Scientific Investigations Report 2010–5070–C
Volcanogenic massive sulfide deposits, also known as volcanic-hosted massive sulfide, volcanic-associated massive sulfide, or seafloor massive sulfide deposits, are important sources of copper, zinc, lead, gold, and silver (Cu, Zn, Pb, Au, and Ag). These deposits form at or near the seafloor where circulating hydrothermal fluids driven by magmatic heat are quenched through mixing with bottom waters or porewaters in near-seafloor lithologies. Massive sulfide lenses vary widely in shape and size and may be podlike or sheetlike. They are generally stratiform and may occur as multiple lenses.
Volcanogenic massive sulfide deposits range in size from small pods of less than a ton (which are commonly scattered through prospective terrains) to supergiant accumulations like Rio Tinto (Spain), 1.5 billion metric tons; Kholodrina (Russia), 300 million metric tons; Windy Craggy (Canada), 300 million metric tons; Brunswick No. 12 (Canada), 230 million metric tons; and Ducktown (United States), 163 million metric tons. Volcanogenic massive sulfide deposits range in age from 3.55 billion years to zero-age deposits that are actively forming in extensional settings on the seafloor, especially mid-ocean ridges, island arcs, and back-arc spreading basins. The widespread recognition of modern seafloor Volcanogenic massive sulfide deposits and associated hydrothermal vent fluids and vent fauna has been one of the most astonishing discoveries in the last 50 years, and seafloor exploration and scientific studies have contributed much to our understanding of ore-forming processes and the tectonic framework for volcanogenic massive sulfide deposits in the marine environment.
Massive ore in volcanogenic massive sulfide deposits consists of greater than 40 percent sulfides, usually pyrite, pyrrhotite, chalcopyrite, sphalerite, and galena; non-sulfide gangue typically consists of quartz, barite, anhydrite, iron oxides, chlorite, sericite, talc, and their metamorphosed equivalents. Ore composition may be Pb-Zn-, Cu-Zn-, or Pb-Cu-Zn-dominated, and some deposits are zoned vertically and laterally.
Many deposits have stringer or feeder zones beneath the massive zone that consist of crosscutting veins and veinlets of sulfides in a matrix of pervasively altered host rock and gangue. Alteration zonation in the host rocks surrounding the deposits are usually well-developed and include advanced argillic (kaolinite, alunite), argillic (illite, sericite), sericitic (sericite, quartz), chloritic (chlorite, quartz), and propylitic (carbonate, epidote, chlorite) types.
An unusual feature of VMS deposits is the common association of stratiform “exhalative” deposits precipitated from hydrothermal fluids emanating into bottom waters. These deposits may extend well beyond the margins of massive sulfide and are typically composed of silica, iron, and manganese oxides, carbonates, sulfates, sulfides, and tourmaline.
First posted March 8, 2012
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Shanks, W.C. Pat, III, and Thurston, Roland, eds., 2012, Volcanogenic massive sulfide occurrence model: U.S. Geological Survey Scientific Investigations Report 2010–5070—C, 345 p.
1. Introduction By W.C. Pat Shanks III and Randolph A. Koski
2. Deposit Type and Associated Commodities By Randolph A. Koski and Dan L. Mosier
3. Historical Evolution of Descriptive and Genetic Knowledge and Concepts By W.C. Pat Shanks III
4. Regional Environment By Klaus J. Schulz
5. Physical Volcanology of Volcanogenic Massive Sulfide Deposits By Lisa A. Morgan and Klaus J. Schulz
6. Physical Description of Deposit By John F. Slack
7. Geophysical Characteristics of Volcanogenic Massive Sulfide Deposits By Lisa A. Morgan
8. Hypogene Ore Characteristics By Randolph A. Koski
9. Hypogene Gangue Characteristics By Randolph A. Koski
10. Exhalites By John F. Slack
11. Hydrothermal Alteration By W.C. Pat Shanks III
12. Supergene Ore and Gangue Characteristics By Randolph A. Koski
13. Weathering Processes By W. Ian Ridley
14. Geochemical Characteristics By W. Ian Ridley
15. Petrology of Associated Igneous Rocks By W. Ian Ridley
16. Petrology of Sedimentary Rocks Associated with Volcanogenic Massive Sulfide Deposits By Cynthia Dusel-Bacon
17. Petrology of Metamorphic Rocks Associated with Volcanogenic Massive Sulfide Deposits By Cynthia Dusel-Bacon
18. Theory of Deposit Formation By W.C. Pat Shanks III
19. Exploration-Resource Assessment Guides By John F. Slack
20. Geoenvironmental Features By Robert R. Seal II and Nadine Piatak
21. Knowledge Gaps and Future Research Directions