Authors / CoAuthors
Leach, D.L. | Bradley, D.C. | Huston, D.L. | Pisarevsky, S.A. | Taylor, R.D. | Gardoll, S.J.
Abstract
Sediment-hosted Pb-Zn (SH Pb-Zn) deposits can be divided into two sub-types: 'clastic-dominated lead-zinc' (CD Pb-Zn) ores hosted in shale, sandstone, siltstone, mixed clastic or as carbonate replacement within a clastic dominated sedimentary sequence and Mississippi Valley-type (MVT Pb-Zn) ores that occurs in platform carbonate sequences, typically in a passive margin tectonic setting. The emergence of CD and MVT deposits in the rock record between 2.02 Ga, the age of the earliest known deposit of these ores, and 1.85-1.58 Ga, a major period of CD Pb-Zn mineralization in Australia and India, corresponds to a time after the 'Great Oxygenation Event' (GOE) ca 2.4 to 1.8 Ga. Contributing to the blooming of CD deposits at ca 1.85-1.58 Ga was the following: a) enhanced oxidation of sulfides in the Earth's crust that provided sulfate and lead and zinc to the hydrosphere; b) development of major redox and compositional gradients in the oceans; c) first formation of significant sulfate-bearing evaporites; d) formation of red beds and oxidized aquifers: e) evolution of sulfate-reducing bacteria; and f) the formation of large and long-lived basins on stable cratons. A significant limitation imposed on interpreting the secular distribution of the deposits is that presently, there is no way to quantitatively evaluate the removal of deposits from the rock record through tectonic recycling. Considering that most of the sedimentary rock record has been recycled, probably most SH Pb-Zn deposits have also been destroyed by subduction and erosion or modified by metamorphism and tectonism so that they are no longer recognizable. Thus, the uneven secular distribution of SH Pb-Zn deposits reflects the genesis of these deposits, linked to Earth's evolving tectonic and geochemical systems, as well a record severely censored by an unknown amount of recycling of the sedimentary rock record.
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nonGeographicDataset
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69934
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Keywords
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- External PublicationScientific Journal Paper
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- economic geology
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- metallogenesis
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- mineral deposits
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- ore
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
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2009-12-08T00:00:00
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