The PACIFIC project: Developing passive seismic techniques for environmentally friendly and cost-efficient mineral exploration

Dr. Charles D. Beard, Postdoctoral Researcher, Sisprobe SAS and Universite Grenoble Alpes

Speaker Bio:

Charlie is a postdoc at Sisprobe and the Université Grenoble Alpes with PACIFIC, an EU project that develops passive seismic techniques for environmentally friendly and cost-efficient mineral exploration. Previously he worked at the British Geological Survey, Edinburgh with HiTech AlkCarb, an EU project that investigated 'HiTech' raw materials (REE + HFSE) associated with alkaline rocks and carbonatites. He did his PhD at McGill University with a thesis on mineral-melt partitioning in alkaline magmatic systems, in collaboration with GFZ Potsdam, Germany. He did his Masters with the Pacific Centre for Isotopic and Geochemical Research at UBC Vancouver, and associated Arctic field mapping with the Geological Survey of Canada. His undergraduate degree is from the University of Bristol.

Charlie’s research combines experiments, natural samples and numerical modelling to investigate magmatic processes, the evolution of the crust and the mantle, and the mineralisation of raw materials critical for renewable energy infrastructure. Recently he have become interested in how mineralogy, geochemistry and petrology can improve 3D geophysical models and ultimately streamline exploration efforts. This is will be the focus of his presentation to the TGDG.

Talk Abstract:

In the PACIFIC project we use two case studies to develop passive seismic techniques for application in mineral exploration: The Marathon PGE-Cu deposit in Ontario, Canada and the Kallak Fe deposits in Sweden. Passive seismic techniques are environmentally friendly and typically cost an order of magnitude less than active seismic surveys. Due to their sensitivity to contrasts in elastic properties, they are best applied to map sedimentary cover sequences and large-scale intrusive or fault structures that focus mineralisation. In special cases, such as with iron or manganese bodies, the mineralisation can be directly imaged.

Drillhole-constrained geological models at test sites allow us to determine (1) which geological features and resolved in our 3D seismic models and (2) develop data processing workflows that minimise the generation of artefacts. At the Marathon deposit most drilling extends ~ 400 m from surface. Our ambient noise surface wave tomography models image the footwall contact of the Coldwell complex, a structure that controls the location of PGE-Cu mineralisation at Marathon, and extend to a depth ~ 2 km from surface. There is, however, little to no contrast in seismic properties between mineralised and unmineralised gabbros at Marathon. At Kallak, a preliminary survey is used to image strongly deformed banded iron formation deposits hosted by gneisses. While there are limitations to the coverage provided by this preliminary survey, high velocity features in the 3D tomographic model correspond to drillhole-defined iron mineralisations, and similar high velocity features are imaged along strike. The strengths and limitations of passive seismic techniques are discussed, and directions of research are presented that aim to improve imaging of geological features at the prospect scale.

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