Institute of Applied Geoscience (IAG)

Microchemical signatures of gold in the porphyry-epithermal environments of the northern Cordillera, Canada

The Yukon Gold Project run through the Mineral Deposits Research Unit (MDRU) at UBC Vancouver permitted a multi disciplinary approach to the study of the metallogeny of the Dawson Range, Yukon. During this project it became clear that early Late Cretaceous Cu-Au porphyries contained gold grains which exhibited a generic and distinctive Bi-Pb signature in the suite of inclusions revealed within polished section. In 2013, the Yukon Geological Survey funded a short program of field work to complete this study, through characterization of gold grains from the Cu-Au-Mo porphyry at Casino, Yukon. This study was published in Yukon Exploration and Geology 2014. These studies will continue through two avenues in 2014/5.

The Casino Orebody
The Casino Orebody

i. Characterization of gold signatures from the Klaza Property, south Yukon.

The study of gold compositions in lode and placer at Casino suggested that epithermal mineralization was present, but distal to the porphyry. Unpublished studies of placer gold from Hayes Creek in the environs of the Sonora Gulch Cu-Au porphyry also suggested a contribution from epithermal sources. The compositional signature of this gold was very similar to placer gold previously reported in placers surrounding the low sulphidation epithermal occurrence at Mount Nansen in southern Yukon.

The Au mineralization at Klaza adjacent to Mt Nansen is currently under development by Rockhaven Resources and comprises low sulphidation mineralization present in an array of sub parallel outcropping veins. A study to be carried out in summer 2014 will characterize variation in the mineralogy of the veins over the outcrop and in particular any systematic variation in gold composition. The aim of the project is primarily to investigate the use of gold mineralogy to interpret variation in mineralizing conditions with the supplementary outcome of establishing local placer- lode relationships.

ii. Establishing gold mineralogy in alkali porphyries in southern and central British Columbia

The identification of generic signatures in gold from the Late Cretaceous porphyries in the Yukon has provided a platform to extend investigations to other porphyry systems in the northern Cordillera. Tom Mileham is undertaking a one year research project from May 1 which will investigate gold signatures from three alkali porphyries in British Columbia. The project will contribute to a coherent data set of compositions of gold from the porphyry- epithermal environment and underpin future work which will apply these findings in the context of exploration.