RADIOCARBON IN HYDROLOGIC SYSTEMS CONTAINING DISSOLVED MAGMATIC CARBON-DIOXIDE

In regions of active volcanism, the presence of magmatic carbon dioxid e (CO2) in regional hydrologic systems provides a radiocarbon-depleted tracer for delineating ground-water transport and mixing processes an d provides a means of assessing regional magmatic carbon fluxes, Varia tions in the stable carbon isotopic composition (delta(13)C) and carbo n-14 values of springs and surface waters from the southern Cascade Ra nge show consistent patterns of carbon isotopic mixing between magmati c, biogenic, and atmospheric CO2 reservoirs. Radiocarbon measurements of waters from the Lassen region in northern California were used to c onstruct a ground-water carbon-14 contour map, revealing principal sub surface flow paths and a broad region of diffuse magmatic CO2 flux.