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

Viewpoints:

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



News:

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:

-----2021-----

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


Comprehensive Geology Conference Calendar



Fitting gaussian populations to the Favona area decrepitation data

The decrepitation results show the total decrepitation from all inclusion types present in the samples. Each sample usually contains several different populations of inclusions which may be the result of zonation during the host mineral deposition. Statistical methods can be used to determine a group of individual gaussian curves which sum to produce the observed decrepitation curve. For this work, I have used the scaled Levenberg-Marquardt algorithm to derive the best fit gaussian component populations. I use skewed gaussian population components as it has been found that they usually produce a better fit to the data envelope.  Using the parameters of these component sub-populations it is possible to make detailed and reproducible temperature comparisons between samples and also to quantify the various populations, particularly any populations in the 200 C to 400 C range, which are typically due to the presence of CO2 rich fluid inclusion populations.

Upper Favona vein

There were probably 6 samples collected in this area. Two sample locations are uncertain due to suspected mis-labeling. These samples represent a high grade gold zone. Samples 1881 and 1882 had 41 g/t gold. Both of these samples also show a peak near 320 C, even though the data shows considerable noise on sample 1882 because the overall decrepitation intensity was extremely low.

1881

1882b


Samples 1884 and 1885 had high gold grades of  79 g/t. These samples probably come from The upper Favona area, although they were mislabeled during sampling and their exact location is yet to be verified.   Sample 1884 shows a prominent low temperature toe on the main peak, and the fit algorithm suggests a separate low temperature, highly skewed population near 320 C. On sample 1885 there is a very prominent low temperature population near 320 C

1884

1885


 
Peak Temperatures - Upper Favona Samples
Sample #
No. of Peaks
Temp
Temp
Temp
Temp
1881 3 308 446 - 588
1882 3 366 -
496
592
1884 3 336 444 - 588
1885 4 344 426 482 588




Mid-depth Favona Vein

Sample 1877 was collected from deeper down in the Favona vein. Although it has very low decrepitation intensity and a rather noisy envelope, there is still a distinct low temperature peak caused by CO2 rich fluid inclusions. This sample has only a low Au grade near 1 g/t. However, the presence of CO2 rich fluid inclusions suggests that this fluid is closely related to the fluid which deposited the high grade Au nearby, and that this location should be regarded as potentially mineralised.


1877


 

Peak Temperatures -   Mid-depth Favona Samples
Sample #
No. of  Peaks
Temp
Temp
Temp
Temp
1877 3 286 434 482 -




Favona South Area


Sample 1886 is from the Favona South area and contains only 0.23 g/t Au. This sample showed visible inhomogeneity and so was split during preparation into 3 samples.  There are significant differences between these 3 results which is typical of strongly zoned quartz.  This sample had much more intense decrepitation, perhaps due to a higher liquid content in the inclusions. There is also still a weak low temperature peak, perhaps even 2 seperate peaks, caused by a high CO2 content.

1886B

1886c

1886A

  
Peak Temperatures -  Favona South Samples
Sample #
No. of Peaks
Temp
Temp
Temp
Temp
Temp
1886B 4 -
342
460
526
584
1886C 4 -
372
446
510 592
1886A
4
244
328
460
-
612





Moonlight Area


Sample 1880 and 1878 from the Moonlight area contained  only very low Au at 0.12 g/t.  One sample, 1880A,  lacks the low temperature peak and it is interpreted that CO2 is absent from this sample. However, sample 1878B does have a low temperature peak caused by CO2 rich inclusions.

1880

1878B

 

Peak Temperatures -  Moonlight samples
Sample #
No. of Peaks
Temp
Temp
Temp
Temp
1880A 3 -
418
540
608
1878B
3
346
438
-
580





General notes on the graphs

In all these graphs, the mathematical fit curve is shown in red. The individual component curves are also summed to generate the SUM curve, which is plotted in yellow. In all cases the SUM curve is almost identical to the mathematical fit and plots on top of the red curve, giving a brown-orange colour.


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