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首页> 外文期刊>Indian medical journal >Cr-rich megacrysts of clinopyroxene and garnet from Lac de Gras kimberlites, Slave Craton, Canada – implications for the origin of clinopyroxene and garnet in cratonic lherzolites
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Cr-rich megacrysts of clinopyroxene and garnet from Lac de Gras kimberlites, Slave Craton, Canada – implications for the origin of clinopyroxene and garnet in cratonic lherzolites

机译：来自Lac de Gras Kimberlites，加拿大奴隶Craton，加拿大的Cr-Rice的Clinopyroxene和石榴石 - 对Clatonic Lherzolites的Clinopyroxene和Garnet起源的影响

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摘要

Kimberlites from the Diavik and Ekati diamond mines in the Lac de Gras kimberlite field contain abundant large (>1?cm) clinopyroxene (Cr-diopside) and garnet (Cr-pyrope) crystals. We present the first extensive mineral chemical dataset for these megacrysts from Diavik and Ekati and compare their compositions to cratonic peridotites and megacrysts from the Slave and other cratons. The Diavik and Ekati Cr-diopside and Cr-pyrope megacrysts are interpreted to belong to the Cr-rich megacryst suite. Evidence for textural, compositional, and isotopic disequilibrium suggests that they constitute xenocrysts in their host kimberlites. Nevertheless, their formation may be linked to extensive kimberlite magmatism and accompanying mantle metasomatism preceding the eruption of their host kimberlites. It is proposed that the formation of megacrysts may be linked to failed kimberlites. In this scheme, the Cr-rich megacrysts are formed by progressive interaction of percolating melts with the surrounding depleted mantle (originally harzburgite). As these melts percolate outwards, they may contribute to the introduction of clinopyroxene and garnet into the depleted mantle, thereby forming lherzolite. This model hinges on the observation that lherzolitic clinopyroxenes and garnets at Lac de Gras have compositions that are strikingly similar to those of the Cr-rich megacrysts, in terms of major and trace elements, as well as Sr isotopes. As such, the Cr-rich megacrysts may have implications for the origin of clinopyroxene and garnet in cratonic lherzolites worldwide.
机译：来自Diavik和Ekati金刚石矿山的金伯利矿，在Lac de Gras Kimberlite领域含有丰富的大（> 1厘米）临床（Cr-Diopside）和石榴石（Cr-Pyrope）晶体。我们向Diavik和Ekati提供了这些甲酰基的第一个广泛的矿物化学数据集，并将它们的组合物与从奴隶和其他胶质剂的裂隙性恒星和甲锭进行了比较。 Diavik和Ekati Cr-Diopside和Cr-Pyrope甲酰丙烯酸酯被解释为属于富含Cr的甲状变基套件。纹理，组成和同位素不平衡的证据表明它们在其宿主金霉素中构成邻烯晶。然而，它们的形成可以与广泛的金伯利岩岩浆制作和伴随其宿主金伯利玻璃爆发之前的伴随的岩白弥赛素相关联。提出，甲酰基的形成可以与失效的金伯拉特有关。在该方案中，通过渗透熔体与周围的耗尽的地幔（最初的Harzburgite）进行富含Cr的富丙烯酸甲纤维。随着这些熔化渗透向外，它们可能会导致将临床和石榴石引入耗尽的地幔，从而形成LOHELZOLITE。这种模型铰链在Lac de Gras的Lachzolitic Closopoce'sens和Garnets的观察中铰接具有与主要和微量元素的富含Cr的富含Cr的富丙烯酸葡萄状的组成，以及Sr同位素。因此，富含Cr的甲状变酰基可能对全球克拉特罗洛丽泽斯的临床起源和石榴石的起源有影响。

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