Una introducción a la metalogenia de Cuba bajo la perspectiva de la tectónica de placas

Six main metallogenic epochs can be distinguished in the geological constitution of the island of Cuba. A first stage from Jurassic to Early Cretaceous times, included a rift episode involving materials from the Bahama and Yucatán continental paleomargin. Base metals sedex deposits (Pb-Zn-Cu) and Mn, associated with gold and silve r, are to be found in the detrital and carbonated series associated to this process. An arc (or arcs) of volcanic islands developed during the Aptian (Neocomian?)-Campanian stage. Three metallotects are to be found associated to the formation and development of this arc: a) the uppermost part of the suprasubduction zone mantle section, where bodies of ophiolitic chromitites occur, b) the back-arc volcanosedimentary submarine series, with volcanogenic deposits of massive sulfides (Kuroko and Cyprus type), Mn oxide exhalative mineralizations and zeolite deposits, and, c) the intrusive series and rocks in the axial zone of the arc, with iron and polymetallic skarn deposits, porphyry copper deposits and Au-Ag epithermal deposits. The first collisional process, between the Yucatán paleomargin and the Cretaceous volcanic arc, as well as the beginning of the collision between the Caribbean plate and the North-American plate, took place during the late Campanian-Danian stage. Orogenic gold mineralizations and, probably, tumgsten deposits date from this period. A volcanic arc, trending E-W, developed in eastern Cuba from Late Danian to Middle Eocene times. Major volcanogenic Mn deposits in Cuba are located within the Paleogene volcanic island arc in eastern Cuba. This volcanic activity also originated some major volcanogenic sulfide deposits, skarn and porphyry copper deposits, as well as zeolite deposits. Known metallotects in this geodynamic environment include: a) the volcanic and volcanosedimentary series located along the axial arc-back arc boundary, with volcanogenic sulfide deposits (Kuroko type) and Mn oxide volcanogenic deposits, and b) granitic intrusives related to the axial arc volcanic, with skarn and porphyry copper deposits. In western and central Cuba, in turn, piggy-back sedimentary basins associated to the collisional process between the Caribbean plate and the North-American plate developed during Danian-Middle Eocene times. Major orogenic gold mineralizations are associated with this process. A series of post-volcanic basins developed during the Middle Eocene-Late Eocene stages in eastern Cuba, some of which are associated to Mn resedimented mineralizations. Meanwhile, the development of sedimentary basins with olistostromes, associated to the collisional process, continued in central and western Cuba. Cuba finally joined the North-American plate at the end of this episode. Orogenic gold mineralizations may also occur in association with these processes. A shelf environment was established in Cuba from Late Eocene to Quatern a ry times. At that point, extensive Fe-Ni-Co laterite crusts (one of the largest examples of this type of deposit worldwide), bauxite crusts, gossan deposits (Fe, Au, Ag), resedimented Mn deposits, and marine and fluvial placer deposits, rich in noble metals, originated

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

El yacimiento Matahambre (Pinar del Río, Cuba): estructura y mineralogía

The Matahambre ore deposit has two types of mineralization: a stratiform mineralization (with Pb-Zn) hosted in black shales, and a vein mineralization (with Cu), hosted in the sandstones of the Lower Jurassic San Cayetano formation. In addition to chalcopyrite, pyrite, sphalerite and Co-Ni sulfoarsenides, minor amounts of Bi-, Ag-, and Pb-selenides and tellurides are common in the vein mineralization. Contrastingly, the stratiform mineralization display a zonal structure: pyite is the dominant sulphide at lower part, and sphalerita and galena at the upper part. In the lower part, sphalerite and other sulphides display evidences to have been replaced by pyrite and chalcopyrite, thus indicating the replacement of a low temperature mineralization by another formed at higher temperature. A sedex model is proposed for these mineralizations, based on the extensional geodynamic setting of the series, the association of stratiform facies with exhalative roots and the association with sedimentary sequences rich in black shales. The whole is deformed by thrusting, possibly caused by reactivation of normal faults in the basin

Valor patrimonial de las pegmatitas del Cap de Creus

Las pegmatitas graníticas del Cap de Creus constituyen un importante elemento de nuestro patrimonio geológico, con importantes aportaciones, tanto por su gran variedad mineralógica como por la información científica que aporta su estudio. El campo pegmatítico presenta extensos afloramientos que facilitan su estudio. Este campo pegmatítico, con unos 400 cuerpos, consta de cuatro tipos de pegmatitas, encajadas en rocas metapelíticas: microclínicas (I), de berilo-columbita (II), de berilo-columbita-fosfatos (III) y de tipo albítico (IV). El grado de evolución de estas pegmatitas aumenta hacia las situadas en zonas más internas, siendo éstas las que contienen una mayor variedad mineral: silicatos, fosfatos, óxidos e hidróxidos (minerales de Nb-Ta, casiterita, gahnita, nigerita, crisoberilo, corindón). Los fosfatos presentan una gran variedad, siendo de la asociación Ca-Fe-Mg-Mn en los tipos menos evolucionados y de Li-Al o Li-Fe-Mn en las más evolucionadas. Algunos fosfatos poco comunes presentes en estas pegmatitas son la herderiderita, berlinita y staneckita.Peer ReviewedPostprint (published version

