Quantifying the Impact of Variable Phyllosilicate Content on Viscosity
Geoscience, University of Wisconsin-Madison, Madison, WI, USA
Viscosity contrast between materials controls how strain is accommodated in polyphase or polylithologic systems. Deformation is preferentially taken up by the weakest phases, resulting in strain localization, which can be expressed as mid-crustal shear zones, salt diapirs, or shale smear in brittle fault zones. Metamorphosed and deformed turbidite beds of the eastern fold belt of the Mt. Isa Inlier, Queensland, Australia provide a unique natural laboratory for quantifying rock viscosities. Here, turbidite beds that represent Bouma horizons A and E have variable mica content and have been variably strained. Using a combination of field-based strain, microstructural, and geochemical analyses, I will develop and apply a methodology for quantifying the viscosity of naturally deformed rocks that is sufficiently general to be used on any polyphase rock. These rheological data will not only further constrain the rheology of the middle crust, but will also improve our ability to quantify viscosity contrasts between materials. This approach could be applied to rocks at any crustal level, and may lead to the development of better mathematical models for shale smear in faults.
AAPG Search and Discovery Article #90199 © 2014 AAPG Foundation 2014 Grants-in-Aid Projects