Authigenic feldspar as an indicator of paleo-rock/water interactions in Permian carbonates of the Northern Calcareous Alps, Austria
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 >= 99.5 mole % Or component. Low oxygen isotope ratios (+16.1 per thousand to +18.1 per thousand SMOW) suggest precipitation from 18 O-enriched, saline fluids at temperatures in excess of nearly equal 140 degrees C. 40 Ar/ 39 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.
Citation Information
Publication Year | 1996 |
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Title | Authigenic feldspar as an indicator of paleo-rock/water interactions in Permian carbonates of the Northern Calcareous Alps, Austria |
DOI | 10.1306/D42682D9-2B26-11D7-8648000102C1865D |
Authors | C. Spotl, M. Kralik, Michael J. Kunk |
Publication Type | Article |
Publication Subtype | Journal Article |
Series Title | Journal of Sedimentary Research |
Index ID | 70018759 |
Record Source | USGS Publications Warehouse |