南极GRV 024237橄辉无球粒陨石的岩石矿物学特征

GRV024237是第19次中国南极科学考察队在南极格罗夫山地区一号冰碛上发现的。主要由粗粒状橄榄石(60vol%)、易变辉石(30vol%)和不透明矿物(10vol%)组成,粗粒橄榄石辉石、颗粒边界呈120°接触角,无球粒,粗粒橄榄石具有明显的反环带结构,这些特征符合典型的橄辉无球粒陨石结构。薄片中橄榄石颗粒的边部到核部化学组成变化显著,边部富镁,Fa6.2—Fa17.5;易变辉石组成比较均一,Fs14.0—Fs15.5;基质不透明矿物富含碳质,充填于大颗粒的间隙及裂隙。岩石学和矿物化学组成两方面都表明GRV024237是一块橄辉无球粒陨石,且属于I型单矿角砾岩,中等FeO/MgO比值,冲击程度较弱,经历了部分熔融。

PETROLOGY AND MINERALOGY OF THE GROVE MOUNTAINS(GRV)024237 UREILITE FROM ANTARCTICA

GRV024237 was found at the No.4 moraine, Grove Mountains, Antarctica in the 19th Chinese Antarctic Research Expedition(CHINARE). GRV024237 consists of granular assemblage of olivine(60vol%), pigeonite(30vol%), the grain boundaries are black and filled by opaque minerals(10 vol%). 120°junctions are common. The chemical compositions of olivine are obviously zonal distribution. The values of olivine Fa are varied between 6.2 and 16.77 from the grain’s rim to core. However, the Fs of pigeonite are quite homogenous, which are between 14.0 and 15.5. The opaque minerals are black carbonaceous material, troilite and Fe-Ni metal. Based on our study, GRV024237 is a monomict ureilite, which is suffered light shock metamorphism and experienced partial melting.