富橄榄石的富Ca,Al组分集合体的矿物岩石学特征及对比研究

富Ca,Al包体、球粒和蠕虫状橄榄石集合体都是早期星云事件的产物。本文探讨了4个富橄榄石的富Ca,Al组分集合体的矿物岩石学特征,并对它们进行了对比。矿物岩石学特征表明含橄榄石边的富尖晶石—辉石型包体和富Ca,Al组分蠕虫状橄榄石集合体都属于星云直接凝聚的产物,而富钙长石—橄榄石型包体(POI)和富Ca,Al组分球粒经历过熔融结晶过程。矿物模式组成表明POI包体和富Ca,Al组分球粒可能是认识典型富Ca,Al包体与球粒之间相互关系的钥匙。蠕虫状橄榄石集合体GRV022459-2C1中尖晶石普遍具有高的FeO含量,表明其蚀变发生于高氧逸度的星云环境。球粒与粗粒富Ca,Al包体可能属于同一热事件的产物,粗粒富Ca,Al包体形成于富Ca,Al矿物富集的区域,Mg,Fe质硅酸盐球粒形成于富Ca,Al矿物缺失的区域,POI包体和富Ca,Al组分球粒可能形成于上述两个区域之间的过渡区域。

Comparation of petrography and mineral chemistry characteristics among olivine and Ca,Al-rich assemblages

Ca-, Al-rich inclusions, chondrules and amoeboid olivine aggregates are the early assemblages of the solar nebula.4 olivine and Ca, Al-rich assemblages were studied to compare with their petrography and mineral chemistry. The petrography and mineral chemistry characteristics argues that spinel-pyroxene-rich inclusion embedded in olivine and Ca, Al-rich amoeboid olivine aggregates are likely assemblages of solar nebular condensates.The plagioclase-olivine inclusions(POIs)and Ca-, Al-rich chondrules were crystallized from melts. The characteristics of mineral modal compositions of POIs and Ca-, Al-rich chondrules argues they probably represent intermediate assemblages between typical refractory inclusions and chondrules.Spinel in amoeboid olivine aggregates(GRV022459-2C1)is the most remarkably FeO-rich in all assemblages, and it indicates alteration of the aggregate happened under high oxygen fugacity.Chondrules and coarse-grained Ca-, Al-rich inclusions are probably crystallized from melt in the same affair.The coarse-grained Ca-, Al-rich inclusions form probably the reservoir of Ca-, Al-rich prior matters, and Mg, Fe silicate chondrules form in the reservoir of Ca-, Al-poor prior matters.POIs and Ca-, Al-rich chondrules form the district between coarse-grained inclusions and Mg, Fe silicate chondrules.