Summary
Early tentative hypotheses, that regional metamorphism may be genetically associated with the formation of mineral deposits are now reasonably confirmed, and the class of metamorphogenic mineral deposits is widely accepted. Two end member models define a range of possibilities occurring in nature: the prograde devolatilization model, and the retrograde leaching model. In the first, the mineralizing fluids are thought to have been generated and to have acquired their solute content within source rocks undergoing prograde metamorphism. Then they flow towards lower pressure zones, possibly accompanied by further reactions with country rocks. Finally, changes in the chemical or physical environment along the flow conduits potentially induce mineral precipitation. Retrograde leaching occurs after peak metamorphism, when a still-hot metamorphic complex is flooded and cooled by waters from outside; this will normally happen during uplift and extensional tectonics, and the resulting convection cells are open to the surface. Metamorphogenic deposits cannot be recognized as such in the field, where they appear as examples of epigenetic hydrothermal mineralization. Only the application of a broad spectrum of laboratory methods allows a correct genetic classification. It is expected that future research will increasingly quantify the evolution of metamorphic terranes through time, similar to modern basin analysis in petroleum geology.
Zusammenfassung
Frühe Beobachtungen über enge Zusammenhänge zwischen regionaler Metamorphose und Lagerstättenbildung wurden in jüngerer Zeit bestätigt, so daß die Klasse der metamorphogenen Lagerstätten nunmehr nahezu gesichert ist. Zwei verschiedene genetische Modelle bilden die Endglieder eines in der Natur vorkommenden Spektrums solcher Lagerstättenbildung: das Modell der prograden Devolatilisierung und das Modell einer retrograden Laugung. Im ersten Fall wurden die lagerstättenbildenden Fluide innerhalb eines Gesteinskörpers gebildet, während dieser eine prograde Metamorphose erlitt; gleichzeitig nahmen die Fluide ihre kennzeichnende Lösungsfracht auf. Danach fließen sie einem Druckgefälle folgend aus dem Bildungsraum ab, z.T. unter weiteren Reaktionen mit Nebengesteinen. Chemische oder physikalische Zustandsänderungen im Verlauf der Fließwege induzieren den Mineralabsatz. Retrograde Laugung hingegen findet statt, wenn ein noch heiβer metamorpher Komplex nach Durchlaufen der maximalen p/T-Bedingungen durch von außen zufließende Wässer geflutet und abgekühlt wird; dies wird gewöhnlich mit Aufstieg und Dehnungstektonik verbunden sein, weshalb die resultierenden Konvektionszellen zur Oberfläche offen sind. Metamorphogene Lagerstätten können nicht nur mit Feldmethoden als solche erkannt werden, da sie dort einfach als epigenetische hydrothermale Mineralisationen erscheinen. Nur die Anwendung eines breiten Spektrums geeigneter Labormethoden erlaubt eine richtige Zuordnung. Es wird erwartet, daß zukünftige Forschung dadurch wesentliche Fortschritte erzielt, daß die Entwicklung metamorpher Komplexe in Zeit und Raum quantitativ untersucht wird, ähnlich wie jene sedimentärer Becken in der modernen Erdölgeologie.
