Field observations and experimental results have shown that skarns and iron deposits related to them and marinefacies volcanic rocks have a bearing, at least in part, on intermediate-basic and intermediate-acidic rocks in regard to their material sources. The contributors have been enriched in mineralizing components during mobilization due to infiltration and metasomatism by NaCl-rich pneumatothermal fluids. When pneumatothermal fluids act on intermedlate-basic rocks, the major components in the rocks will become mobillzed in the nrder of K(or Na)> Fe> Ca> Si> Mg >AI. Among these components, Al exhibits the lowest mobility, followed by Mg, in non-favour for migration. The leaching capacity of hydrothermal solutions or pneumatothermal fluids relative to rock- and ore-forming dements depends chiefly on the type and amount of cations and in ions in the solutions or fluids, pH, Eh, temperature and pressure. Acidic solutions and temperantre increase are favourable for the leaching out of iron, whereas alkaline solutions and pressure increase are favourable for the leaching out of SiO2.
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