Abstract
Low grade hydrothermally metamorphosed mafic rocks from the Iberian Pyrite Belt are enriched in 18O relative to the oxygen isotopic ratio of fresh basalt (+6.5±1‰). The observed δ 18O whole rock values range from +0.87‰ to +15.71‰ corresponding to positive isotopic shifts of +5‰ to +10‰, thus requiring isotopic exchange with fluids under conditions of high water:rock ratios at low temperatures. The lowest δ 18O observed corresponds to an albitized dolerite still and is compatible with independent geochemical data suggesting lower water: rock ratios for the alteration of these rocks.
The isotope data are consistent with the hypothesis that the spilites from the Pyrite Belt were produced by interaction of basaltic material with sea water.
Significant leaching of transition metals from the mafic rocks during alteration coupled with available sulphur isotopic data for the sulphide ores also suggest that sea water may have played an important role in the formation of ore deposits in the Iberian Pyrite Belt.
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References
Aguirre L, Beatriz L, Offler R (1978) Unconformities as mineralogical breaks in the burial metamorphism of the Andes. Contrib Mineral Petrol 66:361–366
Andrews AJ, Fyfe WS (1975) Metamorphism and massive sulphide generation in oceanic crust. Geosci Can 3(2):84–94
Bernard AJ, Soler E (1974) Aperçu sur la province pyriteuse sudibérique. Centenaire Soc Geol Belgique, Liège, 287–315
Bischoff JL, Dickson FW (1975) Seawater-basalt interaction at 200° C and 500 bars: implications for origin of sea-floor heavy metal deposits and regulation of seawater chemistry. Earth Planet Sci Lett 25:385–397
Bjornsson S, Arnorsson S, Tomasson J (1972) Economic evaluation of Reykjanes thermal brine area, Iceland. Am Assoc Petrol Geol Bull 56:2380–2391
Carmichael ISE, Turner FJ, Verhoogen J (1974) Igneous Petrology. Mcgraw-Hill Book Co
Carvalho D (1976) Considerações sobre o volcanismo da região de Cercal-Odmira. Suas relações com a faixa piritosa. Comun Serv Geol Port 60:215–238
Carvalho D (1977) Lineament patterns and hypogene mineralization in Portugal. “Estudos Notas e Trabalhos” do S.F.M. XXIII(3–4):91–106
Carvalhosa AB (1961) Contribuição para o estudo dos ofiolitos do Baixo Alentejo — Espilitos da região de Castro Verde-Messejana. Comun Serv Geol Port 45:371–390
Clayton RN, Mayeda TK (1963) The use of bromine pentafluoride in the extraction of oxygen from oxides and silicates for isotopic analysis. Geochim Cosmochim Acta 27:43–52
Clayton RN, O'Neil JR, Mayeda TK (1972) Oxygen isotope exchange between quartz and water. J Geophys Res 77:3057–3067
Crerar DA, Barnes HL (1976) Ore solution chemistry V. Solubilities of chalcopyrite and chalcocite in hydrothermal solution at 200° C to 350° C. Econ Geol 71:772–794
Cruz Gaspar O (1961) A associação genética dos espilitos com os jazigos de manganês do Baixo Alentejo. “Estudos Notase Trabalhos” S.F.M. XV(1–2):177–196
Edmond JM, Measures C, Mangum B, Grant B, Sclater FR, Collier R, Hudson A, Gordon LL, Corliss JB (1979) On the formation of metal-rich deposits at ridge crests. Earth Planet Sci Lett 46:19–30
Ellis AJ (1979) Explored geothermal systems. In: H.L. Barnes (ed) Geochemistry of Hydrothermal Ore Deposits 2nd edn. Holt, Rinehart and Winston, New York, p 632–683
Ellis AJ, Mahon WAJ (1964) Natural hydrothermal systems and experimental hot water/rock interactions. Geochim Cosmochim Acta 28:1323–1357
Ellis AJ, Mahon WAJ (1967) Natural hydrothermal systems and experimental hot water/rock interactions, Pt. 2. Geochim Cosmochim Acta 31:519–538
Forester RW, Taylor HP (1976) 18O-depleted igneous rocks from the Tertiary complex of the Isle of Mull, Scotland. Earth Planet Sci Lett 32:11–17
Fyfe WS (1974) Hydrosphere solid-earth interaction. Proc Geol Assoc Can. National Conference, St. John's, Newfoundland, p 763–772
Garcia Palomero F (1977) Caracteres geologicos y relaciones morfologicas y geneticas de las mineralizaciones del “anticlinal de Rio Tinto”. Acta Salmanticensia, Tesis de Ciencias
