Cabeço de Vide Ophiolite: structure, age and correlation of an obducted marginal basin on the northern margin of Gondwana

Abstract

The Cabeço de Vide Ophiolite (SW Iberian Massif) offers new insights into the tectonic evolution of the North Africa Gondwana margin. This study presents petrological, structural, and geochronological evidence to reconstruct the Cadomian tectonic evolution of the Cabeço de Vide Ophiolite and discusses possible correlations. The Cabeço de Vide Massif experienced two Cadomian deformation phases (DC1 and DC2). Besteiros thrust (Besteiros Shear Zone) is attributed to DC1, which obducted the Cabeço de Vide Ophiolite onto the Ediacaran series deposited along the Gondwana margin (top-to-E-NE emplacement). DC2 produced a normal-sense ductile shear zone with top-to-the-SE kinematics (Cabeço de Vide Shear Zone). A cross-sectional data analysis combining geochronological evidence with U-Pb dating in calcite (marbles) and zircon (amphibolites, metagranites and metaconglomerates) constrains the age of DC1 between ca. 623–523 Ma. The same analysis suggests a Cambrian age for DC2, between ca. 523–512 Ma. The sequence, timing and kinematics of the major Cadomian structures in the study area align with those described in other sections of the Cadomian Orogen in Iberia, notably the Calzadilla Ophiolite. We propose a correlation between the Cabeço de Vide and Calzadilla ophiolites, which would emerge as two pieces of a single ophiolitic belt. This ophiolitic belt was probably obducted from a primary fore-arc basin setting inland onto Gondwana during the Cadomian Orogeny. The thrusting of the late Ediacaran ophiolites was followed by the collapse of the arc system, which was accommodated by the development of ductile extensional shear zones during the Cambrian (DC2), accompanied by uplifting, erosion and magmatism.