The Lower Lemoine Member of the Waconichi Formation, Abitibi Greenstone Belt, Chibougamau, Quebec: Implications for VMS Exploration

Alexandre Richard Boulerice, Institut national de la recherche scientifique centre Eau Terre Environnement, Québec, QC, Canada, Pierre-Simon Ross, Institut national de la recherche scientifique, Centre Eau Terre Environnement, Quebec City, QC, Canada, Patrick Mercier-Langevin, Geological Survey of Canada, Québec, Canada, Sylvain Lépine, Cogitore Resources Inc., Rouyn-Noranda, QC, Canada and Francois Leclerc, Ministère de l'Énergie et des Ressources naturelles, Val-d'Or, QC, Canada

Contact First Author: Alexandre Richard Boulerice; ABoulerice4817@Gmail.com

Abstract ID#: 34501

 

English Abstract:
The Abitibi greenstone belt (AGB) is host to some of the richest volcanogenic massive sulphide (VMS) deposits in Canada. Only one VMS deposit, Lemoine, has been mined in the Chibougamau district thus far with 0.76 Mt of ore averaging 4.2 wt % Cu, 9.5 wt % Zn, 4.6 g/t Au and 83 g/t Ag. It is hosted in the Waconichi Formation (Roy Group). This MSc study aims at better constraining subunits within the Lemoine Member of the Waconichi Formation, identify emplacement processes and reconstruct its volcanic architecture through field mapping, core logging, petrography and geochemistry.

The study area encompasses the eastern sector of the NE-trending Lower Lemoine Member, where it comprises the intrusive Marelle QFP, the intrusive to extrusive Alpha Rhyolite, the extrusive Lemoine Rhyolite, the intrusive Coco Lake Rhyolite, and the extrusive Lemoine Dacite, Lemoine Andesite and Hangingwall QFP. The Lemoine deposit, 4 km SW of the study area, was located on top of the Lemoine Rhyolite and was overlain by the Hangingwall QFP.

Observations made in the 2014 field season have provided further evidence for the complexity of the volcanic architecture in the study area. For example, the the Alpha Rhyolite was emplaced in two pulses, a first effusive phase on the seafloor quickly overlain by the Lemoine Rhyolite, and a second phase intruding the Lemoine Rhyolite. The early, effusive (lobe-hyaloclastite flow) portion of the Alpha Rhyolite is characterized by a strong chlorite-sericite alteration whereas the intrusive portion is unaltered, showing the strong control of volcanic facies on alteration distribution. Facies mapping and thickness variations provide evidence for the location of possible volcanic vents in the study area,. The location of volcanic vents coupled with the spatial distribution of the hydrothermal alteration help better understand VMS systems and define new vectors for exploration in the eastern sector of the Lower Lemoine Member.

Back to: VMS Deposits and Their Geological Environment I