How CO2 inclusions form from aqueous fluids

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

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

Inclusion shapes can prove heterogeneous FI trapping

Disproportional FI trapping from heterogeneous fluids explains gas-dominant systems

A discussion of H2 analysis by mass spectrometry

A mechanism to form H2 in the MS ioniser during analyses


Sangan skarn Fe deposits, Iran

New model 205 decreptiometer

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:

AGCC expo, Adelaide, Aust. Oct. 14-18 2018


ECROFI, June 24-26, Budapest, Hungary

AOGS, Singapore, 28 Jul-2 Aug 2019

SGA, Glasgow Scotland, Aug. 27-30 2019

Comprehensive Geology Conference Calendar

All non-condensing gases give similar low temperature decrepitation peaks

Although much of the focus of Au exploration and acoustic decrepitation is on the CO2 content of fluid inclusions, other gases such as CH4 and N2 also give the same low temperature decrepitation peaks as seen on CO2 rich samples. This is a consequence of the fact that all these gases, above their critical point temperatures, behave in accordance with the gas law, namely PV=nRT. This behaviour is completely independent of the nature of the gas species and only subject to variations due to the non-ideal behaviour of some gases. However, at the temperatures and pressures used in acoustic decrepitation analyses, these variations from ideallity are very small and do not affect the results at all.

To demonstrate this, I have used the modified Redlich & Kwong equation of state to calculate the behaviour of CO2, CH4 and N2 at 2 different molar volumes using a computer program from Holloway, 1980.  The results, plotted below, show that these 3 gases behave similarly and that decrepitation of inclusions containing any of these gases, or mixtures of these gases, will all develop high internal pressures and decrepitate at low temperatures, as explained in the item: Why CO2 rich fluid inclusions decrepitate at low temperatures.   The small differences between gases due to non-ideallity are of no consequence to the acoustic decrepitation method.

 Consequently, the acoustic decrepitation method will work regardless of the presence of mixtures of these gases or other gases above their critical temperatures.  The reason for using Molar Volume (the inverse of density) in these calculations is that the gaseous components of fluid inclusions formed at the same P-T conditions will have the same molar volume, although their gas densities will differ. (This is a consequence of the fact that 1 mole of any gas at STP occupies the same volume.)

gas equation of state

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