CO (sub 2) degassing in the Oregon Cascades

The carbon isotope content of dissolved inorganic carbon was measured for large cold springs in the central Oregon Cascades. Low (super 14) C activities in some of the springs are interpreted to result from the dissolution of diffuse emissions of magmatic CO (sub 2) , even though volcanic activity has not occurred in this area for more than 1300 yr. On the basis of dissolved magmatic carbon concentrations in the springs, we infer a diffuse magmatic CO (sub 2) degassing rate of 3.4X10 (super 5) kg/yr per kilometer of arc for the central Oregon Cascades. The CO (sub 2) flux calculated from estimates of the mean magmatic intrusion rate and experimentally determined values of CO (sub 2) content in melts is consistent with that determined from our measurements of the dissolved CO (sub 2) flux at springs.