THERMAL CAMERA IMAGING OF ROCK PILES AT THE QUESTA MOLYBDENUM MINE, QUESTA, NEW MEXICO

摘要

Between 1969 and 1981 open pit methods were used to recover the molybdenum ore producing some 317.5 million metric tons of mined rock from the Questa molybdenum mine, which went into nine rock piles. The mine is located in the Sangre de Cristo Mountains of Taos County in northern New Mexico. As part of a multi-disciplinary study to determine the effects of weathering on the long-term stability of the rock piles, we are searching for areas where weathering is occurring within the rock piles. Pyrite oxidation is a weathering process that typically generates large amounts of heat, making it a good candidate for detection by infrared thermography. We conducted surveys of surface temperatures on two rock piles during February and May 2004 using the FLIR SC 3000 infrared thermal camera. Thermal imaging of the rock piles revealed at one rock pile, a "heat vent" of roughly 40 m by 30 m that had the same maximum temperature of 18 deg C during February and May 2004. The maximum temperature of this heat vent was much larger than the ambient temperature in February (0-2 deg C) and May (4-6 deg C). During the February survey, the heat vent had little or no snow cover and appeared to be very wet, whereas the area surrounding the heat vent was snow-covered and frozen at the same time. The heat vent is likely the result of pyrite oxidation within the rock pile. Thermal imaging results from a second rock pile indicate that it is less likely to have a heat vent because the differences between the ambient and maximum surface temperature were much less significant. The small temperature difference could be explained by spatial variations in emissivity from local variations in rock thermal properties or moisture content or by a relatively small heat flux out of the rock pile.