南极格罗夫山陨石岩石学特征Ⅰ:非平衡L3型普通球粒陨石

PETROLOGY OF GROVE MOUNTAINS METEORITES 1:L3 ORDINARY CHONDRITES

我国第16次南极科学考察队在格罗夫山区域的蓝冰表面回收到28块陨石,其中有6块属于非平衡型(即3型)普通球粒陨石。它们保存了原始的岩石矿物学特征,包括非常清晰的球粒结构、基质未重结晶和不透明、橄榄石和低钙辉石颗粒具有明显的成分环带和极不均一的化学组成等。Fe-Ni合金含量、含Fe总量和橄榄石成分综合分析表明这6块陨石全部属于低铁群(L)。因为非平衡普通球粒陨石橄榄石成分变化的PMD(Fa)值与岩石类型亚型有良好的相关性,因此,根据橄榄石Fa的PMD标准这6块陨石被划分为如下亚型:GRV 99019为3.6型,GRV99020、GRV 99021和GRV 99026为3.5型,GRV 99001为3.4型,GRV 99022为3.0—3.4型。

Six of a total of 28 meteorites collected by the 16th CHINARE from Grove Mountains, Antarctica, were classified as L3, and they show highly primitive petrography and mineralogy. In these unequilibrated chondrite, chondrules are very sharp-outlined; fine-grained matrix is almost opaque with few recrystallized grains; olivine and low-Ca pyroxene are commonly zoned, and have wide ranges of composition. Abundance of metallic Fe-Ni, calculated total Fe concentration, and mean Fa content of olivine are within the ranges of L group. Based on Percent Mean Deviation ( PMD) of Fa content of olivine, and its correction with petrographic subtype of unequilibrated ordinary chondrites( Sears et al. , 1982) , these 6 L3 chondrites are subdivided into as following; GRV 99022, 13.0-3.4; GRV 99001, L3.4; GRV 99020, GRV 99021 and GRV 99026, L3.5; GRV 99019, L3.6.