Surface Texture of Zircon Grains from the Sierra Madera Impact Structure, West Texas
EMSL Project ID
13306
Abstract
The Sierra Madera structure in west Texas is a ~12 km well-exposed eroded remnant of a complex impact crater. The structure was last studied in the late 1960’s and early 1970’s and is an excellent site for large- and small-scale deformation studies using modern research techniques When large meteorites impact the Earth’s surface they generate shock waves that radiate outward subjecting rocks to very high transient pressures which produce shock deformational features such as grain fracturing, breccias, shatter cones, twinning, planar elements and planar deformational features (PDFs), diaplectic glasses, and high pressure mineral polymorphs (French, 1998). Previous studies of the Sierra Madera impact structure documented shock deformational features such as breccias, shatter cones, planar deformational features (PDFs) in quartz, grain fracturing, and deformed quartz and carbonate minerals from within the crater (Wilshire et al., 1972).
Planar elements/PDFs and granular surface textures in zircon form in response to impact-generated shock waves in larger (>~90 km diameter) impact structures, (i.e. Sudbury, Chicxulub, Manicouagan, Chesapeake Bay) but these features have not been documented in smaller diameter craters (Bohor et al., 1993; Glass and Liu, 2001).
Unidentified features in zircon grains, tentatively called planar elements, were documented during an age-dating study of the Sierra Madera crater in 2004 and show promise for an in-depth surface texture study (Figure 1, see attached file). These textures are similar to PDFs and granular surface textures (Bohor et al., 1993: Glass and Liu, 2001). Therefore, I propose to document possible shock-induced surface textures on zircons from Permian sandstones within the central uplift of the Sierra Madera crater. Documenting shock-induced surface textures on zircon grains from the Sierra Madera crater will be the first report of these features from a <90 km diameter impact structure and may provide more constraints on the pressures and temperatures in which these features form.
Project Details
Project type
Exploratory Research
Start Date
2005-02-28
End Date
2007-03-22
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members