We report results of petrologic and mineralogical studies of 25 unequilibrated 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 coarser-grained kamacite and Ni-rich metal;Cr exsolved from ferroan olivine,produced needle-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.
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