Isotopic evidence for the origin of an acid sulphate alteration,Styrian basin,Austria |
| |
| Authors: | Ana‐Voica Bojar Stanislaw Halas Hans‐Peter Bojar Janina Szaran |
| |
| Institution: | 1. Institute for Earth Sciences, Graz University, Heinrichstrasse 26, A‐8010 Graz, Austria;2. Mass Spectrometry Laboratory, Institute of Physics, UMCS, 20‐031 Lublin, Poland;3. Department of Mineralogy, Landesmuseum Joanneum, Raubergasse 10, A‐8010 Graz, Austria |
| |
| Abstract: | The Gossendorf volcanic body is the only one in the Styrian basin that shows extensive hydrothermal alteration. K‐Ar dating of primary volcanic biotite and alteration products (alunite) suggests that the emplacement of the volcanic body and hydrothermal alteration took place synchronously, 15 Ma ago. The stable isotope compositions of the alteration products such as opal, barite, pyrite and alunite combined with crystallographia investigations indicate temperatures between 150 and 200 °C for the formation of the alteration zones. The calculated stable isotopic compositions of the parent fluid, responsible for the alteration, show an exogene marine component, which interacted with the host rock. Sulphur isotopic compositions of sulphur, sulphides and sulphates indicate disequilibrium, and progressive oxidation. This fact, combined with the mineral zonation of the alteration zone, reflects not only change in the pH but also change in the fO2 of the ascending fluids. |
| |
| Keywords: | |
|
|
