Abstract

Olivine is the most common rock-forming mineral of the majority of the lithospheric mantle rocks beneath ancient cratons. This study provides the information about an epigenetic olivine in a lherzolite xenolith from the Udachnaya kimberlite pipe (Siberian craton), which is characterized by lower Mg# compared to the rock-forming one (Mg# = 87.4). The iron-rich olivine has been observed in the epigenetic mineral assemblage that forms a kelyphite shell around the rock-forming garnet. Olivine from the kelyphite shell occurs as both homogeneous grains (Mg# = 84.3–85.9) and zoned grains (Mg# = 85.1–87.5). The major and minor elements asymmetric zoning patterns have been found in the rock-forming olivine grains at the contact with the kelyphite shell. These olivine grains have an outer low Mg# (up to 85.9) zone at the contact with the kelyphite shell as the epigenetic olivine grains in the kelyphite shell. We suggest that the iron-rich epigenetic olivine was produced as the result of a reaction between the rock-forming garnet and the primitive kimberlite melt. During this reaction, a hybrid melt was formed in the interstitial space. The hybrid melt was iron-enriched relative to the kimberlite melt. The source of iron for the micro-portions of the interstitial hybrid melt was the rock-forming garnet.

中文翻译：

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来自 Udachnaya 金伯利岩管（西伯利亚克拉通）的 Lherzolite Xenolith 中后生富铁橄榄石的起源

摘要

橄榄石是古代克拉通下方大部分岩石圈地幔岩石中最常见的造岩矿物。这项研究提供了关于来自 Udachnaya 金伯利岩管（西伯利亚克拉通）的锂辉石捕虏体中的后生橄榄石的信息，其特征是与形成岩石的岩石相比（Mg# = 87.4）具有较低的 Mg#。已经在后生矿物组合中观察到富含铁的橄榄石，该组合在岩石形成的石榴石周围形成了石长石壳。来自钾长石壳的橄榄石以均质晶粒 (Mg# = 84.3–85.9) 和分区晶粒 (Mg# = 85.1–87.5) 的形式出现。在与石长石壳接触处的成岩橄榄石颗粒中发现了主要和次要元素不对称的分区模式。这些橄榄石颗粒具有较低的外部 Mg#（高达 85。9) 与钾长石壳接触的区域，作为石长石壳中的后生橄榄石颗粒。我们认为富含铁的后生橄榄石是岩石形成石榴石与原始金伯利岩熔体之间反应的结果。在该反应期间，在间隙空间中形成混合熔体。相对于金伯利岩熔体，混合熔体富含铁。间隙混合熔体的微观部分的铁源是岩石形成的石榴石。