A study of the early solar system through systematic analysis of Antarctic meteorites

在δ^<17>O-δ^<18>O空间中，地球物质的氧同位素比值沿δ^<17>O=0.52×δ^<18>O的质量依赖线绘制，而陨石等地外物质的氧同位素比值则沿陨石类型的质量依赖线绘制。地外物质可分为依赖质量和不依赖质量两类。这反映了早期太阳系中引起同位素不均匀性的过程的发生。因此，陨石的氧同位素特征为了解早期太阳系过程提供了重要的关键。在美国国家极地研究所最近的考察中，在南极洲发现了13000多颗陨石，其中大部分尚未进行氧同位素比分析。在本研究中，我们分析了以下几种南极陨石的氧同位素比值：CO3(ALH-77003,ALH-77307,A-881632,Y-791717,Y-81020,Y-82050), CM2(B-7904,Y-791198,Y-82054,Y-86720,CK5-6(A-881551,Y-82102, uilite (A-881931,Y-74123,Y-790981,Y-791538), Diogenite(Y-74013), eucite (Y-790266,Y-791195,Y-791826,Y-791960,A-880702,A-880761,A-881388), EH6（Y-793225,Y-8414）。除了上面提到的南极陨石外，我们还分析了最近在各地发现的一些陨石。它们包括来自东田、广岛、火星（SNCs）和北非（nwa系列）的陨石。大多数样品在Clayton（1993）所分析的已知陨石群的区域，但也有一些在新的未知区域。这些陨石需要进一步的化学、矿物学和岩石学研究。在研究过程中，我们精确测定了VSMOW、SLAP、NBS28石英、NBS30黑云母、UWG2石榴石、San Carlos橄榄石等国际标准材料的δ^<17>O和δ^<18>O值。这为在SMOW尺度上报道陨石氧同位素比值提供了依据。

The oxygen isotopic ratios of terrestrial materials plot along a mass-dependent line of δ^<17>O=0.52×δ^<18>O in the δ^<17>O-δ^<18>O space, whereas those of extraterrestrial materials such as meteorites plot off the mass-dependent line depending on the types of meteorites. The extraterrestrial materials can be divided into mass-dependent and mass-independent groups. This reflects the occurrence of the processes that induced isotopic heterogeneity in the early solar system. Thus, the oxygen isotopic signatures of meteorites give an essential key to understand the early solar system processes. More than 13,000 meteorites have been found from Antarctica during the recent expeditions by National Polar Research Institute, most of them are yet to be analyzed for oxygen isotopic ratios.In the present study, we have analyzed the oxygen isotopic ratios of the following types of Antarctic meteorites : CO3(ALH-77003,ALH-77307,A-881632,Y-791717,Y-81020,Y-82050), CM2(B-7904,Y-791198,Y-82054,Y-86720,CK5-6(A-881551,Y-82102, Ureilite(A-881931,Y-74123,Y-790981,Y-791538), Diogenite(Y-74013), Eucrite(Y-790266,Y-791195,Y-791826,Y-791960,A-880702,A-880761,A-881388), EH6(Y-793225,Y-8414). In addition to the above Antarctic meteorites, some recent falls and finds from various places have also been analyzed. They include meteorites from Towada, Hiroshima, Mars (SNCs), and North West Africa(NWA-series). Most of the samples analyzed plot in the regions of known meteorite groups by Clayton (1993), but some plot in a new and unkown region. These meteorites need further studies for chemical, mineralogical and petrological examinations.During the course of this study, we have determined precise δ^<17>O and δ^<18>O values of the international standard materials such as VSMOW,SLAP,NBS28 quartz, NBS30 biotite, UWG2 garnet, San Carlos olivine, etc. This gave a basis for reporting the oxygen isotopic ratios of meteorites in the SMOW scale.