Fracture Opening Histories in Quartz-cemented Sandstone
The University of Texas at Austin, Jackson School of Geosciences Austin, Texas
My research will investigate how fracture growth and quartz cement precipitation interact to systematically create and destroy fracture porosity. I will test a new theory of quartz cementation in fractures that can be used to predict fracture porosity evolution as a function of temperature, surface area, and fracture opening history. The contribution of my research will be creating and testing methods to estimate timing and rates of fracture opening. Although a diagenetic model that links quartz precipitation and fracture opening has been proposed and preliminary attempts have been made to unravel the natural by-products of linked synkinematic cement precipitation and fracture opening, no thorough test of the diagenetic model has been made. Moreover, many (perhaps most) of the complex textural features that exist within synkinematic quartz in fractures have yet to be described, mapped, and explained, essential steps in testing the combined structural diagenetic model. Thus a central part of my study will be to unravel the textures in synkinematic cement and show how they can be used to document fracture opening history and to test (and probably modify and improve) the current structural diagenetic model of synkinematic quartz cement. I will quantify the amounts and distributions and textures and compositions of quartz within representative fractures and associated rock mass with conventional petrography, cathodoluminescence imaging, electron back-scatter diffraction, fluid inclusions and orientation contrast imaging.
AAPG Search and Discovery Article #90070 © 2007 AAPG Foundation Grants in Aid