ABSTRACT: Photomultiplier-based imaging of electron beam-induced luminescence, applied to a variety of sandstones of different compositions, ages, and burial histories, reveals that brittle deformation of detrital quartz is more prominent and widespread than previously recognized. Healing of microfractures by precipitation of authigenic quartz within detrital grains masks much of this fracturing from observation using standard petrographic methods.
In addition to its role in compactional grain rearrangement, brittle deformation of detrital quartz is linked to pressure dissolution. Simple concavo-convex grain boundaries, sutured grain boundaries, and stylolites are all accompanied by brittle extension resulting in physical redistribution of material on a microscopic scale.
The crack-seal mechanism of fracture and vein formation is also dramatically confirmed in scanned cathodoluminescence images. Repeated brittle extension along close-spaced (micron-scale) subparallel microfractures, that are subsequently filled by multiple generations of authigenic quartz, attests to a complex history in the development of veins and open fractures.
The abundant grain fractures observed with scanned cathodoluminescence suggest that grain fracturing plays a more important role in sandstone consolidation than has been previously recognized. Sandstones may have hydrodynamic properties greatly different from systems characterized solely by intergranular porosity, and thus these observations have implications for understanding the hydrologic characteristics of siliciclastic rocks in the subsurface.
