Hostname: page-component-78c5997874-t5tsf Total loading time: 0 Render date: 2024-11-10T10:12:23.742Z Has data issue: false hasContentIssue false
  • English
  • Français

Geometry and formation of gypsum veins in mudstones at Watchet, Somerset, SW England

Published online by Cambridge University Press:  29 August 2008

SONJA L. PHILIPP
SONJA L. PHILIPP*
Affiliation:
Geoscience Centre, University of Göttingen, Goldschmidtstr. 3, 37077 Göttingen, Germany
*
*E-mail: Sonja.Philipp@geo.uni-goettingen.de
Get access Rights & Permissions [Opens in a new window]

Abstract

Gypsum veins and faults were studied in red mudstones of the Upper Triassic Mercia Mudstone Group, in the Bristol Channel Basin, exposed in E–W-trending cliffs at Watchet on the Somerset Coast (SW England). In nodular gypsum horizons, individual gypsum nodules are connected by subhorizontal gypsum veins. In evaporite-free mudstone layers, however, dense anastomosing networks of gypsum veins occur. In a 300 m long profile dissected by 28 (mostly) normal faults with small displacements, 24 faults have veins following them, indicating palaeofluid transport along the fault planes. Ninety-seven cross-cutting relationships and mostly perpendicular vein fibres indicate that the veins are primarily extension fractures. The thickest veins in the vein network are subhorizontal (160 measurements), indicating a vertical orientation of the minimum principal compressive stress (horizontal basin compression). Such a stress state may have existed during basin inversion associated with Alpine compression (late Cretaceous to early Tertiary). I propose that the gypsum veins are the result of hydrofracturing. In the gypsum nodules, then presumably consisting of anhydrite, overpressure was generated related to the hydration of anhydrite to gypsum. Stress concentration around the nodules led to rupturing and injection of thin subhorizontal hydrofractures. Some of the calcium-sulphate saturated fluids were then transported upwards along the faults and gained access to evaporite-free mudstone layers where dense anastomosing vein networks developed. Most veins were arrested during their propagation by layers with contrasting mechanical properties (stress barriers). Some veins, however, propagated through the barriers along faults to shallower levels. The dense networks of mineral veins observed in Watchet indicate that hydrofractures can generate a very high temporary permeability in fluid reservoirs.

Keywords

hydrofracturesgypsum veinsfluid overpressurepermeability
Type
Original Article
Information
Geological Magazine , Volume 145 , Issue 6 , November 2008 , pp. 831 - 844
Copyright
Copyright © Cambridge University Press 2008

