My interpretation of carbonaceous material in such deposits is that most is
probably protographite or pyrobitumen, resulting from heating and
devolatilisation of bituminous material in slates and shales, rather than
true "graphite alteration".  However ore-forming fluids commonly carry some
methane and other organic matter, so some of this may conceivably polymerize
and deposit in and around some veins (eg where uranium is present).

Ralph Bottrill

        -----Original Message-----
        From:   Brett Davis [SMTP:[log in to unmask]]
        Sent:   Saturday, November 25, 2000 3:15 AM
        To:     [log in to unmask]
        Subject:        RE: e-mail addresses


        Hi people

        This may be a naive question, but it stems from a paper I was just
reading
        on a gold deposit in the Northern Territory of Australia. The
deposit, Gold
        Creek, has been interpreted as having a phase of graphite
alteration. My
        question is: How common is graphite alteration? I don't know of the
        metamorphic grade of the rocks, but since it is in the Pine Creek
Inlier I
        don't think it is that high. I was under the impression that
graphite
        alteration was a high-grade phenomena. Most graphite I've seen in
gold
        deposits occurs as a residual concentration due to dissolution of
more
        soluble elements and because we were originally dealing with
carbon-bearing
        sediments eg the argillaceous rocks of the Hodgkinson Province in
north
        Queensland.

        Thanks in advance for any info.

        Cheers
        Brett

        Dr Brett Davis
        Group Structural Geologist
        Delta Gold Ltd
        PO Box 152
        Kalgoorlie
        Western Australia 6430
        Australia
        Ph      61-8-9021 7622
        Fax     61-8-9021 3200

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