Subduction Zones of the Caribbean : the sedimentary, magmatic, metamorphic and ore-deposit records UNESCO/iugs igcp Project 546 Subduction Zones of the Caribbean

The International Union of Geosciences (IUGS) and UNESCO IGCP project 546 Subduction Zones of the Caribbean (http://www.ugr.es/~agcasco/igcp546/) was launched in 2007 and scheduled to be completed by the end of the current year 2011. It was set up with the aim of gathering researchers interested in the geological evolution of the Caribbean realm. The development of this region is largely controlled by a number of subduction zones that formed along its margins from the break-up of Pangea during the Jurassic until Present. The current setting is characterized by a very complex plate-tectonic configuration dominated by subduction zones, large-scale strike-slip faults, volcanic arcs and collision belts (Figure 1). The project was built upon previous developments of IGCP project 433 Caribbean Plate Tectonics (2000-2005), of which the Special Volume 4 (Issue 1-2) of Geologica Acta Caribbean Plate Tectonics. Stratigraphic, Magmatic, Metamorphic and Tectonic Events (Iturralde Vinent and Lidiak, 2006) deserves mentioning

Serpentinites and serpentinites within a fossil subduction channel : La Corea mélange, eastern Cuba

A variety of metaultramafic (serpentinite) rocks in La Corea mélange, Sierra de Cristal, eastern Cuba, show differences in chemical, textural and mineralogical characteristics demonstrating a variety of protoliths. The mélange originated during the Cretaceous as part of the subduction channel associated with the Caribbean island arc. This mélange contains high pressure blocks in a serpentinite matrix and occurs at the base of the large tabular Mayarí-Cristal ophiolite. Two principal groups of serpentinites have been identified in the mélange: a) antigorite serpentinite, mainly composed of antigorite and b) antigorite-lizardite serpentinite, composed of mixtures of antigorite and lizardite and bearing distinctive porphyroblasts of diopsidic clinopyroxene. Antigorite serpentinites are closely related to tectonic blocks of amphibolite (representing subducted MORB) and constitute deep fragments of the serpentinitic subduction channel formed during hydration of the mantle wedge. The composition of the antigorite-lizardite serpentinites and the presence of clinopyroxene porphyroblasts in this type of rock suggest that abyssal lherzolite protoliths transformed into serpentinite before and during incorporation (as tectonic blocks) in the shallow part of the subduction channel. Although the studied rocks have different origin, mineralogical compositions and textures, they display similar PGE compositions, suggesting that these elements experienced no significant redistribution during metamorphism. Both types of serpentinites were exposed together in the La Corea mélange during the Late Cretaceous, during obduction of the overriding Mayarí-Baracoa ophiolitic belt that led to exhumation of the subduction channel (mélange)

Ophiolite-Related Ultramafic Rocks (Serpentinites) in the Caribbean Region : a Review of their Occurrence, Composition, Origin, Emplacement and Ni-Laterite Soil Formation

