DELTA-CL-37 VARIATIONS IN SELECTED MINERALS - A POSSIBLE TOOL FOR EXPLORATION

delta(37)Cl values were determined by mass spectrometry of selected mi nerals from different localities and origins. Evaporite minerals, seco ndary sedimentary minerals and magmatic minerals all appear to have sm all delta(37)Cl variations. For evaporite and secondary sedimentary mi nerals, this small variation is caused by the limited fractionation oc curring during precipitation. In magmatic minerals, the small variatio n is caused by the low isotope fractionation in high temperature envir onments. On the other hand, large delta(37)Cl variations are found in late-stage volcanic (fumarolic) environments. Fumarolic minerals forme d from gases have negative delta(37)Cl values relative to SMOG; repeat ed sublimation and condensation result in values as low as - 4.9 parts per thousand. Base metal chlorides formed from the residues have posi tive delta(37)Cl values relative to SMOG, up to + 6 parts per thousand for an atacamite sample. The elevated delta(37)Cl contents of these p otentially economic minerals could be reflected in the waters draining their deposits. The analysis of delta(37)Cl in groundwaters could the n be used as an exploration tool.