摘要
NWA 16071是一块新发现的橄辉无球粒陨石,主要由橄榄石和易变辉石组成,矿物颗粒之间有少量碳质、金属和硫化物等填隙物。NWA 16071陨石具有两种结构区域:一种是粒状结构区域,主要由粗粒橄榄石和易变辉石组成;另一种是嵌晶结构区域,常见易变辉石主晶包裹球形橄榄石和金属球。样品中的橄榄石广泛发育宽20~50μm还原边,边部较核部富镁;辉石主要为易变辉石(En_(83.7)Fs_(8.9)Wo_(7.4)),少量顽火辉石(En_(96.5)Fs_(2.6)Wo_(0.9))出现在橄榄石边部;金刚石呈不规则粒状分布在石墨中;大量方石英分布在褐铁矿脉中。岩石学和矿物化学特征表明,NWA 16071陨石是一块具有嵌晶结构的橄榄石-易变辉石型橄辉无球粒陨石,化学成分落在Ⅲ型低FeO/MgO(高Fo)群范围内。拉曼光谱表明,石墨具有较低的结晶程度,金刚石为冲击成因。硅酸盐矿物普遍存在冲击裂隙、橄榄石发生面状变形和金刚石的出现,表明样品的冲击程度在S5以上。嵌晶结构、陨硫铬铁矿出溶和方石英的存在表明冲击后的温度在1500~1700℃,高温和退火过程消除了部分冲击变质特征。
NWA 16071 is a newly discovered ureilite,primarily composed of olivine and pigeonite,with small amounts of carbonaceous materials,metals,and sulfides filling between mineral particles.This meteorite exhibits two structural areas.One is granular texture area,consisting mainly of coarse-grained olivine and pigeonite.The other one is poikilitic texture area,where it is common to find pigeonite host crystals enclosing spherical olivine and metallic spheres.Olivines in the sample widely displays reduction rims with a thickness of 20 to 50μm,where the rims are richer in Mg than in cores.Pyroxene is predominantly pigeonite(En_(83.7)Fs_(8.9)Wo_(7.4)),with small amounts of enstatite(En_(96.5)Fs_(2.6)Wo_(0.9))appearing at the olivine rims.Diamonds are irregularly granular and distributed within graphite,while a large amount of cristobalite is found in limonite veins.Petrological and mineral chemistry characteristics indicate that NWA 16071 is an olivine-pigeonite ureilite with poikilitic texture,and its chemical composition falls within the range of low FeO/MgO(high-Fo)Ⅲ-type.Raman spectra studies reveal that graphite has a low degree of crystallization,and diamond is of shock origin.Silicate minerals ubiquitously exhibit shock fractures,the planar deformation of olivine and the presence of diamonds suggest that the shock level of the sample is above S5.Poikilitic texture,exsolution of daubreelite,and presence of cristobalite indicate that the temperature after the shock is between 1500 and 1700°C,with high temperatures and annealing processes eliminating some shock metamorphic features.
作者
杨宝琛
缪秉魁
夏志鹏
YANG Baochen;MIAO Bingkui;XIA Zhipeng(Institution of Meteorites and Planetary Materials Research,Guilin University of Technology,Guilin 541006,China;Key Laboratory of Planetary Geological Evolution in Guangxi Universities,Guilin University of Technology,Guilin 541006,China;Guangxi Key Laboratory of Exploration for Hidden Metallic Ore Deposits,Guilin University of Technology,Guilin 541006,China)
出处
《桂林理工大学学报》
北大核心
2025年第1期30-42,共13页
Journal of Guilin University of Technology
基金
国家自然科学基金项目(42403041)
广西科技基地与人才专项(桂科AD23026084)
广西自然科学基金项目(2022GXNSFAA035567,2021GXNSFBA075061)。
