STRATABOUND ORE-DEPOSITS RELATED TO SYNSEDIMENTARY TECTONICS - SOUTH-WEST SARDINIA (ITALY) AND SIERRA-DE-ARACENA (SPAIN) - A COMPARISON

Deposition of stratabound Zn-Pb-Ba ores in the Lower Cambrian carbonates in South-west Sardinia show a distinct relation with the prominent tensional tectonics in the area. A part of the mineral deposits are syngenetic (sedimentary-exhalative), other massive sulfides and/or barite are early diagenetic. Other occurrences (MVT) are from early to late-diagenetic. They are mostly confined to matrix- and cementbreccias which might be dependent on the Cambrian tectonics. The Precambrian-Lower Cambrian (?) carbonates occupying the core of the Aracena anticline, at the boundary between the provinces of Huelva and Badajoz (South-west Spain), are also an important metallotect for Zn-Pb-Ag-Ba mineralization. The ores at Aracena are stratabound (to stratiform) (Sedex) and occur as disseminations or layers in a volcano-sedimentary sequence with carbonate intercalations. Both the carbonate intervals and the ores show evidence of synsedimentary tectonics, like slumpings, slump breccias and neptunian dykes. Their deposition most likely occurred in a subtidal environment controlled by faults. Apparently, in South-west Sardinia and in the Sierra de Aracena, both sedimentary evolution and ore deposition were strictly related, and conditioned by several pulses of tensional tectonics. © 1990 Ferdinand Enke Verlag Stuttgart.