Metasomatism in the Tertiary volcanics of the Wagwater Belt, Jamaica, W.I.

Abstract

The Wagwater Belt represents part of a former inter-arc basin in which approximately 5,000 m of Tertiary sediments and volcanics accumulated. The volcanics are made up of minor amounts of submarine mafic flows and their sedimentary derivatives, and extensive silicic flows, volcanic breccia, conglomerates and tuffs. The mafic flows have been identified as basalts and spilites, and the silicics as dacites and quartz keratophyres. The stable-element geochemistry of the spilites is similar to that of the basalts. Ti, Zr and Y indicate that these mafic rocks were erupted in an intra-plate tectonic setting and are comparable to plateautype tholeiitic basalts. The levels of concentration of the stable elements in the quartz keratophyres are comparable to those of the dacites. The rare-earth elements of these silicic rocks confirm that they belong to the calc-alkaline series. Mineralogical, textural and geochemical data support the view that most of the basalts and dacites in the Wagwater Belt were metasomatized to spilites and quartz keratophyres respectively.