Contrasting metallogenesis of ore-districts of the Italian Alps

The distribution of Mississippi Valley-Type (MVT) and Siliceous Crust-Type (SCT) deposits, in and around the Gorno district of the Central Southern Alps, relates to palaeogeographic and structural constraints during the evolution of the middle-upper Triassic carbonate platforms and during Alpine orogenesis. The most diagnostic MVT features are: (a) the presence of an unconformity above the ore-deposits, (b) open-space filling of carbonate collapse-breccias, (c) the absence of silica. The SCT main characteristics are: (a) the presence of an unconformity underlying the ore-bodies, (B) the high content of silica and, locally, fluorite-barite, (c) a reworked conglomerate/breccia texture that is almost totally silicified. The coexistence of two genetically different types of ore-deposits, one next to other, is due to the geometric superposition of two structural units. A pre-deformational N-S and E-W roughly zonal distribution of the ore-deposits probably relates to palaeogeographic factors.