Predicted equilibrium constants for solid and aqueous selenium species to 300 °C: applications to selenium-rich mineral deposits
Predicted equilibrium constants for solid and aqueous selenium species to 300 °C: applications to selenium-rich mineral deposits
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固体和水相硒在 300 °C 温度下的预测平衡常数：在富硒矿床中的应用
DOI：
10.1016/s0169-1368(03)00038-6
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发表时间：
2003
影响因子：
3.3
通讯作者：
Y. Xiong
中科院分区：
文献类型：
--
作者：
Y. Xiong
在这项研究中，已作出了尝试，以评估在高温下（高达300 °C），通过使用各种外推方法的硒和常见硒化物的溶度积常数的水形态。这项研究预测，即使在相对氧化的条件下（例如磁铁矿-赤铁矿缓冲区所决定的条件下），还原硒物质也是许多地质过程中的主导物质。根据外推的平衡常数和常见含硒矿物相的溶度积常数，提出了成矿流体中硒独立成矿的临界∑Se/∑S比值（摩尔比）。在100 ° C、200 ° C和300 °C时，成矿流体中独立硒成矿作用的最小∑Se/∑S比值应分别至少为100 - 6、100 - 5和100 - 4。对于大型独立硒矿床，如西秦岭的拉尔玛、琼莫金硒矿床和湖北渔塘坝硒矿床，成矿流体的∑Se/∑S比值在200 °C时达到了很高的水平，范围在10 - 10 ~ 10 - 30之间。研究还表明，在常见的矿石矿物中，黄铁矿-铁硒石平衡组合对成矿流体中∑Se/∑S比值的要求最高，其次是辉锑矿-辉锑矿、方铅矿-白铅矿、辰砂-铁锰石和针银矿-钠闪石组合。黄铁矿-硒铁矿组合也可以在相对氧化的条件下形成，其中[∑H2Se]/[∑H2S]比值可以足够高以形成独立的硒铁矿。
In this study, an attempt has been made to assess aqueous speciation of selenium and solubility product constants of common selenides at elevated temperatures (up to 300 °C) by using various extrapolation methods. This study predicts that reduced selenium species are dominant species in many geological processes even under relatively oxidized conditions such as those dictated by the magnetite–hematite buffer. On the basis of extrapolated equilibrium constants and solubility product constants for common Se-bearing mineral phases, critical ∑Se/∑S ratios (molal ratios) in mineralizing fluids are proposed for independent selenium mineralization. The minimum ∑Se/∑S ratios in mineralizing fluids for independent selenium mineralization should be at least ∼10−6, ∼10−5and ∼10−4at 100, 200 and 300 °C, respectively. For giant independent selenium deposits such as the La'erma and Qiongmo Au–Se deposits in the western Qingling mountains, and Yutangba Se deposits in Hubei Province, China, the mineralizing fluids have reached much higher ∑Se/∑S ratios ranging from ∼10−1to ∼10−3at 200 °C. This study also suggests that the equilibrium assemblage of pyrite–ferroselite among the common ore minerals requires the highest ∑Se/∑S ratios in mineralizing fluids, followed in decreasing order by the assemblages of stibnite–antimonselite, galena–clausthalite, cinnabar–tiemannite, and acanthite/argentite–naumannite. The assemblage of pyrite–ferroselite can also be formed under relatively oxidizing conditions where [∑H2Se]/[∑H2S] ratios can be high enough for the formation of independent ferroselite.