低温热液成矿作用中铊有机络合物搬运形式的研究

文章依据等库伦反应外推原理,计算了铊的醋酸(TlAc0)、柠檬酸(TlCit2-)、苹果酸(TlMal-)、草酸(TlOx-)及琥珀酸(TlSuc-)络合物在25～100℃之间的稳定常数。将这些稳定常数输入EQ3/6的DATA0.SUP热力学数据库后,在75℃和100℃温度条件下,对铊的诸物种于低温热液中在不同pH值条件下的分配进行了计算。计算表明,在中性及偏碱性条件下,在75℃还原环境中,自由铊离子(Tl+)所占比例约为55%,TlHS0约占10%,而其余则为铊的有机络合物,并以铊的柠檬酸络合物占绝对优势。在75℃氧化环境中,自由铊离子约占55%,而铊的有机络合物则为45%左右。在100℃还原环境中,自由铊离子所占比例约为20%,TlHS0约占20%,其余则为铊的有机络合物。在100℃氧化环境中,自由铊离子所占比例约为30%,其余则为铊的有机络合物。因而笔者认为,铊的有机络合物,尤其是铊的柠檬酸络合物,在低温热液中对于铊的溶解及搬运起着重要的作用。

A study of thallium organic complexes in transport of thallium in low temperat ure hydrothermal solutions

In this study, the stability constants up to 100 ℃ of thallium organic complexes including TIAc~0(Ac : acetate) , T1Cit~(2-)(Cit : cit-rate) , T1Mal~-( Mal: malonate) , T1Ox~-(Ox: oxalate) , and TISuc~-(Suc : succinate) , were calculated based on the isocoulombic ap-proach. After incorporation of these stability constants into the EQ3/6 DATAO. SUP thermodynamic database, the speciation of thal-lium as a function of pH in a simplified model low temperature hydrothermal solution with organic ligands was calculated. Based on the calculations, the importance of the above organic ccmplexes in the transport of thallium in low temperature hydrothermal solutions up to 100℃ was evaluated. According to EQ3/6 calculations, at 75℃ , under reducing conditions(∑H_2S stable) and in the geologi-cally reasonable pH range, free T1~+ accounts for about 55% of total thallium, THIS~0 for about 10%, and the above thallium com-plexes with organic ligands for the balance with T1Cit~(2-) as a dominant species. At the same temperature and under oxidizing condi-tions(∑SO_4 stable), free T1~+ accounts for about 55% of total thallium, and the above thallium organic complexes for the rest. At 100℃ , under reducing conditions and again in the geologically reasonable pH range, free T1~+ accounts for about 20% of total thaUium, THIS~0 for about 20% , and the thallium organic complexes for the rest. At 100℃ and under oxidizing oonditions, free T1~+ accounts for about 30% of total thallium, and the thallium organic ocmplexes for the rest. It is thus concluded that thallium organic complexes, especially with T1Cit~(2-) as a dominant player, could play an important role in the solubilization and transport of thallium in low temperature hydrothermal solutions.