Apollo 16 - Impact melt sheets, contrasting nature of the Cayley plains and Descartes mountains, and geologic history
Apollo 16 - Impact melt sheets, contrasting nature of the Cayley plains and Descartes mountains, and geologic history
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阿波罗 16 号 - 撞击融化片、凯利平原和笛卡尔山脉的对比性质以及地质历史
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发表时间：
1984
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通讯作者：
R. Schmitt
中科院分区：
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作者：
J. Mckinley;G. J. Taylor;K. Keil;M. Ma;R. Schmitt
阿波罗16号站4号和5号耙样品进行了岩相学、电子探针和中子活化分析。结果与公布的信息（主要和微量元素组成，岩石学信息，年龄测定）nonrake样品站4和5和其他一些阿波罗16号样品的地点相结合。岩性丰度支持这样一种观点（Korotev，1981），即阿波罗16号上土壤成分的变化是由5号站土壤代表的成分与组成上类似于二粒角砾岩（4号站土壤）或碎屑角砾岩（1号、2号和11号站）的成分混合的结果。迪米特角砾岩，由于其有限的发生，显然不是凯莱或笛卡尔地层的组成部分：它们是由南射线陨石坑贡献的表面材料，可能是从这两个地层下面挖掘的事件。辉石，橄榄石，并共存的斜长石组合物内的斜长岩部分的二云母角砾岩桥梁之间的差距差距富镁和铁斜长岩领域。相关堆晶和麻粒碎屑的分析表明，它们是中间物质的来源;因此，复混合角砾岩斜长岩是复混合岩，而不是原始的含铁斜长岩。阿波罗16号撞击熔融岩石的成分表明了一些成分集群。判别和聚类分析的成分数据证实了这些集群的存在和强度，年龄测定和Ir/Au比在每个组。三个集群中的每一个都代表了阿波罗16号区域的一次撞击事件。岩石学信息和年龄测定表明，dimict角砾岩形成约3.92 b.y.前Nectaris事件发生在3.84 ~ 3.92 b.y.之间。凯莱平原是在公元前3.84亿年之后的某个时候由于公元前事件而沉积的。
Apollo 16 stations 4 and 5 rake samples were examined petrographically and by electron microprobe and INAA. Results were combined with published information (major and trace element compositions, petrologic information, and age determinations) for nonrake samples from stations 4 and 5 and some other Apollo 16 sample localities. Lithologic abundances support the idea (Korotev, 1981) that the variation of soil compositions at Apollo 16 is a result of mixing between a component represented by station 5 soil and components much like either the dimict breccias (station 4 soils) or feldspathic fragmental breccias (stations 1, 2, and 11) in composition. Dimict breccias, because of their restricted occurrence, are apparently not a constituent of either the Cayley or Descartes formations: they were contributed to the surface materials by South Ray crater and were probably excavated from beneath both formations by this event. Pyroxene, olivine, and coexisting plagioclase compositions from within the anorthosite portions of dimict breccias bridge the gap between the Mg-rich and ferroan anorthosite fields. Analyses from associated cumulate and granulitic clasts indicate that they are the source of the intermediate material; dimict breccia anorthosites are thus polymict rocks, not pristine ferroan anorthosite. Compositions of Apollo 16 impact melt rocks suggest a number of compositional clusters. Discriminant and cluster analyses of compositional data confirm the existence and strength of these clusters, as do age determinations and Ir/Au ratios within each group. Each of three clusters represents an impact event in the Apollo 16 region. Petrologic information and age determinations indicate that dimict breccias formed approximately 3.92 b.y. ago. The Nectaris event occured between 3.84 and 3.92 b.y. ago, and the Cayley plains were deposited as a result of the Imbrium event sometime later than 3.84 b.y.