凭祥金矿风化剖面中砷的地球化学研究

利用连续提取法结合电子探针分析对龙塘金矿风化剖面中砷的赋存状态及其地球化学行为进行了研究。结果表明金矿区表层土壤中砷含量达588mg/kg,是土壤质量标准的十几至几十倍，该土壤已受到砷的严重污染。风化母岩中砷主要赋存于含砷黄铁矿与毒砂之中，而风化样品中砷主要赋存于晶质氧化铁中，其次为非晶质氧化铁之中，其他三个结合态相对较少。风化初期，含砷黄铁矿与毒砂风化溶解，其中大部分砷被风化溶液淋失，其他砷被氧化铁吸附。非晶质氧化铁结合态砷在风化过程中显示先升后降的趋势，而晶质氧化铁结合态砷则逐渐升高。雨水对表层土壤的冲刷、风化母岩中硫化物的风化溶解、风化产物中氧化铁在饱和条件下的溶解等都会使剖面中的砷释放出来，对周围环境造成潜在的威胁。

Geochemical Study of Arsenic for Gold Deposit Weathering Profile in Pingxiang

Occurrence and geochemical behavior of arsenic was studied with sequential extraction coupled with electronic microprobe analysis for weathering profile of gold depostit in Pingxiang,Guangxi Autonomous District.The results indicate that arsenic concentration is up to 588mg/kg in surface soil of Pingxiang,a concentration which is more than ten to more than thirty times as soil quality criteria,showing the soil has been seriously polluted by arsenic.The arsenic mainly hosted by pyrite and arsenopyrite in parent rocks whereas much arsenic in weathering samples are bound to crystalline iron oxides and amorphous iron oxides with insignificant part bound to other three fractions.In initial stage of weathering,pyrite and arsenopyrite were oxided and dissolved with much arsenic lost and the rest adsorbed by iron oxides Amorphous iron oxide bound arsenic concentrations relative to total arsenic increased first but decreased during weathering whereas crystalline iron oxide bound arsenic increased gradually with weathering.Arsenic may be released and cause potential threat to surrounding environment in some conditions such as rain water eroding surface soil,sulfide minerals in parent rocks weathering and reductive dissolving of iron oxides of weathering product in saturation condition.