Geochemistry of diogenites: Still more diversity in their parental melts
Geochemistry of diogenites: Still more diversity in their parental melts
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DOI：
10.1111/j.1945-5100.2008.tb00641.x
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发表时间：
2008-11-01
影响因子：
2.2
通讯作者：
Franchi, I. A.
中科院分区：
文献类型：
--
作者：
Barrat, J. A.;Yamaguchi, A.;Franchi, I. A.
本文报道了18种闪长岩的常量和微量元素丰度，以及其中3种闪长岩的O同位素。我们的分析显著扩展了闪长岩的组成范围，无论是在富镁方面（例如，陨石山[MET] 00425，MgO = 31.5重量%）和贫镁品种（例如，Dholar 700，MgO = 23重量%）。宽范围的亲铁和亲铜元素丰度很好地解释了不均匀分布的硫化物或金属颗粒内的分析芯片的存在。闪长岩中不相容元素的行为更为复杂，表现为稀土元素模式的多样性。除了少数含有微量磷酸盐的闪长岩样品，其不相容元素丰度与斜方辉石不同，闪长岩中不相容元素丰度的范围，特别是Dy/Yb比值的范围最好由其母体熔体的多样性来解释。我们估计的FeO/MgO比值的闪长岩母体熔体的范围从约1.4至3.5，因此在很大程度上重叠的非累积eucrites获得的值。我们的研究结果排除了通常被接受的观点，即所有的闪长岩形成于母岩熔体更原始的比eucrites在岩浆海洋的结晶。相反，他们指出了一个更复杂的历史，并建议闪长岩来自于岩浆海洋形成的堆晶重熔产生的液体。
We report oil the major and trace element abundances of 18 diogenites, and O-isotopes for 3 of them. Our analyses extend significantly the diogenite compositional range, both in respect of Mg-rich (e.g., Meteorite Hills [MET] 00425, MgO = 31.5 wt%) and Mg-poor varieties (e.g., Dholar 700, MgO = 23 wt%). The wide ranges of siderophile and chalcophile element abundances are well explained by the presence of inhomogeneously distributed Sulfide or metal grains within the analyzed chips. The behavior of incompatible elements in diogenites is more complex, as exemplified by the diversity of their REE patterns. Apart from a few diogenite samples that contain minute amounts of phosphate, and whose incompatible element abundances are unlike the orthopyroxene ones, the range of incompatible element abundances, and particularly the range of Dy/Yb ratios in diogenites is best explained by the diversity of their parental melts. We estimate that the FeO/MgO ratios of the diogenite parental melts range from about 1.4 to 3.5 and therefore largely overlap the values obtained for non-cumulate eucrites. Our results rule out the often accepted view that all the diogenites formed from parental melts more primitive than eucrites during the crystallization of a magma ocean. Instead, they point to a more complex history, and suggest that diogenites were derived from liquids produced by the remelting of cumulates formed from the magma ocean.