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Crustal attenuation as a tracer for the emplacement of the Beni Bousera ultramafic massif (Betico-Rifean belt)

2014; Geological Society of America; Volume: 126; Issue: 11-12 Linguagem: Inglês

10.1130/b31040.1

1943-2674

Antonio M. Álvarez‐Valero, Oliver Jagoutz, Jessica Stanley, Christian D. Manthei, Abdelkader El Maz, Ali Moukadiri, Alison Piasecki,

Geological and Geochemical Analysis

Research Article| November 01, 2014 Crustal attenuation as a tracer for the emplacement of the Beni Bousera ultramafic massif (Betico-Rifean belt) Antonio M. Álvarez-Valero; Antonio M. Álvarez-Valero 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA †Current address: Departamento de Geología, Universidad de Salamanca, 37008 Salamanca, Spain; aav@usal.es. Search for other works by this author on: GSW Google Scholar Oliver Jagoutz; Oliver Jagoutz 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Jessica Stanley; Jessica Stanley 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA §Current address: Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309, USA Search for other works by this author on: GSW Google Scholar Christian Manthei; Christian Manthei 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Abdelkader El Maz; Abdelkader El Maz 2Department of Geology, University Moulay Ismail, Meknes, 11201 Beni M'Hamed, Morocco Search for other works by this author on: GSW Google Scholar Ali Moukadiri; Ali Moukadiri 3Department of Geology, University Mohamed Ben Abdellah, 1796 Fès-Atlas, Morocco Search for other works by this author on: GSW Google Scholar Alison Piasecki Alison Piasecki 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA #Current address: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Antonio M. Álvarez-Valero †Current address: Departamento de Geología, Universidad de Salamanca, 37008 Salamanca, Spain; aav@usal.es. 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Oliver Jagoutz 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Jessica Stanley §Current address: Department of Geological Sciences, University of Colorado, Boulder, Colorado 80309, USA 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Christian Manthei 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Abdelkader El Maz 2Department of Geology, University Moulay Ismail, Meknes, 11201 Beni M'Hamed, Morocco Ali Moukadiri 3Department of Geology, University Mohamed Ben Abdellah, 1796 Fès-Atlas, Morocco Alison Piasecki #Current address: Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Publisher: Geological Society of America Revision Received: 23 Feb 2014 Accepted: 20 May 2014 Received: 28 Nov 2014 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2014 Geological Society of America GSA Bulletin (2014) 126 (11-12): 1614–1624. https://doi.org/10.1130/B31040.1 Article history Revision Received: 23 Feb 2014 Accepted: 20 May 2014 Received: 28 Nov 2014 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Antonio M. Álvarez-Valero, Oliver Jagoutz, Jessica Stanley, Christian Manthei, Abdelkader El Maz, Ali Moukadiri, Alison Piasecki; Crustal attenuation as a tracer for the emplacement of the Beni Bousera ultramafic massif (Betico-Rifean belt). GSA Bulletin 2014;; 126 (11-12): 1614–1624. doi: https://doi.org/10.1130/B31040.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The study of petrology (fieldwork, petrography, and phase diagram modeling) and structural data of the metapelitic granulites and the southern, high-temperature exposed peridotites in the Beni Bousera massif (northern Morocco), combined with results from previous regional studies of the Alborán, suggest a new emplacement mechanism for the mantle rocks in the Betico-Rifean belt. We document two key metamorphic episodes in the granulites within a temperature window of 710–830 ± 50 °C: (1) An earlier prograde high-pressure period (from 9 ± 1.0 to 12 ± 1.0 kbar) characterized by the assemblage garnet + biotite + kyanite + K-feldspar + rutile. Pressure differences of ∼3 kbar are found over a continuous crustal section of ∼1.5 km of exposed granulites that indicate a significant crustal attenuation during exhumation of the ultramafic rocks; and (2) a later post-kinematic low-pressure (5 ± 0.8 kbar) symplectic assemblage of cordierite + spinel + plagioclase + sillimanite.At the scale of the entire Betico-Rifean belt, two main contacts are observed as mirror images in both sides of the Alborán Sea: (1) the long axis of the high-temperature ductile contact between granulites and peridotites occurs in the west side of the Beni Bousera and Ronda massifs, coupled with (2) the consistent high-angle, east-dipping normal fault in the east parts of the belt massifs. The integration of the petrologic results with information on the rotation of both contacts reveals ductile deformation in the lower crust related to the emplacement of the ultramafic rocks in the Betico-Rifean belt along deep-reaching normal faults. The presence of the early high-temperature contact suggests that it was originally a shallow, west-dipping detachment fault developed in a back-arc environment of the east-dipping, retreating subduction zone (current western part of the Gibraltar arc).This scenario is in concordance with the tectonic evolution in western Italy, where anticlockwise Pleistocene rotations associated with northeast-directed thrusting in the Apennines—and coeval with the southeastward motion in the Calabria-Peloritani terrane—were triggered by retreat and rollback of the Adriatic-Ionian slab toward the southeast during the northwest-directed subduction beneath the Calabrian arc. 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