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Aguilera, R. 1995. Naturally Fractured Reservoirs. Tulsa, Oklahoma: PennWell Publishing Company, 521 pp.Google Scholar
Amadei, B. & Stephansson, O. 1997. Rock Stress and its Measurement. London: Chapman & Hall, 490 pp.CrossRefGoogle Scholar
Azam, S. 2007. Study on the geological and engineering aspects of anhydrite/gypsum transition in the Arabian Gulf coastal deposits. Bulletin of Engineering Geology and the Environment 66, 177–85.CrossRefGoogle Scholar
Barton, C. A., Zoback, M. D. & Moos, D. 1995. Fluid flow along potentially active faults in crystalline rock. Geology 23, 683–6.2.3.CO;2>CrossRefGoogle Scholar
Bell, F. G. 2000. Engineering Properties of Soils and Rocks. Oxford: Blackwell.Google Scholar
Bennison, G. M. & Wright, A. E. 1969. The Geological History of the British Isles. London: Edward Arnold Ltd, 406 pp.Google Scholar
Billo, S. M. 1987. Petrology and kinetics of gypsum–anhydrite transition. Journal of Petroleum Geology 10, 73–85.CrossRefGoogle Scholar
Bjørlykke, K. 1997. Lithological control on fluid flow in sedimentary basins. In Fluid Flow and Transport in Rocks (eds Jamtveit, B. & Yardley, B. W. D.), pp. 15–34. London: Chapman and Hall.CrossRefGoogle Scholar
Blounot, C. W. & Dickson, F. W. 1969. The solubility of anhydrite (CaSO4) in NaCl–H2O from 100 to 450°C and 1 to 1000 bars. Geochimica et Cosmochimica Acta 33, 227–45.CrossRefGoogle Scholar
Boehner, R. C., Adams, G. C. & Giles, P. S. 2003. Karst Geology in the Salt-bearing Windsor Group Evaporites and Controls on the Origin of Gypsum Deposits in South-central Cape Breton Island, Nova Scotia. In Mineral Resources Branch, Report of Activities 2002 (ed. Nova Scotia Department of Natural Resources), pp. 9–24. Report 2003–1.Google Scholar
Bons, P. D. 2000. The formation of veins and their microstructures. In Stress, Strain and Structure – a Volume in Honour of W. D. Means (eds M. W. Jessell & J. L. Urai), p. 12. Virtual Explorer 2.Google Scholar
Brenner, S. L. & Gudmundsson, A. 2004 a. Permeability in layered reservoirs: field examples and models on the effects of hydrofracture propagation. In Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geosystems (eds Stephansson, O., Hudson, J. A. & Jing, L.), pp. 643–8. Geo-Engineering Series Vol. 2. Elsevier.Google Scholar
Brenner, S. L. & Gudmundsson, A. 2004 b. Arrest and aperture variation of hydrofractures in layered reservoirs. In The Initiation, Propagation and Arrest of Joints and Other Fractures (eds Cosgrove, J. W. & Engelder, T.), pp. 117–28. Geological Society of London, Special Publication no. 231.Google Scholar
Brenner, S. L. & Gudmundsson, A. 2004 c. Faults, veins and fluid transport in mudstones at Watchet, Somerset, SW England. Geophysical Research Abstracts 6, EGU04-A-01432.Google Scholar
Brenner, S. L. & Gudmundsson, A. 2005. Fluid transport in faults and associated hydrofracture injection into host rocks. Geophysical Research Abstracts 7, EGU05-A-05637.Google Scholar
Byerlee, J. 1993. Model for episodic flow of high-pressure water in fault zones before earthquakes. Geology 21, 303–6.2.3.CO;2>CrossRefGoogle Scholar
Cartwright, J. A. 1997. Polygonal extensional fault systems: a new class of structure formed during the early compaction of shales. In Fluid Flow and Transport in Rocks (eds Jamtveit, B. & Yardley, B. W. D.), pp. 35–56. London: Chapman & Hall.CrossRefGoogle Scholar
Cosgrove, J. W. 2001. Hydraulic fracturing during the formation and deformation of a basin: A factor in the dewatering of low-permeability sediments. American Association of Petroleum Geologists Bulletin 85, 737–48.Google Scholar
Coward, M. P. 1995. Structural and tectonic setting of the Permo-Triassic basins of northwest Europe. In Permian and Triassic rifting in northwest Europe (ed. Boldy, S. A. R.), pp. 7–39. Geological Society of London, Special Publication no. 91.Google Scholar
