P-T Phase Relations of Silicic, Alkaline, Aluminous Mantle-Xenolith Glasses Under Anhydrous and C-O-H Fluid-saturated Conditions
P-T Phase Relations of Silicic, Alkaline, Aluminous Mantle-Xenolith Glasses Under Anhydrous and C-O-H Fluid-saturated Conditions
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DOI：
10.1093/petroj/38.9.1187
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发表时间：
1997-09
影响因子：
3.9
通讯作者：
D. Draper;T. Green
中科院分区：
文献类型：
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作者：
D. Draper;T. Green
对三种硅质、铝质、碱性熔体进行的高压液相线实验，以在许多地幔捕虏体中发现的玻璃为模型，硅酸盐熔体的成分可能是等量的，表明该成分范围的一部分被地球地幔中的铷饱和，长期以来，无水条件下的方辉橄榄岩（或可能是二辉橄榄岩）一直受到人们的关注。岩石学家和地球化学家。许多有用的信息在 XH2O=0·5 的 C-O-H 流体饱和条件下，此类熔体的熔体来自熔体针云母的研究，它与无水相一起存在，类似于火山岩斑晶中的包裹体以及在干燥条件下发现的包裹体。金云母是超镁铁质地幔捕虏体中唯一的液相矿物。另外，当XH2O=1·0时。在 XH2O=0·5 和 3·0 GPa 时，石榴石、蓝晶石许多地幔捕虏体含有离散的硅酸盐玻璃，碳酸盐矿物表现为近液相线相和相，而不是（或除此之外）包裹体（参见液相线表面的形状让人想起碳酸化附录 A 的形状以供参考）。在本文中，我们将提及橄榄岩固相线。这些液体与方辉橄榄石的饱和度，以及离散相捕虏体玻璃（简单地作为捕虏体与计算的熔融二氧化硅活性的比较）表明，这些玻璃和那些在液体矿物中作为包裹体发现的玻璃不会面临循环包裹体玻璃的化学或热障碍。据报道，包体玻璃与方辉橄榄岩地幔共存。此外，来自碱性镁铁质岩浆的地幔捕虏体的结构证据表明，这些熔体可能是流动的。因此，这些来自板内和来自俯冲相关液体技术的物质都可以充当神秘的交代剂。如地幔补品设置。这些玻璃具有广泛的彗星范围，深度约 45-90 公里，在低熔点位置和结构关系中预先富集：它们作为组分被发现，并且可能是挥发物，通过上升和渗滤粒间气泡、不规则斑块、纹理和碱性、镁铁质液体的薄层（沿着似乎润湿所有颗粒表面的薄膜中交叉拐点的地温线。大多数玻璃具有含二氧化碳的固相线橄榄岩），那么随后的低程度最多仅占其部分熔化的几个体积百分比，可以产生最终被捕获为宿主捕虏体的液体，并且有一些远小于 1 体积。 %。捕虏体眼镜。 Xenolith 玻璃具有非常广泛的主要
High-pressure liquidus experiments on three silicic, aluminous, INTRODUCTION alkaline melts, modelled on glasses found in many mantle xenoliths, The compositions of silicate melts potentially in equishow that part of this compositional range is saturated with librium with the Earth’s mantle have long been of interest harzburgite (or possibly lherzolite) under anhydrous conditions. to petrologists and geochemists. Much useful information Under C–O–H fluid-saturated conditions with XH2O=0·5, phloabout such melts has come from the study of melt gopite mica is present along with anhydrous phases similar to those inclusions in phenocrysts in volcanic rocks and in the found under dry conditions. Phlogopite is the sole liquidus phase minerals of ultramafic mantle xenoliths. In addition, when XH2O=1·0. At XH2O=0·5 and 3·0 GPa, garnet, kyanite many mantle xenoliths contain silicate glasses as a discrete and carbonate minerals appear as near-liquidus phases and the phase, rather than (or in addition to) inclusions (see shape of the liquidus surface is reminiscent of that of the carbonated Appendix A for references). In this paper, we will refer peridotite solidus. Saturation of these liquids with harzburgite, and to discrete-phase xenolith glasses simply as xenolith comparisons with calculated melt silica activities, suggests that these glasses and those found as inclusions in minerals as liquids would face no chemical or thermal obstacles to circulating inclusion glasses. Xenolith glasses have been reported amongst and coexisting with harzburgitic mantle. Also, there is from mantle xenoliths hosted by alkaline, mafic magmas textural evidence that these melts may be mobile. Accordingly, these both from intra-plate and from subduction-related teckinds of liquids could act as cryptic metasomatic agents. If mantle tonic settings. The glasses have a wide range of comat ~45–90 km depth is pre-enriched in low-melting-temperature positions and textural relations: they are found as components, and probably volatiles, via the ascent and percolation intergranular blebs, irregular patches, veins, and thin of alkaline, mafic liquids (along geotherms that cross inflections in films that appear to wet all grain faces. Most glasses the solidus of CO2-bearing peridotite), then subsequent low-degree account for, at most, only a few volume percent of their partial melts could yield the liquids that are ultimately trapped as host xenolith, and some much less than 1 vol. %. xenolith glasses. Xenolith glasses have a very wide range of major