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Cathodoluminescence and growth of cassiterite in the composite lodes at South Crofty Mine, Cornwall, England

Published online by Cambridge University Press:  05 July 2018

C. B. Farmer ,
A. Searl  and
C. Halls
C. B. Farmer
Affiliation:
Mining Geology Research Group, Department of Geology, Royal School of Mines, Imperial College, London SW7 2AZ
A. Searl
Affiliation:
School of Earth Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT
C. Halls
Affiliation:
Mining Geology Research Group, Department of Geology, Royal School of Mines, Imperial College, London SW7 2AZ
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Abstract

The cathodoluminescence (CL) of cassiterite (SnO2) from the paragenetic sequence in the lodes at South Crofty Mines has been used in the interpretation of the processes which govern mineral deposition. Luminescence is controlled by the substitution of Ti, Fe and W for Sn in the cassiterite lattice. Ti and W behave as luminescence activators whereas Fe quenches luminescence. The observed colours and intensity of the luminescence are believed to result from the interplay between these effects. Successive generations of cassiterite formed during the separate stages of paragenetic evolution show different luminescence colours. These are believed to reflect changes in bulk composition of the fluid, which is indicated by the systematic variation in the composition of tourmaline in the associated gangue.

CL also reveals details of growth and deformation in individual crystals. Growth textures observed in CL are broad concentric growth banding, oscillatory zoning and sector zoning. Sector boundaries often show a zig-zag form which is indicative of competitive growth of adjacent crystal faces. Interpretation of CL textures is used to support the hypothesis that cassiterite growth took place under two main regimes. These are, firstly, conditions in which fluid pressure decreased abruptly when tectonic reactivation caused dilation of parts of the lode fracture system and secondly, conditions of sustained hydraulic pressure within fractured vein fill. In tectonically induced fractures the crystals are stubby, have non-equivalent growth faces and are commonly tetragonal bipyramidal forms in which sector zoning is invariably present. In hydraulic fractures crystals take a predominantly tetragonal prismatic form. Thus, it is believed that growth under these contrasting conditions leads to distinctive morphology and zoning in cassiterite, providing a basis for typomorphic characterisation.

Keywords

cathodoluminescencecassiteritezoningtypomorphismCornwall
Type
Research Article
Information
Mineralogical Magazine , Volume 55 , Issue 380 , September 1991 , pp. 447 - 458
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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References

