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Rapid fluid inclusion data for exploration (decrepitation)

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New model 216 decreptiometer

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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



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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.



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Using fluid inclusion data in mineral exploration

Rapid data acquisition by the baro-acoustic decrepitation method

An overview of  information and results on using fluid inclusion information in exploration
Kingsley Burlinson
Burlinson Geochemical Services Pty. Ltd.
P.O. Box 37134,   Winnellie,  NT,  0821,     Australia
Ph. +61 411 443 097    (Within Australia  0411 443 097)
decrepitation  <at>  appliedminex.com

Skip down to:     CONTENTS       Case studies by deposit       Case studies by location  You can search this site here

OVERVIEW

Fluid inclusions are trapped remnants of the fluids which formed hydrothermal mineral deposits and provide a unique insight into the chemical and physical conditions  of ore forming fluids. Academic studies of ore deposit genesis have long relied on this vital fluid inclusion data to understand the genesis of ore deposits. But despite the obvious relevance of this information, the exploration community has largely failed to use this data in their routine exploration activities to target potentially economic hydrothermal systems.

Baro-acoustic decrepitation is a simplified method to obtain reproducible, non-subjective fluid inclusion data quickly and without the need for polished thin sections or microscopes. It can provide information about the source fluid environment and targeting vectors on project-scale numbers of samples, at modest price and with quick analytical turnaround. It does not provide fluid salinities or the pedantic levels of precision required in academia, but these aspects are not particularly useful in exploration and frequently just add confusion rather than resolution.

The most important use of baro-acoustic decrepitation is in determining approximate total gas contents of samples, as this data is frequently closely correlated with mineralisation potential. Examples in this documentation show this use as well as others including the  discrimination between samples which are visually identical and in discerning temperature zonation effects within a vein, mine or small exploration area. It can even be used on opaque minerals where microscopy is completely impossible, and many examples from iron oxide minerals are shown here.

The baro-acoustic decrepitation method was wrongly discredited by early work in the 1950's in Canada at a time when the presence of gas-rich fluids in hydrothermal systems was not understood and neither was the thermodynamic behavior of such fluids within inclusions. With the benefit of our currently much improved understanding of fluid systems it is now clear that baro-acoustic decrepitation does in fact provide a very useful and practical mineral exploration technique, particularly given the ability to digitally automate the instrumentation as has been done.

Baro-acoustic decrepitation is not intended to compete with the very high accuracy of slow and painstaking microscopic fluid inclusion research. However, as with soil geochemical surveys, where low cost and speed are more important than extreme accuracy, baro-acoustic decrepitation has a valuable role to play in many types of exploration programme. Although the method is usually applied to quartz samples, it has been used on various minerals including sulphides, haematite, magnetite, fluorite, carbonates and jasperoids.

An extensive database of some 5000 analyses from numerous ore deposits worldwide is the basis for the following information.

 

CONTENTS:

• Fluid inclusion decrepitation for mineral exploration - Overviews
  

• Practical usage of decrepitation in exploration

• Data interpretation

• Theoretical understanding of decrepitation

• Decrepitation instruments

• Discussions

• Papers presented at conferences

• Submitted Papers

Exploration of the Mt. Boppy Au deposit region, Cobar, NSW, Australia:  by K.G. McQueen

Intrusion related gold at Okote, Southern Ethiopia:  by Solomon Geda

Exploring for Au using fluid inclusions in the Tanami region, NT, Australia:  by T. Mernagh

• Published papers

The use of fluid inclusion decrepitometry to distinguish mineralised and barren quartz veins in the Aberfoyle tin-tungsten mine area, Tasmania. (1983)   (abstract)      (full paper, pdf)

An instrument for fluid inclusion decrepitometry and examples of its application. (1988)  (abstract)       (full paper, pdf)

The recognition of variations in sample suites using fluid inclusion decrepitation - applications in mineral exploration (1988)   (abstract)    (full paper, pdf)

Decrepitation studies in gold exploration. A case history from the Cotan prospect, N.T., Aust.  (1991)   (abstract)   (full paper, pdf)

Comparison of decrepitation, microthermometric and compositional characteristics of fluid inclusions in barren and auriferous mesothermal quartz veins of the Cowra Creek gold district, New South Wales, Australia  By: J.A. Mavrogenes et. al., (1995)  (abstract)

Acoustic Decrepitation as a means of rapidly determining CO₂ (and other gas) contents in fluid inclusions and its use in exploration, with examples from gold mines in the Shandong and Hebei provinces, China  (2007)   (full paper, html)

A discussion to point out errors in H₂ analyses of fluid inclusion volatiles by mass spectrometry.  (2013)

Fluid types and their genetic meaning for the BIF-hosted iron ores, Krivoy Rog, Ukraine.  By Marta Sośnicka et.al.  (2015) Extract (PDF file, 3.5 Mbyte) here

Mineral geochemistry of the Sangan skarn deposit, NE Iran: Implication for the evolution of hydrothermal fluid. By Fatemeh Sepidbar et.al. (2017) Extract (PDF file, 5.8 Mbyte)

• Bibliography / References

Decrepitation related references in date order

CASE STUDIES:

• Index by deposit style
  

• Gold deposits

Archaean & Proterozoic hosted quartz vein deposits

Western Australia

Victory mine, Kalgoorlie
Archaen gold - Kalgoorlie
Mt Charlotte, Kalgoorlie
Kalgoorlie
Coolgardie
Southern Cross

Northern Territory, Australia

Tanami and Arunta areas
Arltunga area
Tennant Creek
Pine creek (COTAN project)
Enterprise
Cosmo Howley

Ontario, Canada

Dome mine
Abitibi region, general

Mt Bischoff, Tasmania, Australia
East Kemptville (Mt. Pleasant), Nova Scotia, Canada
Erzgebirge tin greisens, Germany - Czech Republic
Gejiu, Yunnan, China

• Various

Carbonatite

Kapuskasing, Ontario, Canada

 

• Index by location

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