AN INITIAL MINERALOGICAL AND GEOCHEMICAL INVESTIGATION OF STAMP SAND FROM BUFFALO REEF, KEWEENAW BAY, MICHIGAN

Millions of metric tons of stamp sand, a type of legacy mining waste generated from ore crushing for mineral and metal extraction, accumulated along the shoreline of Michigan’s Upper Peninsula from 1850-1932. Stamp sand was obtained from the 23 MMT associated with Buffalo Reef, located in the Keweenaw Bay of Lake Superior. This site is a key breeding ground for lake whitefish and lake trout. This site is well recognized as a key breeding ground for lake whitefish and lake trout. Monitoring data collected by tribal fisheries biologists show a decline in the number of juvenile lake whitefish produced each year, potentially resulting in a local population decline of harvestable lake whitefish that are important to local tribal communities and commercial fishing. While the relationship between sand properties and their effect on lake trout and lake whitefish spawning is currently being studied, critical information remains poorly understood. It is possible that copper and other metals expected to be in the stamp sands are having a broader negative effect on biological communities. Details regarding the variation of mineralogy, geochemistry and grain characteristics of these sands are not well defined. Sands from Buffalo Reef were investigated using mechanical sieving, scanning electron microscopy - energy-dispersive spectroscopy (SEM-EDS). Stamp sand toxicity to zebrafish embryos, as well as microbial diversity on the stamp sands was initially explored. The sand was moderately well sorted, having weakly bimodal grain size distributions (approximately 275 and 195 micrometers). The SEM-EDS data is consistent with light microscopy data and that 10% of grains in some regions of sample material had tin content above 0.1 wt.% and some grains have patchy Mn content of approximately 0.1 to 10 wt.%. No Cu above detection limit (~0.08 wt.%) was observed in grains or lithics. Ongoing biological investigation results include (1) zebrafish embryos exposed to stamp sands showed a significant hatching delay, as well as a reduction or absence of hair cells in the neuromasts of the sensory lateral line and (2) the diversity of microbial communities on stamp sands was extremely low with the most prevalent bacteria being Pseudomonas. Collective results provide a better understanding of mineralogical and geochemical complexity.