PROBABILISTIC ASSESSMENT ON THE ROLE OF STRUCTURAL FEATURES RELATED TO HELIUM OCCURRENCES IN THE FOUR CORNERS REGION OF THE COLORADO PLATEAU, USA

Helium (He), a critical resource derived from the radioactive decay of U and Th in the subsurface, is an irreplaceable component in medical applications, science and engineering, nuclear power generation, and the aerospace industry. The occurrence of gas fields with economic He concentrations (>0.3%) requires tectonic and structural regimes favorable to concentrating He (originally produced in the crystalline basement) within a basin. We quantitatively test the correlation between high-He occurrences and structural features using a new high resolution geophysical aeromagnetic survey in the Four Corners region of the Colorado Plateau, USA. By combining magnetic data, gravity data, topography data, and magnetic and gravity depth profiles, several maps were created via Werner deconvolution algorithms: 1) depth to basement map with basement lineaments/faults, 2) igneous bodies occurrences (size and position), and a 3) flattened basement structural high map. After an extensive analysis, basement faults and igneous intrusive bodies were determined to be the most significant features influencing He accumulations. 88% of all high-He wells occur within 1 km of basement faults and 85% of He wells occur with 1 km of intrusions. As He values rise, the distance to these structural features decreases. Additionally, the influence of basement highs is confirmed to be significant as 88% of known He wells (>0.3%) occur within a structural high, and 91% of the remaining points are near (<1 km) intrusive bodies that could be acting as a local structural high. We present a composite map that acts as a predictive model based on a categorical probability analysis that highlights the importance of targeting zones of intersection of basement faults and igneous bodies as well as incorporating the outline of major basement structural highs. Thus, this work, which utilizes new high resolution geophysical data, provides ample evidence that the release, transportation, and accumulation of historical He gas occurrences in the subsurface are influenced by several structural features, namely, basement lineaments/faults, and igneous intrusions within zones of structural highs.