A Helium Exploration Survey in the Animas Valley, Colorado

Abstract

A soil gas and water helium survey was conducted in the Animas Valley, San Juan Mountains, Colorado, where several thermal springs and wells occur. Warm water emerges from Paleozoic limestone and red beds in two distinct areas of the valley. Detection of soil gas or water helium has proven to be useful geothermal exploration technique world wide, but helium concentrations may be effected by diurnal flux, hydraulic gradient, or unusually large amounts of other gases. Water and soil gas samples were collected along a transect survey, stored in leak proof containers, and then analyzed for helium with a highly modified mass spectrometer. Some negative water helium values (in reference to air) support the idea that carbon dioxide evolving from a local limestone outcrop may be purging helium at one site. However, the contoured soil gas helium data compared favorably with previous interpretations derived from other exploration techniques. In some area, more definitive results were obtained. As with all exploration methods, some limitations are inherent in this technique, and should be considered.