Hajash A Jr (1975) Hydrothermal processes along mid-ocean ridges: an experimental investigation. Contrib Mineral Petrol 53:205–226
Heaton THE, Sheppard SMF (1977) Hydrogen and oxygen isotope evidence for sea-water-hydrothermal alteration and ore deposition, Troodos, Cyprus. In: Volcanic Processes in Ore Genesis. London: Inst Mining and Metallurgy and Geological Society, pp 42–57
Helgeson HC (1970) A chemical and thermodynamic model of ore deposition in hydrothermal systems. Mineral Soc Am Spec Pap 3:155–186
Hemley JJ (1959) Some mineralogical equilibria in the system K2O-Al2O3-SiO2-H2O. Am J Sci 257:241–270
Hoefs J (1973) Stable Isotope Geochemistry. Springer Verlag, New York
Honnorez J, Kirst P (1975) Petrology of rodingites from the equatorial mid-Atlantic fracture zones and their geotectonic significance. Contrib Mineral Petrol 49:233–257
Javoy M (1977) Stable isotopes and geothermometry J Geol Soc, London 133:609–636
Keith TEC, Muffler LJP, Cremer M (1968) Hydrothermal epidote formed in the Salton Sea geothermal system, California. Am Mineral 53:1635–1644
Kinkel Jr AR (1962) Observations on the pyrite deposits of the Huelva District, Spain, and their relation to volcanism. Econ Geol 57(7):1071–1080
Kleyn HFW (1960) Contribution to the geology of the Odemira-Sao Luis region (Southern Protugal). Meded Geol Inst Univ. Amsterdam 255:114
Knauth PL, Lowe DR (1978) Oxygen isotope geochemistry of cherts from the Onverwacht Group (3.4 billion years), Transvaal, South Africa, with implications for secular variations in the isotopic composition of cherts. Earth Planet Sci Lett 41:209–222
Kristmannsdottir H, Tomasson J (1978) Zeolite zones in geothermal areas in Iceland. In: Sand L.B. and Mumpton F.A. (eds) Natural Zeolites, Occurrence, Properties, Use Pergamon Press, p 277–284
Lapwood ER (1948) Convection of a fluid in a porous medium. Proc Cambridge Philos Soc 44:508–521
Liou JG (1971) Synthesis and stability relations of prehnite, Ca2Al2 Si3O10(OH)2. Am Mineral 56:507–531
Lister CRB (1972) On the thermal balance of a mid-ocean ridge. Geophys JR Astron Soc 26:515–535
Lister CRB (1974) On the penetration of water into hot rock. R Astron Soc Geophys J 39:465–509
Mathews A, Beckinsale RD (1979) Oxygen isotope equilibration systematics between quartz and water. Am Mineral 64:232–240
Motll M, Holland HD (1978) Chemical exchange during hydrothermal alteration of basalt by sea water — I. Experimental results for major and minor components of seawater. Geochim Cosmochim Acta 42:1103–1115
Muehlenbachs K, Clayton RN (1972) Oxygen isotope studies of fresh and weathered submarine basalts. Can J Earth Sci 9:172–184
Munhá J (1976) Nota preliminar sobre o metamorfismo na Faixa Piritosa Portuguesa. Comun Serv Geol Port LX:151–161
Munhá J (1979) Blue amphiboles, metamorphic regime and plate tectonic modelling in the Iberian Pyrite Belt. Contrib Mineral Petrol 69:279–289
Norton D, Knight J (1977) Transport phenomena in hydrothermal systems: cooling plutons. Am J Sci 277:937–981
Norton D, Cathles LM (1979) Thermal aspects of ore deposition. In: HL Barnes (ed) Geochemistry of Hydrothermal Ore Deposits 2nd edn. Holt, Rhinehart and Winston, New York, p 611–631
Norton D, Taylor HP (1979) Quantitative simulation of the hydrothermal systems of crystallizing magmas on the basis of transport theory and oxygen isotope data: an analysis of the Skaergaard intrusion. J Petrol 20(3):421–486
Ohmoto H (1972) Systematics of sulfur and carbon isotopes in hydrothermal ore deposits. Econ Geol 67:551–579
Ohmoto H, Rye OR (1974) Hydrogen and oxygen isotope compositions of fluid inclusions in the Kuroko deposits, Japan. Econ Geol 69:947–953
Ohmoto H, Rye OR (1979) Isotopes of sulfur and carbon. In: HL Barnes (ed) Geochemistry of Hydrothermal Ore Deposits 2nd edn. Holt-Rhinehart and Winston, New York, p 509–567
Oliveira VMJ (1971) Breve nota sobre a alteração meteorica do grande filão doleritico do Alentejo e paleogeografia das formações encaixantes. I Chilage, Secção 4:Vol. 2, 781–786
Pearce JA, Cann JR (1973) Tectonic setting of basic rocks determined using trace element analysis. Earth Planet Sci Lett 19:290–300
