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Textural evolution of W-Cu-Sn-bearing hydrothermal veins at Minas da Panasqueira, Portugal

Published online by Cambridge University Press:  05 July 2018

K. A. Foxford ,
R. Nicholson  and
D. A. Polya
K. A. Foxford
Affiliation:
Department of Geology, University of Manchester, Manchester M13 9PL
R. Nicholson
Affiliation:
Department of Geology, University of Manchester, Manchester M13 9PL
D. A. Polya
Affiliation:
Department of Geology, University of Manchester, Manchester M13 9PL
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Abstract

Combined structural and textural studies of the quartz veins of the Panasqueira W-Cu-Sn deposit of central Portugal have revealed the presence of coeval forms of crack-seal and cavity-fill mineral textures. The textures result from the dilational and infilling histories of brittle fractures produced within the host rock by the intrusion of pressurised fluids. Crack-seal textures were produced wherever or whenever crystal growth rates matched or were greater than fracture dilation rates, whereas cavity-fill textures developed wherever or whenever dilation rates were quicker than those of crystal growth. Rates of dilation within the blade-like fissures were naturally lowest at the edges, where types of crack-seal textures were produced, and highest in the cores, where cavity-fill texture formed. During propagation the linkage of adjacent echelon blades, by the rupture of the host-rock straps (bridges) between them, enhanced dilation rates and led to the widespread development of cavity-fill textures. Within the composite fissures so produced, environments in which types of crack-seal textures could form were restricted to the fissure margins and to areas where the tensile strain was sympathetically shared between closely spaced fissures. Textures and minerals characteristic of each fracture environment were able to form simultaneously within the fracture system.

Keywords

crack-sealcavity-filltexturesblade-like fracturesbridgesdilationhydrothermal
Type
Research Article
Information
Mineralogical Magazine , Volume 55 , Issue 380 , September 1991 , pp. 435 - 445
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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References

