Genesis of the manganese deposit of Mazzano Romano (Latium, Italy)

The Mazzano Romano manganese deposit formed during Quaternary, probably in the time interval 442 to 230 ky, by leaching of the pyroclastic rocks of the "Complesso dei tufi stratificati varicolori de La Storta', of the Roman perpotassic province of central Italy. The leaching action was prompted by the presence of a lake in the Mazzano area, and developed during two cycles, each one lasting ca. 40 ky, separated by a sterile phase during which the lake was momentarily filled by new pyroclastic eruptions. Despite being entirely encased within pyroclastic rocks, the Mazzano deposit is not volcanogenic in origin nor is it related to precipitation from hot geothermal waters; rather, it derives from adsorption/precipitation of metal solutes contained in the cold groundwaters at a depth where their redox conditions changed from reduced to oxidized. -from Authors