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

Multidisciplinary research carried out on primary gold ores in the evolving Cretaceous island arc terranes of the Dominican Republic has shown the existence of three groups of deposits and occurrences. The first comprises the Lower Cretaceous ores, including the giant Pueblo Viejo deposit and several uneconomic showings with traces of Au-Ag in the El Valle area west of Miches; comparison of the acid-sulphate hydrothermal system of Pueblo Viejo with the disseminated, one-stage system of the El Valle region accounts for the fundamental differences in gold tonnages and grades between the two districts. The Upper Cretaceous barite-polymetallic (Cu-Zn)-Au-Ag epithermal ores in the northwest Dominican Republic and Haiti form the second group; Cu-Mo anomalies in oxidation zones are consistent with the observed presence of Cu-Mo porphyries at depth. The third group is formed by Upper Cretaceous-Tertiary metasediment-hosted, metamorphic quartz-sulphide, granitic vein swarms of the Miches area. These rocks are the probable source for the Miches lateritic/alluvial gold, which has been reworked during erosion and lateritization. Leaching tests have demonstrated the viability of routes other than cyanidation for gossanous gold-enriched samples from El Valle and Restauracion (northwest 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.