Reply to the comment by Michard et al. on "Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin : The Tanger-Ketama Unit (External Rif, northern Morocco) by Vázquez et al., Geologica Acta 11 (2013), 277-293"

Michard et al. (this issue) commented on certain aspects of the Alpine metamorphism and structural evolution of the Rif belt (Morocco) that were briefly noted in Vázquez et al. (2013). In particular, they criticize our interpretation of an extensional setting during the main metamorphic recrystallization of the Tanger-Ketama Unit that we considered related to slaty cleavage (S1) parallel to the lithological layering generated during the Cretaceous. Michard et al. (this issue) interpret the S1 syn-metamorphic foliation as being related to compressional folds, and the peak metamorphism temperatures, in the Lower Cretaceous sediments, as ranging between 200-300°C. Therefore, they conclude that recrystallization of the Ketama Unit occurred during Miocene thrust nappe tectonics. We explain our view in the following sections

Reply to the comment by Michard et al. on “Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin: the Tanger-Ketama Unit (External Rif, Northern Morocco) by Vázquez et al., GeologicaActa 11 (2013)...

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Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin : the Tanger- Ketama Unit (External Rif, northern Morocco)

The distribution pattern of diagenetic conditions to very low-grade metamorphism in the eastern Rif has been determined based on a study of clay-mineral assemblages and illite crystallinity of Mesozoic metapelites. Low-grade conditions were reached in marbles and also in the Beni-Malek serpentinites, as suggested by the mineral assemblages present in the marbles and antigorite growth in serpentinites. Previous thermochronological data are based on i) 40Ar/39Ar in amphiboles from greenschists, ii) K/Ar in white micas from metasandstones, and iii) fission tracks in apatites and zircons from metasandstones. These data indicate a Late Cretaceous age (∼80 Ma) for the very low- to low-grade metamorphism. We propose an evolutionary model for the Tanger-Ketama Unit consisting of a Lower Cretaceous sequence deposited in half-graben basins over an exhumed serpentinized mantle in a setting similar to the West Galician non-volcanic margin. The sediments underwent diagenesis to very low-grade metamorphism under relatively high heat flow in this extensional setting. Miocene contractional deformation of the Tanger-Ketama Unit resulted in a penetrative crenulation cleavage associated to asymmetric inclined folds. This crenulation developed, mostly by solution-transfer processes, without significant mineral growth. Miocene metamorphism reset the apatite fission-tracks, but metamorphic conditions were not high enough to reset either the K/Ar ages or the zircon fission track

Evidence for surface uplift of the Atlas Mountains and the surrounding peripheral plateaux: Combining apatite fission-track results and geomorphic indicators in the Western Moroccan Meseta (coastal Variscan Paleozoic basement)

This work represents an initial attempt to link the evolution of the topography in relation to the general tectonic framework of western Morocco. For this purpose, in a section of the Western Moroccan Meseta different tools are combined in order to attain the general objective. Apatite fission-track (AFT) data of granitic rocks of the Rabat–Khenifra area give ages around 200 Ma with track length distributions which are compatible with the thermal models already established for the area. An inverse correlation between AFT ages and elevation is observed which is compatible with previous models indicating northward tilting of the whole Western Moroccan Meseta which is younger than 20–25 Ma. In order to test this possibility a detailed analysis of the topography at different scales in the Western Moroccan Meseta has been performed. Results indicate that two open folds with different amplitudes are recognized and that the one with wider wavelength could correspond to a lithospheric fold as previously stated by other authors on the basis of independent geological arguments. The northward tilting proposed based on the AFT data agrees with the results obtained in the analysis of the topography which reinforces the presence of a very open fold with a wavelength of 200–300 km in the north-western limb of the Western Moroccan Meseta

Detrital zircon U–Pb ages in the Rif Belt (northern Morocco): Paleogeographic implications

This dataset include detrital zircon U-Pb zircon age distributions in Mesozoic and Cenozoic rocks from the External Rif and Maghrebian Flysch Complex (Rif belt, Morocco) to test if they from part of the north-western African paleomargin, or if they are related to the Alpine Allochtonous Internal terranes. The data set show ages in the text, tables, and figures. The ages are quoted as 206Pb/238U dates for zircons younger than 1500 Ma and as 207Pb/206Pb dates for zircons older than 1500 Ma. Figures include the U–Pb concordia and the youngest zircon population plots for the studied samples. Zircons were separated using standard heavy-liquid and magnetic techniques in the Department of Geodynamics of the University of Granada. Grains were handpicked and mounted in epoxy, polished, cleaned and gold coated for cathodoluminescence (CL) imaging on a Mira3 FESEM instrument at the John de Laeter Centre (JdLC), Curtin University, Perth, Australia. LA-ICP-MS data collection was performed at the GeoHistory Facility, JdLC, Curtin University, Perth, Australia

