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The implications of reworking on the mineralogy and chemistry of Lower Carboniferous K-bentonites

Published online by Cambridge University Press:  09 July 2018

T. Clayton ,
J. E. Francis ,
S. J. Hillier ,
F. Hodson ,
R. A. Saunders  and
J. Stone
T. Clayton
Affiliation:
Department of Geology, University of Southampton, Southampton SO171B J, UK
J. E. Francis*
Affiliation:
Department of Geology, University of Southampton, Southampton SO171B J, UK
S. J. Hillier*
Affiliation:
Department of Geology, University of Southampton, Southampton SO171B J, UK
F. Hodson
Affiliation:
Department of Geology, University of Southampton, Southampton SO171B J, UK
R. A. Saunders
Affiliation:
Department of Geology, University of Southampton, Southampton SO171B J, UK
J. Stone*
Affiliation:
Department of Geology, University of Southampton, Southampton SO171B J, UK
*
*Current address: Department of Earth Sciences, The University of Leeds, Leeds LS2 9JT, UK
†Current address: Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB15 8QH, UK
‡Current address: Department of Earth Sciences, Trinity College, Dublin 2, Republic of Ireland
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Abstract

Potassium-bentonites have been found in the Courceyan Lower Limestone Shales near Burrington Combe and Oakhill, Somerset, consisting of thin, greenish yellow, plastic clays interbedded within a mudrock and limestone sequence. Mineralogically, the clay fraction is composed of virtually monomineralic interstratified illite-smectite containing 7–10% smectite layers. The clay fraction of the surrounding mudrocks, however, consists of an illite-chlorite dominated assemblage. Their mineral composition, trace element content, and the relative abundance of zircon crystals suggest an origin from burial of montmorillonite originally formed from volcanic ash. The presence of anomalously high trace element contents with both euhedral and rounded zircon grains in the Oakhill K-bentonites suggests a secondary or reworked origin for these samples. In contrast, the presence of a non-anomalous trace element content and large (>100 μm) euhedral zircon grains suggests that the Burrington K-bentonite is primary in origin. Modelling of whole-rock rare-earth element (REE) patterns shows that the Oakhill REE pattern can be derived from the Burrington pattern by the addition of small contributions from zircon and monazite, two major heavy minerals present. These K-bentonites probably represent the oldest Carboniferous K-bentonites so far recorded in the British Isles.

Type
Research Article
Information
Clay Minerals , Volume 31 , Issue 3 , September 1996 , pp. 377 - 390
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1996