Similar content being viewed by others
References
Angel F, Trojer F (1955) Zur Frage des Alters und der Genesis alpiner Spatmagnesite. Radex Rundsch 1955: 374–392
Berning J 1986 The Rössing uranium deposit, South West Africa/Namibia. In:Anhdusser CR, Maske S (eds) Mineral deposits of Southern Africa, Vol II. Geol Soc S Africa, Johannesburg, pp 1819–1832
Cameron EM (1989) Scouring of gold from the lower crust. Geology 17: 26–29
Clar E, Friedrich 0 (1933) Ober einige Zusammenhdnge zwischen Vererzung und Metamorphose in den Ostalpen. Zeitschr Prakt Geol 41: 73–79
Craw D (1990) Regional fluid and metal mobility in the Dalradian metamorphic belt, Southern Grampian Highlands, Scotland. Mineral Deposita 25: 281–288
—— (1989) Tectonically induced hydrothermal activity and gold mineralization adjacent to major fault zones. Econ Geol Monogr 6: 471–478
Dahl N, McNaughton NJ, Groves DI (1987) A lead-isotope study of sulphides associated with gold mineralization in selected gold deposits from the Eastern Goldfields of Western Australia. Univ Western Australia Geol Dept Univ Ext Pub 11: 189–201
Duane MJ, De Wit MJ (1988) Pb-Zn ore deposits of the northern Caledonides: Products of continental scale fluid mixing and tectonic expulsion during continental collision. Geology 16: 999–1002
Ferry JM, Dipple GM (1991) Fluid flow, mineral reactions, and metasomatism. Geology 19: 211–214
Force ER, Eidel JJ,Maynard JB (Eds) (1991 Sedimentary and diagenetic mineral deposits: a basin analysis approach to exploration. Rev Econ Geol 5: 216pp Soc Econ Geol El Paso
Fyfe WS, Henley RW (1973) Some thoughts on chemical transport processes, with particular reference to gold. Mineral Sci Eng 5: 295–303
Fyfe WS, Price NJ, Thompson AB (1978) Fluids in the Earth's crust. Elsevier, Amsterdam, 383pp
Golding SD, McNaughton NJ, Barley ME, Groves DI, Ho SE, Rock NMS, Turner JV (1989) Archean carbon and oxygen reservoirs: Their significance for fluid sources and circulation paths for Archean mesothermal gold deposits of the Norseman-Wiluna belt, Western Australia. Econ Geol Monogr 6: 376–388
Groves DI, Phillips GN (1987) The genesis and tectonic controls on Archean gold deposits of the Western Australian shield: a metamorphic replacement model. Ore Geol Rev 2: 287–322
Grundmann G, Morteani G (1989) Emerald mineralization during regional metamorphism: The Habachtal (Austria) and Leydsdorp (Transvaal, South Africa) deposits. Econ Geol 84: 1835–1849
Kerrich R (1989) Lithophile element systematics of gold vein deposits in Archean greenstone belts: Implications for source processes. Econ Geol Monogr 6: 508–519
Leblanc M, Lbouabi M (1988) Native silver mineralisation along a rodingite tectonic contact between serpentinite and quartz diorite (Bou Azzer, Morocco). Econ Geol 83: 1379–1391
Marshall B, Gilligan LB (eds) (1987) Mechanical and chemical (re)mobilization of metalliferous mineralization. Ore Geol Rev 2: 1-286
Miyashiro A (1973) Metamorphism and metamorphic belts. Allen & Unwin, London, 492pp
Mueller AG, de Laeter JR, Groves DI (1991) Strontium isotope systematics of hydrothermal minerals from epigenetic Archean gold deposits in the Yilgarn Block, Western Australia. Econ Geol 86: 780–809
Nesbitt BE, Muehlenbachs K (1989) Geology, geochemistry, and genesis of mesothermal lode gold deposits of the Canadian Cordillera: Evidence for ore formation from evolved meteoric water. Econ Geol Mongr 6: 553–563
Oliver J (1986) Fluids expelled tectonically from orogenic belts: Their role in hydrocarbon migration and other geologic phenomena. Geology 14: 99–102
Perring CS, Groves DI, Ho SE (1986) Constraints on the source of auriferous fluids for Archean gold deposits. In:Ho SE, Groves DI (eds) Recent advances in understanding Precambrian Gold Deposits. Univ West Australia Publ 11, Perth, pp 287–306
Romer RL (1990) Lead mobilization during foreland metamorphism in orogenic belts. Examples from northern Sweden. Geol Rundschau 79: 693–707
Sibson RH, Moore RMcM, Rankin AH (1975) Seismic pumping-a hydrothermal transport mechanism. J Geol Sac London 131: 653–659
Stumpfl EF (1977) Sediments, ores, and metamorphism: new aspects. Phil Trans R Soc Lond A286: 507–525
Thalhammer R, Stumpfl EF, Jahoda R (1989) The Mittersill scheelite deposit, Austria. Econ Geol 84: 1153–1171
Vokes FM (1971) Some aspects of the regional metamorphic mobilization of pre-existing sulphide deposits. Mineral Deposita 6: 122–129
—— (1976) A review of the base metal deposits of the Norwegian Caledonides. In:Wolf KH (ed) Handbook of Strata-Bound and Stratiform Ore Deposits, Vol 6. Elsevier, Amsterdam, pp 79–128
Yardley B, Bottrell SH, Cliff RA (1991) Evidence for a regional-scale fluid loss event during mid-crustal metamorphism. Nature 349: 151–154
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Pohl, W. Defining metamorphogenic mineral deposits —an introduction. Mineralogy and Petrology 45, 145–152 (1992). https://doi.org/10.1007/BF01163109
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01163109