Dear all,
I am a new member of this list, so I do not know much
about all topics have been discussed in this forum. I
hope what I want to discuss is something new and a
kind of interest for you.
In 1998-1999 I was involved in an exploration program
for a Carlin-style gold target in East Asian region.
>From geological criteria (tectonic setting,
structures, metamorphism and sediment packages), it
seems that our area is very favorable for this type of
mineralization. But, so far we just discovered many
small gold occurrences in a kind of narrow zone of
quartz vein/veinlets hosted by calcareous siltstone to
muddy limestone. No significant carbonate
replacement/disseminated-type gold mineralization
found, even when the host rock seems a 'perfect' one.
In my opinion, it is basically a classical low
sulfidation epithermal gold mineralization, but
differs from most others, hosted by carbonate rocks.
Meanwhile, in December 1998 I was visiting the
carbonate-hosted Mesel gold deposit in North Sulawesi,
Indonesia. Mesel is the only Carlin-type gold deposit
in all Tertiary volcanic arcs of Indonesia nowadays
and it is mined by Newmont. It is really a kind of
replacement and disseminated gold mineralization type
in muddy algal limestone host rock. Alteration zones,
from unaltered limestone, dolomitization,
decalcification, argillitization to strong
silicification, can be well observed. Basically no
quartz veining occurs and sulfides are present very
fine disseminated in the altered host, associated with
submicron-size gold.
So, what are actually the key factors involved when a
hidrothermal fluid passes trough a carbonate rock body
so that it can produce these two very different styles
of gold mineralization?
Are there any other Carlin-style gold deposits
discovered in volcanic arc setting besides Mesel?
In case of Mesel, do you think it is an exceptional
event or not? What I mean, in general, is volcanic arc
setting a reasonable target area for Carlin-search?
Best regards,
Lucas
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Lucas Donny Setijadji
Department of Geological Engineering
Gadjah Mada University, Yogyakarta, Indonesia
E-mail: [log in to unmask]
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