Towards a unified genetic model for the Au-Ag-Cu Pueblo Viejo district, central Dominican Republic

Abstract

The origin of the world-class Pueblo Viejo deposit, central Dominican Republic, remains controversial. In this article we scale up the area of study to the Cabirma del Cerro mining concession, which abuts the Pueblo Viejo mining area, and integrate new data on the stratigraphy, lithogeochemistry and U-Pb geochronology of volcanogenic units with previous descriptions of the geology of the Pueblo Viejo deposit. Volcanic, volcaniclastic and sedimentary lithofacies of the ore-hosting Los Ranchos Formation reveal a progression from deposition in submarine to subaerial environments. Volcanic and hyaloclastite deposits are of exclusive basaltic composition, and were deposited at ca. 122–112Ma. Lithogeochemistry of basaltic rocks indicates tholeiitic and boninitic affinities. Chemostratigraphic relationships denote a progressive shift from LREE-depleted low-Ti island-arc tholeiitic and boninitic lavas to LREE-richer island-arc tholeiitic lavas. Basaltic deposits were intruded by tonalite batholiths and plagiorhyolite stocks at ca. 113–109Ma. These acid intrusives have tholeiitic, M-type affinities. Subsequently, diorites with transitional tholeiitic-calc-alkaline, and monzodiorites and andesitic domes with calc-alkaline affinities were emplaced at 109–106Ma. The progressive lithogeochemical changes throughout the magmatic sequence of the Los Ranchos Formation mirror those in so-called subduction-initiation ophiolites. Hydrothermal alteration and sulfide mineralization are ubiquitous in the area of study, and include volcanogenic massive sulfide (VMS) and epithermal deposit types. By assessing the location of these mineralization types in the stratigraphic sequence, an integrated metallogenic model with two distinct mineralization events is presented: (1) VMS mineralization took place during the subduction-initiation stage of the island-arc, and was genetically associated to LREE-depleted tholeiitic and boninitic basalts; subsequently (2) porphyry Cu(-Mo)-high sulfidation epithermal mineralization at ca. 112Ma was most likely connected to a widespread episode of M-type acid magmatism of tholeiitic affinity during the steady-state or true-subduction regime.