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TitleTill geochemistry and gold grain counts over the Amaruq property (Nunavut): glacial dispersal of a gold deposit in permafrost terrain
Authorde Bronac de Vazelhes, V; Boulianne-Verschelden, N; Beaudoin, G; McMartin, I; Côté-Mantha, O; Simard, M
SourceGAC-MAC 2017; Geological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 40, 2017 p. 85
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20160450
PublisherGeological Association of Canada
MeetingGeological Association of Canada-Mineralogical Association of Canada Joint Annual Meeting 2017; Kingston, ON; CA; May 14-18, 2017
Mediapaper; on-line; digital
File formatpdf
Subjectsmineral deposits; sediment dispersal; mineral exploration; mineralization; till deposits; geochemical surveys
ProgramGEM2: Geo-mapping for Energy and Minerals, Rae Province, Chantrey-Thelon
AbstractUnderstanding the nature of glacial dispersal processes affecting a mineral deposit is challenging, especially in polyphase glacial flow areas, highlighting the need to map glacial deposits in detail, reconstruct the ice-flow history and characterize the mineralization chemical and mineralogical signatures. The Amaruq deposit in central mainland Nunavut is located in the Archean Rae Province of the Churchill craton, within the Woodburn Lake greenstone belt. Gold occurs in three forms in the dominantly BIF-hosted mineralization: (1) inclusions in arsenopyrite, (2) inclusions in pyrrhotite, and (3) free electrum in quartz-carbonate veins associated with base metal sulfides. During the last Wisconsinan glaciation, the Laurentide Ice Sheet shaped the glacial landscape of the Amaruq deposit area into ribbed and streamlined till landforms, indicating a predominant regional ice flow to the NNW. At the local scale, evidence for late ice flows to the NW and WNW was found on striated bedrock surfaces.
A detailed surface till geochemical survey in 2015 over the Amaruq property (100x100m; n=2495) provides a unique opportunity to characterize glacial dispersal from the gold deposit. A robust principal component analysis (PCA) was performed on the till geochemical dataset (<63 µm, aqua regia digestion, ICP-AES&-MS). Results show a strong gold association with silver, arsenic, cobalt, chrome, nickel, copper, antimony and tungsten in the first component (45% of the variance). Kriging of sample scores shows three NNW trending anomalies, down-ice of known mineralization, interpreted as glacial dispersal along the main ice-flow path. In an area of thick till north of the Whale Tail zone, the deposit anomaly reaches the till surface approximately 1.5 km down-ice from the mineralization located beneath a lake. In 2016, 49 till samples were collected from frost boils along four NNW-trending transects over various till terrain types (~250 m spacing). Detailed surficial mapping shows different till types between Mammoth E (thin bouldery till) and Whale Tail (thicker fine-grained till) transects. Along the Mammoth E transect, counts increase to 1015 grains/10 kg 300 m of known mineralized structure, decrease to 523 grains, climb again up to 2433 grains at 1020 m, and return to background at 3 km distance. Only one major peak (1344 grains) is found 1300 m from mineralization along the Whale Tail transect and background is still not reached at 3.1 km distance. This study suggests that landform type and associated till thickness is an important factor when interpreting variations in till composition and glacial transport distances.
Summary(Plain Language Summary, not published)
This poster presents the results of a detailed till geochemical survey completed in 2015 on the Amaruq gold exploration project in central mainland Nunavut. The interpretation of this survey as well as targeted till and mineralized bedrock sampling and surficial geology mapping in 2016 forms part of two MSc thesis research projects to develop till geochemistry and indicator mineral methods for gold exploration in areas underlain by permafrost. The Geological Survey of Canada is involved in co-supervising the students within the Chaire de recherche industrielle CRSNG-Agnico Eagle en exploration minérale at Laval University. The study area is part of the GEM-2 Thelon-Chantrey Rae Project area and the work will contribute to improve drift exploration methods in glaciated terrain underlain by permafrost and support informed decision making for resource exploration and development, and for land use management.