An integrated approach to search for buried porphyry-style mineralization in central British Columbia using geochemistry and mineralogy: a TGI-4 project

Abstract

The Geological Survey of Canada (GSC) and the British Columbia Geological Survey (BCGS) are developing surficial geochemical and mineralogical methods for the detection of buried porphyry-style mineral deposits in drift-covered areas under the federally-funded Targeted Geoscience Initiative 4 Program. One objective is to help define the key components of till that are enriched near such deposits including: 1) porphyry indicator minerals that have survived erosion and transport in the subglacial environment and weathering in an oxidizing surficial environment and 2) trace-element content of the till matrix. Glacial dispersal of both components (heavy minerals and till matrix) is being studied at the Highland Valley, Gibraltar, and Mount Polley mines, and the Woodjam developed prospect which include calc-alkaline Cu-Mo, alkaline Cu-Au, and mixed calc-alkaline and alkaline Cu-Mo-Au porphyry deposits. A second objective is to test biogeochemical methods using spruce and pine tree bark as an exploration tool for buried porphyry-style mineralization. One key contribution of this project will be the reconstruction of the glacial and ice-flow histories at each of the study sites, based on surficial geological mapping and observations of ice-flow indicators on bedrock outcrop. These ice-flow histories will be applied to the interpretation of geochemical and mineralogical dispersal patterns in till and the spatial distribution of commodity and pathfinder elements in plant tissue. Between 2011 and 2013, 309 basal till samples were collected for till-matrix geochemical analyses and 302 basal till samples were collected for examination of heavy and mid-density mineral fractions. In total, 487 biogeochemical samples consisting of the outer bark of lodgepole pine (Pinus contorta) and Engelmann spruce (Picea engelmannii) were collected for geochemical analyses.