Abstract
Advective-dispersive fluid flow through permeable and porous rock causes systematic alteration of the infiltrated rock. O and Sr isotopes can be used as tracers to monitor exchange processes between mineralizing hydrothermal solutions and carbonate host rocks. Fluid infiltration into rock of initially uniform isotopic composition leads to characteristic changes in δ18O and ɛ87Sr in the rock, that depend on infiltration distance, fluid velocity, diffusivity and reaction kinetics. For fast fluid-solid equilibrium during advective flow, the shape of such alteration profiles can be described by the dimensionless Peclet number (P e ), which expresses the fluid flux, infiltration distance and diffusivity. In the case of mineralization from low to moderate temperature solutions, isotope exchange is not instantaneous, but kinetically controlled, and a similar parameter, the Damköhler number (N d ) expressing fluid flux, isotope exchange rate and infiltration distance, becomes more useful. N d - and P e -values have been estimated for various examples of carbonatehosted hydrothermal mineralization in the Eastern Alps (Austria) and the Benue Trough (Nigeria) by modelling O and Sr isotope data from ore (or gangue minerals) and host rock. The values obtained enable a rough differentiation between pervasive and channelled fluid flow as the prevailing transport mechanism to be made. Results indicate that both highly channelled fluid flow through fractures without significant interaction with the wall-rock, and pervasive fluid flow with infiltration distances into the percolated host rock of the order of 100 m, occur near mineral deposits. In the latter case, the extent of O and Sr isotopic alteration of the host rock can be used as an effective exploration tool.
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Akande, O., Zentilli, M., Reynolds, P.H. (1989) Fluid inclusion and stable isotope studies of Pb-Zn-fluorite-barite mineralization in the lower and middle Benue Trough, Nigeria. Mineral. Deposita 24: 183–191
Belocky, R., Pohl, W. (1990) Ostalpenfluide. Unpubl. Report DFG Project Po 270/4-1, Braunschweig, 56 pp.
Bickle, M.J., Baker, J. (1990a) Advective-diffusive transport of isotopic fronts: an example from Naxos, Greece. Earth Planet. Sci. Let. 97:78–93
Bickle, M.J., Baker, J. (1990b) Migration of reaction and isotopic fronts in infiltration zones: assessments of fluid flux in metamorphic terrains. Earth Planet. Sci. Let. 98:1–13
Bickle, M.J., Chapman, H.J. (1990) Strontium and oxygen isotope decoupling in the Hercynian Trois Seigneurs Massif, Pyrenees: evidence for fluid circulation in a brittle regime. Contrib. Mineral. Petrol. 104:332–347
Bickle, M.J., McKenzie, D. (1987) The transport of heat and matter by fluids during metamorphism. Contrib. Mineral. Petrol. 95:384–392
Bird, D.K., Norton, D.L. (1981) Theoretical prediction of phase relations among aqueous solutions and minerals: Salton Sea geothermal system. Geochim. Cosmochim. Acta 45:1479–1493
Blattner, P. (1985) Isotope shift data and the natural evolution of geothermal systems. Chem. Geol. 49:187–203
Blattner, P., Absar, A. (1988) Mass balance and Damköhler numbers in flow systems — fluid throughput at Ohaaki-Broadlands. Proc. 10th Geochemical Workshop Aukland, Nov. 1988, 4 pp.
Blattner, P., Lassey, K.R. (1989) Stable-isotope exchange fronts, Damköhler numbers, and fluid to rock ratios. In: Schott, J., Lasaga, A.C. (eds) Kinetic Geochemistry. Chem. Geol. 78: 381–392
Blattner, P., Williams, J. G. (1991) The Largs high latitude oxygen isotope anomaly (New Zealand) and climatic controls of oxygen isotopes in magma. Earth Planet. Sci. Lett. 103:270–284
Clayton, R.N., Muffler, L.J.P., White, D.E. (1968) Oxygen isotope study of calcite and silicates of the River Ranch No. 1 well, Salton Sea geothermal field, California. Am. J. Sci. 266:968–979
Criss, R.D., Gregory, R.T., Taylor, H.P. (1987) Kinetic theory of oxygen isotopic exchange between minerals and water. Geochim. Cosmochim. Acta 47:1099–1108
Deloule, E., Turcotte, D. L. (1989) The flow of hot brines in cracks and the formation of ore deposits. Econ. Geol. 84:2217–2225
Dullien, F.A.L. (1979) Porous media, fluid transport and pore structure. Academic Press, New York, 396 pp.
