|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Centre for Ore Deposit Research, Geology Department, University of Tasmania, GPO Box 252-79, Hobart, Tasmania 7001, Australia
Corresponding author: e-mail, d.cooke{at}utas.edu.au
A two-fold subdivision for stratiform sediment-hosted Pb-Zn (sedimentary exhalative, sedex) deposits is proposed, based on fundamental differences in the chemistry of the mineralizing brines. The type of sedimentary basin from which the ore fluids are derived, and the lithologies contained within the basin, control these differences in fluid chemistry.
The two discrete brine types capable of transporting Zn and Pb are oxidized brines and reduced, acidic brines. McArthur-type deposits (e.g., McArthur River, Mount Isa, Hilton) precipitate from oxidized (SO42—predominant), acidic to near-neutral brines that evolve from sedimentary basins dominated by carbonates, evaporites, and hematitic sandstones and shales. Selwyn-type deposits (e.g., Sullivan, Rammelsberg, sedex deposits of the Selwyn basin) precipitate from acidic, reduced (H2S-predominant) connate brines that evolved in reduced siliciclastic and shale basins.
Temperature decrease and dilution (fluid mixing), addition of H2S, and pH increase can all be effective depositional processes for Zn and Pb from reduced (Selwyn-type) brines. In contrast, sulfate reduction and/or addition of H2S (via fluid mixing or interaction with earlier formed pyrite) may be the important processes for sphalerite and galena deposition from oxidized (McArthur-type) brines. McArthur-type sedex deposits are intimately associated with siderite or ferroan carbonate alteration halos and most likely precipitate from lower temperature brines than Selwyn-type deposits.
The redox state of the mineralized brines (sulfate or sulfide predominant) is important for controlling minor element associations in the two classes of sedex deposits. Weakly acidic to weakly alkaline oxidized brines can precipitate siderite but are incapable of carrying significant gold, tin, and barium in solution, and as such, McArthur-type deposits do not contain anomalous concentrations of these elements. Reduced, acid brines can carry high concentrations of barium, explaining the common association with barite in these deposits. If reduced sulfur concentrations were sufficient in the mineralizing brines, individual Selwyn-type deposits may contain anomalous or ore-grade gold. If the brines were highly reduced (pyrrhotite-stable), they may have carried high concentrations of tin (e.g., Sullivan). The lack of sulfide-bearing feeder systems in McArthur-type deposits and their common occurrence in Selwyn-type deposits probably also relate to the redox state of the brines.
From a mineral exploration perspective, oxidized sedimentary brines are more likely to produce large tonnage Zn-Pb-Ag deposits that have siderite or ankerite alteration halos and commonly lack barite lenses and vent complexes. By contrast, deposits that form in reduced siliciclastic and shale-dominated basins are more likely to be lower tonnage and to contain barite, vent complexes and may have minor gold or tin credits.
This article has been cited by other articles:
|
|
 |
|
  D. T. A. Symons and D. T. A. Symons Paleomagnetism of the HYC Zn-Pb SEDEX Deposit, Australia: Evidence of An Epigenetic Origin Economic Geology, November 1, 2007; 102(7): 1295 - 1310. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. N. Southgate, T. K. Kyser, D. L. Scott, R. R. Large, S. D. Golding, and P. A. Polito A Basin System and Fluid-Flow Analysis of the Zn-Pb-Ag Mount Isa-Type Deposits of Northern Australia: Identifying Metal Source, Basinal Brine Reservoirs, Times of Fluid Expulsion, and Organic Matter Reactions Economic Geology, September 1, 2006; 101(6): 1103 - 1115. [Full Text] [PDF]
|
|
|
|
|
|
D. L. Huston, B. Stevens, P. N. Southgate, P. Muhling, and L. Wyborn Australian Zn-Pb-Ag Ore-Forming Systems: A Review and Analysis Economic Geology, September 1, 2006; 101(6): 1117 - 1157. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. A. Polito, T. K. Kyser, and M. J. Jackson The Role of Sandstone Diagenesis and Aquifer Evolution in the Formation of Uranium and Zinc-Lead Deposits, Southern McArthur Basin, Northern Territory, Australia Economic Geology, September 1, 2006; 101(6): 1189 - 1209. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. Yang, R. R. Large, S. Bull, and D. L. Scott Basin-Scale Numerical Modeling to Test the Role of Buoyancy-Driven Fluid Flow and Heat Transfer in the Formation of Stratiform Zn-Pb-Ag Deposits in the Northern Mount Isa Basin Economic Geology, September 1, 2006; 101(6): 1275 - 1292. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. H.S. Oliver, J. G. McLellan, B. E. Hobbs, J. S. Cleverley, A. Ord, and L. Feltrin 100th Anniversary Special Paper: Numerical Models of Extensional Deformation, Heat Transfer, and Fluid Flow across Basement-Cover Interfaces during Basin-Related Mineralization Economic Geology, January 1, 2006; 101(1): 1 - 31. