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Prograde and retrograde diagenetic and metamorphic evolution in metapelitic rocks of Sierra Espuña (Spain)

Published online by Cambridge University Press:  09 July 2018

I . Abad*
Affiliation:
Departamento de Geología, Universidad de Jaén, 23071 Jaén, Spain
F. Nieto
Affiliation:
Instituto Andaluz de Ciencias de la Tierra y Departamento de Mineralogía y Petrología, Universidad de Granada, 18002, Granada Spain
D. R. Peacor
Affiliation:
Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109-1063, USA
N. Velilla
Affiliation:
Departamento de Mineralogía y Petrología, Universidad de Granada, 18002, Granada Spain
*
*E-mail: fnieto@ugr.es

Abstract

An unusually complete sequence of pelitic rocks ranging from diagenetic to greenschist-facies metamorphic grades occurs in southern Sierra Espun˜a, Spain. Prograde and retrograde reactions have been studied by X-ray diffraction and electron microscopy (SEM, TEM and AEM). The prograde reaction series, with reactions facilitated by tectonic stress, includes: (1) R4 interstratified illite-smectite in the diagenetic Malaguide Complex that preserves the variable orientation of original smectite packets, and has 1Md polytypism; (2) chemically heterogeneous illite and Na-K dioctahedral white micas that progressively evolve toward chemical and textural equilibrium in the anchizonal Intermediate Units; and (3) thick, defect-free packets of phengite, paragonite and clinochlore which have a typical metamorphic texture, in the Alpujarride Complex. Two superimposed retrograde episodes produced: (a) sudoite at near-peak metamorphic conditions and (b) dioctahedral smectite during low-temperature retrograde diagenesis.

Information

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2003

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