Abstract

Legacy mining areas throughout the world contain widespread contaminated surface and groundwater from both anthropogenic and geogenic sources. Abandoned mine waste can contribute harmful solutes to groundwater and surface water, as metals mobilize through oxidation of sulfide minerals. Geogenic contaminant sources, such as geothermal water and mineralization, may also contribute to groundwater pollution in mining areas. To investigate the relationship between various groundwater contamination sources in legacy mining areas we sampled ~30 cold springs in the East Tintic Mountains of Utah and 8 regional hot springs as a proxy for geothermal water during fall 2019 and spring/summer 2020. Water chemistry data were analyzed using a Principal Components Analysis (PCA), revealing two distinct groundwater systems for hot and cold springs with no apparent mixing between the two. Only one cold spring was clearly enriched in multiple metals (Al, Mn, Co, Ni) relative to other springs but was not located proximal to any significant mining waste rock piles. 87Sr/86Sr ratios were analyzed in a subset of samples to identify flowpaths through carbonate or volcanic rocks. Only two springs had 87Sr/86Sr ratios characteristic of the Eocene and Oligocene volcanic rocks that dominate the surface of the study area (0.707 - 0.708), with all others having ratios indicative of underlying Paleozoic carbonate rocks (0.708 -0.710). Groundwater flow through carbonate rocks is dominated by faults and fractures, with faults appearing to act as barriers rather than conduits to flow. Faults create groundwater compartmentalization within the carbonate rock that isolates water contaminated by mining waste, while the carbonate rocks neutralize acid mine drainage. Groundwater compartmentalization explains the lack of widespread contamination despite the presence of large mining waste piles throughout the area. Mixing between geothermal and shallow groundwater may be the source of high Li, B, and SO42- concentrations in a limited number of springs. Our results suggest that contamination from mining waste is highly localized and that that waters discharging from mining areas overlying faulted carbonate rocks may be less contaminated than previously thought. This study has implications for understanding groundwater contamination dynamics in semi-arid regions impacted by mining.

Degree

MS

College and Department

Physical and Mathematical Sciences; Geological Sciences

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2021-06-21

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd11678

Keywords

groundwater contamination, groundwater mixing, mine waste, acid mine drainage, PCA, structural flowpaths

Language

english

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