--> ABSTRACT: Complex Quartz Overgrowths as Revealed by Microprobe Cathodoluminescence, by Robert K. Suchecki and Salman Bloch; #91030 (2010)

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Complex Quartz Overgrowths as Revealed by Microprobe Cathodoluminescence

Robert K. Suchecki, Salman Bloch

Conventional luminescence petrography of sandstones has only distinguished texturally homogeneous overgrowths of quartz from detrital grains. Microprobe cathodoluminescence, however, reveals extraordinary heterogeneity in overgrowths from a wide variety of locations, geologic ages, sedimentary facies, petrographic textures, and burial histories. The complexity of overgrowths is expressed by distinct luminescent and non-luminescent zones, and flamboyant and irregular textures. Interpretation of features previously undetected by conventional luminescence petrography may result in a better understanding of conditions under which quartz cement forms. Preliminary results for Morrow, Kekiktuk, Ivishak, Cardium, Tuscaloosa, and Middle Jurassic sandstones (offshore Norway) indica e that pressure solution between detrital grains is not a major source of silica cement even in very fine-grained sandstones. In contrast, pressure solution at overgrowth-overgrowth boundaries can produce significant amounts of silica. However, the source of initial silica for the overgrowths that are subsequently pressolved is uncertain in these rocks. Abundant fracturing of quartz grains occurs relatively early in the burial history and can be concurrent with overgrowth development. In most instances the fracturing is not accompanied by significant translation. Oxygen isotope data for quartz overgrowths isolated from their detrital cores suggest that precipitation of cement took place over a relatively narrow temperature range that corresponds to depths shallower than the present-day d pth. In view of the multiple zoning of the overgrowths, the temperatures most likely represent an average of a complex history of multi-event quartz cementation that occurred over a considerable temperature span, but principally at temperatures less than 75°C.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.