Origin and evolution of Cadomian magmatism in SW Iberia: from subduction onset and arc building to a tectonic switching

ABSTRACT

The evolution of the Gondwana along the flank of the West African Craton was complex and is far from understood. Subduction-related activity along this margin spanned between c. 750 and 500 Ma. Sections close to African cratons record the earliest stages, while Autochthonous and Allochthonous domains of the Variscan Belt preserve the latest stages of the arc system, essentially between c. 540 and 500 Ma. The geochemistry of the Ediacaran-early Cambrian siliciclastic series deposited along this Cadomian active margin preserves the evolutionary history of their sources, which are related to activity in the arc and nearby continental areas. In this sense, the SW Iberian Massif (Ossa-Morena Complex) preserves a section of this Ediacaran-early Cambrian peri-Gondwanan arc. Its evolution can be tracked through the characterization of the subduction-related magmatism (including the Mérida Massif) and coeval metasedimentary record (Serie Negra Group and Malcocinado Formation) during a time interval spanning almost 100 m.y., from pre-602 Ma to at least c. 534 Ma. This study reveals that arc magmatism is closely linked with synorogenic deposition in a complex way so far unexplored. Arc recycling is revealed by the isotopic equivalence of synorogenic strata to the first magmatic event (pre-602 Ma), and by geochronological data of the arc-building pulses. The earliest magmatic pulses (c. 602–550 Ma) are characterized by significant crustal input, likely favoured by subduction erosion. Subsequently, magmatism evolved towards larger mantle involvement (c. 540–534 Ma), likely associated with progressive variation in the slab angle. These slab-mantle-upper plate interactions generated changes in the arc dynamics leading to an extensional setting with alkaline magmatism during the Cambrian. This review proposes a model of petrogenetic and geodynamic arc evolution between the Ediacaran and the Early Cambrian. The gathered data could improve the accuracy of future palaeogeographic reconstructions for the northern margin of Gondwana.

GRAPHICAL ABSTRACT

KEYWORDS:

• Geochronology and isotopic tools
• North-African Gondwana margin
• Ediacaran-Cambrian arc
• petrogenetic and geodynamic evolution
• Cadomian terrane

Acknowledgments

We would like to express our gratitude to Francisco Manuel Pereira, Brendan Murphy, and another anonymous reviewer for the suggestions and recommendations that have helped to improve our manuscript. We appreciate their time and effort. We also thank editor Bob Stern for his consideration of our research and his editorial assistance. Financial support has been provided by the Spanish projects PID2020-112489-GB-C21 and PID2020-112489-GB-C22, funded by MCIN/AEI.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The work was supported by the Ministerio de Ciencia, Innovación y Universidades Ministerio de Ciencia, Innovación y Universidades [PID2021-122467NB-C22]; Ministerio de Ciencia, Innovación y Universidades [PID2021-125585NB-I00].