Mineral chemistry and the petrogenesis of eucrites: II. Cumulate eucrites
Mineral chemistry and the petrogenesis of eucrites: II. Cumulate eucrites
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DOI：
10.1016/s0016-7037(96)00411-5
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发表时间：
1996-11
影响因子：
5
通讯作者：
W. Hsu;G. Crozaz
中科院分区：
文献类型：
--
作者：
W. Hsu;G. Crozaz
本文对Moama和Moore县两种堆积长辉长岩的正辉长岩、辉长岩片层和斜长石中的稀土元素和其他微量元素进行了离子探针研究，以重新评价堆积长辉长岩与非堆积长辉长岩之间以及堆积长辉长岩之间的关系。两种陨石中辉石和斜长石的主、次、微量元素含量均高于非堆积长长岩，且摩尔县的微量元素和微量元素含量高于莫阿马县。虽然亚固体平衡抹去了原始火成岩分带，但对矿物的稀土元素模式没有影响。Moama和Moore县鸽长石和斜长石的LREE/HREE比值均高于非堆积长长岩。这表明堆积长长岩来源于稀土分馏型熔体，因此与非堆积长长岩无关。此外，由主微量元素推断的分数结晶程度的不一致以及鸽岩和斜长石中记录的LREE/HREE比值的差异也表明Moama县和Moore县不是在相同的分数结晶序列中形成的。这项研究证实了Ma和Schmitt（1979）早期的观察和结论，并对流行的模型提出了问题。
We carried out an ion microprobe study of REEs and other selected trace and minor element concentrations in orthopyroxene, augite lamellae, and plagioclase of two cumulate eucrites Moama and Moore County in order to reevaluate the relationships between cumulate and noncumulate eucrites and among cumulate eucrites. Pyroxene and plagioclase in these two meteorites are more homogeneous in major, minor, and trace elements than in noncumulate eucrites, and trace and minor element concentrations in Moore County are higher than in Moama. Although subsolidus equilibration erased and original igneous zoning, it did not affect the REE patterns of these minerals. Both pigeonite and plagioclase of Moama and Moore County have higher LREE/HREE ratios than those phases in noncumulate eucrites. This indicates that cumulate eucrites derived from melts with fractionated REE patterns and, thus are not related to noncumulate eucrites. In addition, the inconsistency between degrees of fractional crystallization deduced from major and trace elements and the differences of LREE/HREE ratios recorded in pigeonite and plagioclase also suggest that Moama and Moore County did not form in the same fractional crystallization sequence. This study confirms earlier observations and conclusions of Ma and Schmitt (1979) and poses problems for prevalent models.