Age distribution of lamproites along the Socovos Fault (southern Spain) and lithospheric scale tearing

Lithospheric-scale tearing is commonly linked to the lateral termination of subduction rollback and slab segmentation. The upper-crustal expression of this process can be associated with the development of arcuate orogenic belts (oroclines) generated by a combination of vertical-axis block rotations and strike-slip faulting. However, the link between such strike-slip faults and slab tearing is relatively poorly constrained. We show here an example from the Gibraltar Arc in the westernmost Mediterranean, where lithospheric-scale tear faulting during the Late Miocene accommodated westward subduction rollback. The dextral strike-slip Socovos Fault in the eastern Betics may represent one of the surface expressions of this process. We document a high concentration of mantle-derived volcanic rocks (lamproites) along the Socovos Fault, which were intruded as dikes during the Late Miocene. Phlogopite and whole-rock 40Ar/39Ar ages of lamproites along the Socovos Fault show a spatial age zonation, with older ages (9.3-82 Ma) in the east and younger ages (7.3-7.1 Ma) in the west. This age distribution of the lamproites along the Socovos Fault is compatible with the westward retreat of the lithospheric slab that was active beneath the eastern Betics in the Late Miocene. We therefore hypothesize that tearing allowed pathways for lamproite melts in the subcontinental lithospheric mantle and lower crust with the Socovos Fault channelizing these magmas in the upper crust. (C) 2013 Elsevier B.V. All rights reserved.