PRISM-PLANE AND BASAL-PLANE PARALLEL SUBGRAIN BOUNDARIES IN QUARTZ - A MICROSTRUCTURAL GEOTHERMOBAROMETER

Authors
Citation
Jh. Kruhl, PRISM-PLANE AND BASAL-PLANE PARALLEL SUBGRAIN BOUNDARIES IN QUARTZ - A MICROSTRUCTURAL GEOTHERMOBAROMETER, Journal of metamorphic geology, 14(5), 1996, pp. 581-589
Citations number
36
Categorie Soggetti
Geology
ISSN journal
02634929
Volume
14
Issue
5
Year of publication
1996
Pages
581 - 589
Database
ISI
SICI code
0263-4929(1996)14:5<581:PABPSB>2.0.ZU;2-5
Abstract
Empirical data on quartz subgrain patterns from various metamorphic ro cks show that, at least up to 10 kbar in the stability field of low-qu artz, prismatic subgrain boundaries are dominant whereas basal subgrai n boundaries are not developed. In the high-quartz stability field, bo th prismatic and basal subgrain boundaries occur and form typical rect angular ('chessboard') patterns. The likely reason behind the differen t occurrence of these subgrain patterns is that in high-quartz prismat ic glide becomes as easy as, or probably even easier than, basal glide . The two types of subgrain patterns can be clearly distinguished by o ptical microscopy. Consequently, the occurrence of chessboard subgrain patterns in quartz represents a practicable geothermobarometer. The p ossibilities of its application are far reaching and include the speci fication of deformation conditions at high-grade metamorphism, the rec ognition of syntectonic intrusions and the distinction between pluton emplacement at lower and at higher crustal levels.