Alteration of organic matter in the Viburnum Trend lead-zinc district of southeastern Missouri

The early proterozoic Mississippi Valley-type Pb-Zn-F deposits of the Campbellrand and Malmani Subgroups, South Africa

“…This temperature drop is also associated with a salinity decrease which can be explained by mingling of the brine with less saline ground water of surficial origin. The cooling is consistent with the temperature difference observed between the ore zone and the country rock in the Viburnum Trend, a classic MVT district in the US (Henry et al, 1992). Rapid chemical or thermal changes are also suggested by the sulphide zoning in the breccia bodies in the Zeerust mineralised field (Figs.…”

Fluids and Ore Formation in the Earth's Crust

“…Diagnostic evidence comes from observations that ore deposits are commonly transient thermal anomalies compared to the ambient geothermal gradient, even in areas without any magmatic heat input. For example, fluid inclusions in some sediment-hosted ore deposits record higher temperatures during pulses of hydrothermal Pb-Zn deposition, compared with ambient rock temperatures recorded by the maturation level of organic matter (e.g., Henry et al, 1992;Rowan et al, 2002). Such observations imply that advection of heat by ore-forming fluid flow is fast relative to the conductive dissipation of heat to the surrounding rocks, which places rigorous constraints on the duration of ore formation in sedimentary basins (1000-10'000 years; Cathles and Adams, 2005).…”

Geochemistry of the sediment-hosted disseminated gold deposits in Southwestern Guizhou Province, China /

“…Geological and geochemical evidence show that the ore deposition of SHDG and other strata-bound base metal deposits occurs under reducing environments. Sulfate reduction, through either biodégradation or abio-degradation, plays an important role in the ore-forming processes (Gize and Barnes, 1987;Leventhal, 1990;Henry et al, 1992;Disnar, 1996;Sicree and Barnes, 1996;Bechtel et al, 1998). Low temperature biological sulfate reduction and thermochemical sulfate reduction by organic matter, such as light hydrocarbon gases and organic acids, may be the immediate source of the reduced sulfur in a number of sedimentary, strata-bound ore deposits (Berner, 1970;Barros and Deming, 1983;Trudinger at al., 1985;Krouse et al, 1988;Dixon and Davidson, 1996).…”