一块新发现月球陨石MIL090036的岩相学和矿物学

PETROGRAPHY AND MINERALOGY OF A NEW LUNAR METEORITE MIL 090036

MIL090036是一块在南极新发现的月球陨石,属于斜长岩质月球角砾岩。本文对这块陨石开展详细的岩石学、矿物学特征观察与研究。MIL090036月球陨石具有典型的碎屑结构。碎屑包括岩屑、矿屑和玻屑。岩屑类型有斜长岩岩屑、辉长质斜长岩岩屑、辉长岩岩屑、风化角砾岩岩屑、橄长岩岩屑、微斑熔融角砾岩岩屑、复合角砾岩岩屑等;矿屑有辉石、斜长石、橄榄石、钛铁矿等;玻屑主要为长石质。基质由玻璃质、重结晶的细粒矿物和矿屑胶结组成。辉长岩岩屑中的斜长石(An81-83)和斜长岩中的斜长石(An88-93)较其他碎屑中的斜长石(An90-98)贫钙。岩屑、矿屑和长石质玻屑中的辉石相对贫铁(Fs12-35Wo3-44En22-79),而含玻璃质的辉长岩岩屑中的辉石(Fs37-65Wo10-29En21-49)与基质中的辉石(Fs18-69Wo3-45En14-50)相对富铁。辉长岩质斜长岩中辉石成分变化范围最小(Fs24-27Wo7-14En59-69)。矿屑橄榄石和分布于基质中的橄榄石铁镁含量(Fo57-79)相对岩屑中的橄榄石(Fo67-77)变化范围大。橄榄石Fe/Mn比值为47—83(平均76)、辉石Fe/Mn比值为76—112(平均73),都与月球橄榄石和月球辉石一致。岩石结构、矿物模式组合和化学成分等特征表明MIL090036是来自Apollo和Luna采样范围外的样品。对MIL090036的矿物学、岩石学和化学成分的进一步研究将丰富我们对月表物质组成和演化的认识。

MIL090036 is a newly found meteorite that belongs to a feldspathic lunar breccia .The detailed petrography and mineralogy of this meteorite are investigated in this paper .It has a typical breccia texture that consists of lithic ,＆nbsp;mineral and glass clasts .The rock types of the lithic clasts are anorthosite , gabbroic anorthosite , gabbro , regolith breccia, troctolite, microporphyritic crystalline impact melt , and compound clasts .Mineral fragments include py-roxenes, plagioclase, olivine and ilmenite.Glass clasts are mainly plagioclase .The matrix is composed of melt glass, fine-grained recrystallized minerals and mineral clasts .The plagioclase grains （ An81-83 , An88-93 ） in gabbro and anorthosite clasts are relatively poorer in Ca than clasts in other breccias （ An90-98 ） .Pyroxene grains （ Fs12-35 Wo3-44 En22-79 ） in lithic, mineral and anorthositic melt clasts are relatively poorer in Fe , whereas those in gabbro clasts with melt glass and matrix are relatively enriched in Fe （ Fs 37-65 Wo10-29 En21-49 , Fs18-69 Wo3-45 En14-50 ） .The composition of pyroxene grains in gabbroic anorthosite has a narrow range （ Fs24-27 Wo7-14 En59-69 ） .Olivine grains in mineral fragments and matrix have a wider compositional range （ Fo57-79 ） than those in lithic clasts （ Fo67-77 ） .Fe/Mn molar ratios of olivine （ 47 to 83 with an average of 76 ） and those of pyroxene （ 76 to 112 ） fall in the lunar range .The characteristics of texture , mineral assemblage and composition suggest that the MIL 090036 meteorite is from an area beyond the sampling range of Apollo and Luna .Further petrographic , mineralogical and compositional studies of MIL090036 will enrich our understanding of the composition and evolution of the Moon ’ s surface .