Sheila Ballantyne, PhD
S. Ballantyne1, M. Stewart2, M. Anderson1, C. Venturi3, N. Richardson3, N. Campos3, N. Schoenherr1
1Earth Sciences, University of Toronto, Toronto, Ontario, Canada,
2Department of Earth and Environmental Sciences, Mount Royal University, Calgary, Alberta, Canada,
3Hudbay Minerals Inc., Flin Flon, Manitoba, Canada
Volcanogenic massive sulphide (VMS) deposits are important sources of base and precious metals. Ancient VMS deposits have invariably undergone multi-phase metamorphism and deformation that have altered the ore body architecture. The paragenetic work presented here is part of a PhD project seeking to better understand the processes and controls on fluid-enabled metal remobilization during multi-phase metamorphism and deformation. The approach includes mapping structures and geochemical signatures in 3-dimensions. Expanding our understanding of primary and post-depositional geological controls on spatial distribution, grades, and associations of deformed ore bodies could aid in creating vectors for mineral exploration of ancient VMS systems.
The case study used for this work is the VMS deposits of the Snow Lake camp, in west-central Manitoba, Canada, owned and operated by Hudbay Minerals. Snow Lake is host to eight known VMS deposits, interpreted to have formed via a single metalliferous hydrothermal event ~1.9 Ga. Two deposits in Snow Lake are the focus of this study: in-production Lalor mine and in-development phase 1901 deposit. These deposits are ideal case study sites due to the excellent access to underground workings, significant amounts of drill core, and large drill-core databases that have been generously made available by Hudbay Minerals. Comparing data from each deposit provides unique opportunities to understand how differences in spatial distribution of faults and other large structures that may act as fluid conduits affect ore grades, textures, associations, and type of ore-hosted sulphide remobilization.
A total of fifty-four thin sections have been made and employed for this paragenetic study. Some of the samples come from a deep drift in the Lalor mine that runs perpendicular to the strike of several lithologies, shear zones, and five ore bodies that vary in grade and metal content (Cu+Zn+Ag+Au). The other samples come from drill core that intersect the 1901 deposit. The next steps of this PhD are microanalytical studies, including scanning electron microscope (SEM) and laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) to understand the elemental distribution of the ore bodies and hosting lithologies.
The results of this study will be integrated into a 3D geological model that is being developed as part of this PhD project. Combined with new interpretations of deposit-scale folds and faults, as well as multi-variate analyses correlating litho-geochemical signatures to structures and ore bodies, this work will aid in understanding the controls on ore body architecture in ancient metamorphosed and deformed VMS deposits.