南极GRV 022888和GRV 052408橄辉无球粒陨石的岩石矿物学特征及成因探讨

主要介绍GRV 022888和GRV 052408两块南极陨石的岩相学和矿物化学特征,并在此基础上探讨其成因。GRV 052408陨石主要由橄榄石(~60 vol%)和辉石(~35 vol%)组成,含少量富碳质填隙物(~5 vol%);而GRV022888陨石基本由橄榄石(~98 vol%)构成,仅有很少量辉石,富碳质不透明填隙物含量也较低(~2 vol%)。这两块陨石中的橄榄石都可以见到明显的核部富铁边部富镁的反环带结构。结合岩相学和矿物化学特征,将它们划分为单矿Ⅰ型橄辉无球粒陨石。根据橄榄石-易变辉石-熔体温度计,计算得到两块陨石的形成温度在1 220℃左右。我们的研究结果支持橄辉无球粒陨石为球粒陨石质母体部分熔融后的残余物成因假说。

PETROLOGY,MINERALOGY AND PETROGENESIS OF GROVE MOUNTAINS(GRV)022888 AND 052408 UREILITES FROM ANTARCTICA

Here we report on the petrology and mineralogy of GRV 022888 and GRV 052408 ureilites recovered from the Grove Mountains in Antarctica. Based on the petrologic and mineralogical characteristics, we provide new insight into the origin and evolution of ureilites. The mineral assemblages in GRV 022888 were mainly olivine (~98%), with a few pyroxene and carbonaceous opaque interstitial assemblages (~2%). The GRV 052408 ureilite was composed mainly of olivine (~60%), pyroxene (~35%), and carbonaceous opaque interstitial (~5%) mineral assemblages. The olivines in both meteorites had a distinctly reverse-zoned structure, and the cores had a high Fe content while the rims had a high Mg content. The petrologic characteristics classified both as type-I monomict ureilites. The formation temperature calculated using an olivine-pigeonite-liquid geothermometer was high, at about 1220°C. Our findings suggest that the magma of these ureilites is the partially melted residue of a ureilite parent body, similar to material involved in the formation of chondrites.