Authigenic feldspar as an indicator of paleo-rock/water interactions in Permian carbonates of the Northern Calcareous Alps, Austria
- Univ. Innsbruck (Austria). Inst. fuer Geologie und Palaeontologie
- Bundesforschungs-und Pruefzentrum Arsenal, Vienna (Austria). Geotechnisches Inst.
- Geological Survey, Reston, VA (United States)
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 {ge} 99.5 mole % Or component. Low oxygen isotope ratios (+16.1{per_thousand} to + 18.1{per_thousand} SMOW) suggest precipitation from {sup 18}O-enriched, saline fluids at temperatures in excess of {approximately} 140 C. {sup 40}Ar/{sup 39}Ar plateau-age spectra of five samples range from 145 {+-} 1 to 144 {+-} 1 Ma (Early Berriasian) and suggest that both types of feldspar were formed within an interval that did not exceed {approximately} 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.
- OSTI ID:
- 207877
- Journal Information:
- Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes, Vol. 66, Issue 1; Other Information: PBD: Jan 1996
- Country of Publication:
- United States
- Language:
- English
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