Lower time limit on the UHPM rock exhumation: Discovery of eclogite pebbles in the Late Jurassic conglomerates from the northern foot of the Dabie Mountains, eastern China  

作　　者：Daoxuan Wang Yin Liu Shuangying Li Fuquan Jin 

机构地区：[1]Hefei Univ Technol, Dept Resources & Environm Sci, Hefei 230009, Peoples R China

出　　处：《Chinese Science Bulletin》2002年第3期231-235,共5页

基　　金：This work was supported by a project (Grant No. KZ951-A1-401-07) of the Chinese Academy of Sciences.

摘　　要：Eclogite pebbles are first discovered in late Jurassic conglomerates of the Fenghuangtai Formation from the northern foot of the Dabie Mountains, eastern China. The eclogite shows relatively strong retrograde metamor-phism. The major remnant minerals are garnet, phengite, quartz, rutile, clinozoisite, fingerprint(or worm)-form sym-plectite and pseudomorphic enclosure of coesite in garnet. End-member components of the garnet mainly made up of grossular (27.7%-37.8%), almandinc (45.5%-49.0%) and pyrope (12.3%-25.7%). End-member components of the pyrope is less than 30%, i.e. equivalent to C type eclogite. Si-cations of the phengite are 3.44-3.54 p.f.u. (taking O=11as standard). It is estimated that the pressures are 2.5-3.2 GPa, the temperatures are 600-900℃. Discovery of the eclogite pebbles in the late Jurassic conglomerates from the northern foot of the Dabie Mountains suggests that the HP-UHP metamorphic rocks of the Dabie Mountains, which were formed in Triassic, had been exposed to the surface inEclogite pebbles are first discovered in late Jurassic conglomerates of the Fenghuangtai Formation from the northern foot of the Dabie Mountains, eastern China. The eclogite shows relatively strong retrograde metamorphism. The major remnant minerals are garnet, phengite, quartz, rutile, clinozoisite, fingerprint(or worm)-form symplectite and pseudomorphic enclosure of coesite in garnet. End-member components of the garnet mainly made up of grossular (27.7%–37.8%), almandine (45.5%–49.0%) and pyrope (12.3%–25.7%). End-member components of the pyrope is less than 30%, i.e. equivalent to C type eclogite. Si-cations of the phengite are 3.44–3.54 p.f.u. (taking O=ll as standard). It is estimated that the pressures are 2.5–3.2 GPa, the temperatures are 600–900°C. Discovery of the eclogite pebbles in the late Jurassic conglomerates from the northern foot of the Dabie Mountains suggests that the HP-UHP metamorphic rocks of the Dabie Mountains, which were formed in Triassic, had been exposed to the surface in the late Jurassic or before it by exhumation.

关 键 词：time of EXHUMATION Late JURASSIC Fenghuangtai Formation ECLOGITE pebbles northern FOOT of the DABIE Mountains. 

分 类 号：P578[天文地球—矿物学]