摘要
Northwest Africa(NWA)8599是一块发现于西北非地区的月球角砾岩陨石。岩相学观察和矿物化学分析结果表明,NWA 8599是一块细粒且富含橄榄石的镁质斜长苏长质角砾岩陨石,含有大量矿物碎屑(主要有橄榄石、辉石、已转变为熔长石的钙长石及少量氧化物矿物)和少量镁质斜长岩岩屑(长石丰度>90 vol%)。作者在NWA 8599中观察到一块粗粒高镁橄榄石碎屑(Fo=84~87);该高镁橄榄石碎屑与高镁辉石(Mg^(#)=85~89)和镁钛矿(Mg^(#)=52~54)共生,其中镁钛矿是在月球样品中的首次报道。橄榄石中钙含量及辉石温压计分析结果表明高镁矿物组合可能源于深部月壳的高镁岩石。NWA 8599中镁质斜长岩岩屑呈现较大的模式丰度和粒度变化,暗示了月球镁质斜长岩的多样性,它们可能是月幔翻转过程中深部富镁熔体不同程度混染月壳亚铁斜长岩的结果。
Northwest Africa(NWA)8599 is a lunar breccia meteorite found in Northwest Africa.We performed detailed petrographic and mineralogical study on this lunar meteorite.Our observations reveal that NWA 8599 is an olivine-rich magnesian anorthositic noritic breccia,with abundant mineral fragments and minor fine-grained magnesian anorthosite clasts.Our NWA 8599 sample contains a coarse-grained highly magnesian olivine fragment(Fo=84-87),which is closely associated with highly magnesian pyroxene(Mg^(#)=85-89)and geikielite(Mg^(#)=52-54).The geikielite grains in NWA 8599 are reported for the first time among lunar meteorites and mission-returned lunar samples.The CaO contents in the highly magnesian olivine and thermobarometric calculations of pyroxenes indicate that the highly magnesian mineral assemblage is likely derived from a highly magnesian rock from deep crust of the Moon.Our results show large variations in modal abundance and grain size for the magnesian anorthosites in NWA 8599,indicating diversity of the magnesian anorthositic lithologies in the Moon.We suggest that the magnesian anorthosites may be produced by variable degrees of assimilation of primordial ferroan anorthositic crust by mantle-derived magnesian melt during lunar mantle overturn.
作者
张真光
张浪
杜天然
赵凯
张爱铖
ZHANG Zhenguang;ZHANG Lang;DU Tianran;ZHAO Kai;ZHANG Aicheng(State Key Laboratory of Critical Earth Material Cycling and Mineral Deposits,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China;Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210034,China;CAS Center for Excellence in Comparative Planetary,Hefei 230026,China)
出处
《高校地质学报》
北大核心
2025年第3期286-300,共15页
Geological Journal of China Universities
基金
国家自然科学基金(42025302)资助。
作者简介
张真光,男,2001年生,硕士研究生,研究方向为行星矿物学,E-mail:zhenguangzhang@smail.nju.edu.cn;通讯作者:张爱铖,男,1978年生,教授,主要从事矿物学与地球化学研究,E-mail:aczhang@nju.edu.cn。
