LEAD, TIN, AND PRECIOUS-METAL MINERALIZATION IN THE U. S. VIRGIN ISLANDS.

This regional geochemical study of the U. S. Virgin Islands demonstrates the presence of a widespread base-metal (primarily Pb, Sn, Cu) and precious-metal (primarily Ag) mineralization on all three of the islands. The overall association: Au, Ag, Te, Sn, Pb, Cu, Zn, Sb, Bi, Mo, As and Ba shows a great similarity to that of the Bolivian silver-tin district. The single divergence from the Bolivian association is tungsten, which is totally lacking in the U. S. Virgin Islands. The delineated geochemical patterns transect all exposed rock types on the islands, including the Kingshill Marl of late Miocene age, on St. Croix. Some relationship between the geochemical patterns and the major mapped faults can be seen - especially on St. Croix. K-Ar age dating of rocks from St. Thomas and St. John indicates that they are of Tertiary rather than Cretaceous age. This and the apparent contemporaneity of the mineralization with the St. Croix graben infilling indicate a very late Miocene age for the mineralization.