Petrology of types 4–6 carbonaceous chondrites
Petrology of types 4–6 carbonaceous chondrites
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4-6 型碳质球粒陨石的岩石学
DOI：
10.1029/jb090is02p0c699
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发表时间：
1985
影响因子：
--
通讯作者：
Jeffrey Taylor
中科院分区：
文献类型：
--
作者：
E. Scott;Jeffrey Taylor
我们研究了Coolidge、Karoonda和Pecora Escarpment 82500三种碳质球粒陨石的岩石学，并将它们与已发表的其他已知变质C球粒陨石Yamato 6903和Mulga(West)的描述进行了比较。除柯立芝外，所有岩石都有丰富的基质，通常为80vol%，主要由均一的橄榄石组成，Fa 29-33，以及令人惊讶的不均一斜长石，主要是20-75。它们不透明的矿物学特征表明变质过程中的氧逸度很高：金属Fe、Ni和硫铁矿稀少，磁铁矿和镍黄铁矿丰富，伴生磁黄铁矿、黄铜矿和黄铁矿。可能由于基质丰度较低，柯立芝含有更多的还原矿物：金属Fe、Ni和具有Fa 14的橄榄石。所有C4-6球粒陨石的性质似乎与C3类前体变质的起源一致，其过程类似于普通球粒陨石母体或行星体中的变质过程。然而，与普通球粒陨石母体不同，4-6类物质在CV3母体中与类型3物质不能很好地混合。可以想象，C4-6球粒陨石来自一个或多个独立的母体。
We have studied the petrology of three type 4 carbonaceous chondrites, Coolidge, Karoonda, and Pecora Escarpment 82500, which was previously classified as an LL6 chondrite, and compared them to published descriptions of the other known metamorphosed C chondrites, Yamato 6903 and Mulga (west). All except Coolidge have abundant matrix, typically 80 vol %, composed largely of homogeneous olivine, Fa 29–33, and surprisingly heterogeneous plagioclase, mostly An 20–75. Their opaque mineralogy indicates high oxygen fugacities during metamorphism: metallic Fe,Ni and troilite are rare, and magnetite and pentlandite are abundant with accessory pyrrhotite, chalcopyrite, and pyrite. Possibly because of a lower matrix abundance, Coolidge has more reduced minerals: metallic Fe,Ni and olivine with Fa 14. The properties of all C4–6 chondrites appear to be consistent with an origin by metamorphism of C3-like precursors by processes analogous to those operating in ordinary chondrite parent bodies or planetesimals. However, type 4–6 material was not well mixed with type 3 material in the CV3 parent body, as it was in the ordinary chondrite parent bodies. Conceivably, C4–6 chondrites come from one or more separate parent bodies.