@misc{10481/32090,
year = {2013},
url = {http://hdl.handle.net/10481/32090},
abstract = {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 tracks.},
organization = {Financial support of Research projects
“CSD2006-0041 “TOPO-IBERIA” (CONSOLIDER-INGENIO program of the Ministerio de Ciencia e Innovación, Gobierno de España), Excelencia Project RNM-327 (Junta de Andalucía Government), AECI A/5904/06 and A/010149/07 and Research Group RNM-148 of the Junta de Andalucía.},
publisher = {Universidad de Barcelona; Instituto de Ciencias de la Tierra Jaume Almera},
keywords = {Low-grade extensional metamorphism},
keywords = {Illite crystallinity},
keywords = {Kübler index},
keywords = {Tanger-Ketama unit},
keywords = {External Rif},
keywords = {Northern Morocco},
title = {Evidence of extensional metamorphism associated to Cretaceous rifting of the North-Maghrebian passive margin: The Tanger-Ketama Unit (External Rif, northern Morocco)},
doi = {10.1344/105.000001843},
author = {Vázquez Vílchez, María Mercedes and Asebriy, L. and Azdimousa, A. and Jabaloy Sánchez, Antonio and Booth Rea, Guillermo and Barbero, Luis and Mellini, M. and González Lodeiro, Francisco},
}