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Delineating the structural controls on the genesis of iron oxide–Cu–Au deposits through implicit modelling: a case study from the E1 Group, Cloncurry District, Australia

By
George Case
George Case
Economic Geology Research Centre, James Cook University, Townsville, Queensland, 4810, AustraliaPresent address: US Geological Survey, Alaska Science Center, 4210 University Dr, Anchorage, Alaska 99508, USA
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Thomas Blenkinsop
Thomas Blenkinsop
Economic Geology Research Centre, James Cook University, Townsville, Queensland, 4810, AustraliaSchool of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3XQ, UK
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Zhaoshan Chang
Zhaoshan Chang
Economic Geology Research Centre, James Cook University, Townsville, Queensland, 4810, Australia
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Jan Marten Huizenga
Jan Marten Huizenga
Economic Geology Research Centre, James Cook University, Townsville, Queensland, 4810, AustraliaDepartment of Geology, University of Johannesburg, Auckland Park, Johannesburg, 2006, South Africa
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Richard Lilly
Richard Lilly
Department of Earth Sciences, University of Adelaide, Adelaide, South Australia, 5005, Australia
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John McLellan
John McLellan
Economic Geology Research Centre, James Cook University, Townsville, Queensland, 4810, AustraliaGeological Modelling for Exploration, PO Box 695, Deeragun, Queensland, 4818, Australia
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Published:
January 01, 2018

Abstract

Iron oxide–Cu–Au (IOCG) deposits encompass a range of ore body shapes, including strata-bound replacement ores and hydrothermal breccias. We use the implicit method to make a detailed three-dimensional geological model of a strata-bound IOCG in the Cloncurry District, the E1 Group, to elucidate structural controls on mineralization. This model is compared with the nearby, world-class, Ernest Henry breccia-hosted IOCG deposit. Cu–Au mineralization in the E1 Group occurs as structurally controlled, mainly strata-bound, replacement bodies hosted in metasedimentary and metavolcaniclastic rocks intercalated with barren meta-andesite. Replacement bodies in the E1 Group conform to a series of NNW-plunging folds formed in regional D2 during peak metamorphism. Folding was followed by local D3/regional D4 shortening, which formed a dextral, transpressional Riedel brittle to ductile system along the regional Cloncurry Fault Zone. Modelling suggests that much of the Cu–Au mineralization is controlled by synthetic R structures associated with this Riedel system. The deformation sequence at Ernest Henry is comparable, but differences in host rock rheology, permeability and fluid pressure may explain the variation in ore body types and total Cu–Au resource between the two deposits. The results carry implications for other districts containing these styles of IOCG mineralization.

Supplementary materials: Sup 1: Probability plots of assay data for modelled elements. Plots made in ioGAS software. Power transform applied to y-axes of all elements. Note that Fe, P and S do not follow normal/log-normal distributions. Sup 2: Summary statistics of assay data for modelled elements. A description of the rock type (lithology) codes used in the geological model are available in Sup 3. The 3D models presented in this paper are available as supplementary data online (Sup 4) and may be viewed in the free Leapfrog Viewer program, which can be downloaded from http://www.leapfrog3d.com/. These supplementary files are available at https://doi.org/10.6084/m9.figshare.c.3729946

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Contents

Geological Society, London, Special Publications

Characterization of Ore-Forming Systems from Geological, Geochemical and Geophysical Studies

K. Gessner
K. Gessner
Geological Survey of Western Australia, Australia
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T.G. Blenkinsop
T.G. Blenkinsop
Cardiff University, UK
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P. Sorjonen-Ward
P. Sorjonen-Ward
Geological Survey of Finland, Finland
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Geological Society of London
Volume
453
ISBN electronic:
9781786203342
Publication date:
January 01, 2018

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