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Regolith stratigraphy and gold distribution within tributary palaeochannels near Gindalbie and Kurnalpi, Kalgoorlie Region, Western Australia


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Lynn, SF 1994 , 'Regolith stratigraphy and gold distribution within tributary palaeochannels near Gindalbie and Kurnalpi, Kalgoorlie Region, Western Australia', Coursework Master thesis, University of Tasmania.

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This study investigates two sites within the Roe Palaeodrainage system in the
Kalgoorlie Region of Western Australia. Both are located over southward draining
tributary palaeochannels that have incised into already deeply weathered Archaean
lithologies. The pre-palaeochannel regolith is only partly preserved at Gindalbie due
to the site's proximity to the main trunk palaeoriver. However at Kurnalpi, there is
extensive preservation of the pre-existing laterite profile beneath the palaeochannel
sediments and permits an estimation of the maximum depth of palaeochannel
incision: That is 25-30 metres at Kurnalpi; 40-50 metres at Gindalbie; 60-70 metres
in the trunk channel. The palaeochannel sediments comprise a basal sand facies that is generally
confined to the palaeoriver bed, and a conformable upper clay facies that blankets
the entire palaeodrainage valley. The sediments have also been lateritized, resulting
in an extensive ferruginization of the upper profile (Fe-induration, Fe-nodules and
pisoliths, and mega-mottles), and at least at Gindalbie, a prominent redox front at
18-20 metres depth below which reducing conditions prevail. The sand facies has
been palynologically dated by others as Middle to Late Eocene in age, thus
constraining the lateritization events to pre and post-Eocene.
At Kurnalpi, colluvial/alluvial incision has extensively truncated the upper
profile of both the transported and in-situ regolith. This event has occurred after
post-Eocene lateritization and appears to be confined to the mid and upper slopes of
the catchment area.
At both sites gold mineralization is extensive but is confined to the environs of
the palaeochannels.
At Gindalbie gold is almost exclusively distributed as discrete horizontal
horizons within the palaeochannel sediments below the main redox front, with the
highest grades located directly above the palaeochannel thalweg. No bedrock
mineralization was encountered; and gold distribution appears to be controlled by
groundwater regimes/chemistry and host lithology mineralogy.
At Kurnalpi Archaean lode-style gold mineralization is spatially associated with
supergene gold within both the palaeochannel sediments and the in-situ regolith. The
highest gold grades from both regolith profiles are distributed about a vertical plane
through the channel thalweg, with placer gold located at the base of the
palaeochannel sand facies. All gold mineralization appears to be derived initially
from basement lodes and distribution patterns reflect local controls such as bedrock
structure, basement lithology, channel morphology and groundwater movement.

Item Type: Thesis - Coursework Master
Authors/Creators:Lynn, SF
Keywords: Gold ores, Geology, Stratigraphic
Copyright Holders: The Author
Copyright Information:

Copyright 1994 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.Econ.Geol.)--University of Tasmania, 1995. Includes bibliographical references (p. 65-68)

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