Applied mineral exploration methods, hydrothermal fluids, baro-acoustic decrepitation, CO2 rich fluids #
Newest Topics:

New model 216 decreptiometer

Exploration of the Mt. Boppy Au deposit, NSW

Forensic tests on soil samples


Do IOCG deposits form from CO2 fluids?

How CO2 inclusions form from aqueous fluids (UPDATED)

Understanding heterogeneous fluids : why gold is not transported in CO2-only fluids

Gold-quartz deposits form from aqueous - CO2 fluids: NOT from CO2-only fluids

Discussions why H2 analysis by mass spectrometry is wrong


Gold at Okote, Ethiopia

Kalgoorlie Au data

Sangan skarn Fe deposits, Iran

Studies of 6 Pegmatite deposits

A study of the Gejiu tin mine, China

Exploration using palaeo-hydrothermal fluids

Using opaque minerals to understand ore fluids

Understanding baro-acoustic decrepitation.

An introduction to fluid inclusions and mineral exploration applications.

 Interesting Conferences:


SGA, (Rotorua NZ), FULLY VIRTUAL march 28-31 2022
6th Archean, Perth, W.Aust. RESCHEDULED unknown date 2022

Comprehensive Geology Conference Calendar

Speciation and solubility of gold in CO2-HCl-H2O fluids: MD simulations and solubility experiments


  1.  CSIRO Mineral Resoureces Flagship, Melbourne  
  2.  Monash University, Melbourne, Australia
  3.  McGill University, Montreal, Canada

Increasing evidence of the abundance of water-poor, CO2-rich fluids in orogenic gold deposits indicates that 'exotic' volatile-rich fluids may have played a role in their formation (e.g., Ashanti Belt, Ghana1; Red Lake, Canada2; Sunrise Dam,Australia3). In water-rich, CO2-bearing fluids, CO2 has been suggested to be a pH buffering agent, optimising gold solubility as gold-hydrosulphide complexes4. However, the role of CO2 for gold mobility in water-poor, CO2-rich supercritical fluids is yet to be explored.

We have conducted preliminary gold solubility experiments and ab initio molecular dynamics simulations to investigate this problem. The solubility experiments have been conducted in a titanium autoclave at 340 ºC with 0.01 m HCl, and the amount of water and CO2 were loaded to the cell to ensure the fluid density is in the vapour phase with CO2 mole fraction (CO2/(H2O+CO2)) ranging from 0.1 to 0.84. The results showed that gold solubility has a negative correlation to the CO2 content in the fluids, i.e., decreasing with decreasing water fugacity.

Ab initio MD simulations of the AuCl0 complex (linear [H2O-Au-Cl]0) in the CO2-H2O system were conducted at 340 ºC with CO2 mole fraction from 0.1-0.98 at densities between 0.78-0.15 g/cm3. The MD simulations indicate that the number of hydration water and H-bonds near the AuCl0 complex decreases systematically with increasing CO2 mole fraction. These results are consistent with the experiments, suggesting that H2O as a polarized molecule plays a more active role than the un-polarized CO2 molecule in the fluids, and hydrated chloride species are the main form for transporting gold in the CO2-H2O-HCl system.


  1.  Schmidt-Mumm et al., 1997, Min. Dep. 32:107-118
  2.  Chi et al., 2006, Min. Dep. 40:726-741
  3.  Baker et al., 2010, Econ. Geol. 105:873-894
  4.  Philips and Evans, 2004, Nature, 429:860-863

Goldschmidt 2015 Abstracts