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New constraints on the abundances of phosphorus and sulfur in the lunar core: High-pressure and high-temperature experimental study of the FeSP ternary system
Geochimica et Cosmochimica Acta ( IF 4.5 ) Pub Date : 2022-07-29 , DOI: 10.1016/j.gca.2022.07.024
Kuan Zhai , Yuan Yin , Shuangmeng Zhai

High-pressure and high-temperature experiments for the Fesingle bondSsingle bondP ternary system were performed at 3–5 GPa and 1173–1873 K. We systematically investigated the effect of pressure, temperature, and bulk composition on the phase relationships, on the core crystallization sequences, and on the presence of sulfur and phosphorous in the lunar core. Our experimental results indicate that while up to < 1 wt% phosphorus can be dissolved in solid iron in the Fesingle bondSsingle bondP ternary system at 3 and 5 GPa, S dissolution in solid iron is near negligible. On the iron rich (S + P < 10 wt%) side of the Fesingle bondSsingle bondP phase diagram completely miscible Fesingle bondSsingle bondP liquids were observed. Combined with previous experimental results, the relationship of the sulfur content in the liquid metal (XSliquid) and the partitioning coefficient of phosphorus (DP) between the solid and liquid metal follows an equation of lgDP=-1.8286-17.87×lg1-XSliquid. Tradeoff between the liquidus of the Fesingle bondSsingle bondP system and the (S + P) content of the lunar core well constrain the upper limit of the (S + P) content in the liquid lunar outer core to the concentrations between 8.7 and 13.1 wt%. Using the result of the phosphorus coefficient and our partitioning model, we further assessed the abundances of 6.08–7.15 wt% S, 0.54 ± 0.01 wt% P in the lunar liquid outer core, and 0.05 ± 0.01 wt% S, 0.07 ± 0.01 wt% P in the lunar solid inner core, respectively. Integrating the observed lunar core adiabat and the pressure dependence of the Fesingle bondSsingle bondP liquidus temperature, we propose that the solidification regime in the lunar core will switch from bottom-up to top-down once the abundance of (S + P) in the liquid outer core exceeds 3.5 wt% as the core evolves.



中文翻译:

月核磷硫丰度的新约束:FeSP三元体系的高压高温实验研究

Fe SP 三元体系的高压和高温实验是在 3-5 GPa 和单键1173-1873 单键K 下进行的。我们系统地研究了压力、温度和体积组成对相关系、核心结晶的影响序列,以及月球核心中硫和磷的存在。我们的实验结果表明,在 3 GPa 和 5 GPa 的 Fe SP 三元体系中,虽然高达 < 1 wt% 的磷可以溶解在固体铁中,但单键S在固体铁中的单键溶解几乎可以忽略不计。在 Fe 单键S 单键P 相图的富铁 (S + P < 10 wt%) 侧完全混溶 Fe 单键S单键观察到P液体。结合以往的实验结果,液态金属中硫含量的关系(X小号液体) 和固体和液体金属之间的磷分配系数 ( D P ) 遵循以下方程lgD=-1.8286-17.87×lg1-X小号液体.Fe 单键S 单键P 系统液相线和月核的(S + P)含量之间的权衡将液态月球外核中(S + P)含量的上限限制在8.7和13.1 wt%之间的浓度. 利用磷系数的结果和我们的分配模型,我们进一步评估了月球液体外核中 6.08-7.15 wt% S、0.54 ± 0.01 wt% P 和 0.05 ± 0.01 wt% S、0.07 ± 0.01 wt% 的丰度% P 在月球固体内核中,分别。综合观察到的月核绝热条件和 Fe 单键S 单键P 液相线温度的压力依赖性,我们提出一旦液体中 (S + P) 的丰度,月核中的凝固状态将从自下而上转变为自上而下随着地核的演化,外核超过 3.5 wt%。

更新日期:2022-07-29
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