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References

Austin, R.L. & Davies, R.B. (1984) Problems of recognition and implications of Dinantian conodont biofacies in the British Isles. Pp. 195–228 in: Conodont Biofacies and Provincialism (Clark, D.L., editor). Geol. Soc. Am. Spec. Pap., 196.Google Scholar
Burchette, T.P. (1987) Carbonate-barrier shorelines during the basal Carboniferous transgression: the Lower Limestone Shale Group, South Wales and western England. Pp. 239-263 in: European Dinantian Environments (Miller, J., Adams, A.E. & Wright, V.P., editors). John Wiley, Chichester.Google Scholar
Charoy, B. (1986) The genesis of the Cornubian Batholith (South-West England): the example of the Carnmeneilis Pluton. J. Pet. 27, 571–604.CrossRefGoogle Scholar
Claoue-Long, J.C., Jones, P.J., Roberts, J. & Maxwell, S. (1992) The numerical age of the Devonian- Carboniferous boundary. Geol. Mag. 129, 281–291.Google Scholar
Epstein, A.G., Epstein, J.B. & Harris, A. (1977) Conodont color alteration–an index to organic metamorphism. U.S. Geol. Surv. Prof. Pap. 955, 1–27.Google Scholar
Fleischer, M. & Altschuler, Z.S. (1986) The lanthaaides and yttrium in minerals of the apatite group–an analysis of the available data. Neues Jahrb. Min. Mom 10, 467–480.Google Scholar
Flora, P.A. (1982) The Hercynian trough: Devonian and Carboniferous volcanism in south-western Britain. Pp. 227-242 in: Igneous Rocks of the British Isles (Sutherland, D.S., editor). John Wiley, Chichester.Google Scholar
Francis, E.H. (1970) Review of Carboniferous volcanism in England & Wales, J. Earth Sci. Leeds Geol. Ass. 8, 41–55.Google Scholar
Fujimaki, n. (1986) Partition coefficients of Hf, Zr and REE between zircon, apatite and liquid. Contrib, Mineral. Pet. 94, 42–45.Google Scholar
George, T.N. (1972) The classification of Avonian limestones. J. Geol. Soc. Lond. 128, 221–256.Google Scholar
George, T.N., Johnson, G.A.L., Mitchell, M., Prentice, J.E., Ramsbotrom, W.H.C., Sevastopulo, G.D. & Wilson, R.B. (1976) A correlation of Dinantian rocks in the British Isles. Special Report Geol. Soc. Lond. 7, 87 pp.Google Scholar
Green, G.W. & Welch, F.B.A. (1965) Geology of the country around Wells and Cheddar. Mem. Geol. Surv. G. B., HMSO, London.Google Scholar
Grim, R.E. & Guven, N. (1978) Bentonites–Geology, Mineralogy, Properties and Uses. Developments in Sedimentology, 24. Elsevier, Amsterdam.Google Scholar
Huff, W.D, & Kolata, D.R. (1989) Correlation of Kbentonite beds by chemical fingerprinting using multivariate analysis. Pp. 567–577 in: Quantitative Dynamic Stratigraphy (Cross, T.A., editor). Prentice- Hall, Englewood Cliffs, New Jersey.Google Scholar
Huff, W.D., Merriman, R.J., Morgan, D.J. & Roberts, B. (1993) Distribution and tectonic setting of Ordovician K-bentonites in the United Kingdom. Geol. Mag. 130, 93–100.CrossRefGoogle Scholar
Jeans, C.V., Merriman, R.J & Mitchell, J.G. (1977) Origin of Middle Jurassic and Lower Cretaceous fuller's earths in England. Clay Miner. 12, 11–44.Google Scholar
Leeder, M.R. (1987) Tectonic and palaeogeographic models for Lower Carboniferous Europe. Pp. 1–20 in: European Dinantian Environments (Miller, J., Adams, A.E. & Wright, V.P., editors). John Wiley, Chichester.Google Scholar
Mclennan, S.M. 0989) Rare-earth elements in sedimentary rocks: influence of provenance and sedimentary processes. Pp. 169–200 in: Geochemistry and Mineralogy of Rare-Earth Elements (Lipin, B.R. & McKay, G.A., editors). Reviews in Mineralogy, No. 21, Mineralogical Society of America, Washington DC.Google Scholar
Milodowski, A.E. & Zalasiewicz, J.A. (1991) Redistribution of rare-earth elements during diagenesis of turbidite/hemipelagite mudrock sequences of Llandovery age from Central Wales. Pp. 101-125 in: Developments in Sedimentary Provenance Studies (Morton, A.C., Todd, S.P. & Haughton, P.D.W., editors). Geol. Soc. London. Spec. Publ. No. 57.Google Scholar
Morton, A.C. (1991) Geochemical studies of detrital heavy minerals and their application to provenance research. Pp. 31–45 in: Developments in Sedimentary Provenance Studies (Morton, A.C., Todd, S.P. & Haughton, P.D.W., editors). Geol. Soc. London. Spec. Publ. No. 57.Google Scholar
Morton, A.C. & Knox, R.W. O'B. (1990) Geochemistry of late Palaeocene and early Eocene tephras from the North Sea Basin. J. Geol. Soc. Lond. 147, 425–437.Google Scholar
Perry, E.A. JR. & Hower, J. (1970) Burial diagenesis of Gulf Coast pelitic sediments. Clays Clay Miner 18, 165–177.Google Scholar
Poldervaart, A. (1956) Zircon in rocks. 2. Igneous rocks. Am. J. Sci. 254, 521–544.CrossRefGoogle Scholar
Reynolds, R.C. (1985) NEWMOD, a Computer Program for the Calculation of One-dimensional Diffraction of Mixed-layered Clays. R.C. Reynolds Jr., 8 Brook Dr., Hanover, New Hampshire.Google Scholar
Rhodes, F.H.T., Austin, R.L. & Druce, E.C. (1969) British Avonian (Carboniferous) conodont faunas, and their value in local and intercontinental correlation. Bull. Br. Mus. Nat. Hist. (Geol.), suppl. 5, 313 pp.Google Scholar
Thorez, J. & Pirlet, H. (1978) Petrology of K-bentonite beds in the carbonate series of the Visean and Tournaisian Stages of Belgium. Proc. 6th Int. Clay Conf. Oxford, 323-332.Google Scholar
Upton, B.G.J. (1982) Carboniferous to Permian volcanism in the stable foreland. Pp. 255-275 in: Igneous Rocks of the British Isles (Sutherland, D.S., editor). John Wiley, Chichester.Google Scholar
Walkden, G.M. (1972) The mineralogy and origin of interbedded clay wayboards in the Carboniferous Limestone of the Derbyshire Dome. Geol. J. 8, 143–159.Google Scholar
Walker, G.P.L. (1981) Plinian eruptions and their products. Bull. Volcanol. 44, 223–40.Google Scholar
Watson, E.B. (1979) Zircon saturation in felsic liquids: experimental results and applications to trace element geochemistry. Contrib. Mineral. Pet. 70, 407–419.Google Scholar
Winchester, J.A. & Floyd, P.A. (1977) Geochemical discrimination of different magma series and their differentiation products using immobile elements. Chem. Geol. 20, 325–343.Google Scholar
Winter, J. (1992) Identification of a bentonitic ash layer by crystal morphology of its zircon population (Bed 79, Hasselbachtal, Rheinisches Schiefergebirge). Ann. Soc. Geol. Belg. 115, 683–687.Google Scholar
Wray, D.S. (1995) Origin of clay-rich beds in Turonian Chalks from Lower Saxony, Germany–a rare-earth element study. Chem. Geol. 119, 161–173.Google Scholar
Yurimoto, H., Duke, E.F., Papike, J.J. & Shearer, C.K. (1990) Are discontinuous chondrite-normalised REE patterns in pegmatite granite systems the results of monazite fractionation?. Geochim. Cosmochim. Acta, 54, 2141–2145.Google Scholar