belt, we propose that there are at least two discrete ultrahigh pressure metamorphic belts with different ages and tectonic evolution within the central orogenic belt in China. The first is the South AItun-North Qaidam-North Qinling ultrahigh pressure metamorphic belt of Early Paleozoic age （ -500 -400 Ma）. The Kanfenggou ultrahigh pressure slab is located at its eastern segment. The second is the well constrained Dabie （ 大别 ）-Sulu （苏鲁 ） ultrahigh/high pressure metamorphic belt of Triassic age （-250-220 Ma）. The Xiangfanggou high pressure metamorphic slab is a westward extension of the Dabie-Sulu ultrahigh/high pressure metamorphic belt. The Pb isotopic compositions of the UHP metamorphic rocks from Kanfenggou UHP fragment in East Qinling are different from those of the UHP rocks in Dabie UHP metamorphic belt, but are consistent with those of the rocks from the Qinling rock group and Erlangping （二郎坪） rock group. The East Qinling UHP metamorphic belt does not appear to link with the Dabie-Sulu UHP metamorphic belt. These two ultrahigh metamorphic belts are seAn attempt is made to confirm the existence of the two discrete UHP and HP metamorphic belts in the central orogenic belt in China. Detailed geological mapping and structural and petrological analyses of the Kanfenggou （看丰沟 ） and Xiangfanggou （ 香坊沟 ） slices exposed in the eastern Qinling （秦岭） orogen indicate that they experienced ultrahigh pressure and high pressure metamorphism, respectively. The former, situated in northern Qinling, contains a large volume of fine-grained coesite and quartz pseudomorphs after coesite- and microdiamond-bearing eclogite lenses, whereas the latter, located in southern Qinling, preserves the relicts of a high pressure metamorphic mineral assemblage. Based on extensive fieldwork together with compilations at the scale of the orogenic belt, and a comparison of Pb isotopic compositions between the UHP metamorphic rocks from Kanfenggou slice and the Dabie UHP metamorphic belt, we propose that there are at least two discrete ultrahigh pressure metamorphic belts with different ages and tectonic evolution within the central orogenic belt in China. The first is the South AItun-North Qaidam-North Qinling ultrahigh pressure metamorphic belt of Early Paleozoic age （ -500 -400 Ma）. The Kanfenggou ultrahigh pressure slab is located at its eastern segment. The second is the well constrained Dabie （ 大别 ）-Sulu （苏鲁 ） ultrahigh/high pressure metamorphic belt of Triassic age （-250-220 Ma）. The Xiangfanggou high pressure metamorphic slab is a westward extension of the Dabie-Sulu ultrahigh/high pressure metamorphic belt. The Pb isotopic compositions of the UHP metamorphic rocks from Kanfenggou UHP fragment in East Qinling are different from those of the UHP rocks in Dabie UHP metamorphic belt, but are consistent with those of the rocks from the Qinling rock group and Erlangping （二郎坪） rock group. The East Qinling UHP metamorphic belt does not appear to link with the Dabie-Sulu UHP metamorphic belt. These two ultrahigh metamorphic belts are se

关 键 词：central orogenic belt Kanfenggou Xiangfanggou deep subduction ultrahigh pressure metamorphism eclogite. 

分 类 号：P542[天文地球—构造地质学]