Authigenic quartz microfabrics in Cretaceous turbidites: Evidence for silica transformation processes in sandstones
- Aberdeen Univ. (United Kingdom). Dept. of Geology and Petroleum Geology
The economic significance of quartz cementation in many reservoir sandstones has fueled extensive research into conditions under which the mineral precipitates. The most common manifestation of authigenic quartz is coarse syntaxial overgrowths, but fibrous and equant microcrystalline quartz cements have also been described from several marine sandstones. Ultimate sources of silica in these cases are generally siliceous microfossils or volcanic glass. As such, microcrystalline quartz cements might be expected to have formed via a recrystallization or maturation sequence analogous to that determined for Cenozoic and Mesozoic porcelanites and cherts. However, sandstones often lack evidence for intermediate stages in the silica transformation, and controls on recrystallization processes are consequently unclear. Microcrystalline quartz is a pervasive cement in reservoir sandstones belonging to the Scapa Member of the Lower Cretaceous Valhall Formation. Ten distinct authigenic silica fabrics are recognized in the Scapa sandstones, and the most important are described in this paper. A biogenic source of silica for early diagenetic quartz is established and textural evidence for intermediate opal-CT precipitates is presented. Quartz microfabric associations are interpreted in terms of thermodynamic and kinetic controls on silica diagenesis, and similarities with biogenic cherts are discussed. Finally, conditions of late diagenetic quartz precipitation are considered.
- OSTI ID:
- 49328
- Journal Information:
- Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes, Journal Name: Journal of Sedimentary Research, Section A: Sedimentary Petrology and Processes Journal Issue: 2 Vol. 65; ISSN JSRAEA; ISSN 1073-130X
- Country of Publication:
- United States
- Language:
- English
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