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Type: Report
Title: Geochemistry through cover: Defining geochemical exploration parameters for the Cloncurry Mineral District, Queensland
Author: Lilly, R.
Hannan, K.
Issue Date: 2016
Assignee: Department of Natural Resources and Mines, Queensland Government
Statement of
Richard Lilly and Keith Hannan
Abstract: Three ‘blind target’ trial locations in the Cloncurry Minerals District were chosen with contrasting thicknesses of cover (<10m, 10-20m and about 150m). Two size fractions of the sampled regolith were collected at each site, measured by field portable XRF and then sent to commercial laboratories for analysis by conventional strong acid digestions and proprietary selective extractions. Vegetal matter from selected species was also collected and analysed. In addition, samples of gas were extracted from the regolith to test for evidence of the release of gaseous compounds from oxidising ore minerals at depth. Systematic sampling procedures, standards and duplicates were utilised to permit a thorough examination of survey quality assurance parameters. The regolith geochemical data indicate that surface geochemical anomalism generated by buried mineralisation can be detected through significant cover, comprising regolith +/- variably lithified, post-Proterozoic sediment. The project also demonstrates the continued relevance of ‘traditional’ geochemical techniques, especially for chalcophile elements, in areas of thin to moderate transported cover. All three of the trialled selective leaches produced multi-line discrete anomalies for several metals and anomaly enhancement relative to strong acid digestions in areas of thick cover. Seasonal variation in the availability or extractability of several metals is also evident. The biogeochemical results indicate significant variations in the abundance of certain pathfinder elements between sampled species. However, the species-normalised data reveal multi-element associations and strong, single chalcophile element anomalies that are broadly consistent with the geochemical results. In summary the project trials demonstrate the possibility of two bedrock sources at Cormorant (deep Proterozoic Zn-Ag and shallow Mesozoic polymetallic), a structurally confined Proterozoic bedrock source at Strathfield suggestive of Au-dominant IOCG-related mineralisation, and shallow, low-grade, mafic igneous rock-hosted Cu-Au mineralisation at Battle Axe with the possibility of structurally defined Mo mineralisation.
Keywords: Regolith; geochemistry; partial digest; selective extraction; biogeochemical exploration; vegetation; geobotany; mineralisation
Rights: Copyright status unknown
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Earth and Environmental Sciences publications

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