Subdivision of petrologic type of unequilibrated ordinary chondrites from Antarctica  

作　　者：蒋云 徐伟彪 

机构地区：[1]Laboratory for Lunar and Planetary Science,Purple Mountain Observatory,Chinese Academy of Sciences

出　　处：《Chinese Journal of Polar Science》2009年第2期135-150,共16页极地研究（英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant No.40773046 and 10621303);Experimental Standardization and Sharing of the Polar Region Biological and Geological Sample Project(2005DKA21406);the Minor Planet Foundation of China

摘　　要：We report results of petrologic and mineralogical studies of 25 unequili- brated ordinary chondrites （19 Chinese Antarctic meteorites） using electron microprobe, scanning electron microscopy （SEM） and energy-dispersive X-ray spectrometry （EDS） techniques. With increasing degree of thermal metamorphism, chemical zoning of olivine was erased; plessite was transformed into intergrowths of coarsergrained kamacite and Ni-rich metal; Cr exsolved from ferroan olivine, produced needie-like crystals and coarsened into equant chromite grains; and feldspar crystallized during devitrification of glass and recrystallization of matrix. These features can help to identify different metamorphic grades. Based on the scheme by Sears et al （1982）, we subdivided type 3 Chinese Antarctic ordinary chondrites into petrologic type 3.3 to 4 （3 type 3.3, 3 type 3.4, 1 type 3.5, 2 type 3.6, 2 type 3.7, 5 type 3.8, 3 type 4 ）. This classification scheme is a quite effective way to subdivide Antarctic meteorites. Additionally, we propose to revise the chemical groups of GRV 020032 and GRV 020104 to L and H, respectively.We report results of petrologic and mineralogical studies of 25 unequili- brated ordinary chondrites （19 Chinese Antarctic meteorites） using electron microprobe, scanning electron microscopy （SEM） and energy-dispersive X-ray spectrometry （EDS） techniques. With increasing degree of thermal metamorphism, chemical zoning of olivine was erased; plessite was transformed into intergrowths of coarsergrained kamacite and Ni-rich metal; Cr exsolved from ferroan olivine, produced needie-like crystals and coarsened into equant chromite grains; and feldspar crystallized during devitrification of glass and recrystallization of matrix. These features can help to identify different metamorphic grades. Based on the scheme by Sears et al （1982）, we subdivided type 3 Chinese Antarctic ordinary chondrites into petrologic type 3.3 to 4 （3 type 3.3, 3 type 3.4, 1 type 3.5, 2 type 3.6, 2 type 3.7, 5 type 3.8, 3 type 4 ）. This classification scheme is a quite effective way to subdivide Antarctic meteorites. Additionally, we propose to revise the chemical groups of GRV 020032 and GRV 020104 to L and H, respectively.

关 键 词：ANTARCTICA UOCs thermal metamorphism OLIVINE petrologic type. 

分 类 号：P185.83[天文地球—天文学] P618.130.2