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首页> 外文期刊>Contributions to Mineralogy and Petrology >Experimental study of clinopyroxenite partial melting and the origin of ultra-calcic melt inclusions
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Experimental study of clinopyroxenite partial melting and the origin of ultra-calcic melt inclusions

机译：斜辉石部分熔融的实验研究及超钙熔体包裹体的成因

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Ultra-calcic melt inclusions (UCMI: CaO > 13.5 wt percent and/or caO/Al_2O_3 > 0.9) are magnesian and near-primary liquids trapped in volcanic phenocrysts from mid-ocean ridges, arcs, back-arcs, and ocean islands, UCMI can be subdivided into two classes based on tectonic association and degree of silica saturation: those from arcs are nepheline normative and those from all other localities (silicic UCMI) are hypersthene normative. Silicic UCMI share a number of common features, including primitive host minerals, low alkali contents, and variable ratios of K_2O/TiO_2 ranging to high values. Their compositions are not easily derived by partial melting of mantle lherzolite. Accordingly, we have performed a series of partial melting experiments on three clinopyroxenite compositions at 1.0 to 2.0 GPa to investigate the role of partial melting of clinopyroxene-rich lithologies in silicic UCMI genesis. Estimated solidus temperatures for all three compositions are similar to those of normal peridotites, but 1.0 GPa isobaric melt productivities are higher for clinopyroxenite than for peridotite. High degree partial melts of the clinopy-roxenites are ultra-calcic and have similarities to silicic UCMI, but the experiments produce ultra-calcic liquids only at melt fractions greater than 30 percent and temperature higher than 1,350 deg C at 1.0 GPa. Such temperatures are higher than those likely to be prevailing beneath normal mid-ocean ridges, which suggests that some or all silicic UCMI may originate by a process other than simple partial melting of clinopyroxene-rich lithologies. We consider a possible role for partial melting of depleted harzburgite in the genesis of silicic UCMI.
机译：超钙熔体夹杂物（UCMI：CaO> 13.5 wt％和/或caO / Al_2O_3> 0.9）是镁盐和近主要的液体，来自中洋海脊，弧线，后弧和海洋岛，被困在火山的台晶中。根据构造关联和二氧化硅饱和度，可以将其分为两类：来自弧线的是霞石规范的，来自所有其他地区（硅质的UCMI）的规范的是超粘胶的。硅质UCMI具有许多共同特征，包括原始基质矿物，低碱含量以及K_2O / TiO_2的可变比例到高值。它们的组成不易通过地幔锂铁矿的部分熔融而得到。因此，我们已经对1.0至2.0 GPa的三种斜辉石成分进行了一系列的部分熔融实验，以研究富含斜辉石的岩性的部分熔融在硅质UCMI成因中的作用。三种成分的估计固相线温度都与正常橄榄岩相似，但斜辉石的1.0 GPa等压熔体生产率比橄榄岩高。斜长石-钙长石的高度部分熔融是超钙的，并且与硅质UCMI相似，但实验仅在1.0 GPa的熔融分数大于30％且温度高于1350℃的情况下才产生超钙液体。这种温度高于正常大洋中脊以下可能普遍存在的温度，这表明某些或全部硅质UCMI可能是由于富富富化基层的岩性简单地部分熔融以外的其他过程引起的。我们认为在硅质UCMI的发生中，贫化的Harzburgite的部分熔化可能具有作用。

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