CMIC News update - September 2011-2
CMIC Exploration Initiative - Integrated Footprints of Ore Systems
Prepared by CMIC University Research Team
Executive Summary
As Canadian exploration efforts increasingly focus on remote and concealed targets, the ability to recognize and vector towards large-scale ore-forming systems, from the most distal margins to the high grade cores becomes critically important. This requires a new generation of multi-parameter "footprint" models of high-value mineral deposits. This project will construct fully integrated 3D models of the detectable features of large-scale ore-forming systems, with an emphasis on the geological, mineralogical, geochemical, and physical rock properties of the ore system footprint. The goal is to develop practical models that enable identification of ore-forming systems at district and deposit scales, and the ability to navigate within them.
The focus of the study will be on detectible features in rocks and derivative materials that characterize the size and scalability of the footprint, such that their integration builds an empirically-robust exploration vectoring model. This approach is now possible because of the increasing availability of a wide range of new tools for detection of mineralogical, chemical, and physical rock properties, including space- and airborne instruments as well as hand-held instruments with greater sensitivity and lower detection limits, new inversion models to interpret the measurements, and the computational power to better integrate and visualize all the data. The research will emphasize linkages between different parameters, such as mineralogy and physical rock properties, that enhance the practical applications of geophysics and exploration geochemistry. Because variations in the detectable features of the ore systems, such as alteration, directly affect variations in the physical properties of the rocks, combining the features of the ore-system footprint with petrophysical models will form the basis for better constrained and more meaningful geophysical inversions. Transforming geological knowledge (e.g., mineralogy and geochemistry) into physical rock property information and then detectable features of the ore system is expected to lead to new understanding of how point-source data can be expanded to the inversion volumes.
A key innovation element of this work will be the development of new approaches to footprint models, including data presentation and computational methods for integration of exploration datasets, that will assist in extracting the signatures of productive ore-forming systems from a matrix of detectable features. Working groups will conduct research at several study sites, with the aim of defining a matrix of detectable features of the ore system and integrating those signals into footprint models. The data integration will be focused on industry needs, in terms of exploration models, derivative databases, and inversion tools, but will also result in significant fundamental advances in our understanding of the transfer of elements in the crustal environment.
Background/Rationale
CMIC-Exploration Innovation Consortium partners have identified the need for a matrix of detectable features of three broad categories of Canadian-based deposit types: magmatic, hydrothermal, and basinal deposits. During comprehensive industry-university consultations in March (Toronto), April (Toronto), and May (Ottawa) 2011, several possible integrated study sites for the proposed research were identified. It was recognized that development of fully integrated 3D models of a range of large-scale ore-forming systems would require large-scale multidisciplinary applied research to establish both the far- and near-field geological, mineralogical, geochemical, and geophysical footprints and to integrate that knowledge into the exploration process. The purpose of the footprint models is to progressively decrease the size of the search space during exploration without the significant increases in costs and risks, recognizing that it is a competitive advantage for exploration programs to improve detection at the district scale and to move more quickly and effectively from vectoring to detection. Current exploration successes are limited by the lack of robust, empirical ore system footprints that integrate all types of exploration data at the appropriate scales. Integrated footprint models, for example, relating alteration mineralogy to physical rock properties and thereby to geophysical response, will provide a critical new tool for recognizing and interpreting ore systems from regional to local at the camp scale and from distal to proximal at the deposit scale.
The proposed research, which is closely aligned with the exploration process, will directly impact exploration success and provide a solid foundation for future research directions, such as the fertility of unexplored terranes, deep mapping and detection, and tool development. This proposal outlines the research that will be conducted to populate the footprint models of three key deposit types, the tools that will be used, and the methods to integrate those data. The specific study sites will be determined with project sponsors. Specific research activities are being developed in consultation with the industry partners, including plans for integrating existing exploration data and in-house research in the new studies. This process is being overseen by an industry-led technical board, which has participated directly in the development of this proposal.
Deliverables/Outcomes
The proposed research will construct fully integrated 3D models of the geological, geochemical, and geophysical footprints of large-scale ore systems that are testable and scalable. The models will include data on alteration mineralogy and geochemistry of the host rocks, the structural framework of the ore-forming system, including permeability and fluid dynamic constraints, major and trace element lithogeochemistry, surficial geochemistry, physical rock properties of the host rocks and alteration and their geophysical signatures (gravity/magnetic/electrical/seismic/thermal). The models in each case study will include a fully populated matrix of detectable features of the ore system at multiple scales and include the linked databases from which those features are identified. Key signatures of the ore system, such as the geophysical responses of specific alteration facies or previously unrecognized mineralogical or geochemical attributes of dispersion haloes, will be derived from the vertical and horizontal integration of these datasets within the footprint model. The case studies will include strategies for acquisition of new data to populate or expand the footprint models, including development of new models in other exploration settings. The products will include tools for interpreting the detectable features of the ore systems at different scales and case studies of geophysical data inversions and detection of primary signatures of ore systems in surficial materials. These products will be delivered through research reports and through workshops where sponsors can learn to build their own footprint models from in-house data.
Key deliverables for each of the integrated study sites will be:
1) Integrated maps and sections of the key detectable features of the ore-system footprint, including geological, geophysical, and geochemical signatures.
2) Full characterization of the petrology and mineralogy of the ore system (inside and outside), including barren versus mineralized host rocks with variable alteration/preservation, and especially trace element signatures evident at the local and regional scales.
3) Characterization of the dispersion halo in surficial materials, including both physical and chemical components, in till, stream sediment, and ground waters, and interpretation of the emplacement, weathering, and erosion potential of surficial materials belonging to the ore system.
4) Integration of the ore system footprint with existing geophysical survey data over regions including entire deposit groups and their hosting geological structures.
5) Measurements of physical properties of altered, mineralized, and barren host rocks, in the lab and in situ, and methods to integrate these data into joint 3D inversion models that may be exported to other systems or deposit types.
6) Modifications of existing tools or methods to enhance the measurement and detections of specific geophysical-geochemical-lithogeochemical-geological signatures of the footprints at a range of scales.
University Research Team
Profs. Mike Lesher (Laurentian University) and Mark Hannington (University of Ottawa) are the interim project coordinators. Researchers from 6 other universities are coordinating the development of integrated study sites. For further information please contact Mike Lesher at cmlesher@gmail.com or Mark Hannington at Mark.Hannington@uottawa.ca
