HIGH-PRECISION MEASUREMENT OF CHLORINE STABLE-ISOTOPE RATIOS

We present an analysis procedure that allows stable isotopes of chlori ne to be analyzed with precision sufficient for geological and hydrolo gical studies. The total analytical precision is less-than-or-equal-to +/- 0.09 parts per thousand, and the present known range of chloride in the surface and near-surface environment is 3.5 parts per thousand. As Cl- is essentially nonreactive in natural aquatic environments, it is a conservative tracer, and its deltaCl-37 is also conservative. Th us, the deltaCl-37 parameter is valuable for quantitative evaluation o f mixing of different sources of chloride in brines and aquifers.