PHASE SEPARATION IN (Fe,Co)1 xS MONOSULFIDE SOLID-SOLUTION BELOW 450 C, WITH CONSEQUENCES FOR COEXISTING PYRRHOTITE AND PENTLANDITE IN MAGMATIC SULFIDE DEPOSITS
PHASE SEPARATION IN (Fe,Co)1 xS MONOSULFIDE SOLID-SOLUTION BELOW 450 C, WITH CONSEQUENCES FOR COEXISTING PYRRHOTITE AND PENTLANDITE IN MAGMATIC SULFIDE DEPOSITS
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450 C 以下的 (Fe,Co)1 xS 单硫化物固溶体中的相分离，对岩浆硫化物矿床中磁黄铁矿和镍黄铁矿共存的影响
DOI：
10.2113/gscanmin.40.1.33
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发表时间：
2002
影响因子：
0.9
通讯作者：
M. Fleet
中科院分区：
文献类型：
--
作者：
S. Farrell;M. Fleet
使用密封石英玻璃管实验研究了与钴镍黄铁矿共存的（Fe，Co）1-xS的相关系，温度高达450 °C。具有NiAs型结构（Fe，Co-mss）的（Fe，Co）单硫化物固溶体在低于425°C下突然不混合，成为共存的富Fe（Fe，Co-mss 1; 1C结构）和富Co（Fe，Co-mss 2; 3C结构）相。对于具有52.0 at.% S时，平衡Fe，Co-mss 1固溶线在400 °C下位于约0.83摩尔Fe/（Fe + Co）处，并且随着温度降低逐渐向Fe 1-xS端元组成发散，在105 °C下为0.98摩尔Fe/（Fe + Co）。在400°C下，平衡Fe，Co-mss 2固溶线为约0.37摩尔Fe/（Fe + Co），并且似乎不随温度的降低而显著变化。在平衡磁导率间隙内存在亚稳固溶线，临界温度为425 °C，在0.45和0.50摩尔Fe/（Fe + Co）之间，如单相产物所示，即使经过长时间退火也能保持。自发相分离的窄场以0.75摩尔Fe/（Fe + Co）为中心，并且导致在从高温（800 °C）淬火的产物中的h 01 NiAs型子电池反射的卫星反射。Fe，Co-mss中的可熔性间隙类似于Fe-Ni-S系统中mss的相分离。然而，相分离在Fe，Co-mss（425 - 400°C）中比在mss（400 - 300° C）中稍高的温度下发生，并且最初是不连续的。
Phase relations for (Fe,Co) 1‐xS coexisting with cobalt pentlandite have been studied up to 450 °C using sealed silica glass tube experiments. The (Fe,Co) monosulfide solid-solution with the NiAs-type structure (Fe,Co- mss) unmixes abruptly below 425°C, to coexisting Fe-rich (Fe,Co-mss1; 1C structure) and Co-rich (Fe,Co- mss2; 3C structure) phases. For bulk compositions with 52.0 at.% S, the equilibrium Fe,Co-mss1 solvus is located at about 0.83 molar Fe/(Fe + Co) at 400 °C and progressively diverges toward the Fe1‐xS end-member composition with decrease in temperature to 0.98 molar Fe/(Fe + Co) at 105 °C. At 400°C, the equilibrium Fe,Co-mss2 solvus is at about 0.37 molar Fe/(Fe + Co) and does not appear to vary significantly with decrease in temperature. There is a metastable solvus within the equilibrium miscibility-gap, with a critical temperature at 425 °C between 0.45 and 0.50 molar Fe/(Fe + Co), as indicated by single-phase products that persist even with prolonged annealing. A narrow field of spontaneous phase-separation is centered at 0.75 molar Fe/(Fe + Co), and results in satellite reflections of h0l NiAs-type subcell reflections in products quenched from a high temperature (800 °C). The miscibility gap in Fe,Co-mss is similar to the phase separation of mss in the system Fe‐Ni‐S. However, phase separation occurs at a slightly higher temperature in Fe,Co-mss (between 425 and 400°C) than in mss (between 400 and 300°C), and is initially discontinuous.