• journal_title：Geology
• Contributor：Karl E. Karlstrom ; Laura J. Crossey ; David R. Hilton ; Peter H. Barry
• Publisher：Geological Society of America
• Date：2013-04-01
• Format：text/html
• Language：en
• Identifier：10.1130/G34007.1
• journal_abbrev：Geology
• issn：0091-7613
• volume：41
• issue：4
• firstpage：495
• section：Articles

Helium isotope (³He/⁴He) data from geothermal springs in the Colorado Rocky Mountains (western United States) provide unequivocal evidence for a remarkable mantle-to-groundwater connection, with contributions of up to 27% mantle-derived helium. Hydrochemical modeling of springs shows the mantle helium is associated with high pCO₂ with 76 ± 20% of the CO₂ also derived from endogenic (deep geologic) sources. These springs occur preferentially along faults, have highest ³He/⁴He values above domains of low mantle velocity, and demonstrate unexpectedly widespread neotectonic mantle degassing. Total CO₂ flux through these springs is 3 × 10⁸ mol/yr, a small but persistent contribution to the CO₂ budget and an important baseline for carbon sequestration/leakage studies.