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Open AccessArticle

Permo-Triassic Clastic Rocks from the Ghomaride Complex and Federico Units (Rif Cordillera, N Morocco): An Example of Diagenetic-Metamorphic Transition

1
Departamento de Química Inorgánica, Cristalografía y Mineralogía, Universidad de Málaga, 29071 Málaga, Spain
2
Departamento de Geología and CEACTierra, Universidad de Jaén, Campus Las Lagunillas s/n, 23071 Jaén, Spain
*
Author to whom correspondence should be addressed.
Minerals 2019, 9(12), 738; https://doi.org/10.3390/min9120738
Received: 26 September 2019 / Revised: 20 November 2019 / Accepted: 22 November 2019 / Published: 29 November 2019
(This article belongs to the Special Issue From Diagenesis to Low-Grade Metamorphism)
A detailed characterization of the mineralogy corresponding to the low-grade diagenetic-metamorphic sequence of the clastic rocks from the Beni Mezala antiform has allowed the processes implied in their origin to be stablished, integrating them in the geodynamic evolution of the Rif-Betic mountain range during the Alpine orogeny. A progressive evolution towards chemical and textural equilibrium was observed. The illite “crystallinity” (CIS) ranges from diagenetic-lower anchizone in Ghomaride complex (CIS: 1.50–0.37 Δ°2θ) to epizone in the deepest Federico units (CIS: 0.29–0.21 Δ°2θ). The main phyllosilicates in the diagenetic samples are illite (2M1-1M polytypes) and kaolinite, with mixed-layer illite/smectite and chlorite, but the mixed layers disappear in the lower anchizone samples, which show sudoite and dickite. Pyrophyllite is also present in the upper anchizone (0.43–0.29 Δ°2θ) whereas the epizone samples show muscovite (2M1-3T polytypes), chlorite, paragonite, and intermediate micas. The chlorite geothermometers give a T range of 150 to 400 °C, and the b parameter of 2M1 micas (8.992–9.029 Å) indicates low to intermediate pressure regional metamorphism (1–3 kbar) although the wide range of phengitic substitution in micas and the 3T polytype suggest a wider pressure range in coherence with the clockwise PTt evolution for the Rif Cordillera during the Alpine orogeny.
Keywords: anchizone; Ghomaride; illite “crystallinity”; phyllite; phyllosilicates; polytype; quartzite; SEM/TEM; sandstones; semi-empirical thermometry anchizone; Ghomaride; illite “crystallinity”; phyllite; phyllosilicates; polytype; quartzite; SEM/TEM; sandstones; semi-empirical thermometry
MDPI and ACS Style

Rodríguez-Ruiz, M.D.; Abad, I.; Bentabol, M.J. Permo-Triassic Clastic Rocks from the Ghomaride Complex and Federico Units (Rif Cordillera, N Morocco): An Example of Diagenetic-Metamorphic Transition. Minerals 2019, 9, 738.

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