Hydrologic characterization of the Mary Murphy Mine and vicinity, Chaffe County, Colorado using multiple isotope tracers and dissolved solutes

Fractured rock environments present great challenges to hydrologic characterization due to their structurally heterogeneity which severely limits the effectiveness of traditional approaches. Here we use a suite of environmental isotopes, oxygen-18 (delta18O), tritium (3H), sulfur-35 (35S), tritium/helium (3H/3He), and uranium (234U/238U) along side traditional geochemistry techniques to further characterize the Mary Murphy Mine site.; Hydrograph separation using delta18O showed that groundwater was the dominant contributor to Chalk Creek streamflow, as snowmelt peaked at 26% of contribution. The use of 35S as an independent tracer provided a similar result of 33% at peak snowmelt. 3H/ 3He dating showed apparent ages of near 4 years in monitoring wells near Chalk Creek.; North mine discharges showed the most depleted delta18O values in the mine, and also showed a shorter mean residence time than south discharges based on isotopic amplitude variations of 0.6 ‰ compared to 0.3 ‰.