Print this pageSource-Sink Relationships during Quartz Cementation: A Case Study from the Haushi Group Sandstones, Sultanate of Oman
RAMSEYER, KARL, BERNHARD H. HARTMAN, PETER HOPPE, KATALIN JUHASZ BODNAR, YVES KROGER, and ALBERT MATTER
The late Westphalian to Artinskian Haushi Group in the Interior Oman Sedimentary Basin consists of glaciogenic, marginal marine, coastal plain and fluvial sediments. The sediments presently are at maximum burial and range in depth from outcrop to almost 5000m. This variation allows the study of quartz cementation over a wide depth range.
Authigenic quartz which formed as zoned overgrowths varies from trace amount in outcrop samples to almost 25% of the bulk composition in sandstones buried over 4000m. Evidence from cathodoluminescence, stable isotopes, electron microprobe and fluid inclusion microthermometry supports a multistage origin of authigenic quartz. The diagenetic sequence reveals cogenetic processes leading to different phases of quartz cementation.
At shallow depth, meteoric incursions caused intense dissolution of aluminosilicates and precipitation of quartz and clay minerals. With increasing burial, more quartz precipitated at approx. 1500m associated with an increase of the illite content in I/S mixed-layer clay minerals. Increased pressure solution at detrital grain boundaries at 2600m corresponds with a sharp increase in authigenic quartz at the same depth. Ilitization of kaolinite, observed below 3000m, supplied additional silica for quartz precipitation at elevated temperature. Of these four sources, pressure-solution at detrital grain boundaries is responsible for most of the observed quartz cement.