Mineralogy and genesis of metamorphic manganese deposits from bistrita mountains, eastern carpathians, romania

摘要

The Bistrita Mountains of the Eastern Carpathians contain a schist dominated sequence within which metamorphosed manganese deposits are found as lenses of varying sizes. A wide range of prograde amphibolite facies manganese-rich oxide and silicate mineral assemblages are found including those rich in tephroite, spessartine, pyroxmangite and rhodonite. A retrograde metamorphic and metasomatic overprint, possibly related to the Variscan orogeny, has produced assemblages with aegerine, Mn-rich alkali amphiboles, nambulite, natronambulite and pyrosmalite. Later veins and clusters containing a wide range of hydrated manganese silicates and others, represent a response by teh ores to a superimposed Alpine event. The deposits are deeply weathered, forming hydrated manganese oxides at the surface.