Scott, Peter W.; Jackson, Trevor A.; Dunham, Ansel C.
Author Affiliation, Ana.
Department of Geography and Geology
Economic potential of the ultramafic rocks of Jamaica and Tobago: Contrasting geological settings in the Caribbean
Date of Publication
Ultramafic rocks in Jamaica are dunites with minor lherozolite, often serplentinised, ans are part of a disembered ophiolite complex. In Tobago, dunites, wehrlites, pyroxenites and horblendites from the lower part of a plutonic complex of island arc affinity. The minerals assemblages and chemistry reflect these differences. Chromite in Jamaica is high in Al and Mg, whereas in Tobago it is rich in Fe, as in Alaskan-type intrusives. Ni-Cu-PGE assemblages in Jamaica are pentlandite, with later low temperature heazlewoodite, awaruite and native copper, the latter with Pt and Pd. In Tobago an assemblage of pentlandite, pyrrhotite, pyrite and chalcopyrite is much less affected by later alteration. PGE phases also occur. The dunites in Jamaica have sufficient MgO to be a potential source of olivine. The higher Fe in olivine from Tobago indicates that olivines cumulates in plutonics from island arc settings are a less suitable source of the mineral. Mi-laterites in Jamaica are unlikely because of high topographic relief. The prospect for Mi-laterites in Tobago is low as there is little Ni in the olivines. Chrysotile asbestos, talc and magnesite are absent in both islands. This is probably a consequence of the lack of secondary serpentine recrystallisation to form fibrous chrysolite veins, the deep tectonic level and lack of hydrothermal circulation for magnesite to form, and the absence of metamorphic/metasomatic events and/or late stage extension tectonics which might have yield talc.....
caribbean area; cenozoic; chalcopyrite; chromite; cretaceous; dunite; hornblendite; igneous rocks; jamaica; laterites; mesozoic; metals; metasomatism; mineral assemblages; mineral resources; nesosilicates; olivine; ophiolite; orthosilicates; oxides; pentlandite; peridotites; platinum group; plutonic rocks; plutons; pyrite; pyroxenite; serpentinization; silicates; soils; sphalerite; sulfides; tobago; trinidad and tobago; ultramafics;