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Contributions to Mineralogy and Petrology

, Volume 146, Issue 4, pp 513–528 | Cite as

A reappraisal of episodic burial metamorphism in the Andes of central Chile

  • D. RobinsonEmail author
  • R. E. Bevins
  • L. Aguirre
  • M. Vergara
Original Paper

Abstract

The Jurassic to Miocene sequences of the central Andes, east of Santiago, reputedly show repeated cycles of episodic sub-greenschist facies, burial metamorphism that are identified by sharp breaks in metamorphic grade at major stratigraphic boundaries. This paper presents the first detailed petrochemical analysis of these low-grade metamorphic sequences by examining the progressive development of secondary minerals, reaction progress in mafic phyllosilicates, and topological variations in the low-grade assemblages as a means of testing this model. The results indicate a progressive increase from zeolite facies through to close to the onset of greenschist facies from Miocene to Jurassic rocks. Combined analysis of reaction progress in mafic phyllosilicates and petrochemical relationships of chlorite–pumpellyite–actinolite in metabasites provides no evidence for sharp metamorphic breaks at major stratigraphic boundaries. Integrating the results presented here with the most recent models of stratigraphic/tectonic development of the central Andes shows that the metamorphism took place in two episodes, and was not episodic on a 40-million-year cycle. An absence of sharp breaks in metamorphic grade in any part of the succession, as demonstrated here, shows that the original petrographic establishment of low-grade facies provided insufficient resolution of changes in metamorphic conditions to establish definitive evidence of such breaks. Accordingly, this study suggests that re-assessment of metamorphic breaks reputedly developed in other areas of the Andean Cordillera is imperative in order to resolve the questions raised here about the origin of the low-grade metamorphism.

Keywords

Zeolite Chlorite Metamorphic Grade White Mica Greenschist Facies 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgements

This research has been undertaken thanks to the support from FONDECYT Project 1961108. Additional funding from the Royal Society (REB and DR) is acknowledged. H.W. Days, R. Offler and B. Collins are thanked for their constructive review comments.

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • D. Robinson
    • 1
    Email author
  • R. E. Bevins
    • 2
  • L. Aguirre
    • 3
  • M. Vergara
    • 3
  1. 1.Department of Earth Sciences, Wills Memorial BuildingUniversity of BristolBristol BS8 1RJUK
  2. 2.Department of GeologyNational Museum of WalesCardiffUK
  3. 3.Departamento de GeologíaUniversidad de ChileSantiagoChile

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