Cross-formational flux of aluminium and potassium in Gulf Coast (USA) sediments

Mark Wilkinson*, R. Stuart Haszeldine, Kitty L. Milliken

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The diagenetic dissolution of minerals to form net porosity in oilfield sandstones requires export of major-element constituents. Mass-balance must exist at some size scale, however, this is difficult to identify owing to the depositional variability within sedimentary formations. We have taken sets of whole-rock geochemical data from the Frio Formation of the USA Gulf Coast, for both sandstones and enclosing shales. Graphs of 'mobile'/'immobile' element ratios show a statistically significant decrease of K (mobile) with depth for sandstones, and a corresponding relative increase in Ti, Zr and Hf (immobile) in shales. Data for Al are also suggestive of a net flux from sandstones to shales, although of marginal statistical validity. Assuming that the sediment had an initially uniform chemical composition, then K and possibly Al are exported from sandstones into shales, despite the common assumption of Al immobility. There is insufficient export of K from sandstones to account for the import of K into shales, so another source of K must exist. However, there is probably Al conservation within the Frio Formation, as the calculated outflux from the sands and the influx from the shales approximately balance. More data are required to conclusively settle the question of Al mobility. Aluminium export potentially can preserve permeability within sandstones by reducing the volume of authigenic clay minerals precipitated.

Original languageEnglish
Pages (from-to)147-160
Number of pages14
JournalInternational Association of Sedimentologists Special Publications
Issue number34
Publication statusPublished - 2002


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