Multidisciplinary approach to metallogenic models and types of primary gold concentration in the Cretaceous arc terranes of the Dominican Republic

Synopsis Multidisciplinary research carried out on primary gold ores in the evolving Cretaceous island are terranes of the Dominican Republic has shown the exi stence of three groups of deposits and occurrences. The first comprises the Lower Cretaceous ores, including the giant Pueblo Viejo deposit and severa l uneconomic showings with traces of Au-Ag in the El Valle area west of Mic hes; comparison of the acid-sulphate hydrothermal system of Pueblo Viejo wi th the disseminated, one-stage system of the El Valle region accounts for t he fundamental differences in gold tonnages and grades between the two dist ricts. The Upper Cretaceous barite-polymetallic (Cu-Zn)-Au-Ag epithermal or es in the northwest Dominican Republic and Haiti form the second group; Cu- Mo anomalies in oxidation zones are consistent with the observed presence o f Cu-Mo porphyries at depth. The third group is formed by Upper Cretaceous- Tertiary metasediment-hosted, metamorphic quartz-sulphide, granitic vein sw arms of the Miches area. These rocks are the probable source for the Miches lateritic/alluvial gold, which has been reworked during erosion and lateri tization. Leaching tests have demonstrated the viability of routes other than cyanida tion for gossanous gold-enriched samples from El Valle and Restauracion (no rthwest Dominican Republic). The results of a thiocyanate leach test appear to be the most promising on comparison with those obtained from tests with thiourea and ammoniacal thiosulphate.