Secondary ion mass spectrometry (SIMS) was used to obtain δ18O measurements on ∼20 μm spots in authigenic and detrital quartz from Mississippian sandstones of the western Canadian sedimentary basin. Detrital quartz shows a large range in δ18O (from 5 to 25‰) which overlaps the analyses of authigenic cements (20-34‰). Combining these data with the burial history and precipitation sequence of minerals indicates that meteoric water may have precipitated quartz at temperatures between 15 and 35°C over a period of 180 MA (300-120Ma). This nearly isothermal precipitation may have occluded pores in samples from the central portion of the basin, but quartz precipitation continued up ∼75°C at the basin margin. Conventional bulk analyses of these samples gave δ18O values of 13.4‰ for detrital quartz and 19.8‰ for authigenic quartz. Models based on bulk isotopic analyses can bias the interpretation of the timing of diagenetic quartz precipitation toward much higher temperatures. The SIMS measurements in diagenetic silicates can identify discrete episodes of precipitation allowing a more accurate interpretation for the timing of diagenetic events.
ASJC Scopus subject areas
- Geochemistry and Petrology