Jacklyn Krueger, MSc
J. Krueger1, D. Kontak1, J.F. Montreuil2
1Harquail School of Earth Sciences, Laurentian University, Sudbury, Ontario, Canada
2Red Pine Exploration Inc., Toronto, Ontario, Canada
The Archean (2900-2660 Ma) Michipicoten Greenstone Belt (Superior Province, Canada) hosts several Au deposits attributed to intrusion-related (e.g., Renabie, Magino) and orogenic (e.g., Eagle River, Island Gold) processes. The Wawa Gold Corridor setting is a historical orogenic vein-type Au producer (0.120 Moz Au) centered on the ca. 2745 Ma Jubilee volcanic-plutonic complex; however, recent exploration has defined an early magmatic-hydrothermal gold (MHG) system associated with the intrusion. Here we report results from preliminary studies, based on drill core logging and SWIR analyses, that were initiated to better define the nature of the host intrusion and the posited MHG system and cautiously suggest it may have contributed Au to the later higher-grade orogenic Au vein system. The polyphase dioritic to tonalitic intrusive complex is mainly fine-grained and varies from melano- to leucocratic with minor late-stage leuco-aplitic dikes and coarse mafic pegmatites; hence the system records an evolution to a more felsic and hydrous component. Numerous generations of disseminated and stockwork sulfide (Py-Po-Cpy) mineralization (i.e., 14.16 m @ 1.04 g/t Au) of the MHG system occur through the intrusion with associated biotite alteration that predated fabric development (D1-D3). Drill holes with higher modal pyrite related to the MHG event, as established in our working paragenesis supported with SWIR data, suggest that higher than background Au values associated with early pyrite relates to a sericitic alteration of the host rock. Our finding has several important implications: 1) we have established the presence of a significant zone of Au mineralization in the hybrid setting that pre dates the orogenic Au event; 2) the MHG component should plausibly be considered as a potential source of Au in the later orogenic Au event; 3) geological similarities in terms of age, setting, host rocks, and alteration with the world class 20+ Moz 2740 Ma Cote Gold-Gosselin Au deposit; and 4) highlights the importance of better defining the nature of early MHG systems.