『Abstract
　During supergene alteration of auriferous carbonate ore, the weathering fluids formed are likely to be alkaline and therefore unsuitable as a medium for gold transport as a chloride complex. Secondary gold remobilization in such deposits can often be attributed instead to gold complexing by sulphur-bearing ligands. Gold and silver solubility in the systems Au-S-O2-H2O and Ag-S-O2-H2O respectively, calculated from the thermodynamic data available, is due to complex formation with thiosulphate and bisulphide ligands. The most stable gold complexes, Au(S2O3)2^3- (at f O2＞10^-60) and Au(HS)2^- (at f O2＜10^-60), exist in neutral or alkaline solutions. Like gold, silver forms a stable thiosulphate complex, Ag(S2O3)2^3- in moderately oxidizing, and bisulphide complexes, AgHS⁰ and Ag(HS)2^- in reducing, alkaline media. Silver solubility in highly oxidized, neutral or acid solutions is increased by formation of AgS2O3^-, Ag⁺ and AgSO4^- complexes.
　Colloidal, crystalline and alloyed gold and silver reacted with 0.1 M Na2S2O2 do not, however, demonstrate independent solubility. The rate of gold solubility in 0.1 M Na2S2O3, for example, is increased both by the presence of silver-thiosulphate complexes and alloyed silver. It is possible that such behaviour is due to the formation a mixed metal complex of the type (Au,Ag)(S2O3)2^3-.
　The nature and mineral association of secondary gold in the oxidized zone of carbonate ore at Wau, in Papua New Guinea, is consistent with prior remobillization as a thiosulphate complex. Here the secondary gold is coarsely crystalline, alloyed with 50-75 at％ Ag and enriched at the watertable and with manganese dioxide in the oxidized zone.』

Introduction
Soluble sulphur-species formed during the oxidation of ore sulphide
Gold complex/compound equilibria in the system Au-S-O2-H2O
　Results
Silver complex/compound equilibria in the system Ag-S-O2-H2O
　Results
Colloidal and crystalline gold and silver solubility in Na2S2O3
　Analytical method
　Results
Gold-silver alloy reactivity in Na2S2O3
　Analytical method
　Results
Gold and silver solubility in the system Au-Ag-SO3-H2O
Discussion and implications for ore deposit oxidation
Acknowledgements
References
Appendix
　Calculation of gold solubility in the system Au-S-O2-H2O
　Calculation of silver solubility in the system Ag-S-O2-H2O

硫黄の価数	硫黄化学種	名称
＋６	SO42-	sulfate	硫酸イオン
	HSO4-	bisulfate	硫酸水素イオン
	H2SO4	sulfuric acid	硫酸
＋５	S2O62-	dithinate	二チオン酸イオン
＋４	SO32-	sulfite	亜硫酸イオン
	HSO3-	bisulfite	亜硫酸水素イオン
	SO2	sulfurous acid gas	亜硫酸ガス
(+3.3)	S3O62-	trithionate	三チオン酸イオン
＋３
(+2.5)	S4O62-	tetrathinate	四チオン酸イオン
＋２	S2O32-	thiosulfate	チオ硫酸イオン
	HS2O3-	bithiosulfate	チオ硫酸水素イオン
＋１
０	S0	sulfur	固相硫黄
−１
−２	H2S	hydrogen sulfide	硫化水素
	HS-	bisulfide	硫化水素イオン
	S2-	sulfide	硫化物イオン