SummaryConductivity depth data presentations derived using 1D approximations have become a very popular way to present airborne electromagnetic (AEM) data. While data profiles and a single error limit per station can accompany these presentations there are more information contained in data. This work proposes some ideas for augmenting 1D derived data presentations to highlight two and three-dimensional conductors as well as more detailed error level indication. The 1D conductivity depth algorithm used is an extended version of the S-layer differential transform. The depths calculated with the transform is used also present decay constant values corrected for conductive background responses. Fraser filtered X-component data are used to indicate structural complexity and data fit error levels are used to grey out areas on the depth section presentations where the results are less reliable. To demonstrate these ideas a line of Xcite data over the Abra deposit in Western Australia is analysed. The augmentations add valuable information to the conductivity depth section in the sense of drawing attention the where the 1D assumptions are not valid and should encourage interpreters to pursue 2D or 3D modelling techniques for successfully mapping the ore deposit.

Exploration and mining companies in Australia are faced with the challenge of locating deep ore deposits potentially buried under hundreds of metres of cover sequence materials. This research aims ...

SummaryThe Gairdner Dolerites feature prominently in magnetic and gravity images of South Australia. They are a volcanic intrusive, easily identifiable in SA magnetic images as a set of NNW-SSE linear features. The Gawler Craton Airborne Survey (GCAS) has recently acquired high-resolution magnetic data over these dolerites.AutoMag analysis of magnetic data from the GCAS data is used to study the large number of Gairdner Dolerite dyke anomalies in the study area. A high-resolution (400 metre station spaced) gravity survey reveals that the larger dykes have detectable gravity expressions. We have inverted two selected dyke magnetic anomalies to derive source models with best-estimated thicknesses of 75 and 97 metres and magnetic susceptibilities of .054 and .029 respectively. These models together with density measurements of over 2,900 kg/m3 for the dykes and less than 2,600 kg/m3 for Pandurra Formation which the dykes intrude are used to forward model gravity anomalies with peak amplitudes of 4 to 5 μm/sec2. We plan more detailed gravity traverses over selected dykes to test combined magnetic and gravity inversion with which to constrain depth to the top of basement (where there is a substantial reduction in density contrast).

The North West Shelf, situated in the north-west of Western Australia, is a world-renowned offshore hydrocarbon province with investments of more than A$200 billion to date. However, the quality of...

We present results of 334 ultra-wide band MT stations across an area of 100 km × 100 km in the prospective eastern Gawler Craton. The survey area is situated ~100 km south of the supergiant Olympic...

SummaryThere is an Indian proverb that goes: “Tell me the truth and I’ll believe it for a while. But tell me a story and it will stay with me forever.”

SummaryUnderstanding the mobility of individual elements in the oxidised environment is important for the accurate interpretation of geochemical data from regolith and weathered bedrock samples. In the weathered environment, immobile element geochemistry can reflect primary lithological and in situ mineralisation signatures, whereas mobile elements can help establish the degree and extent of weathering. Three exploration case studies are presented here to demonstrate the application of multielement geochemistry in the weathered environment: An example from the Shorty Creek Project, Alaska (Freegold Ventures), highlights the importance of reviewing and understanding pathfinder elements in soil, weathered bedrock and fresh basement. Here, commodity elements Cu and Zn are highly mobile and relatively depleted in the soils and weathered zone over Cu-Au mineralisation, whereas Au, As, Bi and Sb are less mobile and highly anomalous in the oxidised bedrock and associated soils.The Hermosa Deposit, Arizona (South32), where downhole geochemistry can help map the oxide-fresh rock boundary at the deposit scale. Subtle depletion in mobile elements allows the weathered zone to be identified in altered rhyolites, and Zn:S and Pb:S ratios in the mineralised zone helps distinguish Zn and Pb oxides from Zn and Pb sulphides.A review of residual soils over a Ni-Cu-PGE prospect in Northern Queensland, where immobile elements are reliable discriminants of primary lithologies in highly weathered environments. Zirconium, Y, Th and Nb can be used to distinguish felsic from mafic bedrock, and variations in Cr, V, Al, Fe and Sc in soils confidently identify blind, compositionally distinct mafic-ultramafic bodies.This paper also highlights the importance of collecting high quality, multi-element geochemistry with low detection limits at every stage of exploration.

Gas hydrates consider as one of the prospective natural resource that can supply energy. The seismic method has successfully been applied to locate gas hydrates. Their presence is revealed by botto...

SummaryLoop is a new open source 3D geological and geophysical modelling platform in full development.The new platform consists of 4 main work packages: Knowledge Management: use of AI techniques for knowledge extraction from literature, maps and reports using geological ontology. Geological rules will be encoded to ensure proper knowledge extraction.Geological Event Management: Loop is a time-aware geological modelling platform and the event manager is capturing topological and time relationship between geological objects and structural eventsForward and inverse structural modelling: we will encode structural geological rules in a time-aware context to account for folds (including overprinting), faults, shear zones, unconformities and intrusions. The modelling is based on probabilistic modelling and allows for the definition of an objective function for geology and quantification of uncertainty via posterior probabilities.Uncertainty characterisation and modelling: using stochastic simulations or the result of Bayesian modelling, Loop allows for characterisation and quantification of 3D uncertainty.

The Geological Survey of South Australia (GSSA) designed the Gawler Craton Airborne Survey (GCAS) to provide high resolution magnetic, gamma-ray and elevation data covering the northern portion of ...