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Gold is can be associated with hydrocarbons in hydrothermal gold deposits, but the near-absence of experimental data on gold-hydrocarbon interactions at hydrothermal conditions prevents a quantitative interpretation of this relationship. In this study, we investigate the ability of liquid hydrocarbons to act as gold-transporting ore fluids using experiments on the partitioning of gold between brine (10 wt% NaCl) and 1-dodecanethiol (DDT). Experiments were conducted at 105 °C and 150 °C and <5 bar in a hydrothermal flow-through vessel. Partition coefficients (DAuorg/aq) obtained from the 105 °C and 150 °C experiments range from 10 ± 3.0 to 91 ± 30 at 105 °C and from 4.9 ± 0.9 to 33 ± 6.9 at 150 °C, with averages of 37 ± 33 and 21 ± 12, respectively. Gold concentrations in both the brine (<1 ppm) and DDT (up to 10 ppm) are dependent on the initial bulk concentration of gold (up to 4 ppm) and on the Au loss to the vessel walls during the experiment, as the Au concentrations correlate linearly with Au loss, while DAuorg/aq appears independent of bulk composition and Au loss. This linear dependency results in a stronger Au loss from the oil that bears more Au (DDT), and enables the calculation of DAuorg/aq for zero Au loss, which is 19 ± 21. These findings indicate that DAuorg/aq is a constant at the P-T-X conditions investigated. While these experiments did not directly assess Au solubility in DDT, no indication of Au saturation was observed, suggesting that higher concentrations are possible. The pH of the brine decreases during the experiments, indicating that the DDT underwent deprotonation and possibly decomposition during the partitioning reaction, but the pH does not have an observable effect on the gold concentrations in the brine and DDT. Preferential partitioning of gold into DDT is attributed to bonding with the thiol group, and as thiols compose up to 7 wt% of the total organic sulfur content of crude oils, liquid hydrocarbons have the potential to tran

Conventional wisdom holds that aqueous solutions are the only non-magmatic fluids capable of concentrating metals in the Earth’s crust. The role of hydrocarbons in metal concentration is relegated to providing geochemical barriers at which the metals are reduced and immobilised. Liquid hydrocarbons, however, are also known to be able to carry appreciable concentrations of metals, and travel considerable distances. Here we report the results of an experimental determination of bulk solubilities of Au, Zn, and U in a variety of crude oils at temperatures up to 300 °C and of the benchtop-scale transport experiments that simulate hydrocarbon-mediated re-deposition of Zn at 25–200 °C. It has been demonstrated that the metal concentrations obtained in solubility experiments are within the range of concentrations that are typically considered sufficient for aqueous fluids to form ore bodies. It has also been shown that Zn can be efficiently transported and re-deposited by hydrocarbons. These results provide direct evidence of the ability of natural crude oils to mobilise metals available in hydrocarbon-associated host rocks, and transport them in concentrations sufficient to contribute to ore-forming processes.