Environmental and Engineering Geoscience; August 2009; v. 15; no. 3;
p. 175-195; DOI: 10.2113/gseegeosci.15.3.175
© 2009 Association of Engineering Geologists
Fluid Flow Estimates in Molybdenum Mine Rock Piles Using Borehole Temperature Logs
MARSHALL REITER1
1 New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology801 LeRoy Place, Socorro, NM 87801
Temperature logs at 18 drill-holes in the four large Roadside rock piles at the molybdenum mine near Questa, NM, allow the fitting of equations representing heat transfer to temperature data, providing estimates of vertical and horizontal flow. From first-order approximations, the analyses indicate considerable fluid flow and heat transfer by advection, which is consistent with previous models. Because the rock piles are typically water unsaturated (liquid not encountered in the rock pile at drill-holes above the Red River), and because vapors are observed coming from the ground surface at some locations, most of the fluid flux in the rock piles is likely gas phase. Temperature logs at the 18 sites and sample characterizations at many of the sites indicate that pyrite oxidation may often occur preferentially over a depth interval of 
10–20 m, which is at depths of 
to 
of the depth of the drill-hole. Flows deduced from the T logs indicate that 1) pyrite oxidation is an important driver of present flow; 2) large amounts of air flow occur in the rock piles, consistent with necessary oxygen for pyrite oxidation; 3) present-day three-dimensional flows are possible in the rock piles; 4) thermal conditions in the rock piles are very heterogeneous; and 5) flow patterns are complicated and may vary with time. Temperature increases of 2–20°C are noted near the water table at the base of the rock piles in a few wells, indicating advection of heat from the rock pile and possible deep pile fluid circulation.
Key Words: Geothermal Studies • Waste Rock Piles • Fluid Flow • Temperature Logs
Copyright © 2009 by Association of Engineering Geologists
