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The Arltunga goldfield area, NT,
Australia
Conclusions
The gold in this area was transported
in and deposited from fluids rich in CO2.
The auriferous quartz formed from these pregnant fluids can be
readily identified and distinguished from other barren quartz using the
decrepitation method, which is a useful additional
exploration tool in this region.
Discussion
The Arltunga goldfield is some 100 Km ENE of Alice Springs, NT, and was
discovered in 1887, along with the nearby White Range gold deposits,
some 5 Km away and the Winnecke deposits.
20 samples were collected from the Arltunga area from old mullock
dumps, and 5 samples were obtained from the White range mine during its
operation in 1985.
Gold mineralisation occurs within quartz veins hosted by proterozoic
gneisses and schists.
The locations are shown here. Precise, individual sample location
details are not available.
NOTE: the following location map does not work if you are using ie 6 as your browser. If you
only see a map of USA, use firefox >3 instead. It works.
The green marker is Alice Springs town. The red marker is the Arltunga
goldfield where 19 samples numbered 330964 to 330983 were collected.
The Yellow
marker is the White range mine area, from which 5 samples were
analysed. The
cyan marker is the Winnecke goldfield. No samples have been analysed
from there. Click on the coloured pin icons for location details.
These samples 330964 to 330983 were all collected from the old Arltunga
workings area, within a radius of about 1 Km from the crossroads.
Sample 330964 was of float from the old mill site and is probably
spilled ore. Note the substantial low temperature CO2
decrepitation peak.
Samples 330965 - 330967 were from old workings pits beside the road.
Again these samples have substantial low temperature decrepitation
caused by CO2 rich fluids.
Samples 330968-330970 were from old workings east of the road, on a
small hill. Only one of these samples (330970, blue) has substantial
low temperature CO2 caused decrepitation.
Samples 330971-330973 were of quartz collected from a nearby alluvial
watershed, unassociated with old workings. They are presumably barren
quartz and all of these lack low temperature decrepitation.
Samples 330974 & 330975 were from a small pit at the crossroads.
They show essentially no decrepitation at all!
Samples 330976-330978 were from small workings WNW of the crossroads.
These samples do decrepitate above 400 C, but lack any low temperature
decrepitation.
Sample 330979 was from from quartz outcrop (presumably barren) on a
hilltop NW of the crossroads. It has no decrepitation at all.
Samples 330980-330983 were from mullock dumps at old workings on in
this same area NW of the crossroads. Three of these samples have low
temperature decrepitation indicating the presence of CO2
rich fluids.
The White Range mine
Three of the 5 samples from the White ridge mine area have substantial
low temperature decrepitation caused by CO2 rich fluids. The
other 2 samples have low level decrepitation at low temperatures,
indicating traces of CO2 rich fluids.
Summary
No gold analyses on these samples are available. However, based on the
proximity to old workings, it is clear that most samples which are
probably auriferous also have significant low temperature
decrepitation, while most of the barren control samples lacked
decrepitation at low temperatures.
It is concluded that the gold in this region is strongly associated
with CO2
rich fluids, which are readily detected in the quartz by the
decrepitation analyses. There are multiple types of quartz in the area,
which cannot be distinguished visually. These other types of
quartz either lack all decrepitation, or only decrepitate at high
temperatures above some 400 C. It is probable that these other quartz
types are not associated with gold mineralisation, but they can be
easily distinguished from potentially auriferous quartz using
decrepitation analyses.
Thin sections were made of 7 of the samples to visually examine the
fluid inclusions. These observations will be added here.
Conclusions
The gold in this area was transported in and deposited from fluids rich
in CO2.
The auriferous quartz formed from these pregnant fluids can be readily
identified and distinguished from other barren quartz using the
decrepitation method, which is a useful additional
exploration tool in this region.
Applied Mineral Exploration
Discussion and research relevant to mineral
exploration. 
