Elsevier, Journal of Volcanology and Geothermal Research, 1-2(148), p. 152-164
DOI: 10.1016/j.jvolgeores.2005.03.019
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Noble gas and N2 compositions have been determined in paleofluids of core samples from geothermal wells in the Larderello area, Italy. The results were coupled with hydrogen and carbon isotope compositions of similar fluids from an independent batch of samples to provide constraints on the origin of the fluids. The fluids trapped during early-stage hydrothermal circulation are characterized by relatively high 40Ar/36Ar and N2/Ar ratios (332≤40Ar/36Ar≤564 and 248≤N2/Ar≤4197, respectively) and indicate the presence of radiogenic 40Ar and excess N2 when compared to air/asw (air saturated water). The fluid inclusions related to late-stage hydrothermal activity show low N2/Ar and 40Ar/36Ar ratios (309≤40Ar/36Ar≤354 and 47