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首页> 外文期刊>Contributions to Mineralogy and Petrology >Carbonate-rich melt infiltration in peridotite xenoliths from the Eurasian–North American modern plate boundary (Chersky Range, Yakutia)
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Carbonate-rich melt infiltration in peridotite xenoliths from the Eurasian–North American modern plate boundary (Chersky Range, Yakutia)

机译：来自欧亚-北美现代板块边界（谢尔盖山脉，雅库特）的橄榄岩异岩中富含碳酸盐的熔体渗透

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A suite of mainly spinel peridotite and subordinate pyroxenite xenoliths and megacrysts were studied in detail, enabling us to characterize upper mantle conditions and processes beneath the modern North American–Eurasian continental plate boundary. The samples were collected from 37-Ma-old basanites cropping out in the Main Collision Belt of the Chersky Range, Yakutia Republic (Russian Far East). The spinel lherzolites reflect a mantle sequence, equilibrated at temperatures of 890–1,025 °C at pressures of 1.1–2 GPa, with melt extraction estimated to be around 2–6 %. The spinel harzburgites are characterized by lower P–T equilibration conditions and estimated melt extraction up to 12 %. Minor cryptic metasomatic processes are recorded in the clinopyroxene trace elements, revealing that percolating hydrous fluid-rich melts and basaltic melts affected the peridotites. One of the lherzolites preserves a unique melt droplet with primary dolomite in perfect phase contact with Na-rich aluminosilicate glass and sodalite. On the basis of the well-constrained P–T frame of the xenolith suite, as well as the rigorously documented melt extraction and metasomatic history of this upper mantle section, we discuss how a carbonated silicate melt infiltrated the lherzolite at depth and differentiated into an immiscible carbonate and silicate liquid shortly before the xenolith was transported to the surface by the host basalt. Decreasing temperatures triggered crystallization of primary dolomite from the carbonate melt fraction and sodalite as well as quenched glass from the Na-rich aluminosilicate melt fraction. Rapid entrainment and transport to the Earth’s surface prevented decarbonatization processes as well as reaction phenomena with the host lherzolite, preserving this exceptional snapshot of upper mantle carbonatization and liquid immiscibility.
机译：详细研究了一套主要为尖晶石的橄榄岩和次要的辉石岩的异岩和巨晶，这使我们能够描述现代北美-欧亚大陆板块边界下的上地幔条件和过程。样品是从在雅库特共和国（俄罗斯远东地区）切尔斯基山脉主碰撞带中切出的37Ma的Basanite收集的。尖晶石水辉石反映出地幔序列，在890–1,025°C的温度和1.1–2 GPa的压力下达到平衡，熔体萃取率约为2–6％。尖晶石尖晶石的特征在于较低的P–T平衡条件，据估计熔融提取率高达12％。在斜向辉石微量元素中记录了次要隐密的交代过程，揭示了渗漏的含水富液熔体和玄武质熔体对橄榄岩的影响。其中一种锂铁矿与原始白云石保持独特的熔滴，并与富钠的铝硅酸盐玻璃和方钠石完美地接触。基于异种岩体套件的受约束的PT框架，以及该上地幔剖面的严格记录的熔体提取和交代史，我们讨论了碳酸盐硅酸盐熔体如何深入渗入锂铁矿并分化为异质碳酸盐和硅酸盐液体在异种岩被主体玄武岩运至表面之前不久。温度的降低触发了白云石从碳酸盐熔体馏分和方钠石的结晶，以及淬火玻璃从富含钠的铝硅酸盐熔体馏分的结晶。快速夹带和运输到地球表面可防止脱碳过程以及与宿主锂铁矿的反应现象，从而保留了上地幔碳化和液体不混溶性的出色表现。

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