Petrological Study of Martian Meteorites

对火星陨石进行了详细的岩石学研究。特别强调要研究火星堆积型和玄武岩型雪角闪石中岩浆包裹体的赋存状态和成因。火星陨石中的岩浆包裹体非常小，直径约10-100微米，产于斑晶矿物(橄榄石和辉石)中。除了火成岩玻璃外，它们主要由橄榄石、法赛石、斜长石、硅石矿物或钾长石组成，非常重要，因为它们拥有关于其母岩浆和形成条件的直接信息。两个二辉橄榄岩(累积型)闪锌矿(ALH77005和Yamato-793605)具有几乎相同的矿物组合，尽管两者的岩性略有不同。它们可能是由火星母岩浆产生的，其化学成分类似于典型的玄武岩陨石(谢尔果蒂陨石)。二辉橄榄岩陨石中橄榄石中的岩浆包裹体与辉石中的岩浆包裹体具有不同的矿物组合和矿物组成。这种差异可能与它们所处的岩浆分离结晶阶段不同有关。在这两个二辉橄榄质雪榴石中发现了钾长石，其共存岩浆的水蒸气压力估计不到1千巴。对玄武岩(大G735等)中的岩浆包裹体也进行了详细的调查。它们的矿物组合与二辉橄榄石中的矿物组合不同，似乎是在偏稳定的条件下结晶的。DaG735可能形成为累积玄武岩性，在玄武岩熔体中含有大量斑晶橄榄石。

The petrological study on Martian meteorites was carried out in details. Especially it was stressed to investigate the occurrence and to clarify the genesis of magmatic inclusions that occur in Martian cumulative and basaltic shergottites. Magmatic inclusions in Martian meteorites are very small with about 10-100 micrometers across, and occur in phenocrystic minerals (olivine and pyroxene). They consist mainly of olivine, fassaite, plagioclase, a silica mineral, or Kaersutite in addition to igneous glass, and are very important because they have direct information on their parent magmas and formational conditions. Two lherzolitic (cumulative) shergottites (ALH77005 and Yamato-793605) have a nearly same mineral assemblage, although the two show slightly different lithologies. They may have been produced from Martian parent magmas that have chemical compositions similar to a typical basaltic meteorite (the shergotty meteorite). It was also clarified that magmatic inclusions occurring in olivine in the lherzolitic meteorites are different in mineral assemblages and mineral compositions from those in pyroxene. This difference may be due to their different stages of magmatic fractional crystallization. Kaersutite was found o to occur in the two lherzolitic shergottites, and the water vapor pressure of their coexisting magmas was estimated to be less than 1 kilo bars. Magmatic inclusions in basaltic shergottites (DaG735, and so on) also were surveyed in details. They differ in mineral assemblage from those in the lherzolitic shergottites, and seem to have crystallized on a meta-stable condition. The DaG735 may have formed as a cumulative basaltic lithology, which contains a large number of phenocrystic olivine in a basaltic melt.