Refined tectonic evolution of the Betic-Rif orogen through integrated
3-D microstructural analysis and Sm-Nd dating of garnet porphyroblasts
Domingo Aerden
Universidad de Granada, Spain, Universidad de Granada, Spain, Universidad de Granada, Spain, Universidad de Granada, Spain, Universidad de Granada, Spain
Corresponding Author:[email protected]
Author ProfileThomas P Farrell
Boise State University,, Boise State University,, Boise State University,, Boise State University,, Boise State University,
Author ProfileMohamed L. Bouybaouene
Département de Géologie, Université de Rabat, Département de Géologie, Université de Rabat, Département de Géologie, Université de Rabat, Département de Géologie, Université de Rabat, Département de Géologie, Université de Rabat
Author ProfileAbstract
High-resolution microstructural analysis of porphyroblast inclusion
trails integrated with Sm-Nd garnet geochronology has provided new
insight into the tectonic history of the Betic-Rif orogen. Three
principal age groups of porphyroblast are demonstrated with distinctly
oriented inclusion-trails. Inclusion-trail curvature axes or ‘FIA’
(Foliation Inflexion/Intersection Axes) are shown to represent
‘fossilized’ crenulation axes from which a succession of different
crustal shortening directions can be deduced. The regional consistency
of inclusion-trail orientations and their geometric relationship with
several sets of macroscopic folds reveal the composite character of the
Gibraltar Arc formed by a superposition of different folding directions
and associated lineations. Bulk-garnet ages of 35-22Ma obtained from 5
micaschist samples of the Alpujarride-Sebtide complex (ASC) and of
35-13Ma from 4 micaschists of the Nevado-Filabride complex (NFC) allow
to deduce NNE-SSW directed shortening in the Late Eocene changing to
NW-SE shortening in the early Oligocene, alternating with suborthogonal
NE-SW shortening during the Miocene. These directions can be related to
a major swing in the direction of relative Africa-Iberia plate-motion
known from kinematic modeling of magnetic seafloor anomalies, and
dynamic interference between plate convergence and suborthogonal
‘tectonic escape’ of the Alboran Domain thereafter. Coupled to
previously established P-T-t paths, the new garnet ages support a common
tectono-metamorphic evolution of the ASC and NFC since the Late Eocene.
However, while the first became exhumed in the Middle-Miocene (15Ma),
the second experienced a re-subduction prior to being exhumed itself
about 5 Myr later.