Rambaud Perez F (1970) El sinclinal Carbonifero de Rio Tinto y sus mineralizaciones asociadas. Mem Inst Geol Mineral Espana 71:229p
Routhier P, Lecolle M, Roger G, Aye F, Molière P, Boyer C, Picot P (1977) Amas sulfures volcano-sédimentaires. La ceinture sud-ibérique à amas sulfures dans sa partie espagnole médiane. Tableau géologique et métallogénétique. Rapport final de l'action concertée. DGRST n∘ 74–7:1181
Schermerhorn LJG (1970) Mafic geosynclinal volcanism in the lower Carboniferous of South Portugal. Geol en Mijnb 48(6):439–449
Schermerhorn LJG (1971a) An outline stratigraphy of the Iberian Pyrite Belt. Bol Geol Mineral 82(III–IV):239–268
Schermerhorn LJG (1971b) Pyritite emplacement by gravity flow. Bol Geol Mineral 82(III–IV):304–308
Schermerhorn LJG (1975a) Pumpellyite facies metamorphism in the Spanish Pyrite Belt. Petrologie I(1):71–86
Schermerhorn LJG (1975b) Spilites, regional metamorphism and subduction in the Iberian Pyrite Belt. Some comments. Geol. en Mijnb. 54(1–2):23–35
Seyfried W, Bischoff JL (1977) Hydrothermal transport of heavy metals by sea water: the role of seawater/basalt ratios. Earth Planet Sci Lett 34:71–77
Sheppard SMF (1977) Identification of the origin of ore-forming solutions by the use of stable isotopes. In: Volcanic Processes in Ore Genesis.(London: Institution of Mining and Metallurgy and Geological Society, p 25–41
Spooner ETC (1977) Hydrodynamic model for the origin of the ophiolitic cupriferous pyrite ore deposits of Cyprus. In: Volcanic Processes in Ore Genesis. London: Institution of Mining and Metallurgy and Geological Society, p 58–71
Spooner ETC, Beckinsale RD, England PC, Senior A (1977) Hydration, 18O enrichment and oxydation during ocean floor hydrothermal metamorphism of ophiolitic meta-basic rocks from E. Liguria, Italy. Geochim Cosmochim Acta 41:857–871
Spooner ETC, Beckinsale RD, Fyfe WS, Smewing JD (1974) 18O enriched ophiolitic metabasic rocks from E. Liguria (Italy), Pindos (Greece), and Troodos (Cyprus). Contrib Mineral Petrol 47:41–62
Spooner ETC, Fyfe WS (1973) Sub-sea-floor metamorphism, heat and mass transfer. Contrib Mineral Petrol 42:287–304
Soler E (1973) L'association spilites quartz keratophyres du SudOuest de la Peninsule ibérique. Geol en Mijnb 52(5):277–288
Strauss GK (1970) Sobre a geologia de la provincia piritifera del Suroeste de la Peninsula Iberica y de sus yacimentos, en especial sobre la mina de pirita de Lousal (Portugal). Mem Inst Geol Mineral Espana 77
Strauss GK, Madel J, Alonso FF (1977) Exploration practice for strata-bound volcanogenic sulphide deposits in the Spanish-Portuguese Pyrite Belt. In: DD Klemm and HY Schneider (eds) Time-and-Strata-Bound Ore Deposits Springer p 56–91 Berlin Heidelberg New York
Taylor HP (1974) The application of oxygen and hydrogen isotope studies to problems of hydrothermal alteration and ore deposition. Econ Geol 69:843–883
Taylor HP (1979) Oxygen and hydrogen isotope relationships in hydrothermal mineral deposits. In: HL Barnes (ed) Geochemistry of Hydrothermal Ore Deposits, 2nd edn. Hold, Rinehart and Winston, New York p 236–277
Tomasson J, Kristmannsdottir H (1972) High temperature alteration minerals and thermal brines, Reykjanes, Iceland. Contrib Mineral Petrol 36:123–134
Wenner DB, Taylor HP (1971) Temperatures of serpentinization of ultramafic rocks based on 18O/16O fractionation between co-existing serpentine and magnetite. Contrib Mineral Petrol 32:165–185
Williams D (1966) Volcanism and are deposits. Freiberger Forsch. C210:93–111
Williams D, Stanton RL, Rambaud F (1975) The Planes-San Antonio pyritic deposit of Rio Tinto, Spain: its nature environment and genesis. Trans. Inst. Mineral Metall 84:B73-B82
Wolery TJ, Sleep NH (1976) Hydrothermal circulation and geochemical flux at mid-ocean ridges. J Geol 84:249–275
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Munhá, J., Kerrich, R. Sea water basalt interaction in spilites from the Iberian Pyrite Belt. Contr. Mineral. and Petrol. 73, 191–200 (1980). https://doi.org/10.1007/BF00371394
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DOI: https://doi.org/10.1007/BF00371394