Introducción a la metalogenia del Mn en Cuba

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

Rocas volcánicas de las series Inferior y Media del Grupo El Cobre en la Sierra Maestra (Cuba Oriental): volcanismo generado en un arco de islas tholeiítico

A set of 11 samples of igneous rocks from the lower and middle Cobre Group of the Sierra Maestra (SE Cuba) were analyzed. These rocks are volcanic and hypoabyssal bodies with porp hyritic texture and predominantly plagioclase phenocrystals. Their composition ranges from basalt to dacite and shows a tholeiitic trend with low K contents. The REE concentrations are low and, when normalized to chondrite, show a flat pattern with no relative enrichment in either LREE or HREE. In addition, these rocks present a slight enrichment in LILE and a strong Nb negative anomaly, typical of island arc tholeiites. Because of their geochemistry, the rocks of the Sierra Maestra are comparable to those of the Ke rmadec arc in the SW Pacific. Finally, the low REE content, the flat REE pattern, as well as the low uncompatible element contents, are similar to the IAT Series present in the Caribbean Volcanic Arcs. All these new data on the Pa l e ogene volcanism suggest that the tectonic models proposed for the origin of the Sierra Maestra Arc should be revised

Mineralogy, geochemistry and sulfur isotope characterization of Cerro de Maimón (Dominican Republic), San Fernando and Antonio (Cuba) lower Cretaceous VMS deposits: Formation during subduction initiation of the proto-Caribbean lithosphere within a fore-arc

The volcanic-arc Lower Cretaceous Maimón (Dominican Republic) and Los Pasos (Cuba) Formations, representative of the oldest magmatism recorded in the Caribbean island arc, host most of the known volcanogenic massive sulfide (VMS) deposits in the Greater Antilles. On the basis of new lithogeochemical data, basalts of the Maimón Formation are classified as fore arc basalts (FAB), boninites and less abundant low-Ti (LOTI) and normal island-arc tholeiites (IAT), and those of the Los Pasos Formation as LOTI and IAT. Felsic volcanics from the two formations are geochemically analogous and present mantle-type (M-type), boninitic and tholeiitic signatures, classifying as FIV-type, typical of post-Archaean VMS-bearing juvenile volcanic suites. This lithogeochemical data is indicative of formation in a fore-arc environment just after subduction initiation in association with initial extensional regimes and associated boninitic and tholeiitic melts that originated in the shallow mantle. Within this tectonic framework, rocks of the Los Pasos Formation and associated VMS deposits likely formed at a slightly later stage than those of the Maimón Formatio

La Margarita and Los chivos Manganese deposits (Eastern Cuba)

The stratiform ore deposits o f Los Chivos and La Margarita manganese , consist o f ore-rich beds (massive, mainly constituted by botrioidal todorokite), and ore-poor beds (todorokite cementing vulcanoclastics). They are associated to jasper and celadonite beds. Hydrothermal alteration occurs at the basis of the deposits, and this indicates the proximity of exhalative centers. According to textural evidences, synsedimentary and diagenetic ore removilization is also presen

Geology, fluid inclusion and sulphur isotope characteristics of the El Cobre VHMS deposit, Southern Cuba

