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Origin of Gold from the Golfo Dulce Placer Province, Southern Costa Rica

  • Jevan P. Berrangé
Part of the Circum-Pacific Council for Energy and Mineral Resources Earth Science Series book series (CIRCUM-PACIFIC, volume 16)

Abstract

The Golfo Dulce goldfield has been mined since pre-Columbian times and currently produces at least twice as much gold as the entire Tilarán-Aguacate Gold Province in northern Costa Rica. The gold is mainly concentrated in eluvial, colluvial, and alluvial placers in the Osa Group (late Pliocene) and the Puerto Jiménez Group (late Pleistocene-Holocene) that unconformably overlie the Nicoya Complex basement (Late Cretaceous-early Tertiary). This is a segment of oceanic crust characterized by EMORB-type basalts typical of a back arc basin such as the Mariana Trough.

Studies of the geographic and stratigraphic distribution of the placer gold, its habit and composition, and the associated heavy mineral suite, demonstrate conclusively that it was locally derived from the nearby Nicoya Complex. The gold was initially concentrated in epithermal auriferous quartz lodes in the basalts, and in interlayered pelagic sediments, by hot circulating fluids (seawater and magmatic fluids) related to one or more of three submarine volcanic events. Translative plate movement and subsequent obduction and isostatic uplift of this segment of oceanic crust during development of the Southern Central America Orogen allowed weathering and erosion of the ophiolite complex. This produced native gold and gold in solution that was concentrated during several cycles as placers in the associated sediments.

The primary gold deposits of the Southern Central America Orogen, in Costa Rica and Panamá, appear to include two distinct types and occur as (1) epithermal Au−Ag+(P−Zn−Cu) deposits of late Tertiary age associated with calc-alkaline acid-intermediate intrusives and/or volcanics in the inner arc, or (2) as epithermal low-Ag deposits in ophiolite terrains of the outer arc. These probably originated by hydrothermal activity related to submarine basaltic volcanism in an extensional environment such as aback arc basin, and are significantly older—Late Cretaceous to early Tertiary. The Golfo Dulce goldfield is the most westerly occurrence of an “ophiolite gold province.” The recognition that virtually uncratonized oceanic crust in this region forms the “source beds” for gold deposits suggests that similar ophiolitic terrains in the eke urn-Pacific and Caribbean should be regarded as gold exploration targets.

Keywords

Gold Deposit Oceanic Crust Versus Versus Versus Versus Versus Versus Versus Versus Versus British Geological Survey 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Circum-Pacific Council for Energy and Mineral Resources 1995

Authors and Affiliations

  • Jevan P. Berrangé
    • 1
  1. 1.Overseas DirectorateBritish Geological SurveyKeyworth, NottinghamshireUK

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