Original paper

Clay minerals in Upper Permian evaporites from the Northern Calcareous Alps (Alpine Haselgebirge Formation, Austria)

Spötl, Christoph

European Journal of Mineralogy Volume 4 Number 6 (1992), p. 1407 - 1420

47 references

published: Dec 15, 1992
manuscript accepted: Mar 18, 1992
manuscript received: Nov 1, 1991

DOI: 10.1127/ejm/4/6/1407

BibTeX file

ArtNo. ESP147050406017, Price: 29.00 €

Download preview PDF Buy as PDF

Abstract

Abstract The clay mineral assemblages of argillaceous halites, mudrocks, and sandstones from the Upper Permian Alpine Haselgebirge Formation are composed of dioctahedral illite and trioctahedral Mg-chlorite (clinochlore) plus varying traces of quartz ± alkali feldspar ± magnesite. Interstratified clay phases are entirely absent. Illite contains < 5 % smectite and is predominantly of the 1Md/1M polytype with < 20 % 2M1 component. Chlorite is likewise non-expandable and belongs to the lib polytype. SEM and TEM investigations show that most clay particles are well-crystallized, suggesting that they formed diagenetically. Measurements of "illite crystallinity" show distinct ranges for each lithology with almost no overlap. Hikes from halites yield the lowest IC values (mean 0.42 ± 0.02 Δ°2θ), implying and incipient anchizonal overprint. IC values from mudrock and sandstones samples, however, are significantly higher (mean values of 0.47 ± 0.01 and 0.56 ± 0.03, respectively) and indicate high-grade diagenesis rather than anchimetamorphism. The low IC values of illites from halite samples probably reflect the high availability of potassium in these evaporites.

Keywords

clay mineral diagenesisevaporitesillite crystallinitythermal historyNorthern Calcareous AlpsAustria