Allegre, C.J., Provost, A., and Jaupart, C. (1981) Oscillatory zoning: A pathological case of crystal growth. Nature, 294, 223–8.CrossRefGoogle Scholar
Allman-Ward, P., Halls, C., Rankin, A. H., and Bristow, C. M. (1982) An intrusive hydrothermal breccia body at Wheal Remfry in the western part of the St. Austell granite pluton, Cornwall. In Metallization associated with acid magmatism (Evans, A. M., ed.), Wiley, 1–28.Google Scholar
Bertrandt Zytkowiak, M., Chimczak, E., and Gordon, W. S. (1988) Cathodoluminescence spectra of thin tin oxide films. Acta Phys. Polonica, A73, 535-41.Google Scholar
Bhalla, R. J. R. S. B. and White, E. W. (1971) Intrinsic cathodoluminescence emission from willemite single crystals. J. Lumin., 4, 194–200.CrossRefGoogle Scholar
Bodnar, R. J. and Cline, J. S. (1990) Microthermo-metric and phase behaviour of magmatic-hydrother-mal fluid inclusions: An analysis based on PVTX data for the system albite-H2O-NaCl. PACROFI III Abstracts, Toronto, p. 17.Google Scholar
Collins, J. H. (1882) On some Cornish tin stones and tin capels (second part). Mineral. Mag., 4, 103-16.Google Scholar
Deer, W. A., Howie, R. A., and Zussman, J. (1986) Rock-forming Minerals, Volume IB: Disilicates and Ring Silicates (2nd ed.) Longman Scientific & Technical, Harlow, U.K. Google Scholar
Dines, H. G. (1956) The metalliferous mining region of southwest England. Mem. Geol. Survey, U.K., H.M.S.O., London, 795 p.Google Scholar
Dowty, E. (1976) Crystal structure and crystal growth: II. Sector zoning in minerals. Am. Mineral., 61, 460–9.Google Scholar
Dulski, P. (1980) Spurenanalyse als Hilfsmittel bei der geochemischen Untersuchung der Genese bolivianscher Zinnerzlagerstatten. Verlag von Dietrich Reimer, Berlin, 79 pp.Google Scholar
Eadington, P. J. (1988) The solubility of cassiterite in hydrothermal solutions in relation to some lithological and mineral associations of tin ores. In Recent advances in the geology of granite-related mineral deposits (Taylor, R. P. and Strong, D. F., eds.), 25–32.Google Scholar
Farmer, C. B. and Halls, C. (in press) Controls on cassiterite mineralisation at South Crofty Mine, Cornwall, United Kingdom. Proceedings of the 8th IAGOD Symposium Ottawa 1990. Google Scholar
Fleet, M. E., MacLean, P. J., and Barbier, J. (1989) Oscillatory-zoned As-bearing pyrite from strata-bound and stratiform gold deposits: An indicator of ore fluid evolution. Econ. Geol. Monograph 6, 356-62.Google Scholar
Flett, J. S. (1903) Note on some brecciated stanniferous veinstones from Cornwall. Sum. Prog. Geol. Serv. for 1903, 150-62.Google Scholar
Goldschmidt, V. M. (1937) The principles of distribution of chemical elements in minerals and rocks. J. Chem. Soc, 655-73.CrossRefGoogle Scholar
Grant, P. R. and White, S. H. (1978) Cathodolumin-escence and microstructure of quartz overgrowths. In Scanning Electron Microscopy, 197811 (Johari, O., ed.), 789-94.Google Scholar
Hall, M. R. and Ribbe, P. H. (1971) An electron microprobe study of luminescence centres in cassiterite. Am. Mineral., 56, 31–46.Google Scholar
Haase, C. S., Chadham, J., Feinn, D., and Ortaleva, P. (1980) Oscillatory zoning in plagioclase feldspar. Science, 209, 272-4.CrossRefGoogle ScholarPubMed
Henwood, W. J. (1843) On the metalliferous deposits of Cornwall and Devon. Trans. Roy. Geol. Soc. Cornwall, 5, 1–386.Google Scholar
Henry, D. J. and Guidotti, C. V. (1985) Tourmaline as a petrogenetic indicator mineral: an example from the staurolite-graded metapelites of NW Maine. Am. Mineral, 70, 1–15.Google Scholar
Hosking, K. F. G. (1964) Permo-carboniferous and later primary mineralisation of Cornwall and Southwest Devon. In Present views of some aspects of the geology of Cornwall and Devon (Hosking, K. F. G., Shrimpton, G. J., eds), 150th Anniversary Volume, Royal Geological Society of Cornwall, 201-45.Google Scholar
Hosking, K. F. G., Stanley, C. J., and Camm, G. S. (1987) The occurrence, nature and genesis of wood tin in Southwest England. Trans. Royal Geol. Soc. Cornwall, 21, 153–212.Google Scholar
Huppert, H. E., Sparks, R., Stephen, J., Wilson, J. R., Hallworth, M. A., and Leith, A. M. (1987) Laboratory experiments with experiments with aqueous solutions modelling magma chamber processes; II, Cooling and crystallisation along included planes. In Origins of igneous layering (Parsons, I., ed.), NATO Advanced Study Institutes Series, Series C: Mathematical and Physical Sciences, 196, 539-68.CrossRefGoogle Scholar
Izoret, L., Marnier, G., and Dusausoy, Y. (1985) Characterisation cristallochimique de la cassiterite des gisements d'etain et de tungstene de Galice, Espagne. Can. Mineral., 23, 221-31.Google Scholar
