Introducción a la metalogenia del Mn en Cuba

X. CAZAÑAS, Joan-Carles MELGAREJO

Abstract


Several metallogenetic episodes for manganese formation can be distinguished in the island of Cuba. The Jurassic series contains stratiform deposits of manganese silicates and oxides. These deposits are associated to sedex stratiform deposits. Exhalative mineralizations of manganese oxides are also produced during the formation of the Cretaceous volcanic arc. However, it is the Paleogene volcanic island arc of eastern Cuba which contains most of the volcanogenic deposits of manganese oxides, including both those already mined, as well as those with the most ore reserves. The manganese ore deposits from the Paleogene island arc can occur as veins or, more often, as stratiform deposits hosted in different lithostratigraphic units. Stratiform deposits display ve rtical zoning, having the following sequence from the basis to the top: jaspilites, massive oxide bodies (constituted by todorokite) and tuffs (cemented by oxides). A strong celadonitic alteration occurs at the basis of the bodies, and a zeolitic-hematitic alteration can occur at the top. The mineralizations are volcanogenic-exhalative and were formed either on the innermost part of the island arc or in the back arc basin, in all cases in submarine environments. The mineralizing fluids probably reached the submarine bottom through the synsedimentary faults that controlled the formation of subbasins. The Middle-Eocene piggy-back basins contain manganese mineralizations associated to thin beds of volcanosedimentary rocks interbedded in limestones. Field evidences (lack of alterations at the bottom and absence of jaspilites) and textural evidences (mineralization as clasts, associated with jaspilite fragments) indicate that these deposits were formed by sedimentary removilization by submarine bottom streams of preexisting ores in the Lowe r-Middle Eocene volcanosedimentary series. The Neoautochtonous sediments also contain resedimented manganese ores formed by alluvial processes in subaereal environment.

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