Quamby 3D Model

URL: https://geoscience.data.qld.gov.au/dataset/ds000006

3D geological and geophysical modelling was used in conjunction with mineral potential modelling to assess unrealised Cu-Au potential in the Quamby area in the Eastern Succession of the Mount Isa Inlier. This report documents the process used by the Geological Survey of Queensland, including 3D modelling and geophysical inversion, to create a Common Earth Model for 3D mineral potential modelling over the Quamby Project area. The area is divided into three main geological domains - the Mary Kathleen, Constantine and Soldiers Cap Domains.
The Quamby Project area contains the major operating Ernest Henry Cu-Au mine as well as other significant Cu-Au projects and is highly prospective for a range of mineralisation styles including Cu\xb1Au\xb1Fe deposits and stratabound sediment-hosted Cu deposits. Mesozoic and Cenozoic sediments cover more than 70% of the project area. Although interpreted cover depths are generally less than 150m, much of the area remains under-explored.

A 3D geological model was created using GOCAD and SKUA software incorporating new interpretations from recent mapping by the Geological Survey of Queensland as well as drillhole and seismic data. This 3D model was used as a starting model to constrain potential field inversions yielding 3D physical property models
The 3D physical property models show the distribution of the density and magnetic susceptibility properties within the topmost 2.5km of the crust within the project area. These property distributions can be used to directly assist exploration targeting and allow interpretation of the regional structural and geological setting. In particular the property models can be used to define structural breaks and alteration pathways.

Literature reviews were undertaken over the major Cu-Au deposits within the Quamby Project area with relevant references collated into an appendix. Available information on mineralisation including depositional environment, fluid source and geophysical characteristics within both the Mary Kathleen and Constantine Domains \(the project area\xb4s two main prospective domains\) was used to create targeting criteria, called evidential properties, which were tested using a Weights-of-Evidence approach.

A Common Earth Model was prepared containing the lithological and physical rock properties from the inversions and properties representing the identified targeting criteria for Au-Cu mineralisation. For the Weights-of-Evidence modelling the Common Earth Model also contains training cells, representing known mineral occurrence sites.

The Weights-of-Evidence modelling method assesses the relationship between the identified evidential properties and the training cells. The evidential properties within the study area found to have a strong association with mineralisation include the geological complexity, distance to faults and fault curvature, geochemical anomalies and anomalous regions within the density and magnetic susceptibility models \(derived from the inversions\). 3D mineral potential models were created by combining the statistically significant evidential properties for each domain.

The 3D mineral potential models represent the relative probability of each individual cell within the model hosting Cu-Au mineralisation. Mineral potential models were generated separately for the Mary Kathleen and Constantine Domains as the style of mineralisation and significant evidential properties were different in each domain. As well as highlighting locations of known mineralisation, the mineral potential models show extensions along trends and define high potential areas under shallow cover in previously unexplored regions.

Organization: Geological Survey of Queensland