Barton, P. B., Bethke, P. M., and Roedder, E. (1977) Environment of ore deposition in the Creede mining district, San Juan mountains, Colerado: part III progress toward the interpretation of the chemistry of ore-forming fluid of the OH vein. Econ. Geol., 72, 1–24.CrossRefGoogle Scholar
Berner, R. A. (1980) Diagenetic chemical processes II: precipitation, dissolution and authigenic procecces. In Early diagenesis: a theoretical approach, Princeton University Press, 241 pp.CrossRefGoogle Scholar
Blaettler, A. J. (1985) Structural analysis of the fault pattern in the tungstentin mine of Panasqueira, Portugal. Unpublished thesis. University of Geneva, 77 pp.Google Scholar
Buckley, H. E. (1957) Crystal Growth. J. Wiley & Sons, New York, 571 pp.Google Scholar
Bussink, R. W. (1984) Geochemistry of the Panasqueira tungsten-tin deposit, Portugal. Unpublished Ph.D thesis, University of Utrecht, Netherlands.Google Scholar
Cox, S. F. (1987) Antitaxial crack-seal vein microstruc-tures and their relationship to displacement paths. J. Struct. Geol., 9, 779-88.CrossRefGoogle Scholar
Cox, S. F. and Etheridge, M. A. (1983) Crack-seal fibre growth mechanisms and their significance in the development of oriented layer silicate microstruc-tures. Tectonophys., 92, 147-70.CrossRefGoogle Scholar
de Caritat, P. (1990) Persistence of quartz disequilib-rium in groundwater flows. Terra Nova, 2, 53-9.CrossRefGoogle Scholar
Dickson, J. A. D. (1983) Graphical modelling of crystal aggregates and its relevance to cement diagnosis. Phil. Trans. Roy. Soc. London, A309, 465–502.Google Scholar
Dietrich, D. and Grant, P. R. (1985) Cathodolumin-escence petrography of syntectonic quartz fibres. J. Struct. Geol., 7, 541-53.CrossRefGoogle Scholar
d'Orey, F. C. (1967) Tungsten-tin mineralisation and paragenesis in the Panasqueira and Vale das Ermida mining districts, Portugal. Comunic. Serv. Geol., Portugal, 52, 117-67.Google Scholar
Elwell, D. and Scheel, H. J. (1975) Crystal growth from high temperature solutions. Academic Press, London, 634 pp.Google Scholar
Fournier, R. O. (1985) The behaviour of silica in hydrothermal solutions. In: Berger, B. R. & Bethke, P. M. (eds): Reviews in Economic Geology, 2, 45–61.Google Scholar
Grigorev, D. P. (1965) Ontogeny of Minerals. Israel program for scientific translations, Jerusalem, 260 pp.Google Scholar
Halls, C. 1987 A mechanistic approach to the paragenetic interpretation of mineral lodes in Cornwall. Proc. UssherSoc, 6, 548-54.Google Scholar
Hebblethwaite, R. P. B. and Antao, A. M. (1982) A report on the study of dilation patterns within the Panasqueira orebody. Unpublished Beralt Tin and Wolfram, Portugal report.Google Scholar
Helgeson, H. C. and Lichtner, P. C. (1987) Fluid flow and mineral reactions at high temperatues and pressures. J. Geol. Soc. London, 144, 313-26.CrossRefGoogle Scholar
Hubbert, M. K. and Rubey, W. W. (1959) Role of fluid pressure in mechanics of overthrust faulting, 1, Mechanics of fluid filled porous solids and its application to overthrust faulting. Geol. Soc. Amer. Bull., 70, 115-66.Google Scholar
Hulin, C. D. 1929. Structural controls of ore deposition. Econ. Geol., 24, 15–49.CrossRefGoogle Scholar
Inverno, C. and Ribeiro, M. L. (1980) Fracturacas e catejo nas Minas da Argemela (Fundão). Comunic. Serv. Geol. Portugal, 66, 185-94.Google Scholar
Jaeger, J. C. 1963. Extension failures in rocks subject to fluid pressure. J. Geophys. Research, 68, 6066–7.CrossRefGoogle Scholar
Kelly, W. C. and Rye, R. O. (1979) Geologic, fluid inclusion and stable isotope studies of the tin-tungsten deposits of Panasqueira, Portugal. Econ. Geol., 74, 1721–822.CrossRefGoogle Scholar
Marignac, C. (1982) Geologic, fluid inclusions and stable isotope studies of the tin-tungsten deposits of Panasqueira, Portugal-a discussion. Ibid, 77, 1263–6.Google Scholar
Nicholson, R. and Pollard, D. D. (1985) Dilation and linkage of echelon cracks. Struct. Geol., 7, 583-90.CrossRefGoogle Scholar
Norton, D. (1979) Transport phenomena in hydro-thermal systems: the redistribution of chemical components around cooling magmas. Bull. Mineral., 102, 471-86.Google Scholar
Philips, W. J. (1986) Hydraulic fracturing effects in the formation of mineral deposits. Trans. Inst. Mining Metatl., 95, 17–24.Google Scholar
Pollard, D. D. (1973) Derivation and evaluation of a mechanical model for sheet intrusions. Tectonophys., 19, 233-69.CrossRefGoogle Scholar
Pollard, D. D. and Aydin, A. (1988) Progress in understanding jointing over the past century. Geol. Soc. Amer. Bull., 100, 1181–204.2.3.CO;2>CrossRefGoogle Scholar
Pollard, D. D. Segal, P., and Delaney, P. T. 1982 Formation and interpretation of dilatant echelon cracks. Ibid. 93, 1291-303.Google Scholar
Polya, D. A. (1989) Chemistry of the mainstage ore-forming fluids of the Panasqueira W-Cu(Ag)-Sn deposit, Portugal: implications for models of ore genesis. Econ. Geol., 84, 1134-52.CrossRefGoogle Scholar
Polya, D. A. (1990) Pressure dependence of wolframite solubility for hydrothermal vein formation. Trans. Inst. Mining Metall., 99, B120-4.Google Scholar
Ramsay, J. G. (1980) The crack-seal mechanism of rock deformation. Nature, London, 284, 135–9.Google Scholar
Ramsay, J. G. and Huber, M. I. (1983) The techniques of modern structural geology, Vols. 1 and 2, Academic Press, London, p. 307 and 700.Google Scholar
Robert, F. and Brown, A. C. (1986) Archean gold bearing quartz veins at the Sigma mine, Abitibi greenstone belt, Quebec: part II vein paragenesis and hydrothermal alteration. Econ. Geol., 81, 593–616.Google Scholar
Secor, D. T. (1965) Role of fluid pressure in jointing. Amer. J. Sci., 263, 633-46.CrossRefGoogle Scholar
Snee, L. W., Sutter, J. F., and Kelly, W. C. (1988) Thermochronology of economic deposits: dating the stages of mineralisation at Panasqueira, Portugal, by high precision 40Ar/39Ar age spectrum techniques on muscovite. Econ. Geol., 83, 335-54.CrossRefGoogle Scholar
Thadeu, D. (1951) Geologia do couto mineiro da Panasqueira, Communic. Serv. Geol. Portugal, 32, 5–64.Google Scholar