M. Kralik Michael J. Kunk C. Spotl 1996 <div><div id="12461042" class="article-section-wrapper js-article-section js-content-section " data-section-parent-id="0"><p>Dolostones interbedded with Upper Permian evaporites at the base of the Northern Calcareous Alps contain abundant authigenic K-feldspar. Two petrographically, structurally, and isotopically distinct generations of K-feldspar can be distinguished: crystals composed of an inclusion. rich core and a clear rim, and optically unzoned, transparent crystals. Both feldspar types have essentially identical K-feldspar end-member compositions with &gt;= 99.5 mole % Or component. Low oxygen isotope ratios (+16.1 per thousand to +18.1 per thousand SMOW) suggest precipitation from<span>&nbsp;</span>¹⁸<span>&nbsp;</span>O-enriched, saline fluids at temperatures in excess of nearly equal 140 degrees C.<span>&nbsp;</span>⁴⁰<span>&nbsp;</span>Ar/<span>&nbsp;</span>³⁹<span>&nbsp;</span>Ar plateau-age spectra of five samples range from 145 + or - 1 to 144 + or -1 Ma (Early Berriasian) and suggest that both types of feldspar were formed within an interval that did not exceed nearly equal 2 m.y. Rb/Sr model ages range from 152 to 140 Ma, assuming that the burial diagenetic regime was buffered with respect to strontium by the associated marine Permian evaporites. Authigenic K-feldspar records two distinct events of hot brine flow, most likely triggered by tectonic movements (detachment) and by an increase in the subsurface temperature in response to thrust loading.</p></div></div> application/pdf 10.1306/D42682D9-2B26-11D7-8648000102C1865D en Society for Sedimentary Geology Authigenic feldspar as an indicator of paleo-rock/water interactions in Permian carbonates of the Northern Calcareous Alps, Austria article