HYDROTHERMAL ALTERATION OF ROCKS IN EPITHERMAL DEPOSITS AND IN AREAS OF RECENT HYDROTHERMAL ACTIVITY

Abstract

In paleovolcanic provinces, metasomatism and mineralization are often found to have developed simultaneously in the same structural settings. The emplacement of ore veins, however, are known to have been controlled by the sources of mineral matter rather than by the scope and intensity of metasomatic processes. The redistribution of mineral matter in volcanic rocks is especially active in zones of argillization where large accumulations of ore minerals are usually concentrated in modern hydrothermal systems. In epithermal gold-silver ore deposits, however, argillization zones are usually localized above the ore-bearing zones, and sporadic metallic mineralization in their metasomatic rocks is usually insignificant within or outside of ore fields. Most of hydrothermal systems from areas of modern volcanism are comparable with paleohydrothermal systems which are widely developed outside of ore-bearing areas and have no efficient sources of metallic matter.