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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >High-pressure melting of carbonated eclogite and experimental constraints on carbon recycling and storage in the mantle
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High-pressure melting of carbonated eclogite and experimental constraints on carbon recycling and storage in the mantle

机译：碳酸盐榴辉岩的高压熔融及地幔中碳循环和储存的实验约束

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High-pressure experiments (5-10 GPa, corresponding to approximately 150-300 km depth in the mantle) have been conducted on a basalt+calcite mixture in order to constrain the fate of carbonates carried on subducted ocean floor. At 5 GPa, carbonate breakdown occurs between 1100 and 1150 ℃, and coincides with silicate melting. At 6.5 GPa and above, only carbonatitic melts were produced and the solidus temperature is located below 1000 ℃. Liquid immiscibility is observed at the transition from silicate to carbonate melting (6 GPa and 1300 ℃). The carbonatitic solidus in the eclogite is located 4 GPa higher in pressure than in the peridotitic system. This is due to the difference of silicate mineralogies involved in carbonation reactions. In addition, carbonates produced in the present study are calcium-rich (Ca/(Ca+Fe+Mg)ca. 0.80), in striking contrast to those produced by melting of carbonated peridotite (Ca/(Ca+Fe+Mg) ca. 0.50). Carbonated eclogite should therefore be considered as a potential source for the most abundant carbonate type worldwide, but it is stressed that carbonatitic magmatism cold be a multistage process. Compared to pressure-temperature paths of subducting slabs, the present results suggest that carbonates will most likely be removed from the slab before reaching 300 km, and are unlikely to be introduced by subduction either in the transition zone or in the lower mantle. Therefore, the deep carbon cycle appears to be restricted to the upper mantle (300 km or shallower depths). Carbonate-enriched portions located in cooler parts of the slab (fractures) could allow for oxidized carbon introduction to deeper mantle regions, but more experiments at higher pressures are necessary to evaluate this hypothesis. Because carbonagitite production from carbonated eclogites occurs in the diamond stability field, the present experimental results lend further support to recent models of diamond formation involving carbonated melts in the mantle.
机译：为了限制俯冲海底携带的碳酸盐的结局，对玄武岩+方解石混合物进行了高压实验（5-10 GPa，相当于地幔中约150-300 km的深度）。在5 GPa时，碳酸盐分解发生在1100至1150℃之间，并且与硅酸盐熔融同时发生。在6.5 GPa和更高的温度下，仅产生碳酸盐熔体，固相线温度低于1000℃。在从硅酸盐到碳酸盐熔融（6 GPa和1300℃）的过渡过程中观察到液体不混溶。榴辉岩中的碳酸盐固相线的压力比橄榄岩体系中的高4 GPa。这是由于参与碳酸化反应的硅酸盐矿物学的差异。此外，本研究中产生的碳酸盐富含钙（Ca /（Ca + Fe + Mg）ca。0.80），这与碳酸盐橄榄岩熔融产生的碳酸盐（Ca /（Ca + Fe + Mg）ca 0.50）。因此，碳化榴辉岩应被认为是全球最丰富的碳酸盐类型的潜在来源，但要强调的是，碳岩性岩浆作用冷是一个多阶段过程。与俯冲板的压力-温度路径相比，目前的结果表明，碳酸盐最有可能在到达300 km之前从板中清除，并且无论是在过渡带还是在下地幔中都不太可能通过俯冲来引入。因此，深层碳循环似乎仅限于上地幔（300 km或更浅的深度）。位于板较冷部分（裂缝）中的富含碳酸盐的部分可以允许将氧化的碳引入到更深的地幔区域，但是需要在更高的压力下进行更多的实验才能评估该假设。因为从碳酸化榴辉岩中生产碳辉石是在钻石稳定领域中进行的，所以本实验结果进一步支持了涉及地幔中碳酸盐熔体的钻石形成的最新模型。

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