Geochemistry of the Wijinnedi-Snare, Courageous-MacKay, and Lac du Rocher/Camsell Lake volcanic belts of the Slave craton

Benjamin Williams1, Brian Cousens1, Alexandra Berger1, Luke Ootes2, Valerie Jackson2 and Michael A Hamilton3, (1)Carleton University, Ottawa, ON, Canada, (2)Northwest Territories Geoscience Office, Yellowknife, NT, Canada, (3)University of Toronto, Toronto, ON, Canada

Contact First Author: Benjamin Williams; benjaminwilliams@cmail.carleton.ca

Previously Published Material: Earlier/preliminary findings were presented at the 2014 Yellowknife Geoscience Forum, NWT.

Abstract ID#: 35532

 

English Abstract:
Archean volcanic belts throughout the Slave craton host gold deposits, several volcanogenic massive sulphide (VMS) deposits and numerous VMS prospects. This study provides a comprehensive comparison of three bimodal volcanic belts across the southern Slave craton; the ca. 2674 Ma Wijinnedi-Snare volcanic belt; the Courageous-MacKay volcanic belt, with ca. 2810 Ma basement overlain by ca. 2700 Ma Cycle I and ca. 2670 Ma Cycle II volcanic packages; and the ca. 2672 Ma Lac du Rocher/Camsell Lake volcanic belt.

Mafic volcanic rocks are tholeitiic to calc-alkaline and display MORB – BABB signatures, with flat chondrite-normalized patterns. The associated intermediate and felsic volcanic components are calc-alkaline and have two predominant chondrite-normalized patterns; the first group shows enrichment in LREE and a steep HREE slope, while the second has similar LREEs, a negative Eu anomaly, and a distinctly flat HREE pattern.

Within the Courageous-MacKay belt, Cycle I volcanic unit hosts the DEB VMS deposit, while the Cycle II sequence hosts the Tundra, Salmita and FAT gold deposits. The lower stratigraphic felsic unit hosting the DEB deposit are FII rhyolites, referred to a Superior craton-type classification scheme. While FIII rhyolites are characteristic of most large VMS deposits in the Superior, FII rhyolites are host to a number of Archean VMS deposits. The depositional settings of all three volcanic belts are consistent with a VMS-bearing environment, with VMS-like occurrences recorded at multiple locations.

Neodymium (Nd) isotope analyses of whole-rock samples were targeted for individual belts, stratigraphic levels, and relationship to basement material. Intermediate to felsic volcanic rocks from Wijinnedi-Snare belt have εNdi values between +0.9 and +2.1. Lac du Rocher samples have εNdi between +2.0 and +2.5. The Courageous-MacKay belt has a range between εNdi of +0.7 and +5.2. The data indicate that volcanic rocks include a dominant mantle component, with some crustal assimilation, regardless of proximity to basement. Results are anticipated to advance the knowledge of the Slave craton stratigraphy, provide further insights into Archean magmatism, and assist in the identification of VMS prospective volcanic belts.

Back to: Canadian Cratons Through Time: 4.0 Ga of Chemical Evolution and Tectonism