南极格罗夫山陨石的磁化率  

Magnetic susceptibility of meteorites collected in Grove Mountains, Antarctica

作　　者：罗红波[1,2,3] 林杨挺[2] 胡森[2,3] 刘焘[2,3] 冯璐[2,3] 缪秉魁[2,4] 

机构地区：[1]中国科学院地球化学研究所,贵阳550002 [2]中国科学院地质与地球物理研究所地球深部重点实验室,北京100029 [3]中国科学院研究生院,北京100049 [4]桂林工学院广西地质工程中心重点实验室,桂林541004

出　　处：《岩石学报》2009年第5期1260-1274,共15页Acta Petrologica Sinica

基　　金：中国科学院知识创新方向性项目( kzcx2-yw-110);国际极地年中国行动计划资助

摘　　要：我国在南极格罗夫山发现并收集到大量南极陨石,需要一种无损、快速简单的分类方法。陨石磁化率(χ)的主要贡献是其中的铁镍金属,因而有可能成为一种简便有效的分类参数。同时,磁化率是陨石的一个重要物理参数。我们在国内首次开展陨石磁化率的研究,通过对模拟陨石磁化率样品的测量,证明可以通过不同取向的测量平均,将样品的大小和形状等几何因素的影响减小在仪器的测量精度范围之内。完成了首批613块南格格罗夫山陨石的磁化率测量,除普通球粒陨石外,还包括火星陨石、灶神星陨石、碳质球粒陨石、中铁陨石、橄榄陨铁、橄辉无球粒陨石等特殊类型。根据质量磁化率,可以划分大部分H、L、LL群陨石。特别重要的是,磁化率对于划分非平衡的普通球粒陨石化学群提供了更为可靠的参数。格罗夫山H群陨石的磁化率分布与南极其他地区的陨石十分相似,二者相对降落型陨石均向低质量磁化率方向平移0.2(10gχ,10^(-9)m^3/kg),反映了风化作用对南极陨石磁化率的平均影响程度;格罗夫山L群陨石的质量磁化率分布同样较降落型陨石偏低0.2左右,但南极其他地区的陨石与沙漠陨石的磁化率分布相似,二者均更为离散和偏低,可能反映了不同的风化程度。Discovery of a large number of meteorites from the Grove Mountains (GRV) region, Antarctica, demands a non-destructive and efficient method of classifying meteorites. Magnetic susceptibility (chi) of meteorites was mainly contributed by metallic Fe-Ni, hence a potentially important criterion of classification of meteorites. In addition, magnetic susceptibility is a fundamental parameter of meteorites. In this paper we report the first measurements of magnetic susceptibility of Grove Mountains meteorites. Experiments on simulation samples demonstrated that deviation of magnetic susceptibility measurement due to various sizes and shapes of the samples is less than 1%, within the analytical precision. Magnetic susceptibility of the first classified 613 Grove Mountains meteorites was measured, including martian meteorites, eucrites, carbonaceous chondrites, ureilites, mesosiderites and pallasite. Most ordinary chondrites of H, L and LL groups can be classified according to magnetic susceptibility. Moreover, magnetic susceptibility is more reliable for classification of unequilibrated ordinary chondrites. The distribution pattern of magnetic susceptibility of H-group of Grove Mountains meteorites is nearly identical to that of other Antarctic meteorites, both with the mass normalized magnetic susceptibility (log chi, 10(-9) m(3)/kg) lower by 0.2 than that of meteorite falls, indicative of terrestrial weathering effects of Grove Mountains meteorites. Magnetic susceptibility of L-group of Grove Mountains meteorites also shifts to lower values by 0.2 as H-group. In contrast, L-group of other Antarctic and desert meteorites shows scattered distribution patterns, probably indicative of various weathering degrees.

关 键 词：南极陨石 球粒陨石 陨石分类 磁化率 风化作用 

分 类 号：P691[天文地球—地质学]