Origine, qualité chimique et normes législatives des eaux de sources et des eaux minérales embouteillées au Maroc

International audienc

Datación por trazas de fisión de circones rosados asociados a la secuencia volcano-sedimentaria de Irra (Caldas)

Secuencias volcanoclásticas predominantemente andesiticas pertenecientes a la Formación Irra, miembro B. afloran en la margen Oriental del Rio Cauca al Occidente de Manizales. Datación por trazas de fisión en circones rosados reportan edades cercanas al límite Mioceno-Plioceno e indican actividad volcánica entre la Formación Combia (10-8 Ma) y la base del Complejo Ruíz Tolima (4 Ma).Volcaniclastic sequences, mainly andesitic, belonging to the Irra Formation. Member B. crop out in the eastern margin of the Cauca River west of Manizales. Fission track dating of pink zircons yields ages close to the Miocene-Pliocene limit and indicate volcanic activity intermediate between the Combia Formation (10-8 Ma) and the base of the Ruiz-Tolima Complex (4 Ma)

Reply to the comment by Michard et al. on "Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin : The Tanger-Ketama Unit (External Rif, northern Morocco) by Vázquez et al., Geologica Acta 11 (2013), 277-293"

Michard et al. (this issue) commented on certain aspects of the Alpine metamorphism and structural evolution of the Rif belt (Morocco) that were briefly noted in Vázquez et al. (2013). In particular, they criticize our interpretation of an extensional setting during the main metamorphic recrystallization of the Tanger-Ketama Unit that we considered related to slaty cleavage (S1) parallel to the lithological layering generated during the Cretaceous. Michard et al. (this issue) interpret the S1 syn-metamorphic foliation as being related to compressional folds, and the peak metamorphism temperatures, in the Lower Cretaceous sediments, as ranging between 200-300°C. Therefore, they conclude that recrystallization of the Ketama Unit occurred during Miocene thrust nappe tectonics. We explain our view in the following sections

Structure and exhumation of the Cap des Trois Fourches basement rocks (Eastern Rif, Morocco)

International audienceThe Cap des Trois Fourches (Eastern Rif, northern Morocco) metamorphic basement exposes two major tectonic units, namely the Taïdant unit underthrusting the overlying Tarjât tectonic unit. The Tarjât tectonic unit is composed of metamorphic rock originating from detrital material. This upper Tarjât tectonic unit exhibits: (1) orthogneiss bodies being Paleozoic in age and (2) evidences showing a retromorphose during the Alpine orogenesis. U-Pb SHRIMP zircon geochronology from the orthogneiss bodies has yielded Sakmarian (early Permian) ages for the intrusion of their protoliths. The lower Taïdant unit is formed of green and brown shales associated with quartzite beds. A Mesozoic age is commonly accepted for this unit.The internal structure of the Tarjât tectonic unit consists in km-scale folds trending ENE-WSW with an up-dip direction towards the SE. This compressional deformational stage was superimposed on internal thrust sheets controlled by ductile shear zones with a SW-vergent transport sense. The lower Taïdant unit shows conspicuous bedding associated with a penetrative foliation outlining a monocline structure dipping gently towards the NW. The major ductile-brittle detachment fault bounding the upper Tarjât tectonic unit from the lower Taïdant unit –i.e. the local basement– exhibits evidences for a top-to-the-west sense of motion. We assume that this specific fault is the prolongation into the Cap des Trois Fourches area of the extensional detachment previously described in the Temsamane area. Therefore, this low angle detachment fault is a major tectonic element extending hundreds of km through the Eastern Rif. We postulate that this major detachment roots deep in the Eastern Rif basement. This detachment is cut at the surface by the Nekor normal-sinistral strike-slip fault that separates thin 24–32 km thick metamorphic Eastern Rif crust from the 50–55 km thick crust of the Western Rif. This transtensive fault system exhumes the Rif middle crust, represented by the Temsamane massif units, along the Nekor sinistral STEP boundary at the southern edge of the Betic-Rif subduction system

Reply to the comment by Michard et al. on "Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin: The Tanger-Ketama Unit (external Rif, northern Morocco) by Vázquez et al., Geologica Acta 11 (2013)

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