Scheelite bearing quartz veins from Poblet (Catalonian Coastal Ranges): Characterisation of fluid inclussions and genetic model

Scheelite-bearing quartz veins from Poblet, trending in a NE-SW direction, are hosted by calcic granitoids of Late Hercynian age in the southern part of the Catalonian Coast Range. Fluid inclusions from quartz and scheelite have been characterized using microthermometry, Raman microspectrometry and Scanning Electron Microscopy. Except for type I inclusions (not observed in scheelite), similar inclusions have been observed in both minerals. One recognizes, in order of formation : Type I inclusions containing brine, daughter phases (halite, sylvite and sometimes iron chloride) and incidentally trapped minerals (ankerite, siderite, muscovite, K-felspar and unidentified species). Type II(L) inclusions have a low salinity (1 to 6 % eq. NaCl) and homogenize in the liquid phase in the range of 300-400 °C or under critical conditions near 400 °C. Type II(V) are low density, CO2-poor aqueous inclusions, homogenizing in the gas phase in the range of 350-420 °C. Type II(V') have higher CO2 contents. Type II inclusions appear as samples of an initially hypercritical fluid, trapped at different stages of its evolutions towards two subcritical fluids. Type III inclusions indicate later circulation of a colder, low-salinity solution (Th : 150 to 300 °C ; salinity : 0 to 3.5 % NaCl wt %). Abundant iron contents in type I inclusions suggest some interaction at elevated temperature (400 to 600°C) with a biotite granite (Whitney et al., 1985). P-T conditions compatible with measurements performed on type II inclusions are about 400 °C and 0.8 kbar, in a range similar to that determined for the Djbel Aouam occurrence in Hercynian Morocco (Cheilletz, 1984). Equivalent conditions have been postulated for scheelite precipitation at Poblet

Styles of Alteration of Ti Oxides of the Kimberlite Groundmass: Implications on the Petrogenesis and Classification of Kimberlites and Similar Rocks

The sequence of replacement in groundmass perovskite and spinel from SK-1 and SK-2 kimberlites (Eastern Dharwar craton, India) has been established. Two types of perovskite occur in the studied Indian kimberlites. Type 1 perovskite is found in the groundmass, crystallized directly from the kimberlite magma, it is light rare-earth elements (LREE)-rich and Fe-poor and its ΔNNO calculated value is from −3.82 to −0.73. The second generation of perovskite (type 2 perovskite) is found replacing groundmass atoll spinel, it was formed from hydrothermal fluids, it is LREE-free and Fe-rich and has very high ΔNNO value (from 1.03 to 10.52). Type 1 groundmass perovskite may be either replaced by anatase or kassite along with aeschynite-(Ce). These differences in the alteration are related to different f(CO2) and f(H2O) conditions. Furthermore, primary perovskite may be strongly altered to secondary minerals, resulting in redistribution of rare-earth elements (REE) and, potentially, U, Pb and Th. Therefore, accurate petrographic and chemical analyses are necessary in order to demonstrate that perovskite is magmatic before proceeding to sort geochronological data by using perovskite. Ti-rich hydrogarnets (12.9 wt %-26.3 wt % TiO2) were produced during spinel replacement by late hydrothermal processes. Therefore, attention must be paid to the position of Ca-Ti-garnets in the mineral sequence and their water content before using them to classify the rock based on their occurrence

Stratigraphy of lower Cambrian and unconformable lower Carboniferous beds from the Valls unit (Catalonian coastal ranges)

The Palaeozoic rocks outcropping around Valls are divided into two stratigraphic units. The boundary between both is an unconformity. The lower unit is composed by nearshore platform sediments and a Lower Cambrian age is indicated according to ichnotaxa content. The upper unit consists of pink nodular limestones and dark limestones, and it is followed by siliciclastic Culm Facies rocks. These limestones contain conodonts of the uppermost Tournaisian at its base (anchoralis-latus Zone) and lower Bashkirian (Namurian B) in the upper part. This condensed carbonate sequence was coeval with the thick siliciclastic Culm sedimentation in the surrounding areas.Consejo Interinstitucional de Ciencia y Tecnología; AMB94-0953-CO2-01Consejo Interinstitucional de Ciencia y Tecnología; DGE-PB95-1047Consejo Interinstitucional de Ciencia y Tecnología; PB98-155