Damaged Rocks Index as a Structural Attribute Predictor for Gold Mineralization.

Jean-Jacques Royer and Maria Kakurina and Pablo Mejia-Herrera. ( 2015 )
in: 35th Gocad Meeting - 2015 RING Meeting, ASGA

Abstract

Several gold deposits are related to fault systems that control metals’ transport and accumulation through relatively high permeable discontinuous structures. However, some gold deposits form during the same deformation event but occur at locations far from the main faults. In those cases, due to the rock mass heterogeneity, the fracture systems caused by damage on the surrounding geological formations create permeable structures favorable to ore-deposit formation. A geo-mechanical 3D restoration model was used to estimate strains developed during deformation tectonic events (shortening, extension, shearing) assuming elastic isotropic rock properties. If this approach can be implemented steps by steps for each deformation phases, it is difficult to guess the appropriate non-damaged mechanical property to be assigned to each rock types, as only today elastic property (i.e not damaged) are accessible. In areas where the later secondary tectonic events can be neglected, we propose a new SKUA/Gocad-based approach which consists in estimating the total deformation from initial depositional to present time using the geologic-stratigraphic 3D Voxet model. This procedure gives access to the total deformation strain tensor εt that can be compared with those ε't calculated applying the classical geomechanical restoration method. Using an inverse type approach, the boundary conditions and mechanical rock properties can be estimated till the error between those two strain tensors being minimal. Mapping the obtained error can help in improving the initial 3D Skua model, or guessing the presence of unidentified faults. The method is then applied for prognosticating the presence of off-fault gold deposits in the Mount Pleasant region, Western Australia.

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BibTeX Reference

@INPROCEEDINGS{Royer2GM2015,
    author = { Royer, Jean-Jacques and Kakurina, Maria and Mejia-Herrera, Pablo },
     title = { Damaged Rocks Index as a Structural Attribute Predictor for Gold Mineralization. },
 booktitle = { 35th Gocad Meeting - 2015 RING Meeting },
      year = { 2015 },
 publisher = { ASGA },
  abstract = { Several gold deposits are related to fault systems that control metals’ transport and accumulation through relatively high permeable discontinuous structures. However, some gold deposits form during the same deformation event but occur at locations far from the main faults. In those cases, due to the rock mass heterogeneity, the fracture systems caused by damage on the surrounding geological formations create permeable structures favorable to ore-deposit formation. A geo-mechanical 3D restoration model was used to estimate strains developed during deformation tectonic events (shortening, extension, shearing) assuming elastic isotropic rock properties. If this approach can be implemented steps by steps for each deformation phases, it is difficult to guess the appropriate non-damaged mechanical property to be assigned to each rock types, as only today elastic property (i.e not damaged) are accessible. In areas where the later secondary tectonic events can be neglected, we propose a new SKUA/Gocad-based approach which consists in estimating the total deformation from initial depositional to present time using the geologic-stratigraphic 3D Voxet model. This procedure gives access to the total deformation strain tensor εt that can be compared with those ε't calculated applying the classical geomechanical restoration method. Using an inverse type approach, the boundary conditions and mechanical rock properties can be estimated till the error between those two strain tensors being minimal. Mapping the obtained error can help in improving the initial 3D Skua model, or guessing the presence of unidentified faults. The method is then applied for prognosticating the presence of off-fault gold deposits in the Mount Pleasant region, Western Australia. }
}