Fletcher, R.C., Hofmann, A.W. (1974) Simple models of diffusion and combined diffusion-infiltration metasomatism. In: Hofmann, A.W., Giletti, B.J., Yoder, H.S., Yundi, R.A. (eds) Geochemical Transport and Kinetics. Carnegie Inst. Washington Publ. 634
Frank, W, Frimmel, H.E., Grum, W. (1991) Untersuchungen von Strontiumisotopen und Flüssigkeitseinschlüssen ostalpiner Lagerstätten. Teil 2: Strontiumisotopenuntersuchungen der Barytvorkommen im Bereich des Otterzuges (N.Ö.) und der Antimonitvererzung Schlaining (Bgld.). Unpubl. Report Ministry Econ. Affairs, 54 pp., Vienna
Frimmel, H.E. (1988) Strontium isotopic evidence for the origin of siderite, ankerite and magnesite mineralizations in the Eastern Alps. Mineral. Deposita 23:268–275
Frimmel, H.E. (1989) Einsatzmöglichkeiten der Strontium-Methode in der Lagerstättengeologie am Beispiel der Barytlagerstätte Kogel/Brixlegg (Tirol). Arch. f. Lagerst.forsch. Geol. B.-A. 11:127–146
Frimmel, H.E. (1991) Isotopic constraints on fluid/rock ratios in carbonate rocks: barite-tetrahedrite mineralization in the Schwaz Dolomite, Tyrol (Eastern Alps, Austria). Chem. Geol. 90:195–209
Frimmel, H.E., Papesch, W. (1990) Sr, O and C isotopic study of the Brixlegg barite deposit, Tyrol (Austria). Econ. Geol. 85:1162–1171
Goldstein, S. (1953) On the mathematics of exchange processes in fixed columns: I. Mathematical solutions and asymptotic expansions. Proc. Roy. Soc. London, A219:151–171
Hesse, J., Bender, M.L., Schilling, J.G. (1986) Evolution of the ratio of Strontium-87 to Strontium-86 in seawater from Cretaceous to Recent. Science reports 231:979–984
Holser, W.T. (1984) Gradual and abrupt shifts in ocean chemistry. In: Holland, H.D., Trendall, A.F. (eds) Patterns of change in earth evolution. Springer, Berlin Heidelberg New York, pp. 123–143
Kessen, K.M., Woodruff, M.S., Grant, N.K. (1981) Gangue mineral 87Sr/86Sr ratios and the origin of the Mississippi Valley-type mineralization. Econ. Geol. 76:913–920
Lange, S., Chaudhuri, S. (1983) Strontium isotopic evidence for the origin of barites and sulfides from the Mississippi valley-type ore deposits in southeast Missouri. Econ. Geol. 78:1255–1261
Lassey, K.R., Blattner, P. (1988) Kinetically controlled oxygen isotope exchange between fluid and rock in one-dimensional advective flow. Geochim. Cosmochim. Acta 52:2169–2175
Lichtner, P.C. (1985) Continuum model for simultaneous chemical reactions and mass transport in hydrothermal systems. Geochim. Cosmochim. Acta 49:779–800
Mohr, H. (1954) Über die Schwerspatlagerstätten des Semmering-gebietes (N.Ö.). Bergu. Hüttenmänn. Mh. 99:101–112 and 121–138
Nabelek, P.I. (1987) General equations for modeling fluid/rock interaction using trace elements and isotopes. Geochim. Cosmochim. Acta 51:1765–1769
Norton, D. (1988) Metasomatism and permeability. Am. J. Sci. 288:604–618
Spooner, E.T.C., Beckinsale, R.D., England, P.C., Senior, A. (1977) Hydration, 18O-enrichment and oxidation during ocean floor hydrothermal metamorphism of ophiolitic metabasic rocks from E. Liguria, Italy. Geochim. Cosmochim. Acta 41:857–871
Taylor, H.P. Jr. (1977) Water/rock interactions and the origin of H2O in granitic batholiths. J. Geol. Soc. London 133:857–871
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Frimmel, H.E. Isotopic fronts in hydrothermally mineralized carbonate rocks. Mineral. Deposita 27, 257–267 (1992). https://doi.org/10.1007/BF00193396
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DOI: https://doi.org/10.1007/BF00193396