Distribution of gold and rhenium between nickel-iron and silicate melts: implications for the abundance of siderophile elements on the Earth and Moon
Distribution of gold and rhenium between nickel-iron and silicate melts: implications for the abundance of siderophile elements on the Earth and Moon
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DOI：
10.1016/0016-7037(74)90144-6
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发表时间：
1974-05
影响因子：
5
通讯作者：
K. Kimura;R. Lewis;E. Anders
中科院分区：
文献类型：
--
作者：
K. Kimura;R. Lewis;E. Anders
利用放射性示踪剂研究了1400-1600°C下镍铁熔体和玄武岩熔体之间的Au和Re分配平衡。金属/硅酸盐分配系数比早先的估计高1-3个数量级，如下所示。莫纳罗亚玄武岩-Fe 10 Ni 90：DAu= 3.3 × 104，DRe=（2.4−89）× 104。戈尔达海岭玄武岩-Fe 10 Ni 90：DAu=（18−75）× 104。合成月岩-Fe 70 Ni 30：DAu≥ 2 × 104，DRe≥ 2 × 103。Au在镍铁和莫纳罗亚火山玄武岩之间分布的实验Δ G 1800 °为−40 kcal/mole，相比之下，简单Au 3+离子反应的计算值约为−110 kcal/mole。据推测，这种差异代表了Au（III）通过与配体（如Cl−、H2O等）形成络合物的稳定性。月球玄武岩中的金丰度与测量的DAu大致一致，但陆地玄武岩中的金丰度高出两个数量级。这种差异可能反映了地球岩石圈上层挥发物的络合作用，以及在吸积的最后阶段金属的氧化破坏。在没有金属相的情况下，亲铁微量元素将仍然被困在上地幔和地壳中。
The distribution equilibrium of Au and Re between nickel-iron and basaltic melts was studied at 1400–1600°C, using radioactive tracers. Metal/silicate distribution coefficients were 1–3 orders of magnitude higher than earlier estimates, as follows. Mauna Loa basalt—Fe10Ni90:DAu= 3.3 × 104,DRe= (2.4−89) × 104. Gorda Ridge basalt—Fe10Ni90:DAu= (18−75) × 104. Synthetic lunar basalt—Fe70Ni30:DAu≥ 2 × 104,DRe≥ 2 × 103. The experimentalΔG1800°for the distribution of Au between nickel-iron and Mauna Loa basalt is −40 kcal/mole, compared to a calculated value of about −110 kcal/mole for a reaction involving simple Au3+ions. Presumably the difference represents stabilization of Au(III) by complex formation with ligands such as Cl−, H2O, etc.Gold abundances in lunar basalts are roughly consistent with the measuredDAu, but those in terrestrial basalts are two orders of magnitude too high. This discrepancy may reflect complexing by volatiles in the Earth's upper lithosphere, as well as oxidative destruction of metal in the final stages of accretion. In the absence of a metal phase, siderophile trace elements would remain trapped in the upper mantle and crust.