Some Isotopic and Geochemical Constraints on the Origin and Evolution of the Central Andean Basement (19°–24°S)

  • Klaus-Werner Damm
  • Russell S. Harmon
  • Shari Kelley

Abstract

The Central Andes of northern Chile and northwestern Argentina developed in a largely autochthonous, intracontinental setting during Proterozoic and Palaeozoic times through a recurrent sequence of extensional and compressional tectonic regimes. Exposed pre-Mesozoic rocks comprise an intricate collage of crustal complexes consisting of metamorphosed basement, intrusive rocks, and weakly metamorphosed volcanic and sedimentary strata that rest upon and are intruded by various plutonic lithologies. U-Pb Proterozoic protolith ages range from 1460 to 1210 Ma and are broadly supported by Nd-and Sr- isotope model ages. Three Preandean orogenic cycles are recognized: (1) from c. 560 to 520 Ma, (2) from c. 505 to 405 Ma, and (3) from c. 350 to 240 Ma. Apatite and zircon fission track ages indicate the earliest crustal thickening and slowest cooling within the Precordillera south of c. 23°S, in the Limon Verde complex, and in the Cordon de Lila and Sierra Almeida intrusives. Further to the north, fission track ages for zircon reflect partial annealing during the Eocene magmatic event in this region, whereas apatite ages range from 40 to 25 Ma throughout the entire Precordillera. Preandean intrusive suites vary from dioritic to granitic in bulk composition. A combination of structural and field evidence, age relations, geochemical data, and isotopic data permit discrimination between anorogenic (A-type) and synorogenic (S-type) intrusives, and point to a predominantly crustal origin for all parental magmas. No I-type granitoids are observed in the Preandean basement. Pb-Pb and Sr-Nd isotopie systematics suggest a pedogenesis for the plutonic rocks involving variable extents of mixing between lower crustal sources and lower/upper crustal assimilants. During Phanerozoic orogenic cycles, anorogenic intrusions and related continental tholeiites, generated during extensional episodes, were followed by synorogenic rocks produced when the tectonic regime changed to one of compression and crustal thickening.

