We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Shock-induced formation of kyanite (Al<sub>2</sub>SiO<sub>5</sub>) from sillimanite within a dense metamorphic rock from the Ries crater (Germany).
- Authors
Stähle, Volker; Altherr, Rainer; Koch, Mario; Nasdala, Lutz
- Abstract
A dense (?~3.34 g cm-3) garnet-sillimanite-rich metamorphic rock from the suevite breccia of the Ries impact crater was studied by scanning-electron microscopy and Raman microprobe spectroscopy. In the strongly shocked rock clast kyanite was formed from sillimanite under momentary high pressures of natural shock waves. Kyanite aggregates were found as thin (~0.3-2.0 µm) seams along grain boundaries between, and fractures within, sillimanite grains. Within these seams kyanitec-axes are oriented perpendicular to original grain boundaries and fractures. In addition, larger (up to 10 µm) isolated kyanite grains were rarely found within host sillimanite. Filamentary kyanite aggregates and isolated crystals typically show shrinkage cracks due to volume decrease (~10%). Locally, broad interstices between sillimanite crystals are filled with aluminosilicate glass containing a high volume fraction of sub-micrometer-sized euhedral crystals. The silica-rich glass suggests incongruent melting of sillimanite at local post-shock temperatures significantly higher than 1,300°C. The edges of adjacent sillimanite grains are thermally and chemically altered. The local generation of temperature spikes is attributed to strong shock wave interactions due to very high shock impedance contrasts.
- Subjects
RIES (Germany); GERMANY; SILLIMANITE; METAMORPHIC rocks; CYANITE; RAMAN spectroscopy; PRESSURE
- Publication
Contributions to Mineralogy & Petrology, 2004, Vol 148, Issue 2, p150
- ISSN
0010-7999
- Publication type
Article
- DOI
10.1007/s00410-004-0599-6