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
• Publication Date: 2013-01-01
• Authors: Mercedes Vázquez-...; Lahcen Asebriy; Ali Azdimousa; A. Jabaloy; Guillermo Booth‐Rea; L. Barbero; Marcellο Mellini; Francisco Gonzále...
• Keywords: Crenulation; Amphibole

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