Ultramafic rocks, mainly serpentinized peridotites of mantle origin, are mostly associated with the ophiolites of Mesozoic age that occur in belts along three of the margins of the Caribbean plate. The most extensive exposures are in Cuba. The ultramafic-mafic association (ophiolites) were formed and emplaced in several different tectonic environments. Mineralogical studies of the ultramafic rocks and the chemistry of the associated mafic rocks indicate that most of the ultramafic-mafic associations in both the northern and southern margins of the plate were formed in arc-related environments. There is little mantle peridotite exposed in the ophiolitic associations of the west coast of Central America, in the south Caribbean in Curacao and in the Andean belts in Colombia. In these occurrences the chemistry and age of the mafic rocks indicates that this association is mainly part of the 89 Ma Caribbean plateau province. The age of the mantle peridotites and associated ophiolites is probably mainly late Jurassic or Early Cretaceous. Emplacement of the ophiolites possibly began in the Early Cretaceous in Hispaniola and Puerto Rico, but most emplacement took place in the Late Cretaceous to Eocene (e.g. Cuba). Along the northern South America plate margin, in the Caribbean mountain belt, emplacement was by major thrusting and probably was not completed until the Oligocene or even the early Miocene. Caribbean mantle peridotites, before serpentinization, were mainly harzburgites, but dunites and lherzolites are also present. In detail, the mineralogical and chemical composition varies even within one ultramafic body, reflecting melting processes and peridotite/melt interaction in the upper mantle. At least for the northern Caribbean, uplift (postemplacement tectonics) exposed the ultramafic massifs as a land surface to effective laterization in the beginning of the Miocene. Tectonic factors, determining the uplift, exposing the peridotites to weathering varied. In the northern Caribbean, in Guatemala, Jamaica, and Hispaniola, uplift occurred as a result of transpresional movement along pre-existing major faults. In Cuba, uplift occurred on a regional scale, determined by isostatic adjustment. In the south Caribbean, uplift of the Cordillera de la Costa and Serrania del Interior exposing the peridotites, also appears to be related to strike-slip movement along the El Pilar fault system. In the Caribbean, Ni-laterite deposits are currently being mined in the central Dominican Republic, eastern Cuba, northern Venezuela and northwest Colombia. Although apparently formed over ultramafic rocks of similar composition and under similar climatic conditions, the composition of the lateritic soils varies. Factors that probably determined these differences in laterite composition are geomorphology, topography, drainage and tectonics. According to the mineralogy of principal ore-bearing phases, Dominican Ni-laterite deposits are classified as the hydrous silicate-type. The main Ni-bearing minerals are hydrated Mg-Ni silicates (serpentine and "garnierite") occurring deeper in the profile (saprolite horizon). In contrast, in the deposits of eastern Cuba, the Ni and Co occurs mainly in the limonite zone composed of Fe hydroxides and oxides as the dominant mineralogy in the upper part of the profile, and are classified as the oxide-type

Mapping participatory planning in Havana: patchwork legacies for a strengthened local governance

In 2019, Cuba approved a new political constitution that calls for deepening citizen participation to strengthen local governance. The emerging decentralization processes and the role of new actors in urban development open new possibilities for inclusive planning. While citizen participation is widely documented in the global South and under Western liberal democracy regimes, participatory urban planning in the context of Southern socialist cities such as Havana has been less scrutinized. This paper aims at mapping the framings, trajectories and legacies of such participatory planning initiatives. Based on mapping workshops and desktop research, we find that participatory initiatives within Havana are spatially dispersed, sporadic, lacking at the city level, and occurring in isolation at the neighbourhood level. We argue that establishing sustained participatory urban planning practices in Havana requires decision makers to scale outwards and upwards the lessons learned from existing initiatives to foster a city-wide participatory planning strategy

The Geology of Chile

6 páginas.-- Book review of "The Geology of Chile", by Teresa Moreno and Wes Gibbons (eds.) (2007). Geological Society. London (United Kingdom). 414 pages, 286 figures including maps, charts and pictures; 27, 5 x 21 cm, ISBN 978-1- 86239-219-9 (hardback) and ISBN 978-1-86239-220-5 (softback).Peer reviewe

Chromite and platinum group elements mineralization in the Santa Elena Ultramafic Nappe (Costa Rica): geodynamic implications

Chromitites associated with strongly altered peridotite from six distinct localities in the Santa Elena ultramafic nappe (Costa Rica) have been investigated for the first time. Santa Elena chromitites commonly display a compositional variation from extremely chromiferous (Cr/(Cr+Al)=0.81) to intermediate and aluminous (Cr/(Cr+Al)=0.54). This composition varies along a continuous trend, corresponding to calculated parental liquids which may have been derived from the differentiation of a single batch of boninitic magma with Cr-rich and (Al, Ti)-poor initial composition. Fractional precipitation of chromite probably occurred during differentiation of the boninitic melt and progressive metasomatic reaction with mantle peridotite. The distribution of platinum group elements (PGE) displays the high (Os+Ir+Ru)/(Rh+Pt+Pd) ratio typical of ophiolitic chromitites and, consistently, the platinum group minerals (PGM) encountered are mainly Ru-Os-Ir sulfides and arsenides. Textural relations of most of the platinum group elements suggest crystallization at magmatic temperatures, possibly under relatively high sulfur fugacity as indicated by the apparent lack of primary Os-Ir-Ru alloys. The chemical and mineralogical characteristics of chromitites from the Santa Elena ultramafic nappe have a strong affinity to podiform chromitites in the mantle section of supra-subduction-zone ophiolites. Calculated parental melts of the chromitites are consistent with the differentiation of arc-related magmas, and do not support the oceanic spreading center geodynamic setting previously proposed by some authors