Dart, C. J., McClay, K. & Hollings, P. N. 1995. 3D analysis of inverted extensional fault systems, southern Bristol Channel basin, UK. In Basin Inversion (eds Buchanan, J. G. & Buchanan, P. G.), pp. 393–413. Geological Society of London, Special Publication no. 88.Google Scholar
Davison, I. 1995. Fault slip evolution determined from crack-seal veins in pull-aparts and their implications for general slip models. Journal of Structural Geology 17, 1025–34.CrossRefGoogle Scholar
Domenico, P. A. & Schwartz, F. W. 1998. Physical and Chemical Hydrogeology, 2nd ed. New York: Wiley, 506 pp.Google Scholar
Durney, D. W. & Ramsay, J. G. 1973. Incremental strains measured by syntectonic crystal growth. In Gravity and Tectonics (eds de Jong, K. A. & Scholten, R.), pp. 67–96. New York: Wiley.Google Scholar
El Tabakh, M., Schreiber, B. C. & Warren, J. K. 1998. Origin of fibrous gypsum in the Newark Rift Basin, eastern North America. Journal of Sedimentary Research 68, 88–99.CrossRefGoogle Scholar
Faybishenko, B., Witherspoon, P. A. & Benson, S. M. (eds) 2000. Dynamics of Fluids in Fractured Rocks. AGU Geophysical Monograph Series, Washington, D.C., 400 pp.CrossRefGoogle Scholar
Fisher, D. M. & Brantley, S. L. 1992. Models of quartz overgrowth and vein formation – deformation and episodic fluid-flow in an ancient subduction zone. Journal of Geophysical Research 97, 20043–61.CrossRefGoogle Scholar
Fisher, D. M., Brantley, S. L., Everett, M. & Dzvonik, J. 1995. Cyclic fluid flow through a regionally extensive fracture network within the Kodiak accretionary prism. Journal of Geophysical Research 100, 12881–94.CrossRefGoogle Scholar
Forbes, B. G. 1958. Folded Permian gypsum of Ripon Parks, Yorkshire. Yorkshire Geological Society Proceedings 31, 351–8.CrossRefGoogle Scholar
Gillespie, P. A., Walsh, J. J., Watterson, J., Bonson, C. G. & Manzocchi, T. 2001. Scaling relationships of joint and vein arrays from The Burren, Co. Clare, Ireland. Journal of Structural Geology 23, 183–201.CrossRefGoogle Scholar
Goldstein, A. G. & Collins, E. W. 1984. Deformation of Permian strata overlying a zone of salt dissolution and collapse in the Texas Panhandle. Geology 12, 314–17.2.0.CO;2>CrossRefGoogle Scholar
Gudmundsson, A. 1990. Emplacement of dikes, sills and crustal magma chambers at divergent plate boundaries. Tectonophysics 176, 257–75.CrossRefGoogle Scholar
Gudmundsson, A. 1999. Fluid overpressure and stress drop in fault zones. Geophysical Research Letters 26, 115–18.CrossRefGoogle Scholar
Gudmundsson, A. 2000. Active fault zones and groundwater flow. Geophysical Research Letters 27, 2993–6.CrossRefGoogle Scholar
Gudmundsson, A. & Brenner, S. L. 2001. How hydrofractures become arrested. Terra Nova 13, 456–62.CrossRefGoogle Scholar
Gudmundsson, A., Fjeldskaar, I. & Brenner, S. L. 2002. Propagation pathways and fluid transport of hydrofractures in jointed and layered rocks in geothermal fields. Journal of Volcanology and Geothermal Research 116, 257–78.CrossRefGoogle Scholar
Gustavson, T. C. 1980. Collapse chimneys, collapse surfaces, and breccia zones. In A Report of the Progress of Nuclear Waste Isolation Feasibility Studies (eds Gustavson, T. C. et al. ), pp. 88–91. Geology and Geohydrology of the Palo Duro Basin, Texas Panhandle, The University of Texas at Austin, Bureau of Economic Geology Geological Circular, vol. 80.Google Scholar
Gustavson, T. C., Hovorka, S. D. & Dutton, A. R. 1994. Origin of satin spar veins in evaporite basins. Journal of Sedimentary Research A 64, 88–94.Google Scholar
Halferdal, L. B. 1960. Gypsum deposit at Peace Point, northern Alberta. Alberta Research Council Internal Report 12.Google Scholar
Haneberg, W. C., Mozley, P. S., Moore, J. C. & Goodwin, L. B. (eds) 1999. Faults and Subsurface Fluid Flow in the Shallow Crust. Washington D.C.: American Geophysical Union, 222 pp.CrossRefGoogle Scholar
