南极格罗夫山陨石岩石学特征Ⅱ:平衡型普通球粒陨石

我国第16次南极科考队回收的28块陨石中,除1块火星陨石、1块HED陨石和6块非平衡L3型陨石外,其余20块为平衡型普通球粒陨石。根据橄榄石的平均Fa值、低Ca辉石的平均Fs值和Fe-Ni金属含量将这20块陨石分别划分为H、L和LL等化学群;根据球粒结构、基质重结晶程度和矿物成分对这些陨石进行岩石类型的划分。由于平衡型普通球粒陨石已达热力学平衡,橄榄石和低Ca辉石的成分相当均一,并且平均Fa和Fs值均与陨石的含Fe总量呈很好的反比关系,因此橄榄石平均Fa值和低钙辉石平均Fs值是平衡型陨石重要的化学群分类标准。20块平衡型普通球粒陨石的化学-岩石类型为:6个H群(3个H4、1个H5和2个H6)、9个L群(3个L4、1个L5和5个L6)和5个LL群(2个LL4、3个LL5)。

PETROLOGY OF GROVE MOUNTAINS METEORITES II :EQUILIBRATED ORDINARY CHONDRITES

Of a total of 28 meteorites collected in Grove Mountains, Antarctica, by the 16th CHIN-ARE, there are 20 equilibrated ordinary chondrites. The others include 1 martian meteorite, 1 HED meteorite and 6 L3 ordinary chondrites. These 20 equilibrated ordinary chondrites are classified into chemical groups of H, L and LL, respectively, based on mean Fa content of oli-vine, mean Fs of low - Ca pyroxene and abundance of Fe-Ni metal. Their petrographic types of 4 to 6 are assigned according to structures of chondrules, degree of recrystallization of matrix and homogeneity of composition of major phases. Classification of these 20 equilibrated ordinary chondrites are as following; 6 meteorites of H group (3 H4, 1 H5 and 2 H6) , 9 of L group (3 L4, 1 L5 and 5 L6) and 5 of LL group (2 LL4 and 3 LL5).