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YOUNG PERIDOTITIC DIAMONDS FROM THE MIR KIMBERLITE PIPE

机译：MIR金伯利岩管的年轻橄榄石

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MINERAL inclusions in diamonds contained in the explosive volcanic rocks known as kimberlites provide an important record of geochemical processes in the continental lithosphere. Samarium-neodymium model ages as old as 3.2 Gyr have been obtained for many peridotitic mineral inclusions(1-4), pointing to the great antiquity of the host 'peridotitic' diamonds (relative to the age of the associated kimberlites) and hence an extended period of residence in the sub-continental mantle. Here we report trace-element data from garnet inclusions in peridotitic diamonds from the Mir kimberlite pipe, Siberia, which appear to be inconsistent with this interpretation. The heterogeneous distribution of tine trace elements both within and among discrete garnets from single diamonds are indicative of rapid crystal growth leading to solid-melt disequilibrium on a local scale. The conditions for survival of these heterogeneities within individual garnet crystals are tightly constrained by diffusion kinetics, which would rapidly homogenize the trace-element distributions in the sub-continental mantle. Thus, while it seems clear that peridotitic diamonds and their inclusions are derived from ancient lithospheric material, our data require that they crystallized shortly before the eruption of the kimberlite 360 Myr ago(5). [References: 21]
机译：爆炸性火山岩（称为金伯利岩）中所含钻石的矿物夹杂物为大陆岩石圈的地球化学过程提供了重要记录。许多橄榄石矿物包裹体都获得了年龄高达3.2吉尔的mar钕模型（1-4），这表明宿主``橄榄石''钻石的古代（相对于相关的金伯利岩的年龄）并因此得到了扩展在次大陆幔中居住的时期。在这里，我们报告了西伯利亚Mir金伯利岩管中橄榄石钻石中的石榴石包裹体中的微量元素数据，这似乎与这种解释不一致。来自单个钻石的离散石榴石内部和之中的叉齿痕量元素的异质分布表明晶体快速生长，导致局部范围的固熔不平衡。石榴石晶体中这些异质性的生存条件受到扩散动力学的严格限制，扩散动力学将迅速使次大陆幔中的痕量元素分布均匀化。因此，虽然似乎很清楚橄榄石钻石及其包裹体是从古老的岩石圈物质中提取出来的，但我们的数据要求它们在金伯利岩360 Myr爆发之前不久就结晶了（5）。 [参考：21]

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