南极格罗夫山100块陨石的矿物-岩石学特征

PETROGRAPHY,MINERAL CHEMISTRY AND CLASSIFICATION OF 100 METEORITES COLLECTED FROM THE GROVE MOUNTAINS,ANTARCTICA

本文主要报道了南极格罗夫山新回收的100块陨石的岩石学和矿物化学特征。并根据矿物-岩石学特征,划分了它们的化学-岩石类型:6块属于非平衡型普通球粒陨石(H3和L3群各3块);92块属于平衡型普通球粒陨石,包括:H群24块(13块H4,10块H5,1块H6),L群64块(2块L4,44块L5,18块L6),LL群4块(3块LL4,1块LL5);另外两块属于石-铁陨石。6块非平衡型普通球粒陨石保存了原始的岩石学和矿物化学特征,包括:清晰的球粒结构、橄榄石和低钙辉石具有明显的成分环带以及极不均一的化学组成等。92块平衡型普通球粒陨石中的橄榄石和低钙辉石显示出均一的化学组成,表明它们达到了一定的热力学平衡。这些普通球粒陨石受到的风化作用以W1和W2为主,所占比例高于90%,表明南极陨石受到的风化作用不强烈。有约40%的陨石样品受到了强烈的冲击作用,并产生冲击脉或者冲击囊,它们是研究高压冲击矿物和冲击作用的理想样品。

Petrography and mineral chemistry of 100 meteorites collected from the Grove Mountains, Antarctica, were studied and their chemical-petrographic types were assigned. The chemicalpetrographic types of these meteorites are presented below. Six are unequilibrated ordinary chondrites, including three H3 and three L3; 92 meteorites are equilibrated ordinary chondrites, including 24 H-group （13 H4, 10 H5, 1 H6）, 64 L-group （2 L4, 44 L5, 18 L6） and 4 LL-group （3 LL4, 1 LL5） ; the other two belong to stone-iron meteorites. In 6 unequilibrated ordinary chondrites, chondrules are well-shaped, and olivine and low-Ca pyroxene are commonly zoned and have wide ranges of composition. The olivine and low-Ca pyroxene in the other 92 equilibrated ordinary chondrites have similar composition, respectively, and to some degree it reflected thermodynamics equilibration in olivine and low-Ca pyroxene. All ordinary chondrites, consisting of predominant weathering degrees of W1 and W2 （ 〉 90% ）, suggest a weak weathering among Antarctica meteorites. - 40 % meteorites experienced severe shock metamorphism, as indicated by the presences of shock-induced melt veins and pockets. These heavily shocked meteorites provide us with natural samples for study of high-pressure polymorphs of minerals.