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The past-producing Pine Point lead-zinc mining district, Northwest Territories, Canada, provides a unique opportunity to study the role of glacial dynamics in a thick, continuous till succession that has not been influenced by the underlying bedrock topography. Parts of the Pine Point mining district are covered by >20 m of subglacial Quaternary sediments (till) associated with the former Laurentide Ice Sheet. Till facies exposed in unreclaimed open-pit K-62 have been classified into four separate units. Micro- and macrosedimentological analyses were undertaken to identify the change in subglacial stress during sediment deposition and across till unit boundaries. An analysis of high- and low-angle microshears (lineations) in thin sections produced from these till units indicate that there is a noticeable decrease in the abundance of low-angle shear features immediately below till unit boundaries. The deformation of low-angle shears in the underlying tills was likely caused by remobilization of the overlying till unit. This remobilization is consistent with aggradation-constant entrainment decay mechanisms for subglacial till emplacement and accretion and subglacial dispersion models. Resume: Le district minier de Pine Point, ancien producteur de plomb et zinc dans les Territoires-du-Nord-Ouest (Canada), offre une occasion unique d'etudier le role de la dynamique des glaces dans une sequence epaisse et continue de till n'ayant pas ete influencee par le relief de substrat rocheux sous-jacent. Des secteurs du district minier de Pine Point sont recouverts de >20 m de sediments quaternaires sous-glaciaires (till) associes a l'ancien inlandsis laurentidien. Des facies de till exposes dans la fosse non restauree K-62 ont ete classes dans quatre unites distinctes. Des analyses micro- et macrosedimentologiques ont ete realisees afin de cerner les variations des contraintes sous-glaciaires durant le depot de sediments et entre les unites de till. Une analyse de microcisaillements (lineations) fortement et faiblement inclines en lames minces dans ces unites de till indique une diminution perceptible de l'abondance des elements de cisaillement faiblement inclines immediatement sous les limites d'unites de till. La deformation des cisaillements faiblement inclines dans des tills sous-jacents est probablement le resultat de la mobilisation des unites de till sus-jacentes. Cette mobilisation concorde avec des mecanismes d'alluvionnement-decomposition par entrainement constant pour la mise en place/l'accretion sous-glaciaires de tills et des modeles de dispersion sous-glaciaire., Introduction The role of subglacial sediments in the movement of continental ice sheets is important but not entirely understood (Benn and Evans 1998; Boulton 2006; Evans et al. 2006; Menzies [...]

Indicator mineral research is currently being undertaken in partnership with the Nova Scotia Department of Natural Resources and Renewables at the Brazil Lake lithium-cesium-tantalum (LCT) pegmatites in southwest Nova Scotia as part of the Geological Survey of Canada's Targeted Geoscience Initiative (TGI) program. The pegmatites, discovered in 1960, are well known from previous detailed bedrock mapping and surficial studies and are informally named based on their relative geographic positions as the South and North pegmatites. The South pegmatite naturally outcrops, and both pegmatites are surrounded by spodumene-rich boulders on the surface of the thin till-covered (<4 m) drumlinized glacial landscape. For these reasons, the pegmatites are excellent sites to test indicator mineral exploration methods for Li and associated critical elements (e.g., Ce, Ta). Five pegmatite samples were collected for detailed study and analysis of potential indicator minerals. Close to the pegmatite and up to 13 km down ice (south-southeast), 87 bulk (10-14 kg), till sediment samples were collected for indicator mineral analysis. A total of 105 till samples were collected around the pegmatite and across the region for matrix geochemistry. A preliminary list of indicator minerals includes mid-density (e.g., spodumene, tourmaline, blue apatite) and high-density mineral species (e.g., columbite-tantalite, cassiterite) and this list is expected to expand as the detailed studies progress. Trenches dug in the Fall of 2022 to collect till samples on the proximal down ice (south) sides of both pegmatites revealed abundant spodumene pebbles and small cobbles in the till, indicating that the local till should display strong indicator mineral and matrix geochemical signatures derived from the pegmatites. [ABSTRACT FROM AUTHOR]

Till sampling for matrix geochemistry and indicator mineralogy, in conjunction with LiDAR-based surficial mapping, is ongoing (since 2019) in the Brazil Lake Li-Cs-Ta-(LCT) pegmatite district of southwestern Nova Scotia, a region that has seen increased staking and exploration activity for critical minerals (e.g., Li, Cs, In, Sn, and Ta). Recently, the Nova Scotia Geological Survey, in collaboration with the Geological Survey of Canada, have undertaken research to increase exploration success in regions covered by glacial sediments by documenting how critical minerals and elements are dispersed in till from the pegmatites at Brazil Lake. Newly available LiDAR data assisted to decipher past glacial trajectories, which in turn, influenced targeted sampling locations. A total of 105 till samples were collected from varying distances up-ice, overlying, and down-ice of the Brazil Lake pegmatites to define the extent of dispersal from the known pegmatites, and from the surrounding areas to provide regional background context and assess the potential for additional pegmatites buried by extensive till cover in the region. Samples collected for till matrix geochemical analysis were submitted to test the applicability of different acid digests (sodium peroxide fusion, 4-acid, lithium metaborate fusion, and aqua regia). Three size fractions of till were analyzed and assessed for their efficacy in detecting dispersal: coarse sand (1.0-2.0 mm), silt and clay (<0.063 mm), and clay (<0.002 mm). This presentation includes the geochemical results and surficial geological interpretations to date as they pertain to the geometry of glacial dispersal trains, net glacial dispersal in the region, the effects of multiple glaciations on till provenance, depositional history, and the potential for additional critical and base-metal mineralization. [ABSTRACT FROM AUTHOR]