Gold and tin of fluid-magmatic systems: causes of combination-separation of concentration elements

The aim of the investigation is to reveal possible causes of isolation and co-occurrence of the economically significant concentrations of gold and tin. Comparative analysis of the different-rank factors that influenced migration and concentration of these elements show that different geochemical properties of Au and Sn are responsible for isolation of their big concentrations giving rise to independent metallogenic provinces, zones, and ore nodes. These differences resulted in individualization of the element migration ways to the level of ore concentration within the fluid-magmatic columns. Three main factors influenced the Au and Sn migration activity: different patterns of metal connection with the melt structure, different relation with oxygen, and different relation with other strong oxidizers. By the moment when ore-bearing fluid became isolated from magmas, the metallogenic signature of the melts, contrasting in redox-potential, had already been defined that was confirmed by the fact that tin ores associate predominantly with the granitoids of ilmenite series and gold ores - with those of magnetite series. The fluid-magmatic systems with an intermediate degree of the melt reduction-oxidation may be considered the potential producers of the combined metal concentrations. In these cases, the combined concentrating of tin and gold is plagued by an opposite direction of the oxidation-reduction reactions when their most common minerals are formed: the main migration form of Sn +2 must be oxidized (with cassiterite portioning), and the forms of Au + or Au +3 must be reduced (with native gold portioning). Probably, because of this the combined tin and gold concentrations are dominated by one of the metals with a tendency of accumulation in different-stage mineral complexes.

作 者：   作者單位：   刊 名： 世界地質（英文版）  英文刊名： GLOBAL GEOLOGY  年，卷(期)： 2009 12(3)  分類號： P5  關鍵詞： gold   tin   migration   concentrating   fluid-magmatic systems   redox-potential  

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