This paper presents and reviews the processes responsible for the distribution and formation of regolith and associated landscapes of the Yilgarn Craton and highlights their implications for mineral exploration. It provides an analysis of regolith geology investigations that were conducted in many districts of contrasting contemporary geomorphic and climatic conditions. The Yilgarn Craton is composed of Archaean rocks, predominantly granitoids, that are crossed by north‐northwest‐trending belts of greenstones. It has an arid to humid climate at present. The gently undulating landsurface forms a partial etchplain and the topography is largely related to bedrock lithologies and a complex history of valley development and aggradation. Deep weathering has affected most lithologies and geological provinces across the craton. The depth of the weathered mantle may be as much as 150 m, but it varies considerably and rock outcrop may occur in any part of the landscape. The main factors influencing extent of weathering are rock type, mineralisation and deformation. Palaeomagnetic dating of deeply weathered regolith profiles suggest that they formed throughout the Phanerozoic. An idealised profile commonly comprises fresh bedrock, grading upwards into saprock and saprolite, commonly bleached towards the top, especially on felsic or sheared mafic rocks. This is overlain by a clay‐rich and/or quartz‐rich zone, a mottled zone and a ferruginous, bauxitic or siliceous upper zone. These horizons are formed by a combination of weathering and landscape processes. Landscape processes would have been continuous throughout the weathering period, with major environmental changes triggering particular erosional and depositional events. Thus, upper horizons, mottled zone, ferruginous duricrust and silcrete have developed in residuum, colluvium and alluvium of various ages. Weathering is the result of interaction between the hydrosphere, biosphere and lithosphere. During weathering some of the components of primary minerals are leached and secondary minerals are formed as residua. The pathways by which these minerals form are varied and complex. Biota were present in the regolith and it is likely that they and their associated chemical reactions played a significant part in the weathering process, as well as inorganic chemical processes. The final product of weathering of all rocks is a mineral assemblage of least soluble minerals (kaolinite, hematite, goethite, maghemite, gibbsite, anatase and boehmite) and the most resistant primary minerals (quartz, zircon, chromite, muscovite and talc), although neoformation of several generations of hematite, goethite, kaolinite and gibbsite may occur. Poorly crystalline minerals are an important constituent in surface or near‐surface materials. In addition, the more soluble minerals, including carbonates, sulfates and halides, occur in arid environments. The principal effects of weathering on element distributions relates leaching and retention of a range of elements to mineral transformations in th...

Curvilinear Th/U anomalies evident on radiometric imagery over southwestern Victoria were plotted on topographic maps and the corresponding exposures investigated in the field. These exposures were found to be dominated by quartz-rich ferruginous duricrusts, which, based upon detailed profile descriptions and petrographic studies, are interpreted as marginal-marine sediments of the Dorodong Sands and Loxton-Parilla Sands. Similarly oriented linear magnetic anomalies evident on aeromagnetic imagery for the Branxholme area are coincident with concentrations of detrital ferruginous magnetic gravels. These are interpreted as having been derived from weathering profiles developed in the Dorodong Sands and may have subsequently been concentrated in swales between Dorodong Sands ridges. Thus the curvilinear Th/U anomalies and magnetic anomalies are both spatially and genetically related to prior shorelines or strandlines. Some of the strandlines are covered by 4 Ma basalts, and were deposited between 6.6 and 4 Ma, i.e. very Late Miocene to Early Pliocene. Elsewhere the strandlines have a more extended time range, with the youngest strandline allocated a ca 3.5 Ma age. Strandlines at Branxholme are also younger and are regarded as Mid-Pliocene in age. The extent of the older shorelines suggests that the major Late Miocene -Pliocene marine transgression into the Murray Basin also covered most of southwestern Victoria, much further inland than previously recognised. The variable orientation of the oldest strandlines appears to reflect a phase of syndepositional uplift of the Dundas Tablelands, causing changes in the configuration of the regressing Pliocene shoreline. The strandlines can be used as a datum for Neogene tectonism, and indicate fault displacements of up to 180 m and total uplift of up to 300 m, although faulting in the north was less intense. Most tectonism was relatively short-lived and probably occurred between 6 and 4 Ma, i.e. Early Pliocene; the 4 Ma basalts overlying the strandlines show no evidence of faulting. Earlier faulting in the Late Miocene initiated subsidence of the prominent Hamilton Graben (identified by subsurface mapping underneath the basalt), with further movement in the Early Pliocene during deposition of the Dorodong Sands.

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Logging of exploration drillholes is a routine practice and its accuracy is essential for resource evaluation and planning in the minerals industry. Logged compositions record a set of material types with standardized mineralogy and texture characteristics. The material types logged may vary due to diversities in mineralization and geology, but also due to subjective biases and human error, leading to significant challenges for the industry. Thus, there is a need to validate the field logging whereby the material types and their percentages are adjusted to reconcile with laboratory assay values, while retaining the physical characteristics and geological context. We introduce the Auto-Validation Assistant (AVA) algorithm that applies data mining methods to geologists' validation patterns recorded in a training process over hundreds of intervals of iron ore exploration drillholes. The AVA modifies the material types selected in the logged composition and their percentages according to geological rules learned in the training process, and proposes to the geologist a number of validated compositions with optimized geochemistry and mineralogical hardness, while also considering visible properties such as chip shape and color. Using the confidence value provided with each validated composition, the geologist can make informed validation decisions and remains in control of the validation process, while harnessing computational power. Experiments were conducted to evaluate the auto-validated compositions generated by AVA: one to analyze the acceptance rate of the AVA generated compositions by geologists for 1,996 intervals in drillholes from different sites; and the other to compare manual and AVA-validated compositions using 14,600 drillholes from one entire deposit. The results showed the acceptance rate of AVA-validated compositions (without further change) of 74.3%, leading to significant time savings over tedious manual validation, while demonstrating that AVA provides comparable but more consistent results. The algorithm is fast and repeatable and can be adapted to different material types and training datasets, with potential applications beyond iron ore exploration.