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Stalder and A. Rozendaal Distribution and geochemical characteristics of barite and barium-rich rocks associated with the Broken Hill-type Gamsberg Zn-Pb deposit, Namaqua Province, South Africa South African Journal of Geology, March 1, 2005; 108(1): 35 - 50. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. D.K. Gauert Stratiform coticule-barite-sulphide horizons in the sediment-hosted Tsongoari-Omupokko Pb-Cu-Ba-Zn-Ag prospects, Kaokoland, Namibia South African Journal of Geology, March 1, 2005; 108(1): 87 - 118. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Rozendaal, M. Stalder, and D. Alchin Wall rock alteration and lithogeochemical haloes associated with the sediment-hosted Rosh Pinah Zn-Pb-Ag deposit in the Pan African Gariep Belt, southwestern Namibia South African Journal of Geology, March 1, 2005; 108(1): 119 - 134. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. E. Kesler Ore-Forming Fluids Elements, January 1, 2005; 1(1): 13 - 18. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. I. Groves, R. M. Vielreicher, R. J. Goldfarb, and K. C. Condie Controls on the heterogeneous distribution of mineral deposits through time Geological Society, London, Special Publications, January 1, 2005; 248(1): 71 - 101. [Abstract] [PDF]
|
|
|
|
|
|
T. Ireland, R. R. Large, P. McGoldrick, and M. Blake Spatial Distribution Patterns of Sulfur Isotopes, Nodular Carbonate, and Ore Textures in the McArthur River (HYC) Zn-Pb-Ag Deposit, Northern Territory, Australia Economic Geology, December 1, 2004; 99(8): 1687 - 1709. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. F. Slack, J. A. Dumoulin, J. M. Schmidt, L. E. Young, and C. S. Rombach Paleozoic Sedimentary Rocks in the Red Dog Zn-Pb-Ag District and Vicinity, Western Brooks Range, Alaska: Provenance, Deposition, and Metallogenic Significance Economic Geology, November 1, 2004; 99(7): 1385 - 1414. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. L. Leach, E. Marsh, P. Emsbo, C. S. Rombach, K. D. Kelley, and M. Anthony Nature of Hydrothermal Fluids at the Shale-Hosted Red Dog Zn-Pb-Ag Deposits, Brooks Range, Alaska Economic Geology, November 1, 2004; 99(7): 1449 - 1480. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. F. Slack, K. D. Kelley, V. M. Anderson, J. L. Clark, and R. A. Ayuso Multistage Hydrothermal Silicification and Fe-Tl-As-Sb-Ge-REE Enrichment in the Red Dog Zn-Pb-Ag District, Northern Alaska: Geochemistry, Origin, and Exploration Applications Economic Geology, November 1, 2004; 99(7): 1481 - 1508. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. D. Kelley, D. L. Leach, C. A. Johnson, J. L. Clark, M. Fayek, J. F. Slack, V. M. Anderson, R. A. Ayuso, and W. I. Ridley Textural, Compositional, and Sulfur Isotope Variations of Sulfide Minerals in the Red Dog Zn-Pb-Ag Deposits, Brooks Range, Alaska: Implications for Ore Formation Economic Geology, November 1, 2004; 99(7): 1509 - 1532. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. P. Davis and T. P. Davis Mine-Scale Structural Controls on the Mount Isa Zn-Pb-Ag and Cu Orebodies Economic Geology, May 1, 2004; 99(3): 543 - 559. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Canet, P. Alfonso, J.-C. Melgarejo, and S. Jorge V-RICH MINERALS IN CONTACT-METAMORPHOSED SILURIAN SEDEX DEPOSITS IN THE POBLET AREA, SOUTHWESTERN CATALONIA, SPAIN Can Mineral, June 1, 2003; 41(3): 561 - 579. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. W. Hitzman, M. W. Hitzman, N. A. Reynolds, D. F. Sangster, C. R. Allen, and C. E. Carman Classification, Genesis, and Exploration Guides for Nonsulfide Zinc Deposits Economic Geology, June 1, 2003; 98(4): 685 - 714. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. A. Johnson, C. A. Johnson, and B. J. Skinner Geochemistry of the Furnace Magnetite Bed, Franklin, New Jersey, and the Relationship between Stratiform Iron Oxide Ores and Stratiform Zinc Oxide-Silicate Ores in the New Jersey Highlands Economic Geology, June 1, 2003; 98(4): 837 - 854. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. G. Betts, D. Giles, and G. S. Lister Tectonic Environment of Shale-Hosted Massive Sulfide Pb-Zn-Ag Deposits of Proterozoic Northeastern Australia Economic Geology, May 1, 2003; 98(3): 557 - 576. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. K. Druschel, G. K. Druschel, M. Labrenz, T. Thomsen-Ebert, D. A. Fowle, and J. F. Banfield Geochemical Modeling of ZnS in Biofilms: An Example of Ore Depositional Processes Economic Geology, September 1, 2002; 97(6): 1319 - 1329. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. E. Playford, P. E. Playford, and M. W. Wallace Exhalative Mineralization in Devonian Reef Complexes of the Canning Basin, Western Australia Economic Geology, November 1, 2001; 96(7): 1595 - 1610. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. R. Cooke, D. R. Cooke, and D. C. McPhail Epithermal Au-Ag-Te Mineralization, Acupan, Baguio District, Philippines: Numerical Simulations of Mineral Deposition Economic Geology, January 1, 2001; 96(1): 109 - 131. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
