Indicator-mineral signatures of the Casino porphyry Cu-Au-Mo deposit, Yukon

Abstract

This open file reports the results of an indicator mineral case study carried out around the Casino porphyry Cu-Mo-Au deposit in the unglaciated terrain of the west central Yukon. The research was part of the Geological Survey of Canada's (GSC) Targeted Geoscience Initiative 5 (TGI-5) Program. The purpose of the study was to test the use of indicator minerals as a porphyry Cu exploration tool in unglaciated terrain. At 22 sites around the deposit, a bulk stream sediment sample was collected to document the indicator mineral signature of the deposit. Steam water and stream silt samples were also collected at the same sites to compare geochemical to heavy mineral signatures. This open file presents indicator mineral abundance data for the bulk stream sediment samples. The Casino deposit has an obvious indicator mineral signature in the <2 mm heavy (>3.2 specific gravity (SG)) and mid-density (2.8-3.2 SG) fractions of stream sediments that consists of, in order of usefulness: gold>chalcopyrite>molybdenite>sphalerite>jarosite>goethite>pyrite that is detectable at least 14 km downstream. Similar indicator mineral patterns in other creeks indicate the presence of additional porphyry style mineralization nearby. Detailed characterization of the mineral chemistry of tourmaline and scheelite that is in progress will determine their suitability for porphyry Cu exploration in this unglaciated terrain. Government and exploration surveys will benefit from the addition of indicator mineral sampling to routine stream sediment sampling protocols.