Often the alteration can be complex and difficult to decipher because alteration zones from adjacent veins will overlap one another. Mineralogy Cu, Fe, Pb, Zn sulfides and sulfosalts predominate. The common minerals are pyrite, chalcopyrite, bornite, galena, sphalerite, tennantite, tetrahedrite, enargite, chalcocite and digenite. Pyrrhotite is absent, its absence placing an upper temperature limit on the mesothermal ores. Many of the listed minerals are important silver carriers and as such much of the world s silver comes from deposits of this type.
Paragenetic sequences are extremely complex and often the subject of debate.
At a minimum they indicate deposition of the ores over a long period of time. The list of gangue minerals is brief, and stands in contrast to the ore minerals. Important gangue minerals are calcite, quartz, siderite, ankerite and dolomite. Stable isotopes support a magmatic origin for the sulfur, and at least early in the paragenesis a significant magmatic water component. This model is not without its problems.