⁴⁰ Ar/ ³⁹ Ar ages of crystallization and recrystallization of rock-forming polyhalite in Alpine rocksalt deposits

Abstract

Ar data from the region. Illite crystallinity points to temperatures of c. 200 8C. The peak temperature of overprint was at c. 180 8C in the Berchtesgaden mine (vitrinite reflectance, fluid inclusions) and .240 8C in the Altaussee mine (fluid inclusions). These temperatures are below the value of 255 8C, where polyhalite starts to dehydrate. Disturbed age spectra patterns result from multiphase polyhalite growth; however, single phases and completely recrystallized fabrics yield good results. As in the Alpine test case, polyhalite may characteristically serve as a geochronometer for diagenetic and very-low-grade metamorphic processes.

Multiple isotope tracers from Permian-Triassic hydrated sulfates: Implications for fluid-mineral interaction

“…1). The two units of the Eastern Alps are characterised by the presence of representative and well exposed Permian-Triassic evaporitic deposits (Schorn et al, 2013;Leitner et al, 2013). Description of samples from various locations, mineralogy, texture as well as the age of the deposits are given in the supplementary material.…”

“…Permian-Triassic sulfates of Eastern Alps were thermally overprinted (Leitner et al, 2013;Bojar et al, 2016). Using illite crystallinity, vitrinite reflectance and fluid inclusions in anhydrite, Leitner et al (2013) estimated peak overprint temperatures affecting polyhalite bearing deposits at c. 200°C.…”

“…Matsubaya and Sakai (1973) demonstrate that anhydrites and gypsum were rehydrated subsequently by various mechanisms. By using a different method, namely the 40 Ar/ 39 Ar dating, Leitner et al (2013) conclude that the radiogenic system of Permian polyhalites from the Eastern Alps is not recording formation ages but subsequent Permian and Alpine events.…”

“…The origin of polyhalite of Permian age from the Zdrada platform and Peribaltic Basin of Poland was investigated by Peryt et al (1998) and Peryt et al (2005), the authors concluding that it formed by reaction of anhydrite with marine brines. By determining the age of polyhalite by 40 Ar/ 39 Ar method, Schorn et al (2013) and Leitner et al (2013) linked tectonic events and mineral textures from the Northern Calcareous Alps.…”

Advances in 40 Ar/ 39 Ar dating: from archaeology to planetary sciences – introduction

“…Leitner et al (2013) propose a novel approach and apply 40 Ar/ 39 Ar dating to a K-rich mineral, polyhalite (Fig. 5).…”