Multi-media geochemistry and surficial geology of the Yava Pb deposit, southeastern Cape Breton Island, Nova Scotia, Canada

Abstract

A detailed multi-media geochemical study was conducted over the east zone of the Yava lead deposit, southeastern Cape Breton Island. A 2 × 2 km grid was centred over the projected subcrop of the east ore zone and sample sites were located at 250 m spacing. Samples collected at each site included: (1) Balsam fir ( Abies balsamea ); (2) A 1 -horizon (organic humus) soil; and (3) C-horizon till. In addition, stream sediment samples were collected at approximately 250 m spacing along first and second order streams that transect the grid. Overburden drilling of a drumlin located in the grid, to the northeast of the ore zone, and a till fabric study were conducted in conjunction with the geochemical survey. The drumlin is cored by a silty/sandy till and overlying moderately-compacted silty till. The entire study area, including the drumlins, is blanketed by a loosely-compacted sandy till. The silty upper drumlin till and surface sandy till were deposited by NE and NNE ice flows respectively. Analysis of mineralized sandstone clasts from the two uppermost till facies in the overburden holes returned values of ≤3.05% Pb and ≤2.65% Zn. Our data indicate the Yava deposit has a robust geochemical signature, mostly for Pb and Zn in the −230 (−62.5 μm) mesh fraction and heavy mineral separates (−60+230 (−250+62.5 μ m) mesh fraction) of tills and stream sediments and ash of Balsam fir twigs. These data clearly delineate the subcrop of the east ore zone. The distribution of Ag, Cd, As and Sb within all sample media varies substantially and generally are less reliable for outlining the location of the deposit. Till clast distribution and till geochemical data indicate that NNE-trending dispersal in the upper sandy till sheet was minimal. Large NE-trending ribbon-shaped Pb and Zn “anomalies” in the −230 (−62.5 μm) mesh fraction of this till reflect inheritance of mineralization from the underlying drumlin core till with NE dispersion and possibly additional base metal mineralization along the margin of the sedimentary basin. The geochemical data for heavy mineral separates from both till and stream sediments mirror the results from the −230 (−62.5 μm) mesh fraction but are not recommended for future studies because of high sample preparation costs. Balsam fir is the most cost-efficient, yet geochemically effective, sample medium. Humus geochemistry reflects hydromorphic processes and is not recommended for future surveys.