Two-stage collision: Exploring the birth of Pangea in the Variscan terranes

TLDR: The Variscan suture exposed in NW Iberia contains a stack of terranes including two allochthonous units with continental affinity and Gondwanan provenance (Upper and Basal Units), separated by an ophiolite belt where the most common units show protolith ages at c. 395-Ma as mentioned in this paper.

About: This article is published in Gondwana Research.The article was published on 2014-03-01 and is currently open access. It has received 93 citations till now. The article focuses on the topics: Continental margin & Supercontinent.

Figures

Fig. 2. (a) Geological map of the allochthonous complexes of the NW Iberian Massif (Galicia region), and (b) composite cross section, showing the distribution and general structure of the terranes involved in the Variscan suture. The location and name of the most representative units are indicated.

Fig. 5. Sketch showing the present plate distribution in the North Caribbean region. Initial interaction between the North American and Caribbean plates generated the HP terranes and ophiolites located in northern Cuba and Hispaniola. The opening of a long pull-apart basin, which can be followed for more than 2500 km from east to west, transected the HP belts and generated new oceanic lithosphere in the Gonâve microplate. (Modified after an original NASA image with additional information from Wikimedia Commons; see also García-Casco et al. (2008) and references therein for additional information about the geology of the Caribbean region).

Fig. 4. Reconstructions showing (a) dextral motion between Gondwana and Laurussia, which favored the opening of a rather ephemeral pull-apart basin at c. 395 Ma with generation of new oceanic lithosphere, and (b) the second and final collision at c. 380– 370 Ma, which caused the accretion of buoyant oceanic lithosphere followed by new sub- duction affecting the margin of Gondwana, thereby developing a second HP–LIT metamor- phic belt. The two different HP belts and the ophiolitic units dated at c. 395 Ma can be identified in the allochthonous terranes that outline the Variscan suture from Iberia to the Bohemian Massif.

Fig. 3. Reconstructions of (a) the Rheic Ocean realm at the Silurian — Devonian boundary, and (b) the initial collision between Gondwana and Laurussia at c. 410–400 Ma, following the complete closure of the Rheic Ocean. This collision caused subduction of the most external margin of Gondwana and generated the HP–UHP metamorphic belt preserved in the allochthonous Upper Units exposed in the Variscan suture. The true Rheic Ocean suture is not represented in the mapped area of NW Iberia.

Fig. 1. Terranes and oroclines of the Variscan belt (Martínez Catalán, 2011). Arcs: BA, Bohemian; CIA, Central Iberian; IAA, Ibero-Armorican; MCA, Massif Central. Zones of the Iberian Massif: CIZ, Central Iberian; CZ, Cantabrian; GTMZ, Galicia-Trás-os-Montes; OMZ, Ossa-Morena; SPZ, South Portuguese; WALZ, West Asturian-Leonese. Shear zones and faults: BCSZ, Badajoz-Cordoba; JPSZ, Juzbado-Penalva; LPSZ, Los Pedroches; NPF, North Pyrenean; PTSZ, Porto–Tomar; SISZ, Southern Iberian. Location of the geological map and section presented in Fig. 2 are also shown.