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Gélifraction expérimentale d'arènes de roches cristallines: bilan d'essais de longue durée
Author(s) -
Etlicher Bernard,
Lautridou Jean Pierre
Publication year - 1999
Publication title -
permafrost and periglacial processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.867
H-Index - 76
eISSN - 1099-1530
pISSN - 1045-6740
DOI - 10.1002/(sici)1099-1530(199901/03)10:1<1::aid-ppp293>3.0.co;2-5
Subject(s) - geology , quartz , feldspar , massif , mineralogy , granulometry , silt , comminution , geomorphology , grain size , geochemistry , materials science , paleontology , sediment , metallurgy
Nineteen samples of grus derived from granite and other igneous rocks from the Massif Central (France) were submitted to 1500 freeze–thaw cycles. The thermal regime was a daily alternation from −12°C to +20°C. Important frost shattering was observed on all samples, mainly at the beginning of the experiment. Grain size curves reveal significant increases (20 or 30%) in granules (1 to 5 mm particles) and fine sand (0.05 to 0.08 mm). Three types of response can be identified: (1) Coarse elements are reduced more rapidly than fine sand and silt. An increase in granules (1 to 4 mm) and stability in the sand and loam particles can be observed. Polymineral grains are substantially affected by comminution, but not quartz. (2) There is a translocation of the cumulative grain size curve, and an increase in particles at every size (granule and sand and silt). Quartz is as strongly affected by comminution as polymineral grains. (3) There is a moderate increase in granules and a strong increase in fine sand and silt. Overall, quartz and polymineral grains are at the origin of these different responses which are the result of the tectonic and structural history of the rocks from which the grus is derived. No mineral has a uniform response to freeze–thaw activity, and it is not possible to define a general resistance scale, although quartz is more susceptible than feldspar. Copyright © 1999 John Wiley & Sons, Ltd.