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Metamorphic evolution of Triassic rocks from the transition zone between the Maláguide and Alpujárride complexes (Betic Cordilleras, Spain)

¹ Departamento de Química Inorgánica, Cristalografia y Mineralogía, Facultad de Ciencias, Campus de Teatinos, Universidad de Málaga, Apartado n° 59, E-29071, Málaga, Espanña
² Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Facultad de Ciencias, E-18071 Granada, España
³ Departamento de Mineralogía y Petrología, Facultad de Ciencias, Campus de Fuentenueva, Universidad de Granada, E-18002 Granada, España

^* E-mail: mdruiz{at}uma.es

A complete sequence of mineral assemblages ranging from late diagenesis to the epizone has been identified in Triassic rocks from "intermediate units" between the Alpujárride and the Maláguide complexes (Betic Cordillera, Spain). These units appear as a set of tectonic slices, the uppermost showing lithological characteristics similar to the Maláguide complex, which change as depth increases, towards lithologies typical of the Alpujárride complex. The study was carried out by X-ray diffraction, optical microscopy, electron microprobe and X-ray fluorescence. The mineralogical composition shows a clear vertical evolution: A dickite-bearing assemblage, characteristic of the upper slices is replaced by sudoite ± pyrophyllite-bearing assemblages, these by trioctahedral chlorite-rich assemblages, and finally by paragonite-bearing assemblages. Examination of bulk-rock chemistries indicates that most of the mineralogical changes are the result of the increasing metamorphic grade, with the exception of chloritoid; its growth does appear to be partly controlled by the rocks chemistry (it is Al₂O₃ dependent). The evolution of the metamorphic assemblages occurred prior to emplacement of the slices by thrusting and reveals a progressive transition in metamorphic grade between both complexes, although some discontinuities in the KI values between consecutive slices are observed.

Key-words: chlorite, illite, paragonite, phyrophyllite, sudoite, X-ray diffraction, electron microprobe analysis: X-ray fluorescence, low-grade metamorphism, Maláguide complex, Alpujárride complex, Betic Cordilleras.

This article has been cited by other articles:

				M. D. Ruiz Cruz Na-BEARING WHITE MICAS FROM TRIASSIC ROCKS OF THE TRANSITION BETWEEN THE MALAGUIDE AND ALPUJARRIDE COMPLEXES (BETIC CORDILLERA, SPAIN) Clays and Clay Minerals, June 1, 2008; 56(3): 344 - 358. [Abstract] [Full Text] [PDF]

				M. D. R. CRUZ, F. FRANCO, C. S. DE GALDEANO, and J. NOVAK Evidence of contrasting low-grade metamorphic conditions from clay mineral assemblages in Triassic Alpujarride-Malaguide transitional units in the Betic Cordilleras, Spain Clay Minerals, June 1, 2006; 41(2): 619 - 636. [Abstract] [Full Text] [PDF]

				M. D. Ruiz Cruz and C. Sanz de Galdeano COMPOSITIONAL AND STRUCTURAL VARIATION OF SUDOITE FROM THE BETIC CORDILLERA (SPAIN): A TEM/AEM STUDY Clays and Clay Minerals, December 1, 2005; 53(6): 639 - 652. [Abstract] [Full Text] [PDF]