Keywords

Zircon Fractionation Cretaceous Jurassic Lithosphere 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Bachmann G, Grauert B, Kramm U, Lork A, Miller H (1986) Oberkambrischer Magmatismus im Grundgebirge Nordwest Argentiniens: Isotopengeologische Untersuchungen an Granitoiden der Intrusivkomplexe von Santa Rosa de Tastil und Cañani. Berl Geowis Abh A, Sonderbd Geowiss Lateinamerika Kolloq: 111–112Google Scholar
  2. Bachmann G, Grauert B, Kramm U, Lork A, Miller H (1987) El magmatismo del cambrio Medio/Cambrico Superior en el basamento del Noroeste Argentino: investigaciones isotopicas y geochronologicas sobre los granitoides de los complejos intrusivos de Santa Rose de Tastil y Canani. X Congr Geol Argent Actes 4: 125–127Google Scholar
  3. Chappell BW, White AJR (1974) Two contrasting granite types. Pac Geol 8: 173–174Google Scholar
  4. Coira B, Davidson J, Mpodozis C, Ramos V (1982) Tectonic and magmatic evolution of the Andes in northern Argentina and Chile. Earth Sci Rev, 18: 303–332CrossRefGoogle Scholar
  5. Collins WJ, Beams SD, White AJR, Chappell BW (1982) Nature and origin of A-type granites with particular reference to southeastern Australia. Contrib Mineral Petrol 80: 189–200CrossRefGoogle Scholar
  6. Coney P (1980) Cordilleran metamorphic core complexes: an overview. Geol Soc Am Mem 153: 7–31Google Scholar
  7. Dalziel IWD, Forsythe RS (1985) Andean evolution and the terrane concept. In: Howell DG (ed) Tectonostratigraphic Terranes of the Circum-Pacific Region. Earth Sciences Series, Circum-Pacific Council for Energy and Mineral Resources 1: 565–581Google Scholar
  8. Damm K-W, Pichowiak S, Harmon RS, Todt W, Omarini R, Niemeyer H (1990) Pre-Mesozoic Evolution of the Central Andes — the basement revisited. Geol Soc Am Spec Pap 241: 101–126Google Scholar
  9. Damm, K-W, Pichowiak S, Harmon RS, Todt W, Breitkreuz C, Buchelt M (1991) The Cordon de Lila Complex, Central Andes, N-Chile: An Ordovician Continental Volcanic Province Geol. So Am Spec Paper 265: 179–188Google Scholar
  10. Goldstein SL (1988) Decoupled evolution of Nd and Sr isotopes in the continental crust and the mantle. Nature 336: 733–738CrossRefGoogle Scholar
  11. Harmon RS, Barreiro BA, Moorbath S, Hoefs J, Francis PW, Thorpe RS, Denteile B, McHugh J, Viglino JA (1984) Regional O-, Sr-, and Pb-isotope relationships in late Cenozoic calc-alkaline lavas of the Andean Cordillera. J Geol Soc 141: 803–822CrossRefGoogle Scholar
  12. Longstaffe FJ, Clarks AH, McNutt RH, Zentilli M (1983) Oxygen isotopic compositions of Central Andean plutonic and volcanic rocks. Earth Planet Sci Lett 64: 9–18CrossRefGoogle Scholar
  13. Nur A, Ben Avraham Z (1977) Lost Pacifica continent. Nature 270: 41–43CrossRefGoogle Scholar
  14. Nur A, Ben Avraham Z (1982) Oceanic plateaus, the fragmentation of continents and mountain building. J Geophys Res 87: 3644–3661CrossRefGoogle Scholar
  15. Nur A, Ben Avraham Z (1983) Displaced terranes and mountain building. In: Hsu KJ (ed) Mountain building processes. Academic Press, London, pp 73–84Google Scholar
  16. Omarini RH, Cordani UG, Viramonte JG, Salfity JA, Kawashita K (1984) Estudio geochronologico Rb-Sr de Faja Eruptiva de la Puna en el sector de San Antonio de los Cobres, provincia de Salto. 9 Congr Geol Argent Actos 3: 146–158Google Scholar
  17. O’Neil JR, Chappell BW (1977) Oxygen and hydrogen isotope relations in the Berridale batholith. J Geol Soc Lond 133: 559–571CrossRefGoogle Scholar
  18. O’Neil JR, Shaw SE, Flood RH (1977) Oxygen and hydrogen isotope compositions as indicators of granite genesis in the New England batholith, Australia. Contrib Mineral Petrol 62: 313–328CrossRefGoogle Scholar
  19. Peacock MA (1931) Classification of igneous rock series. J Geol 39: 65–67CrossRefGoogle Scholar
  20. Pearce JA, Harris NBW, Tindle AG (1984) Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. J Petrol 25: 956–983Google Scholar
  21. Pitcher WS, Atherton MP, Cobbing EJ, Beckinsale RD (1985) Magmatism at a plate edge — the Peruvian Andes. Blackie-Halsted Press, 328 ppGoogle Scholar
  22. Ramos VA (1988) Late Proterozoic-Early Paleozoic of South America — a collisional history. Episodes 11: 168–173Google Scholar
  23. Rogers G (1985) A geochemical traverse across the north Chilean Andes. PhD Thesis, The Open University Milton Keynes, 333 pp (unpubl)Google Scholar
  24. Scheuber E, Andriessen PAM (1990) The kinematic and geodynamic significance of the Atocama Fault Zone, northern Chile. J Struct Geol 12: 243–257CrossRefGoogle Scholar
  25. Stacey JS, Kramers JD (1975) Approximation to terrestrial lead isotope evolution by a two-stage model. Earth Planet Sci Lett 26: 207–221CrossRefGoogle Scholar
  26. Wilner AP, Miller H, Lottner US (1985) The evolution of the Andean convergent plate margin in the early Paleozoic between latitudes 15°S and 34°S. Communicaciones 35: 257–259Google Scholar
  27. Zartman RE, Haines SM (1988) The plumbotectonic model for Pb isotopic systematics among major terrestrial reservoirs — a case for bidirectional transport. Geochim Cosmochim Acta 52: 1327–1339CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1994

Authors and Affiliations

  • Klaus-Werner Damm
  • Russell S. Harmon
    • 1
  • Shari Kelley
  1. 1.Isotopie Geosciences LaboratoryBritish Geological SurveyKeyworth, NottinghamUK

Personalised recommendations