Using strain parameters from 3D restoration modelling to estimate distant off-fault gold potentials, Mount Pleasant Area, Western Australia

Abstract:

Gold deposits are used to be related to fault systems that control metals' transport and accumulation through relatively high permeable discontinuous structures. However, some coeval gold deposits occur at locations far from the main faults. In this case, the permeability of the rock mass is caused by internal damage developed during a deformation event. It is possible to model such development using restoration tools and, consequently, to estimate the strain tensor that measures the deformation. This contribution may provide an explanation of such off-fault gold deposits and certain deformation parameters may be used for a new targeting in exploration surveys. In the present research two SKUA-GOCAD restoration methods were applied to the golden-rich Mount Pleasant area in Western Australia and compared afterwards. One of the restoration methods, provided by the RestorationLab plugin, is based on the Finite Element method and requires a geomechanical model of the area. Another method, GeoChron, is based on the transformation of the coordinates of the present time to a new curvilinear coordinate system of the depositional time. The resulting strain tensors of both methods were used to calculate deformation attributes which together with dilation were studied to estimate their correlation with known gold occurrences using logistic regression function. Therefore, some of the attributes obtained by the RestorationLab approach show higher probability to observe the gold deposit, however, the highest correlation with the gold occurrences was achieved with the gradient of the deformation attribute, obtained by the GeoChron.