Abstract
Shallowly plunging and branching pipe systems in Lease and Bobbejaankop Granite at the Zaaiplaats mine are host to major tin mineralization. Detailed textural study of Maggs Pipe indicates that dissolution of the granite was a major process in the formation of open space which provided permeability for the passage of hydrothermal fluids, and sites for the precipitation of ore and gangue minerals. The pipe formation process initiates with the dissolution of granite quartz and subsequently extends to feldspar dissolution, particularly in the central portion of Maggs Pipe. Spaces created by mineral dissolution are filled by hydrothermal phases and the relict feldspar matrix becomes progressively more altered toward the centre of the pipe. The distribution of alteration and infill minerals defines a zoning pattern which, from the outer margin to the central core, includes calcite-quartz, chlorite (± cassiterite, albite, fluorite) and synchisite-calcite zones. It is postulated that quartz and feldspar dissolution resulted from interaction between the granite and hydrothermal fluids containing alkali-chloride, -fluoride or -carbonate complexes which had separated from the granite magma during crystallization. Preliminary observations on several other pipes at Zaaiplaats indicate that quartz and feldspar dissolution was a major procress in forming the pipe systems.
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References
Balitskiy, V.S.: Alteration of granite and pegmatite under the influence of alkaline silica-containing hydrothermal solutions at high pressure. Dokl. Acad. Sci. USSR 171:222–225 (1966)
Blanchard, R.: Some pipe deposits of eastern Australia. Econ. Geol. 42:265–304 (1947)
Cathelineau, M.: The hydrothermal alkali metasomatism effects on granitic rocks: quartz dissolution and related subsolidus changes. J. Petrol. 27:945–965 (1986)
Cheilletz, A., Giuliani, G.: Role de la déformation du granite dans la genèse des episyénites feldspathiques des massifs de Lovios-Geres (Galice) et de Zaer (Maroc Central). Mineral. Deposita 17:387–400 (1982)
Clarke, G.H., Patterson, R.G., Taylor, R.G.: The nature and origin of brecciation and mineralization at the White Crystal ore deposit, Ardlethan tin mine, New South Wales. Aust. J. Earth Sci. 32:343–348 (1985)
Coetzee, J.: The Lease granite — a granophyric, miarolitic mineralized granite at the apical region of a tin-tungsten system. Trans. Geol. Soc. South Africa 89:335–345 (1986)
Crocker, I.T.: The Zaaiplaats Tinfield, Potgietersrus district. In: Annhaeusser, C.R. and Maskie, S. (eds.) Mineral Deposits of Southern Africa. Johannesburg, Geol. Soc. South Africa 1287–1299 (1986)
Fournier, R.O.: The behaviour of silica in hydrothermal solutions. In: Berger, B.R. and Bethke, P.M. (eds.) Geology and geochemistry of epithermal systems. Reviews in Econ. Geol. 2:45–61 (1985)
Grant, N.J., Halls, C., Sheppard, S.M.F., Avila, W.: Evolution of the porphyry tin deposits of Bolivia. Mining Geol. Spec. Issue 8:151–173 (1980)
Groves, D.I., McCarthy, T.S.: Fractional crystallization and the origin of tin deposits in granitoids. Mineral. Deposita 13:11–26 (1978)
Kynaston, H.: The red granite of the Transvaal Bushveld and its relation to ore deposits. Proc. Geol. Soc. South Africa 12:21–31 (1909)
Kynaston, H., Mellor, E.T.: The geology of the Waterberg tinfields. Geol. Surv. South Africa Memoir 4:114 (1909)
Lenthall, D.H. and Hunter, D.R.: The geochemistry of Bushveld granites in the Potgietersrus tin-field. Precambrian Research 5:359–400 (1977)
Leroy, J.: The Margnac and Fanay uranium deposits of the La Crouzille district (western Massif Central, France). Econ. Geol. 73:1611–1634 (1978)
Leroy, J.: Episyénitisation dans le gisement d'uranium du Bernardan (Marche): comparaison avec les gisements similaires du nordouest du Massif Central Français. Mineral. Deposita 19:26–35 (1984)
Merensky, H.: The rocks belonging to the area of the Bushveld Granite Complex in which tin may be expected, with descriptions of the deposits actually found. Trans. Geol. Soc. South Africa 11:25–42 (1908)
Pollard, P.J., Taylor, R.G.: Progressive evolution of alteration and tin mineralization: controls by interstitial permeability and fracture-related tapping of magmatic fluid reservoirs in tin granites. Econ. Geol. 81:1795–1800 (1986)
Reknagel, R.: On the origin of South African tin deposits. Trans. Geol. Soc. South Africa 12:168–202 (1909)
Rykl, D., Stemprok, M.: Hydrothermal reaction of water and some inorganic solutions with the Cinovec granite at 300 and 400°C and 50 MPa pressure: an experimental study. Proc. Seventh Quadrennial IAGOD Symposium (Schweizerbart, Stuttgart) 437–447 (1988)
Söhnge, P.G.: The structure, ore genesis and mineral sequence of the cassiterite deposits in the Zaaiplaats tin mine, Potgietersrus district, Transvaal. Trans. Geol. Soc. South Africa 47:157–181 (1944)
South African Committee for Stratigraphy (SACS): Stratigraphy of South Africa Part 1 (Compiler L.E. Kent), South Africa Geol. Surv. Handbook 8:690 (1980)
Strauss, C.A.: The geology and mineral deposits of the Potgietersrus tin-fields. Geol. Surv. South Africa Memoir 46:252 (1954)
Taylor, R.G.: Geology of tin deposits (Elsevier, Amsterdam) 543 p (1979)
Taylor, R.G., Pollard, P.J.: Pervasive hydrothermal alteration in tin-bearing granites and implications for the evolution of orebearing magmatic fluids. In: Taylor, R.P. and Strong, D.F. (eds.) Recent advances in the geology of granite-related mineral deposits. C.I.M. Spec. Vol. 39:86–95 (1988)
Von Gruenewaldt, G., Strydom, J.H.: Geochemical distribution patterns surrounding tin-bearing pipes and the origin of mineralizing fluids at the Zaaiplaats tin mine, Potgietersrus district. Econ. Geol. 80:1201–1211 (1985)
Wagner, P.A.: Economic geology. In: Wagner, P.A., Rogers, A.W., Hall, A.L., Houghton, S.H. (eds.) The Union of South Africa, Handbuch der Regionalen Geologie, Heidelberg, Carl Winters, 7/7a:161–222 (1929)
Witt, W.K.: Fracture-controlled feldspathic alteration in granites associated with tin mineralization in the Irvinebank-Emuford area, northeast Queensland. Aust. J. Earth Sci. 34:447–462 (1987)
Witt, W.K.: Evolution of high-temperature hydrothermal fluids associated with greisenization and feldspathic alteration of a tin-mineralized granite, northeast Queensland. Econ. Geol. 83:310–334 (1988)
Wyart, J., Sabatier, G.: Solubilité du quartz dans les solutions des sels alcalins sous pression au-dessus de la température critique. C.R. Acad. Sci. 240:2157–2159 (1955)
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Pollard, P.J., Taylor, R.G. & Tate, N.M. Textural evidence for quartz and feldspar dissolution as a mechanism of formation for Maggs Pipe, Zaaiplaats tin mine, South Africa. Mineral. Deposita 24, 210–218 (1989). https://doi.org/10.1007/BF00206444
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DOI: https://doi.org/10.1007/BF00206444