Metamorphic, microstructural and isotopic studies of mylonites
Recent advances in tectono-thermal models of orogenic belts require that the timing of thrust stacking and its relationship to the thermal history be evaluated. Before measuring radiometric ages of mylonites in thrust zones, it is critical to document the size of texturally and mineralogically equilibrated domains. A constancy of partition coefficients for the major and minor elements of minerals in textural equilibrium would be consistent with trace elements and isotopic equilibrium. Preliminary studies along the Brevard zone show non-equilibrium assemblages even in the highest strain mylonites. Such disequilibrium prohibits the use of whole rock ages to estimate the last episode of deformation; mineral ages probably give better estimates. The authors anticipate using a variety of radiometric systems on minerals in the fault zones to decipher the ages of thrusting. Recent deep drilling in the Kola Peninsula has revealed the availability of large volumes of fluids in the 4.5 to 9 km interval with temperatures over 150/sup 0/C. The presence of such fluids in deep crustal environments should accelerate the rates of reactions, crack propagation, hydrolytic weakening, dynamic recrystallization and recovery processes. Accelerated hydration reactions could also provide zones for development of faults. Microstructural analysis of mylonites from successively deeper structural levels will indicate the predominant mode of deformation and will test the traditional view of increasing ductility with depth. Geochemical and stable isotope analyses of the mylonites may also reveal enrichment of metals from possible deep crustal fluids.
- Research Organization:
- Virginia Polytechnic Institute and State Univ., Blacksburg (USA)
- OSTI ID:
- 6323009
- 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
GEOLOGIC FAULTS
GEOLOGIC MODELS
TECTONICS
METAMORPHIC ROCKS
CHEMICAL COMPOSITION
ISOTOPE DATING
MECHANICAL PROPERTIES
CRACK PROPAGATION
EPIDOTES
FELDSPARS
GEOCHEMISTRY
ISOTOPE RATIO
METAMORPHISM
MICROSTRUCTURE
MINERALOGY
RECRYSTALLIZATION
ROCK MECHANICS
AGE ESTIMATION
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CALCIUM COMPOUNDS
CALCIUM SILICATES
CHEMISTRY
CRYSTAL STRUCTURE
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
IRON COMPOUNDS
IRON SILICATES
MECHANICS
MINERALS
OXYGEN COMPOUNDS
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
580100* - Geology & Hydrology- (-1989)
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)
580400 - Geochemistry- (-1989)