Chronology of the Pueblo Viejo epithermal gold-silver deposit, Dominican Republic: formation in an Early Cretaceous intra-oceanic island arc and burial under ophiolite.

The Pueblo Viejo deposit (production to 1996:166 t Au, 760 t Ag) is located in the Dominican Republic on the Caribbean island of Hispaniola and ranks as one of the largest high-sulfidation/acid-sulfate epithermal deposits (reserves in 2007: 635 t Au, 3,648 t Ag). One of the advanced argillic ore bodies is cut by an inter-mineral andesite porphyry dike, which is altered to a retrograde chlorite-illite assemblage but overprinted by late-stage quartz-pyrite-sphalerite veins and associated low-grade Au, Ag, Zn, Cd, Hg, In, As, Se, and Te mineralization. The precise TIMS U-Pb age (109.6±0.6 Ma) of the youngest zircon population in this dike confirms that the deposit is part of the Early Cretaceous Los Ranchos intraoceanic island arc. Intrusion-related gold-sulfide mineralization took place during late andesite-dacite volcanism within a thick pile (>200 m) of carbonaceous sand- and siltstones deposited in a restricted marine basin.The high-level deposit was shielded from erosion after burial under a late Albian (109-100 Ma) ophiolite complex (8 km thick), which was in turn covered by the volcano-sedimentary successions (>4 km) of a Late Cretaceous-Early Tertiary calc-akaline magmatic arc. Estimates of stratigraphic thickness and published alunite, illite, and feldspar K-Ar ages and closure temperatures (alunite 270±20C, illite 260±30C, K-feldspar 150C) indicate a burial depth of about 12 km at 80 Ma. During peak burial metamorphism (300C and 300 MPa), the alteration assemblage kaolinite + quartz in the deposit dehydrated to pyrophyllite. Temperature-time relations imply that the Los Ranchos terrane then cooled at a rate of 3-4C/Ma during slow uplift and erosion

Mesozoic and Cenozoic Plate Evolution of the Caribbean Region

The reconstruction of Caribbean plate history is an uncertain task, but a task that has intrigued generations of geologists. Each worker has turned to the task of historical interpretation influenced by a particular set of experiences or a special approach, and the results have been accordingly varied. A complete history of interpretations would form the subject of a fascinating chapter in the history of geological philosophy, but such is not the purpose of this chapter. Instead, I will dwell on a set of data that call for what I believe to be a relatively conservative view of Cretaceous and Tertiary plate history. My own interpretation is based heavily on my own or my students’ field experiences in the northeastern West Indies, Guatemala, Belize, and Venezuela, as well as extensive field excursions in Hispaniola, Jamaica, the Lesser Antilles, Central America, and the Dutch Antilles. I am further heavily influenced by the results of the Deep Sea Drilling Project (DSDP), Leg 15, which produced information of fundamental interest in the Venezuelan and Colombian Basins, and by several dissertations of the Princeton University group in northern Venezuela