Abstract
An objective method for generating statistically sound objective regolith-landform maps using widely accessible digital topographic and geophysical data without requiring specific regional knowledge is demonstrated and has application as a first pass tool for mineral exploration in regolith dominated terrains. This method differs from traditional regolith-landform mapping methods in that it is not subject to interpretation and bias of the mapper. This study was undertaken in a location where mineral exploration has occurred for over 20 years and traditional regolith mapping had recently been completed using a standardized subjective methodology. An unsupervised classification was performed using a Digital Elevation Model, Topographic Position Index, and airborne gamma-ray radiometrics as data inputs resulting in 30 classes that were clustered to eight groups representing regolith types. The association between objective and traditional mapping classes was tested using the ‘Mapcurves’ algorithm to determine the ‘Goodness-of-Fit’, resulting in a mean score of 26.4% between methods. This Goodness-of-Fit indicates that this objective map may be used for initial mineral exploration in regolith dominated terrains.
Highlights
Regolith is the surface expression of the entire unconsolidated or secondarily recemented cover that overlies coherent bedrock that has been formed by weathering, erosion, transport, and/or deposition of older material [1]
We present and discuss a statistical comparison between the newly proposed objective mapping method and traditional regolith-landform mapping followed by the examination of this application of this technique to mineral exploration
With the number of regolith mapping units of the traditional regolith map reduced to eight, it becomes much easier to visualize the distribution of broad regolith types
Summary
Regolith is the surface expression of the entire unconsolidated or secondarily recemented cover that overlies coherent bedrock that has been formed by weathering, erosion, transport, and/or deposition of older material [1]. 80% of basement rocks in Australia are covered by regolith [8,9]. Given that these basement rocks are known to host numerous economically viable ore deposits of various commodities in South Australia (e.g., Olympic Dam Cu-Au-REE-U; Carrapateena Cu-Au; Middleback Ranges Fe2 O3 : Figure 1), they are highly prospective for mineral exploration. The area used in this study covers 3866 km within the southern region of the Gawler Craton (Figure 1) and includes a variety of landscape and vegetation features. The oldest basement rocks are preserved in the south of the study area and are poorly exposed The vegetation varies across the sub-regions but mainly comprises low open woodlands of Western Myall (Acacia papyrocarpa) and Black Oak (Casuarina pauper) trees over sparse shrub understoreys of Bluebush (Maireana spp.), Saltbush (Atriplex spp.), and Spinifex (Triodia spp.).
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