Hostname: page-component-586b7cd67f-rdxmf Total loading time: 0 Render date: 2024-11-25T16:39:29.088Z Has data issue: false hasContentIssue false
  • English
  • Français

Constraints on the age and genesis of the Llanrwst and Llanfair–Talhaiarn orefields, North Wales from K–Ar and Rb–Sr studies

Published online by Cambridge University Press:  01 May 2009

R. Haggerty ,
S. H. Bottrell ,
R. A. Cliff  and
D. C. Rex
R. Haggerty
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
S. H. Bottrell
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
R. A. Cliff
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
D. C. Rex
Affiliation:
Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK
Get access Rights & Permissions [Opens in a new window]

Abstract

The Llanrwst Pb–Zn and Llanfair–Talhaiarn Cu–Pb–Zn orefields contain vein mineralization similar to Lower Palaeozoic-hosted base metal deposits elsewhere in the British Isles, which are believed to have formed in the late Palaeozoic. K–Ar and Rb–Sr data on intensely sericitized wallrock material indicate that the main phase of mineralization at both orefields occurred between the mid-Devonian and theTournasian (386–350 Ma). The latest veins at Llanrwst formed in Visean–Westphalian times. Gangue mineral Sr isotope compositions indicate a mixture of radiogenic wallrock-derived Sr with less radiogenic Sr, with a poorly-defined trend to more radiogenic compositions with time.

The age of the main mineralization precludes dewatering of Carboniferous basins as a source of ore fluid. More generally Sr isotopes rule out unmodified basinal brines or metamorphic fluids as mineralizing agents, since their Sr content would be too radiogenic. Local sources of unradiogenic Sr are available at Llanrwst in metadolerites and calcareous sandstones and at Llanfair–Talhaiarn in thin Ludlow Limestone beds.

Type
Articles
Information
Geological Magazine , Volume 132 , Issue 4 , July 1995 , pp. 387 - 398
Copyright
Copyright © Cambridge University Press 1995

