Carbon solubility in core melts in a shallow magma ocean environment and distribution of carbon between the Earth's core and the mantle
Carbon solubility in core melts in a shallow magma ocean environment and distribution of carbon between the Earth's core and the mantle
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DOI：
10.1016/j.gca.2008.06.023
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发表时间：
2008-09-15
影响因子：
5
通讯作者：
Walker, David
中科院分区：
文献类型：
--
作者：
Dasgupta, Rajdeep;Walker, David
通过电子探针分析，在饱和石墨的Fe和Fe-5.2 wt.% Ni熔体中，碳在2000℃时的溶解度为5.8 +/- 0.1 wt.%， 2200℃时的溶解度为6.7 +/- 0.2 wt.%， 2410℃时的溶解度为7.4 +/- 0.2 wt.%，这与岩浆海的地核/地幔分异有关。这些溶解度略低于低压文献值，并且明显低于更高压力下的计算值[例如，Wood B. J.（1993）岩心中的碳]。地球的星球。科学。[j].科学通报。在分析不确定度范围内，Fe-5.2 wt.% Ni熔体的C溶解度随温度的变化趋势与纯Fe相似或略低（类似于0.2-0.4 wt.%）。岩心熔体和地幔残余硅酸盐的碳含量及其与我们的溶解度数据和现今地幔碳含量估算值的比较，分别约束了岩浆海洋中硅酸盐和金属熔体之间的碳分配系数D-C（硅酸盐/金属）。从球粒陨石到亚球粒陨石的整个可能的地球体积碳含量范围，D-C（硅酸盐/金属）为10（-4）比1。但是对于类似1000ppm的大块地球碳，D-C（硅酸盐/金属）介于10（-2）和1之间。利用2200℃岩浆海洋中可能的D-C（硅酸盐/金属）的完整范围，我们预测地球核心的最大碳含量类似于6-7 wt.%，而对于地球整体碳浓度类似于1000 ppm的情况，首选值为0.25 +/- 0.15 wt.%。(C) 2008 Elsevier Ltd版权所有。
The solubility of carbon in Fe and Fe-5.2 wt.% Ni melts, saturated with graphite, determined by electron microprobe analysis of quenched metal melts was 5.8 +/- 0.1 wt.% at 2000 degrees C, 6.7 +/- 0.2 wt.% at 2200 degrees C, and 7.4 +/- 0.2 wt.% at 2410 degrees C at 2 GPa, conditions relevant for core/mantle differentiation in a shallow magma ocean. These solubilities are slightly lower than low-pressure literature values and significantly beneath calculated values for even higher pressures [e.g., Wood B. J. (1993) Carbon in the core. Earth Planet. Sci. Lett. 117, 593-607]. The trend of C solubility versus temperature for Fe-5.2 wt.'% Ni melt, within analytical uncertainties, is similar to or slightly lower (similar to 0.2-0.4 wt.%) than that of pure Fe. Carbon content of core melts and residual mantle silicates derived from equilibrium batch or fractional segregation of core liquids and their comparison with our solubility data and carbon content estimate of the present day mantle, respectively, constrain the partition coefficient of carbon between silicate and metallic melts, D-C(silicate/metal) in a magma ocean. For the entire range of possible bulk Earth carbon content from chondritic to subchondritic values, D-C(silicate/metal) of 10(-4) to 1 is derived. But for similar to 1000 ppm bulk Earth carbon, D-C(silicate/metal) is between 10(-2) and 1. Using the complete range of possible D-C(silicate/metal) for a magma ocean at 2200 C, we predict maximum carbon content of the Earth's core to be similar to 6-7 wt.% and a preferred value of 0.25 +/- 0.15 wt.% for a bulk Earth carbon concentration of similar to 1000 ppm. (C) 2008 Elsevier Ltd. All rights reserved.