Volcanic domes and gold mineralization in the Pueblo Viejo district, Dominican Republic |
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| Authors: | C E Nelson |
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| Institution: | (1) 2360 23rd Street, Boulder, Colorado 80304, USA e-mail: cnelson945@aol.com Tel.: +1-303-9399517; Fax: +1-303-9399517, US |
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| Abstract: | Gold mineralization in the Pueblo Viejo district, Dominican Republic, is spatially and temporally related to a series of
Early Cretaceous volcanic domes. Separate but overlapping hydrothermal cells, centered on the domes, together deposited more
than 40 million oz. of gold, 240 million oz. of silver, 3 million tonnes of zinc, and 0.4 million tonnes of copper. Two principal
deposits (Moore and Monte Negro) and a number of smaller deposits (Cumba, Mejita, Upper Mejita, Banco V, Arroyo Hondo I and
II) have contributed ore since mining commenced in 1975. New geologic mapping has identified a series of previously unrecognized
volcanic domes that vary from andesite to dacite in composition. A dacite porphyry dome intrudes epiclastic sediments in the
Moore deposit and is surrounded by a baked contact metamorphic aureole. Crumble breccias of mixed epiclastic and pyroclastic
origin mantle andesite domes in the Monte Negro, Cumba, and Mejita deposits. Epiclastic volcanic sediments surrounding each
of the domes reflect the composition of the local source rock. Andesite domes of the Monte Negro deposit are surrounded by
andesitic volcaniclastic sediments. Epiclastic sediments surrounding a dacite porphyry dome in the Moore deposit contain detrital
quartz eyes and debris flows of dacite porphyry. A series of at least seven volcanic centers interfinger, overlap, and are
interbedded with locally derived epiclastic sediments. Field relations indicate that volcanic dome emplacement, epiclastic
sediment accumulation, hydrothermal alteration, and gold mineralization were coeval events. Domes were emplaced in a shallow
subaqueous environment on the flanks of an emergent volcanic edifice. Hydrothermal cells responsible for gold mineralization
are controlled by high-angle faults. These same faults influenced the emplacement of volcanic domes, an essential step in
the development of gold ore in the Pueblo Viejo district.
Received: 15 March 1999 / Accepted: 29 September 1999 |
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