Abstract
40Ar/39 Ar stepwise heating on one hydrothermal anhydrite and two partly hydrothermalized feldspars from a borehole in Vulcano volcano show that the initial trapped Ar does not have a constant isotopic composition. The constant 40Ar/36Ar ratio of the anhydrite, 306±3, is not a well-defined endmember for the two feldspars, which record a variety of fluid compositions. As the system is young (<100 ka), radiogenic Ar is much less than excess Ar.
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Villa, I.M., Taddeucci, G. K-Ar datability of altered rocks: variability of excess Ar in hydrothermal minerals. Bull Volcanol 54, 84–86 (1991). https://doi.org/10.1007/BF00278209
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DOI: https://doi.org/10.1007/BF00278209