Abstract

Comprehensive studies of peridotitic xenoliths from the Udachnaya kimberlite (Yakutian diamond province, Siberian craton) confirm that garnet shows inverse correlation of its volumetric percentage with its Cr₂O₃ contents in refertilizated peridotites, but no such correlation is observed in depleted peridotites. The correlation relationship plots as an isosceles hyperbola, which is consistent with the existing knowledge of origin of refertilized peridotite. The bulk content of aluminum is proportional to the garnet percentage both in depleted and refertilized peridotites, but Al₂O₃ in the rock correlates with Cr₂O₃ in garnet only in the refertilized varieties, while the two parameters are independent in depleted mantle rocks. According to the modeling of refertilization-related composition changes in the Udachnaya peridotites, garnet percentages are directly proportional to the amount of clinopyroxene (Gnt = 0.879*Cpx + 0.022, R² = 0.78) and inversely proportional to that of olivine (Gnt = 0.026/Ol^3.141, R² = 0.79). As the shares of Gnt and Cpx increase from minimum values, orthopyroxene first increases (to 0.16) and then decreases since 0.65 Ol, 0.09 Cpx, and 0.10 Gnt. This model can constrain the place of the parent rock in the refertilization series knowing Cr₂O₃ contents in separate garnet grains. The average refertilization degree of lithospheric mantle in the region estimated from the compositions of more than 800 garnet xenocrysts in the Udachnaya kimberlite is expressed in the rock modal composition as: Ol = 0.72, Opx = 0.15, Gnt = 0.07, and Cpx = 0.06 (median values).

中文翻译：

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来自 Udachnaya 金伯利岩（西伯利亚克拉通）的捕虏体和捕虏晶的岩石圈再肥化趋势

摘要

对 Udachnaya 金伯利岩（雅库特钻石省，西伯利亚克拉通）橄榄岩包体的综合研究证实，石榴石的体积百分比与其在再利用橄榄岩中的Cr ₂ O ₃含量呈负相关，但在贫化橄榄岩中未观察到这种相关性。相关关系绘制为等腰双曲线，与现有的再肥橄榄岩成因认识一致。在贫化橄榄岩和再肥橄榄岩中，铝的整体含量与石榴石百分比成正比，但岩石中的Al ₂ O ₃与 Cr ₂ O _{3 相关}在石榴石中仅在重新施肥的品种中，而在耗尽的地幔岩石中这两个参数是独立的。根据 Udachnaya 橄榄岩中与再肥有关的成分变化的模型，石榴石百分比与单斜辉石的数量成正比 (Gnt = 0.879*Cpx + 0.022, R ² = 0.78)，与橄榄石的数量成反比 (Gnt = 0.026) /O1 ^3.141，R ² = 0.79)。随着 Gnt 和 Cpx 的份额从最小值增加，斜方辉石首先增加（到 0.16），然后从 0.65 Ol、0.09 Cpx 和 0.10 Gnt 开始减少。该模型可以在已知 Cr ₂ O _{3 的情况}下约束母岩在再肥系列中的位置单独的石榴石颗粒中的含量。根据Udachnaya金伯利岩中800多颗石榴石异种晶的成分估计，该地区岩石圈地幔的平均再肥化程度在岩石模态成分中表示为：Ol = 0.72，Opx = 0.15，Gnt = 0.07，Cpx = 0.06（中值）。