During the formation of porphyry deposits, hot, acidic fluids flow outward altering the chemistry and physical properties of surrounding rocks over an area that can exceed 10 square kilometres and depths greater than one kilometre. These areas of alteration are known as lithocaps. Lithocaps are common around BC porphyry deposits, but their size can make it difficult to locate the porphyry copper-gold deposits that can be near the centre.
This project is characterizing the mineralogical, geochemical and physical properties of lithocaps at three porphyry copper-gold deposits in BC. This will help to identify (vector) the higher temperature parts of lithocaps that are more likely to host porphyry copper-gold deposits. The result will be new techniques and protocols to guide exploration for porphyry copper-gold deposits.
Exploration for deeper porphyry copper-gold deposits is difficult in certain regions because they are hidden by clay-quartz lithocaps. This project will establish a new set of criteria to improve the chances of identifying rocks nearest to porphyry deposits.
This project fits under Geoscience BC’s Strategic Objective of ‘Identifying New Natural Resource Opportunities’ and our goal to:
• Continue regional-scale surveys that deliver large data sets in support of identifying prospective targets and increasing discovery rates of deposits.
Specifically, this project will:
• Increase interest for porphyry exploration in advanced argillic altered rocks (lithocaps) of BC;
• Produce new detailed alteration maps for advanced argillic altered rocks of BC;
• Establish new techniques to use in advanced argillic altered rocks above porphyry deposits using quartz cathodoluminescence, clay mineralogy and rock geochemical characteristics; and
• Train a highly qualified person.
By generating a clearer understanding of the minerals that occur above and around known porphyry copper-gold deposits in BC, this study will provide data and tools to mineral explorers to find new deposits more efficiently. This will help to encourage exploration and to attract investment in BC. The information will be publicly available, and will be a useful tool in guiding natural resource decisions.
The research is being conducted at sites in the Northwest and North Central Regions of British Columbia, but the findings will be applicable across BC. Samples from three porphyry copper-gold deposits are being collected and analyzed for this project:
• Kemess North in the North Central Region;
• Alunite Ridge-Sofia district in the Toodoggone area of the North Central Region; and
• Tanzilla deposit, near Dease Lake in the Northwest Region.