Potassium in the Earth's core?
Potassium in the Earth's core?
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DOI：
10.1016/s0012-821x(02)00593-9
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发表时间：
2002-06-20
影响因子：
5.3
通讯作者：
Wood, BJ
中科院分区：
文献类型：
--
作者：
Gessmann, CK;Wood, BJ
在2.5-24 GPa和1500- 1900 ℃温度范围内测定了K和Na在液态Fe-S-O合金和硅酸盐熔体之间的分配。在无硫铁合金的实验中，碱金属元素表现出完全亲石的行为。然而，当加入S时，K和Na开始进入Fe-液相，它们的分配系数D-t（= [I]（Meta）/[I]（silicate））与Fe-S-O液相的O含量（和FeO活性）以及硅酸盐熔体的组成密切相关。对于钾，含30% S和8% O的硫化铁液，D-K近似于1.0。升高温度导致0在Fe-硫化物液体中的溶解度增加和DK的相应更高的值。另一方面，增加压力会略微降低D-K值。假设一个行星核心含有10重量%的硫和4-8重量%的氧，那么几百ppm的K将存在于铁硫化物液体中，如果它在低压下分离，例如在一个小的行星体，如火星。如果像最近提出的那样，地核在一个深岩浆海洋的底部分离，那么它的最高可能K含量约为250 ppm。后者将产生大约20%的核心总热量生产。然而，K只能存在于地核中，如果在其形成过程中的某个时候，一个离散的富O FeS液体从硅酸盐地幔中分离出来。最后，在我们的实验中产生的硫化物组合物意味着S和O的组合可能对地核的轻元素含量有显着贡献。(C)2002 Elsevier Science B. V.保留所有权利。
The partitioning of K and Na between liquid Fe-S-O alloys and silicate melt has been determined over the pressure and temperature range 2.5-24 GPa and 1500-1900degreesC. In experiments with S-free Fe alloys, the alkali elements show completely lithophile behaviour. When S is added, however, K and Na begin to enter the Fe-liquid phase and their distribution coefficients D-t (= [I](meta)/[I](silicate)) correlate strongly with 0 content (and FeO activity) of the Fe-S-O liquid and with the composition of the silicate melt. For potassium, D-K is similar to1.0 for Fe-sulphide liquid containing 30% S and 8% O. Increasing temperature leads to increasing 0 solubility in the Fe-sulphide liquid and correspondingly higher values of DK. Increasing pressure on the other hand slightly reduces D-K values. Given a planetary core containing 10 wt% S and 4-8 wt% O, then several hundred ppm K would be present in the Fe-sulphide liquid if it segregated at low pressures, e.g. in a small planetary body such as Mars. If, as has recently been suggested, the Earth's core separated at the base of a deep magma ocean, then its highest possible K content is about 250 ppm. The latter would generate approximately 20% of the total heat production of the core. K can only be present in the core, however, if, at some time during its formation, a discrete O-rich FeS liquid separated from the silicate mantle. Finally, the sulphide compositions produced in our experiments imply that a combination of S and 0 could contribute significantly to the light element content of the Earth's core. (C) 2002 Elsevier Science B.V. All rights reserved.