Progressive deformation textures in granite form from incipient to advanced strains
In the South Mountain Metamorphic Core Complex (Phoenix, Arizona) a Tertiary granite intruded a Precambrian gneiss. Detachment on a low-angle normal fault followed and cut through the slowly cooling intrusion. The resulting tectonic rock types are granitic gneiss, mylonite, and a cataclasite. Quartz is always deformed. At high T a preferred lattice orientation (PLO) developed at incipient strain. The texture suggests grain boundary migration in low-strain areas and recrystallization in local shear zones. Grain boundary orientations due to migration tend to be bidirectional and independent of the orientation of the involved crystals, but are thought to be dependent on local strain axes. At advanced strains and lower T old large grains decay along deformation bands, by recrystallization and subgrain development. At high strains the grain size is small and stable. The PLO is strongly dependent on the distribution of inhomogeneties (e.g. plag), which due to S/C mesofabric causes the fabric outline to be oblique. Biotite tears apart along faults // and perpendicular (001). Open faults are filled with K-spar, leucoxene and opaques. New biotite grows along two-phase boundaries (qz/plag) suggesting efficient diffusion of its components and chemical interaction with plag. This process causes the mylonite to become a layered rock. Pseudotachylite in the cataclastite developed at biotite grade. Chlorite is mainly a post-tectonic-hydrothermal phase. Cataclastic particles are later cut by ductile faults; thus plastic and cataclastic deformation modes were interactive.
- Research Organization:
- Univ. of New Hampshire, Durham (USA)
- OSTI ID:
- 6460491
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ARIZONA
GRANITES
PETROGENESIS
PETROLOGY
BIOTITE
CRYSTAL STRUCTURE
METAMORPHIC ROCKS
MINERALOGY
QUARTZ
TERTIARY PERIOD
CENOZOIC ERA
CHALCOGENIDES
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGY
IGNEOUS ROCKS
MICA
MINERALS
NORTH AMERICA
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLUTONIC ROCKS
ROCKS
SILICATE MINERALS
SILICON COMPOUNDS
SILICON OXIDES
USA
580300* - Mineralogy
Petrology
& Rock Mechanics- (-1989)