altération des roches encaissantes

CONT: La dissolution, la recristallisation et la bréchification des roches hôtes carbonatées [...] sont des éléments communs de pratiquement tous les gîtes de type Mississippi-Valley. Ces effets, qui s'accompagnent d'une silicification et d'une dolomitisation, constituent la principale forme d'altération des roches encaissantes dans les districts à minéralisations de [ce type].

CONT: Wall rock alteration. Frequently alongside veins or around irregularly shaped orebodies we find alteration of the country rocks. This may take the form of colour, textural, mineralogical or chemical changes, or any combination of these. ... the higher the temperature of deposition of the ore minerals the more intense is the alteration. This alteration, which shows a spatial and usually a close temporal relationship to ore deposits, is called wall rock alteration.