Carbonate-hosted lead-zinc ore deposits and pyrite thus form. Commonly MVT deposits form by the combination of hydrocarbon pyrolysis liberating zinc-lead ions and sulfur to form an acidic solution which dissolves the host carbonate formation and replaces it with massive sulfide accumulations. This may also take the morphology of fault-hosted stockworks, massive tabular replacements and so forth. Porous limestones may form disseminated ores, however most MVT deposits are massive sulfides with knife-like margins between carbonate and sulfide mineralogies. Ore minerals in carbonate replacement deposits are typically lead sulfide, galena, and zinc sulfide sphalerite. Weathered equivalents form anglesite, cerussite, smithsonite, hydrozincite and secondary galena and sphalerite
Mineral hydration Mineral hydration Mineral hydration is an inorganic chemical reaction where water is added to the crystal structure of a mineral, usually creating a new mineral, usually called a "hydrate". In geological terms, the process of mineral hydration is known as "retrograde alteration" and is a process occurring in retrograde metamorphism. It commonly accompanies metasomatism and is often a feature of wall rock alteration around ore bodies. Hydration of minerals occurs generally in concert with hydrothermal circulation which may be driven by tectonic or igneous activity. There are two main ways in which minerals hydrate. One is conversion of an oxide