Herman, G. C. 2005. Joints and veins in the Newark basin, New Jersey, in regional tectonic perspective. In Newark Basin – View from the 21st Century (ed. Gates, A. E..), pp. 75–116. 22nd Annual Meeting of the Geological Association of New Jersey, College of New Jersey, Ewing, New Jersey.Google Scholar
Johnston, J. D. & McCaffrey, K. J. W. 1996. Fractal geometries of vein systems and the variation of scaling relationships with mechanism. Journal of Structural Geology 18, 349–58.CrossRefGoogle Scholar
Jowett, E. C., Cathles, L. M. & Davis, B. W. 1993. Predicting depths of gypsum dehydration in evaporitic sedimentary basins. American Association of Petroleum Geologists Bulletin 77, 402–13.Google Scholar
Kamerling, P. 1979. The geology and hydrocarbon habitat of the Bristol Channel Basin. Journal of Petroleum Geology 2, 75–93.CrossRefGoogle Scholar
Kasprzyk, A. 1995. Gypsum-to-anhydrite transition in the Miocene of southern Poland. Journal of Sedimentary Research A 65, 348–57.Google Scholar
Keulen, N. T., Den Brok, S. W. J. & Spiers, C. J. 2001. Force of crystallisation of gypsum during hydration of synthetic anhydrite rock. In 13th DRT conference: Deformation Mechanisms, Rheology, and Tectonics. Noordwijkerhout, The Netherlands.Google Scholar
Leslie, A. B., Spiro, B. & Tucker, M. E. 1993. Geochemical and mineralogical variations in the upper Mercia Mudstone Group (Late Triassic), southwest Britain: correlation of outcrop sequences with borehole geophysical logs. Journal of the Geological Society, London 150, 67–75.CrossRefGoogle Scholar
Macdonald, G. J. F. 1953. Anhydrite-gypsum equilibrium relations. American Journal of Science 251, 884–98.CrossRefGoogle Scholar
Maugis, D. 2000. Contact, Adhesion and Rupture of Elastic Solids. Springer Series in Solid-State Sciences, vol. 130. Berlin: Springer, 464 pp.CrossRefGoogle Scholar
McClay, K. & Ellis, P. G. 1987. Analogue models of extensional fault geometries. In Continental Extensional Tectonics (eds Coward, M. P., Dewey, J. F. & Hancock, P. L..), pp. 100–25. Geological Society of London, Special Publication no. 28.Google Scholar
McCaffrey, K. J. W., Lonergan, L. & Wilkinson, J. J. 1999. Fractures, Fluid Flow and Mineralization. Geological Society of London, Special Publication no. 155, 328 pp.Google Scholar
Means, W. D. & Li, T. 2001. A laboratory simulation of fibrous veins: some first observations. Journal of Structural Geology 23, 857–63.CrossRefGoogle Scholar
Murray, R. C. 1964. Origin and diagenesis of gypsum and anhydrite. Journal of Sedimentary Petrology 34, 512–23.Google Scholar
Nelson, R. A. 1985. Geologic Analysis of Naturally Fractured Reservoirs. Houston, Texas: Gulf Publishing, 320 pp.Google Scholar
Nemcok, M., Gayer, R. & Miliorozos, M. 1995. Structural analysis of the inverted Bristol Channel Basin: implications for the geometry and timing of fracture porosity. In Basin Inversion (eds Buchanan, J. G. & Buchanan, P. G..), pp. 355–92. Geological Society of London, Special Publication no. 88.Google Scholar
Neuzil, C. E. 1995. Abnormal pressures as hydrodynamic phenomena. American Journal of Science 295, 742–86.CrossRefGoogle Scholar
Osborne, M. J. & Swarbrick, R. E. 1997. Mechanisms for generating overpressure in sedimentary basins: A reevaluation. American Association of Petroleum Geologists Bulletin 81, 1023–41.Google Scholar
Peacock, D. C. P. & Sanderson, D. J. 1999. Deformation history and basin-controlling faults in the Mesozoic sedimentary rocks of the Somerset coast. Proceedings of the Geologists Association 110, 41–52.CrossRefGoogle Scholar
Philipp, S. L. & Gudmundsson, A. 2006. Gypsum veins as hydrofractures in layered and faulted mudstones: implications for reservoir permeability. In 11. Symposium Tektonik, Struktur- und Kristallingeologie (eds Philipp, S. L., Leiss, B., Vollbrecht, A., Tanner, D. & Gudmundsson, A..), pp. 164–7. Göttingen: Göttinger Universitätsverlag.CrossRefGoogle Scholar
