--> Abstract: Cathodoluminescent Textures and the Origin of Quartz in the Mississippian Barnett Shale, Fort Worth Basin, Texas, by Petro K. Papazis and Kitty Milliken; #90039 (2005)

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Cathodoluminescent Textures and the Origin of Quartz in the Mississippian Barnett Shale, Fort Worth Basin, Texas

Petro K. Papazis and Kitty Milliken
The University of Texas at Austin, Austin, TX

Mudrocks from the Mississippian Barnett Shale in north-central Texas contain a substantial proportion of silt-size (10-62 µm) quartz crystals with diverse cathodoluminescent (CL) textures. Samples used in this study include 32 polished thin sections from two cores from Erath and Wise counties, and from outcrop samples in Lampasas and San Saba counties in central Texas. CL textures show that the quartz component in these mudrocks is present in several distinct forms. Many brightly luminescent detrital grains have weakly luminescent rims. Irregularly-shaped regions several tens of microns across consist of siliceous microbreccias in which relatively bright luminescent angular clay-size quartz fragments are surrounded by a matrix of dark luminescent quartz. Authigenic quartz is also present as darkly luminescent material in healed intragranular fractures within brightly luminescent detrital grains. Finally, quartz is localized as replacements of marine skeletal debris. Overall, authigenic quartz dominates the quartz fraction in mudrocks of the Barnett. Thus, silica geochemistry and diagenesis is an area of compelling interest for understanding the physical properties of the Barnett.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005