Information about these fluids is an invaluable aid in mineral exploration. Conventional academic methods of analysing fluid inclusions are too slow and tedious to be of practical application in typical mineral exploration activities. However, the academic data from numerous studies does show that CO2 is an exceptionally important indicator when exploring for most types of gold deposit. Because the baro-acoustic decrepitation method is a rapid and reliable method to measure CO2 contents in fluids, it can be used to study a spatial array of data and it is an invaluable and practical exploration method. Measurements of temperatures of fluid inclusions does not usually help in mineral exploration as hydrothermal minerals deposit over a wide temperature range and there is no specific temperature which is indicative of mineralisation. However, if temperatures are available on a large spatial array of samples, then temperature trends may be a useful exploration method to find the hottest part of the system, which is presumably the location of the best economic mineralisation. Baro-acoustic decrepitation is the most practical method to determine temperatures of the large numbers of samples required. Salinities of fluid inclusions are of limited use in exploration and are difficult to measure. However, they can be used to recognise intrusion related hydrothermal systems.

1. A Seminar
On
“FLUID INCLUSION IN ORES”
Submitted by-
Miss. VISHAKHA NATHANI

2. CONTENT
What is Fluid inclusion?
Where and when are they trapped?
Types of fluid inclusions
How it can be studied?
Applications in ore geology
Case studies
 Cu
 Au

3. FLUID INCLUSION
WHAT? WHERE? WHEN?
Tiny bubbles of fluid trapped in mineral
Composition- host melt
<100 um in size (10 microns generally)

4. HOST MINERALS
• Sphalerite, cassiterite, quartz, calcite,
dolomite, fluorite, halite, Apatite,
Topaz and baryte. (Shepherd 1985)
• Some feldspar in granites also contains
fluid inclusions.

5. Classification based on time of entrapment
Primary
Secondary
Pseudosecondary

6. Primary fluid inclusion
• Formed during the formation of the enclosing
crystal
• Trapped along growth zones and crystal faces
• Indicates conditions of formation

7. Classification based on time of entrapment
Primary
Secondary
Pseudosecondary

8. Secondary fluid inclusion
Trapped in the fractures
Caught due to healing of fractures
Occurs as :
• Trails
• Clusters
Cut across grain boundaries

9. FIGURE SHOWING GROWTH ZONE OF CRYSTAL AND MICRO FRACTURE

10. FIGURE SHOWING PRIMARY AND SECONDARY FLUID INCLUSION
P
S

11. Classification based on time of entrapment
Primary
Secondary
Pseudosecondary

12. Pseudosecondary fluid inclusion
Trapped during formation of host mineral
Occurrence:
• Along trails
• Ends abruptly against grain boundaries or one of
the growth zones

13. FIGURE SHOWING ALL THE THREE TYPES OF FLUID INCLUSIONS

14. COMPOSITION
• The composition of trapped fluid varies
• Vapour or liquid phase- H2O
• Gas phase - CO2, CH2, H2S, Cl, Br, F, I
• Solid phase- S, Na, K, Ca, Mg, Fe and their salts
• E.g. Halite (NaCl)

15. HOW TO STUDY?
Methods used to analyse fluid inclusions
• Manual manipulation under the microscope
• Micro thermometry (-200⁰C to1500⁰C )
• Laser Raman microprobe
• Laser ablation with mass spectrometry
• Baro-acoustic decrepitation

16. PHOTO OF
LASER RAMAN
SPECTROMETER
AND EXAMPLE
OF SPECTRA
FOR THE GAS
AND AQUEOUS
PHASES IN A
FLUID INCLUSION

17. • P-T-X of the fluid system.
• Salinity of the aqueous fluid.
• Composition of the fluid.
• Gas composition of the fluid.
• Density of fluid-by Tmf and Th and
isochores
INFORMATION WE CAN GET….

18. PRACTICAL APPLICATIONS
• Mineral Exploration: For hydrothermal
deposits e.g. gold, silver, copper etc.
• CO2
• Salinity
• Temperature

19. MINERAL
EXPLORATION AND
FLUID INCLUSION
Gas
Fluid inclusion with two phases
Fluid inclusion with three phases
Fluid inclusion with multiple phases

20. FLUID INCLUSIONS IN COPPER
DEPOSITS
• If the hydrothermal fluid is
highly saline, above 23%
NaCl.
• Halite can crystallise upon
cooling with solid crystals
present.
• Such fluids usually occur in
porphyry copper deposits or
the core of igneous intrusion
derived fluid systems.
• Saline inclusions are less
common.

21. FLUID INCLUSIONS IN GOLD
A CASE STUDY
Hollinger-McIntyre mine area, Ontario, Canada

22. EXAMPLES
• The Cowra goldfield in NSW, Australia
• The Woods Point gold deposit, Victoria, Australia
• The Brusson gold mine, northern Italy
• Kalgoorlie area archean deposits, Western
Australia

23. SUMMARY
• Tiny bubbles trapped in crystal of mineral gives information
about its temp., pressure, salinity, density, composition etc.
• If minute crystals are present in the inclusion, such
as halite, sylvite, hematite, or sulphides are present, they
provide direct clues as to the composition of the original fluid.
• Used for petroleum exploration, mineral exploration,
sedimentary facies environment and diagenesis, morphometric
grades, paleohydrogeology, air inclusions in ice cores etc.
• Different methods are used for the analysis and assay of
samples are analysed.
• Used for hydrothermal ore deposits.

24. REFERENCES
• 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.
J.A. Mavrogenes, R.J. Bodnar, J.R. Graney, K.G. McQueen, Kingsley
BurlinsonJournal of geochemical exploration, 54/3 (1995) pp167-175
• Study of Fluid Inclusions: Methods, Techniques and Applications K. R.
Randive, K. R. Hari ,M. L. Dora , D. B. Malpe and A. A. Bhondwe, Gondwana
Geological Magzine., V. 29(1 and 2), June and December, 2014. pp19-28
• Relation of fluid inclusion geochemistry to wallrock alteration and
lithogeochemical zonation at the Hollinger-McIntyre gold deposit, Timmins,
Ontario, Canada Ted J. Smith, Stephen E. Kesler, CIM Bulletin, April 1985,
pp35-46.