Pollard, D. D. & Segall, P. 1987. Theoretical displacement and stresses near fractures in rocks: with application to faults, points, veins, dikes, and solution surfaces. In Fracture Mechanics of Rocks (ed. Atkinson, B..), pp. 277–349. London: Academic Press.CrossRefGoogle Scholar
Ramsay, J. G. 1980. The crack-seal mechanism of rock deformation. Nature 284, 135–9.CrossRefGoogle Scholar
Ray, R., Sheth, H. C. & Mallik, J. 2007. Structure and emplacement of the Nandurbar–Dhule mafic dyke swarm, Deccan Traps, and the tectonomagmatic evolution of flood basalts. Bulletin of Volcanology 69, 537–51.CrossRefGoogle Scholar
Richardson, W. A. 1920. The fibrous gypsum of Nottinghamshire. Journal of the Mineralogical Society 19, 77–95.CrossRefGoogle Scholar
Rubin, A. M. 1995. Propagation of Magma-Filled Cracks. Annual Review of Earth and Planetary Sciences 23, 287–336.CrossRefGoogle Scholar
Savin, G. N. 1961. Stress Concentrations around Holes. London: Pergamon, 430 pp.Google Scholar
Shearman, D. J., Mossop, G., Dunsmore, H. & Martin, M. 1972. Origin of gypsum veins by hydraulic fracture. Transactions of the Institution of Mining and Metallurgy B 81, 149–55.Google Scholar
Sibson, R. H. 1994. Crustal stress, faulting and fluid flow. In Geofluids: Origin, Migration, and Evolution of Fluids in Sedimentary basins (ed. Parnell, J..), pp. 69–84. Geological Society of London, Special Publication no. 78.Google Scholar
Simms, M. J. & Ruffell, A. H. 1990. Climatic and biotic change in the late Triassic. Journal of the Geological Society, London 147, 321–7.CrossRefGoogle Scholar
Singhal, B. B. S. & Gupta, R. P. 1999. Applied Hydrogeology of Fractured Rocks. London: Kluwer.CrossRefGoogle Scholar
Spence, D. A., Sharp, P. W. & Turcotte, D. L. 1987. Buoyancy-Driven Crack-Propagation – a Mechanism for Magma Migration. Journal of Fluid Mechanics 174, 135–53.CrossRefGoogle Scholar
Stauffer, D. & Aharony, A. 1994. Introduction to Percolation Theory. London: Taylor & Francis.Google Scholar
Stewart, A. J. 1979. A barred-basin marine evaporite in the upper Proterozoic of the Amadeus Basin, central Australia. Sedimentology 26, 33–62.CrossRefGoogle Scholar
Stowell, J. F. W., Watson, A. P. & Hudson, N. F. C. 1999. Geometry and population systematics of a quartz vein set, Holy Island Anglesey, North Wales. In Fractures, Fluid Flow and Mineralization (eds McCaffrey, K. J. W., Lonergan, L. & Wilkinson, J. J..), pp. 7–16. Geological Society of London, Special Publication no. 155.Google Scholar
Taber, S. 1916. The growth of crystals under external pressure. American Journal of Science 26, 532–56.CrossRefGoogle Scholar
Taber, S. 1918. The origin of veinlets in the Silurian and Devonian strata of central New York. Journal of Geology 26, 56–73.CrossRefGoogle Scholar
Timoshenko, G. P. & Goodier, J. N. 1970. Theory of Elasticity. London: McGraw Hill, 608 pp.Google Scholar
van der Pluijm, B. A. & Marshak, S. 2004. Earth Structure, 2nd ed. New York: McGraw Hill, 656 pp.Google Scholar
van Hoorn, B. 1987. The South Celtic Sea/Bristol Channel Basin: origin, deformation and inversion history. Tectonophysics 137, 309–34.CrossRefGoogle Scholar
Vermilye, J. M. & Scholz, C. H. 1995. Relation between vein length and aperture. Journal of Structural Geology 17, 423–34.CrossRefGoogle Scholar
Whittaker, A. & Green, G. W. 1983. Geology of the country around Weston-super-Mare, memoir for 1:50,000 geological sheet 279. New series, with parts of sheet 263 and 295. Geological Survey of Great Britain, Institute of Geological Sciences. London: Her Majesty's Stationery Office, 147 pp.Google Scholar
Wiltschko, D. V. & Morse, J. W. 2001. Crystallization pressure versus ‘crack seal’ as the mechanism for banded veins. Geology 29, 79–82.2.0.CO;2>CrossRefGoogle Scholar
Ziegler, P. A. 1990. Geological Atlas of Western and Central Europe, 2nd ed. Den Haag: Elsevier & Shell Internationale Petroleum Maatschappij, B. V., 239 pp.Google Scholar
Supplementary material: File

Philipp Supplementary Material

Colour Figures.doc

Download Philipp Supplementary Material(File)
File 5.7 MB