Large Seafloor Volcanic-hosted Massive Sulfide Deposits: Discovered and
Undiscovered
Peter A. Rona, Institute of Marine and Coastal Sciences and Department of Geological
Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ 08901-8521
(rona@marine.rutgers.edu)
Some hundreds of sites of massive sulfides have been found hosted in volcanic rocks at
global spreading axes and submarine volcanoes on ocean ridges and in volcanic island
arcs (fore- and back-arc settings; Rona and Scott, 1993; Hannington et al., 2004).
However, relatively few of these deposits are in the 5 million tonne class, the size that a
leading marine mining company identifies as prospective. A large gap exists between
these seafloor massive sulfides and the largest volcanic-hosted massive sulfide deposits
on land in the 100 million tonne range like the Kidd Creek deposit of eastern Canada,
interpreted as an analog of modern seafloor volcanic-hosted massive sulfide deposits
(Hannington et al., 1999).
This size gap is largely an artifact of the present early stage of ocean exploration. If such
giant massive deposits exist on the seafloor, where are they likely to be found? Spreading
axes and submarine fore-arc volcanoes remain prospective for discovery of giant massive
sulfide deposits. However, even more likely are relict deposits at sites in oceanic and
transitional lithosphere generated in these tectonic settings and now underlying ocean and
back-arc basins (Rona, 2008). Challenges are to advance understanding of how massive
sulfide deposits evolve as they move away from active sites of formation with the aging
lithosphere by drilling (e.g., the assemblage of large massive sulfide mounds spanning
over 100,000 years at the TAG hydrothermal field on the Mid-Atlantic Ridge) and to
develop appropriate exploration methods to detect properties that reside with the deposits
as they age, such as a magnetic signature of crustal alteration by hydrothermal processes
(Rona, 1978; Tivey et al., 1996).
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massive sulfide deposit, Western Abitibi subprovince, Canada, In Hannington, and
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Deposit, Western Abitibi Subprovince, Canada:, Economic Geology, Monograph 10,
Preface and introduction, 1-28.
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Mineralization: New Perspectives, Economic Geology 88, 1935-1975.
Tivey, M.A., Rona, P.A., Kleinrock, M.C., 1996. Reduced crustal magnetization beneath
relict hydrothermal mounds, TAG hydrothermal field, Mid-Atlantic Ridge, 26oN,
Geophysical Research Letters 23, 3511-3514.