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

Bevins, R. E. & Robinson, D., 1988. Low grade metamorphism of the Welsh Basin Lower Palaeozoic succession: an example of diastathermal metamorphism?. Journal of the Geological Society, London 145, 363–66.CrossRefGoogle Scholar
Bottrell, S. H., Greenwood, P. B., Yardley, B. W. D., Shepherd, T. J. & Spiro, B., 1990. Metamorphic and postmetamorphic fluid flow in the low-grade rocks of the Harlech Dome, north Wales. Journal of Metamorphic Geology 8, 131–43.CrossRefGoogle Scholar
Burke, W. H., Dension, R. E., Heatherington, E. A., Keopnick, R. B., Nelson, H. F. & Otto, S. B., 1982. Variations of sea-water 87Sr/86Sr throughout Phanerozoic time. Geology 10, 516–19.2.0.CO;2>CrossRefGoogle Scholar
Evans, J. A., 1989. A note on Rb—Sr whole-rock ages from cleaved mudrocks in the Welsh Basin. Journal of the Geological Society, London 146, 901–4.CrossRefGoogle Scholar
Evans, J. A., 1991. Resetting of Rb—Sr whole-rock ages during Arcadian low-grade metamorphism in north Wales. Journal of the Geological Society, London 148, 703–10.CrossRefGoogle Scholar
Fitches, B., 1987. Aspects of veining in the Welsh Lower Palaeozoic Basin. In Deformation of Sediments and Sedimentary Rocks (eds Jones, M. E. and Preston, R. M. F.), pp. 325–42. Geological Society Special Publication no. 29.Google Scholar
Gawthorpe, R. L., Gutteridge, P. & Leeder, M. R., 1989. Late Devonian and Dinantian basin evolution in northern England and North Wales. In The Role of Tectonics in Devonian and Carboniferous Sedimentation in the British Isles (eds Arthurton, R. S., Gutteridge, P., and Nolan, S. C.), pp. 1–23. Yorkshire Geological Occasional Publication No. 6. London: Wigley and Sons.Google Scholar
Ineson, P. R. & Mitchell, J. G., 1974 a. K—Ar isotopic age determinations from some Lake District mineral localities. Geological Magazine 111, 521–37.CrossRefGoogle Scholar
Ineson, P. R. & Mitchell, J. G., 1974 b. K–Ar isotopic age determinations from some Scottish mineral localities. Transactions of the Institution of Mining and Metallurgy 83, B13–B18.Google Scholar
Ineson, P. R. & Mitchell, J. G., 1975 a. K—Ar isotopic age determinations from some Welsh mineral localities. Transactions of the Institution of Mining and Metallurgy 84, B7–B16.Google Scholar
Ineson, P. R. & Mitchell, J. G., 1975 b. Discussions and contributions of Ineson and Mitchell, 1974 and 1975. Transactions of the Institution of Mining and Metallurgy 84, B120–B121.Google Scholar
Kesler, S. E., Jones, L. M. & Ruiz, J., 1988. Strontium isotopic geochemistry of Mississippi valley-type deposits, east Tennessee: implications for age and source of mineralizing brines. Geological Society of America Bulletin 100, 1300–7.2.3.CO;2>CrossRefGoogle Scholar
Kokelaar, B. P., 1988. Tectonic controls of Ordovician arc and marginal basin volcanism in Wales. Journal of the Geological Society, London 145, 759–76.CrossRefGoogle Scholar
LeMesurier, W. E. & Rex, D. C., 1991. The Marie Byrd Land volcanic province and its relation to the Cainozoic West Antarctica rift system. In The Geology of Antarctica (ed. Tingey, R. J.), pp. 249–84. Oxford: Oxford Science Publications.Google Scholar
Morton, J. P., 1985. Rb—Sr dating of diagenesis and source clays in the Upper Devonian black shales of Texas. Geological Society of America Bulletin 96, 1043–9.2.0.CO;2>CrossRefGoogle Scholar
Parnell, J. & Swainbank, I., 1990. Pb—Pb dating of hydrocarbon migration into a bitumen-bearing ore deposit, North Wales. Geology 18, 1028–30.2.3.CO;2>CrossRefGoogle Scholar
Pattrick, R. A. D. & Russell, M. J., 1989. Sulphur isotopic investigation of lower Carboniferous vein deposits of the British Isles. Mineralium Deposita 24, 148–53.CrossRefGoogle Scholar
Phillips, W. J., 1972. Hydraulic fracturing and mineralization. Journal of the Geological Society of London 128, 337–55.CrossRefGoogle Scholar
Phillips, W. J., 1983. Discussion and contributions: Genetic problems related to base-metal deposits in sediments. Transactions of the Institution of Mining and Metallurgy 92, B102.Google Scholar
Ravenhurst, C. E., Reynolds, P. H., Zentilli, M., Krueger, H. W. & Blenkinsop, J., 1990. Formation of Carboniferous Pb—Zn and barite mineralization from basin-derived fluids, Nova Scotia, Canada. Economic Geology 84, 1471–89.CrossRefGoogle Scholar
Raybould, J. G., 1974. Ore texture, paragenesis and zoning in the lead-zinc veins of mid-Wales. Transaction of the Institution of Mining and Metallurgy 88, B112–B119.Google Scholar
Russell, M. J., 1972. North-south geofractures in Scotland and Ireland. Scottish Journal of Geology 8, 75–84.CrossRefGoogle Scholar
Samson, I. M. & Banks, D. A., 1988. Epithermal base-metal mineralization in the Southern Uplands of Scotland: nature and origin of the fluids. Mineralium Deposita 23, 1–8.CrossRefGoogle Scholar
Steiger, R. H. & Jager, E., 1977. Subcommission on geochronology: convention of the use of decay constants in geo- and cosmochronology. Earth and Planetary Science letters, 36, 359–62.CrossRefGoogle Scholar
Warren, P. T., Price, D., Nutt, M. J. C. & Smith, E. G., 1984. Geology of the country around Rhyl and Denbigh. Memoirs of 1:50000 Geology sheets 95 and 107 and parts of sheets 94 and 106. London: HMSO.Google Scholar
Wilkinson, I. & Smith, M., 1988. Basement fractures in North Wales: their recognition and control on Caledonian deformation. Geological Magazine 125, 301–6.CrossRefGoogle Scholar