Mineralogical and Geochemical Constraints on Arsenic Mobility in a Philippine Geothermal Field

Arsenic is usually associated with sulphide minerals formed in the geothermal environment. However, sulphide minerals are prone to dissolution after contact with meteoric water under surface oxidizing conditions. Secondary precipitates that form from the dissolution of the primary sulfides exert a greater influence on arsenic mobility in the geothermal environment. Fe-hydroxides have very good affinity with dissolved arsenate and are stable under most surface oxidizing conditions. Both amorphous silica directly precipitated from geothermal fluids and possibly a kaolinite alteration can host a small significant amount of arsenic. These silicates are also more stable under a wide range of pH and redox conditions.     

菲律宾地热场中矿物和地球化学条件对砷迁移的制约

砷总是与硫化物共同形成于地热环境中。然而,在地表氧化条件下硫化物与雨水接触后易溶解。在地热环境中硫化物溶解后的二次沉淀物对砷的迁移有着重大的影响。溶解的砷酸盐易被铁的氢氧化物固定,且铁的氢氧化物在大多数的地表氧化条件下都可以稳定存在。地热流体中无定形SiO_2的迅速沉淀和高岭石化可以固定大量的砷。这些硅酸盐可以稳定的存在于较宽泛的pH和氧化还原条件下。菲律宾地热场中矿物和地球化学条件对砷迁移的制约@Chelo PASCUA$Graduate School of Natural Scienceand Technology,Kanazawa University,Ishikawa,Japan …