Chemically induced fracturing in alkali feldspar
- Author(s)
- K.S. Scheidl, Anne-Kathrin Schäffer, E. Petrishcheva, G. Habler, F.D. Fischer, J. Schreuer, R. Abart
- Abstract
Fracturing in alkali feldspar during Na-K cation exchange with a NaCl-KCl salt melt was studied experimentally. Due to a marked composition dependence of the lattice parameters of alkali feldspar, any composition gradient arising from cation exchange causes coherency stress. If this stress exceeds a critical level fracturing occurs. Experiments were performed on potassium-rich gem-quality alkali feldspars with polished (010) and (001) surfaces. When the feldspar was shifted toward more sodium-rich compositions over more than about 10 mole %, a system of parallel cracks with regular crack spacing formed. The cracks have a general (h0l) orientation and do not correspond to any of the feldspar cleavages. The cracks are rather oriented (sub)-perpendicular to the direction of maximum tensile stress. The critical stress needed to initiate fracturing is about 325 MPa. The critical stress intensity factor for the propagation of mode I cracks, K, is estimated as 2.30-2.72 MPa m (73-86 MPa mm) from a systematic relation between characteristic crack spacing and coherency stress. An orientation mismatch of 18° between the crack normal and the direction of maximum tensile stress is ascribed to the anisotropy of the longitudinal elastic stiffness which has pronounced maxima in the crack plane and a minimum in the direction of the crack normal.
- Organisation(s)
- Department of Mineralogy and Crystallography, Department of Lithospheric Research
- External organisation(s)
- Ruhr-Universität Bochum (RUB), Montanuniversität Leoben
- Journal
- Physics and Chemistry of Minerals
- Volume
- 41
- Pages
- 1-16
- No. of pages
- 16
- ISSN
- 0342-1791
- DOI
- https://doi.org/10.1007/s00269-013-0617-1
- Publication date
- 01-2013
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 105116 Mineralogy, 1051 Geology, Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/e26e2336-ec70-4530-82cd-4b22ffa9e81d