Illite dates record deep fluid movements in petroleum basins

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doi: 10.1144/petgeo.3.2.133
Authors:Darby, D.; Wilkinson, M.; Fallick, A. E.; Haszeldine, R. S.
Author Affiliations:Primary:
University of Glasgow, Department of Geology and Applied Geology, Glasgow, United Kingdom
Scottish Universities Research and Reactor Centre, United Kingdom
Woods Hole Oceanographic Institute, United States
Volume Title:Petroleum Geoscience
Source:Petroleum Geoscience, 3(2), p.133-140. Publisher: Geological Society Publishing House, London, United Kingdom. ISSN: 1354-0793
Publication Date:1997
Note:In English. 28 refs.; illus., incl. geol. sketch map, 3 tables, sect.
Summary:K-Ar age dates of authigenic illite from sandstones in the UK south Central Graben have a bimodal distribution. In contrast to established hypotheses of thermal triggers, this illite growth is explained by changes in hydrogeological history. Fluid motion during burial can hence be dated. Illite growth at 84-58 Ma on the graben margins was coincident with rapid subsidence of the Graben axis and consequent expulsion of pore fluids onto the margins. This event pre-dated both overpressure, and the secondary migration and accumulation of hydrocarbon in the region. Illite growth was probably caused by increased solute transport rates during pore fluid motion. Illite growth on an axial high (33-30 Ma) occurred during overpressured conditions. This was triggered either by: (1) downward fluid migration as a consequence of overpressure release. These fluids carried carboxylic acids or hydrocarbons from the highly overpressured Kimmeridge Clay Formation into the less pressured Fulmar Sandstone Formation; or (2) a decrease in water-rock ratios as fluid flow declined within the sandstones, as a consequence of overpressure build-up. Published experiments show that illite growth is favoured by low water-rock ratios.
Subjects:Basins; Fluid dynamics; Illite; Jurassic; K/Ar; Kimmeridge Clay; Mesozoic; Overpressure; Permeability; Petroleum; Petroleum exploration; Porosity; Pressure; Secondary migration; Sedimentary basins; Sheet silicates; Silicates; Subsidence; Upper Jurassic; Atlantic Ocean; Central Graben; North Atlantic; North Sea; Fulmar Sandstone Formation
Coordinates:N560000 N620000 E0080000 W0080000
Abstract Numbers:98M/11
Record ID:1998012339
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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