The role of early formed structures on the development of the world class St Ives Goldfield, Yilgarn, WA

Miller, John; Blewett, Richard; Tunjic, Janet; Connors, Karen

doi:10.1016/j.precamres.2010.08.002

Cited by 47 publications

(12 citation statements)

References 36 publications

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“…; Miller et al . ). A general implication from our present model results is that under favourable far‐field stress conditions, sites of maximum fault curvature (bends) within a fault step‐over structure are optimal sites to localize shear strain, dilation and fluid flux and thus are likely to be favourable sites for mineralization.…”

Section: Discussionmentioning

confidence: 99%

Modelling fault reactivation and fluid flow around a fault restraining step‐over structure in the Laverton gold region, Yilgarn Craton, Western Australia

et al. 2012

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Laverton is an important region in the Yilgarn Craton for gold mineralization. Previous studies suggested that the premineralization structure was dominated by a fault restraining step‐over structure with the Wallaby fault and Sunrise Shear Zone as the key fault splays hosting the world‐class Wallaby and Sunrise Dam gold deposits, respectively. Two major gold mineralization phases occurred during two of a series of tectonic events with different far‐field stress orientations. 3D coupled deformation and fluid flow modelling was used to investigate the effects of varying far‐field stress orientations on reactivation of the fault structure in the region. The results show that structural reactivation is sensitive to regional shortening directions. Two shortening directions are identified to be favourable for reactivation of the Wallaby fault and Sunrise Shear Zone: (i) NW–SE shortening and (ii) ENE–WSW to E–W shortening. The reactivated segments exhibited localization of shear strain and dilation as well as fluid focusing at locations corresponding to the Wallaby and Sunrise Dam deposits. This is in contrast to the models with shortening direction between NNW–SSE and NE–SW, which showed little fault reactivation at both locations. These results support previous independent interpretations of the controls on gold mineralization at Laverton. The two shortening directions favourable for structural reactivation inferred from the models are consistent with the kinematics of the two main gold mineralization events in the region. Our results suggest that strain localization, dilation and fluid focusing during structural reactivation could be some of the key factors governing gold mineralization at Laverton.

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Section: Discussionmentioning

confidence: 99%

Modelling fault reactivation and fluid flow around a fault restraining step‐over structure in the Laverton gold region, Yilgarn Craton, Western Australia

et al. 2012

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“…During this deformation event, existing structures, such as the Boulder Lefroy Fault Zone, which passes through Heron South, were reactivated as sinistral strike slip faults. Localized deflections, step-overs, and local higher order structures produced during D 4b are associated with the main mineralizing event in the region (Cox and Ruming, 2004;Blewett et al, 2010;Miller et al, 2010). The D 5 period of dextral transtension produced north-northeast-trending strike-slip high-angle faults.…”

Section: Geologic Settingmentioning

confidence: 96%

“…The D 5 period of dextral transtension produced north-northeast-trending strike-slip high-angle faults. These structures may also be associated with a gold mineralizing event at various sites in the region (Connors et al, 2002;Ruming, 2006;Blewett et al, 2010;Miller et al, 2010). The D 6 period is not documented in the St. Ives Goldfield.…”

Section: Geologic Settingmentioning

confidence: 99%

Lithologic mapping using Random Forests applied to geophysical and remote-sensing data: A demonstration study from the Eastern Goldfields of Australia

2018

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The Eastern Goldfields of Western Australia is one of the world's premier gold-producing regions; however, large areas of prospective bedrock are under cover and lack detailed lithologic mapping. Away from the near-mine environment, exploration for new gold prospects requires mapping geology using the limited data available with robust estimates of uncertainty. We used the machine learning algorithm Random Forests (RF) to classify the lithology of an underexplored area adjacent to the historically significant Junction gold mine, using geophysical and remotesensing data, with no geochemical sampling available at this reconnaissance stage. Using a sparse training sample, 1.6% of the total ground area, we produce a refined lithologic map. The classification is stable, despite including parts of the study area with later intrusions and variable cover depth, and it preserves the stratigraphic units defined in the training data. We assess the uncertainty associated with this new RF classification using information entropy, identifying those areas of the refined map that are most likely to be incorrectly classified. We find that information entropy correlates well with inaccuracy, providing a mechanism for explorers to direct future expenditure toward areas most likely to be incorrectly mapped or geologically complex. We conclude that the method can be an effective additional tool available to geoscientists in a greenfield, orogenic gold setting when confronted with limited data. We determine that the method could be used either to substantially improve an existing map, or produce a new map, taking sparse observations as a starting point. It can be implemented in similar situations (with limited outcrop information and no geochemical data) as an objective, data-driven alternative to conventional interpretation with the additional value of quantifying uncertainty.

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“…As summarized in Blewett et al (2010), major extension occurred during basin development and deposition of the greenstone sequences in the Eastern Goldfields between 2720 Ma and 2670 Ma (e.g., Groves and Batt, 1984;Hammond and Nisbet, 1992;Miller et al, 2010;Squire et al, 2010;Swager and Griffin, 1990;Swager, 1997;Williams and Currie, 1993;Williams et al, 1989;Williams and Whitaker, 1993). This extensional event is thought to control the broad NNW-trending grain of the region , but just how these earliest structures are inferred and interpreted remains ambiguous (Miller et al, 2010).…”

Section: Structural Evolutionmentioning

confidence: 99%

“…Weinberg and van der Borgh (2008) have argued that some small deposits in the region of Leonora were associated with the earliest, D 1 , and the latest, D 5 , extensional events. In any case, early structures played a significant direct or indirect role in controlling gold deposition (e.g., Miller et al, 2010). However, little is known about the nature of the earliest structures because of overprinting by later deformation, or because it is simply not recorded by the younger rocks exposed.…”

Section: Introductionmentioning

confidence: 99%

Early deformation in the Eastern Goldfields, Yilgarn Craton, Western Australia: A record of early thrusting?

Cohalan

Weinberg

Squire

et al. 2015

Precambrian Research

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The role of early formed structures on the development of the world class St Ives Goldfield, Yilgarn, WA

Cited by 47 publications

References 36 publications

Modelling fault reactivation and fluid flow around a fault restraining step‐over structure in the Laverton gold region, Yilgarn Craton, Western Australia

Modelling fault reactivation and fluid flow around a fault restraining step‐over structure in the Laverton gold region, Yilgarn Craton, Western Australia

Lithologic mapping using Random Forests applied to geophysical and remote-sensing data: A demonstration study from the Eastern Goldfields of Australia

Early deformation in the Eastern Goldfields, Yilgarn Craton, Western Australia: A record of early thrusting?

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