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Dissolved gases in the DOSECC Cajon Pass Well: First year results
Author(s) -
Evans William C.,
White L. D.,
Kharaka Yousif K.
Publication year - 1988
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl015i009p01041
Subject(s) - radiogenic nuclide , carbon dioxide , dissolved organic carbon , methane , geology , carbonate , mineralogy , organic matter , δ13c , isotopes of carbon , mantle (geology) , environmental chemistry , stable isotope ratio , analytical chemistry (journal) , total organic carbon , geochemistry , chemistry , oceanography , physics , organic chemistry , quantum mechanics
Fluid sampled from granitic rock near the 2 km depth in the DOSECC Cajon Pass well contained He, H 2 , CH 4 , C 2 H 6 , and C 2 H 4 in concentrations much greater than in air‐saturated water. The dissolved helium, which ranged in concentration from 0.6 to 0.8 µmole/kg‐fluid, was almost entirely radiogenic (³He/ 4 He = 0.06 Ra). The δ 13 C‐CH 4 value (−36 per mil) and (C 2 H 6 + C 2 H 4 )/CH 4 ratios (0.02 ‐ 0.05) indicate that the dissolved methane (50‐55 µmoles/kg‐fluid) was produced by thermogenic breakdown of organic matter. Measured pCO 2 values were very low, about 10 −5 atm., and the carbon isotopes (δ 13 C = −18.9 per mil) point to an organic source such as plant root respiration for the dissolved carbonate species. No evidence of mantle volatiles was found despite proximity of the well to the San Andreas fault.