GRV 050202:一块含难熔包体与小行星表土角砾的普通球粒陨石

GRV 050202: An ordinary chondrite contains refractory inclusions and regolith breccia

GRV 050202是中国南极科考队在南极格罗夫山地区发现的一块普通球粒陨石,为了了解其性质特征,对该陨石光薄片进行了光学显微镜、扫描电子显微镜观察及电子探针分析.结果显示,该陨石由非平衡区域和平衡区域组成,非平衡区域岩石类型为3.6型,平衡区域为5型,两区域均为L群,该陨石冲击变质程度和风化等级分别为S1和W1.此外,该陨石非平衡区域包含有混染外来物质的表土角砾及普通球粒陨石中少见的两个富钙铝难熔包体(Calcium-Aluminum Refractory Inclusions,CAIs)和一个蠕虫状橄榄石集合体(Amoeboid Olivine Aggregate,AOA). GRV 050202中的表土角砾在基质粒度、碎屑矿物特征、结构成分及表面撞击产物等方面与非平衡型普通球粒陨石中的基质及其他角砾具有差异.难熔包体中方钠石、霞石及磷灰石等次生矿物相指示,L群普通球粒陨石母体经历过含P流体蚀变.

GRV 050202 is an ordinary chondrite collected by the Chinese Antarctic Research Expedition(CHINARE) in the Grove Mountains,Antarctic. In order to understand its properties,we have conducted research on the thin section of this meteorite using optical microscopy,scanning electron microscopy and electron probe microanalysis. The results show that GRV 050202 is composed of an unequilibrated area and an equilibrated area. The petrologic type of the unequilibrated area is type 3.6,while the equilibrated area is type 5,and both of which are divided into L group. The shock stage and weathering grade of GRV 050202 are S1 and W1,respectively. In addition,the unequilibrated area contains regolith breccia contaminated with foreign materials,two calcium-aluminum refractory inclusions(CAIs) and an amoeboid olivine aggregate(AOA) which are rare in ordinary chondrites. The regolith breccia in GRV 050202 differs from the matrix and other breccias in unequilibrated ordinary chondrites in terms of its matrix particle size,detrital mineral characteristics,structure,composition,and surface impact products. Secondary mineral phases such as sodalite,nepheline,and apatite in the refractory inclusions indicates that the parent body of the L group chondrites has experienced P-bearing fluid alteration.