Potential for Sullivan-type Pb-Zn-Ag deposits in modern sedimentary basins
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LETTER
Potential for Sullivan-type Pb-Zn-Ag deposits in modern sedimentary basins John F. Slack 1,2 Received: 19 February 2020 / Accepted: 28 May 2020 # This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2020
Abstract Numerous modern sedimentary basins contain geological features similar to those associated with the giant (150 Mt) Sullivan PbZn-Ag deposit (British Columbia) in the Mesoproterozoic Belt-Purcell Basin. Important features at Sullivan include a large synsedimentary mud volcano that hosts the stratabound and partly stratiform sulfide ores, an underlying vent complex of altered and mineralized rocks, and mafic sills in the shallow to deep footwall. High-resolution 3D seismic profiles of the North Sea region and the South China Sea, as well as other late Mesozoic to Cenozoic basins such as the Irish Rockall Basin, suggest the presence of mafic sill complexes with overlying fluid-escape pipes, mud volcanoes, and hydrothermal vent complexes of diverse size and shape. Although fluid-escape pipes and related discordant features in modern sedimentary basins are widely accepted as being linked to hydrocarbon generation and resources, potential for metal concentrations in these basins should also be tested. Evaluating this possibility can be done using high-resolution seismic surveys followed by deep drilling. Keywords Clastic-dominated Pb-Zn . Sullivan deposit . Rift basins . Mafic sills . Hydrothermal vent complexes . North Sea region . South China Sea
Introduction Stratiform clastic-dominated sulfide deposits of Zn + Pb ± Ag (CD Zn-Pb) occur in Proterozoic and Phanerozoic sedimentary basins dominated by shale or siltstone with generally minimal carbonate and few if any volcanic rocks (Leach et al. 2005; Emsbo et al. 2016). In contrast to volcanogenic massive sulfide (VMS) Cu + Zn ± Pb ± Au ± Ag deposits, for which at least 400 examples are documented in the world oceans (Petersen et al. 2019), modern analogs of CD Zn-Pb deposits are unknown. The metalliferous deposits of the Red Sea have been linked by some workers to ancient CD Zn-Pb systems, but the former exhibit important differences in terms of metal signature (high Cu, low Pb) and occurrence in a basalt-floored rift setting
Editorial handling: K. Kelley * John F. Slack [email protected] 1
U.S. Geological Survey (Emeritus), National Center, MS 954, Reston, VA 20192, USA
2
Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, NL A1B 3X5, Canada
(e.g., Laurila et al. 2015). Other studies have proposed that the Cu ± Zn deposits of Guaymas Basin, Middle Valley, and Escanaba Trough represent modern analogs of ancient CD Zn-Pb deposits (Goodfellow et al. 1993), but these three deposits differ fundamentally in having relatively low Pb contents and being localized in sediment-covered spreading centers. Stratiform CD Zn-Pb deposits are still commonly referred to by the term Sedex (sedimentary-exhalative), based on models that involve predominant syngenetic mineraliza
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