Publication Date:
2013-03-22
Description:
Helium isotope ( 3 He/ 4 He) 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 p CO 2 with 76 ± 20% of the CO 2 also derived from endogenic (deep geologic) sources. These springs occur preferentially along faults, have highest 3 He/ 4 He values above domains of low mantle velocity, and demonstrate unexpectedly widespread neotectonic mantle degassing. Total CO 2 flux through these springs is 3 x 10 8 mol/yr, a small but persistent contribution to the CO 2 budget and an important baseline for carbon sequestration/leakage studies.
Print ISSN:
0091-7613
Electronic ISSN:
1943-2682
Topics:
Geosciences
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