The El Cobre deposit is located in eastern Cuba within the volcanosedimentary sequence of the Sierra Maestra Paleogene arc. The deposit is hosted by tholeiitic basalts, andesites and tuffs and comprises thick stratiform barite and anhydrite bodies, three stratabound disseminated up to massive sulphide bodies produced by silicification and sulphidation of limestones or sulphates, an anhydrite stockwork and a siliceous stockwork, grading downwards to quartz veins. Sulphides are mainly pyrite, chalcopyrite and sphalerite; gold occurs in the stratabound ores. Fluid inclusions measured in sphalerite, quartz, anhydrite and calcite show salinities between 2.3 and 5.7 wt% NaCl eq. and homogenisation temperatures between 177 and 300°C. Sulphides from the stratabound mineralisation display ∂34S values of 0‰ to +6.0‰, whilst those from the feeder zone lie between −1.4‰ and +7.3‰. Sulphides show an intra-grain sulphur isotope zonation of about 2‰ usually, ∂34S values increase towards the rims. Sulphate sulphur has ∂34S in the range of +17‰ to +21‰, except two samples with values of +5.9‰ and +7.7‰. Sulphur isotope data indicate that the thermochemical reduction of sulphate from a hydrothermal fluid of seawater origin was the main source of sulphide sulphur and that most of the sulphates precipitated by heating of seawater. The structure of the deposit, mineralogy, fluid inclusion and isotope data suggest that the deposit formed from seawater-derived fluids with probably minor supply of magmatic fluids

Rocas volcánicas de las series Inferior y Media del Grupo El Cobre en la Sierra Maestra (Cuba Oriental): volcanismo generado en un arco de islas tholeiítico

Se han analizado once muestras de rocas volcánicas (basaltos, andesita basáltica, ande sitas y dacitas) localizadas en la parte inferior y media de las series del Grupo El Cobre en la Sierra Maestra (este de la Isla de Cuba). Las muestras corresponden (excepto la muestra M8) a cuerpos hipoabisales, y se componen principalmente de fenocristales de plagioclasas, con un predominio de texturas porfíricas. De acuerdo a los contenidos de SiO2, FeO total, MgO y K2O, las rocas presentan una tendencia tholeiítica con bajos contenidos en K. Los contenidos de REE son bajos y presentan un patrón normalizado a los valores condríticos prácticamente no fraccionado (plano) desde las LREE a las HREE. Los elementos trazas muestran un ligero enriquecimiento en large-ion lithophile elements (LILE), y una marcada anomalía negativa de Nb, caracteristico de muchas tholeiítas de arcos de islas. La composición química de los clinopiroxenos también es similar a la que presentan los clinopiroxenos de las tholeiítas de arcos de islas. Las características geoquímicas ( elementos mayores y trazas) de las rocas analizadas son similares a las del arco volcánico de Kermadec en Pacífico SW. Por último, los bajos contenidos en REE, el patrón de REE con morfología plana, así como los bajos contenídos en elementos incompatibles (K, Rb, Zr, Th) son similares a los de las series tipo IAT presentes en el arco volcánico del Caribe. Estos nuevos datos sobre el volcanismo del Paleógeno de la Sierra Maestra sugieren que los modelos de placas tectónicas que han sido propuestos para explicar el origen del arco volcánico de Sierra Maestra deben ser revisado

Mineralogy, geochemistry and sulfur isotope characterization of Cerro de Maimón (Dominican Republic), San Fernando and Antonio (Cuba) lower Cretaceous VMS deposits: Formation during subduction initiation of the proto-Caribbean lithosphere within a fore-arc

The volcanic-arc Lower Cretaceous Maimón (Dominican Republic) and Los Pasos (Cuba) Formations, representative of the oldest magmatism recorded in the Caribbean island arc, host most of the known volcanogenic massive sulfide (VMS) deposits in the Greater Antilles. On the basis of new lithogeochemical data, basalts of the Maimón Formation are classified as fore arc basalts (FAB), boninites and less abundant low-Ti (LOTI) and normal island-arc tholeiites (IAT), and those of the Los Pasos Formation as LOTI and IAT. Felsic volcanics from the two formations are geochemically analogous and present mantle-type (M-type), boninitic and tholeiitic signatures, classifying as FIV-type, typical of post-Archaean VMS-bearing juvenile volcanic suites. This lithogeochemical data is indicative of formation in a fore-arc environment just after subduction initiation in association with initial extensional regimes and associated boninitic and tholeiitic melts that originated in the shallow mantle. Within this tectonic framework, rocks of the Los Pasos Formation and associated VMS deposits likely formed at a slightly later stage than those of the Maimón Formatio