Jackson, N. J., Willis-Richards, J., Manning, D. A. C., and Sams, M. (1989) Evolution of the Cornubian orefield, S.W. England. Part II: Mineral deposits and ore-forming processes: Econ. Geol., 84/5, 1101-33.CrossRefGoogle Scholar
Jolliff, B. L., Papike, J. J., Shearer, C. K., and Laul, J. C. (1986) Tourmaline as a recorder of pegmatite evolution: Bob Ingersoll pegmatite, Black Hills, South Dakota. Am. Mineral., 71, 472–500.Google Scholar
Kohnke, E. E. (1962) Electrical and optical properties of natural stannic oxide crystals. J. Phys. Chem. Solids, 23, 1557-62.CrossRefGoogle Scholar
Loomis, T. P. (1982) Numerical simulation of crystallisation processes of plagioclase in complex melts: the origin of major and oscillatory zoning in plagioclase. Contrib. Min. Petrol., 81, 219-29.CrossRefGoogle Scholar
MacAlister, D. A. (1906), Pt. II, Mining. In: The geology of Falmouth and Truro and of the mining district of Cambourne and Redruth (Sheet 352). Mem. Geol. Surv. Eng. and Wales, 335 pp.Google Scholar
Machel, H. G. (1985) Cathodoluminescence in calcite and dolomite and its chemical interpretation. Geo-science Canada, 12, 139-17.Google Scholar
Marshall, D. J. (1988) Cathodoluminescence of geological materials, Unwin-Hyman, Boston, 146 pp.Google Scholar
Mendelssohn, M. J., Milledge, H. J., Vance, E. R., Nave, E., and Woods, P. A. (1978) Internal radio-active haloes in diamonds. In Industrial Diamond Review, 31-6, London.Google Scholar
Möller, P., Dulski, P., Szack, W., Malow, G., and Riedel, E. (1988) Substitution of tin in cassiterite by tantalum, niobium, tungsten, iron and manganese. Geochim. Cosmochim. Ada, 52, 1497–503.CrossRefGoogle Scholar
Moore, F. and Howie, R. A. (1979) Geochemistry of some Cornubian cassiterites. Mineral. Deposita, 14, 103–7.CrossRefGoogle Scholar
Mullin, J. W. (1972) Crystallisation (Second Edition), Butterworths, London, 480 pp.Google Scholar
Nakamura, Y. (1973) Origin of sector zoning in igneous clinopyroxenes. Am. Mineral., 58, 986-90.Google Scholar
Neiva, A. M. R. (1974) Geochemistry of tourmaline (schorlite) from granites, aplites and pegmatites from northern Portugal. Geochim. Cosmochim. Ada, 38, 1307-17.CrossRefGoogle Scholar
Power, G. M. (1968) Chemical variation in tourmaline from South-west England. Mineral. Mag., 36, 1078-89.Google Scholar
Ramboz, C., Pichavant, M., and Weisbrod, A. (1982) Fluid immiscibility in natural processes: use and misuse of fluid inclusion data. Chem. Geol., 37, 1–8.Google Scholar
Raven, M. J. and Dickson, J. A. D. (1989) Fir-tree zoning: an indicator of pulsed crystallisation in calcite cement crystals. Sediment. Geol., 65, 249-59.CrossRefGoogle Scholar
Reeder, R. J. and Grams, C. (1987) Sector zoning in calcite cement crystals: Implications for trace element distribution in carbonates. Geochim. Cosmochim. Ada, 51, 187-94.CrossRefGoogle Scholar
Reeder, R. J. and Prosky, J. L. (1986) Compositional sector zoning in dolomite. J. Sed. Pet., 56, 237–7.Google Scholar
Rémond, G. (1973) Exemples d'identification et de localisation des elements en traces dans les minéraux luminescents (cassitérites), à l'aide de l'analyseur ionique. Bull. Soc. franç. Mineral. Crist., 96, 183-98.Google Scholar
Ruck, R., Dusausoy, Y., Nguyen Trung, C., Gaite, J-M., and Murciego, A. (1989) Powder EPR study of natural cassiterites and synthetic SnO2 doped with Fe, Ti, and Na and Nb. Eur. J. Mineral., 1, 343-52.CrossRefGoogle Scholar
Searl, A. (1989) Saddle dolomite: a new view of its nature and origin. Mineral. Mag., 53, 547-55.Google Scholar
Sunagawa, I. (1977) Natural crystallisation. J. Crystal Growth, 42, 214-23.CrossRefGoogle Scholar
Searl, A. (1984) Growth of crystals in nature. In Materials Science of the Earth's Interior (Sunagawa, I., ed.), Tokyo, Terra Scientifica, 63–105.Google Scholar
Swinden, T. R. (1984) An investigation of the variations in optical properties and chemical composition of cassiterite in Cornish tin deposits. Unpubl. Ph.D. thesis, Camborne School of Mines.Google Scholar
Thiel, B. and Helbig, R. (1976) Growth of SnO2 single crystals by vapour phase reaction method. Crystal Growth, 32, 259-64.CrossRefGoogle Scholar
Varlamoff, N. (1949) Relations entre les faciés des cristaux de cassitérite de la region Kalima (Congo Beige) et la geologie de leurs gisements. Ann. Soc. Geol. Belg., 72, 289–316.Google Scholar
Wolf, D. and Espozo, E. (1972) Zur Geochemie bolivianischer Kassiterite. Z. Angewandte Geol., 18, 459-68.Google Scholar