Provenance constraints from detrital zircon U–Pb ages in the NW Iberian Massif: implications for Palaeozoic plate configuration and Variscan evolution

Abstract

Detrital zircons from pre-orogenic Upper Ordovician to Devonian low-grade metasedimentary rocks have been dated by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) to: (1) constrain the variations of zircon age populations within the autochthonous sequences of NW Iberia; (2) compare U-Pb detrital zircon ages with previous data; (3) test the hypothesis of the Armorica microplate as a peri-Gondwanan terrane separated from Gondwana. The similarity in the ages of detrital zircons found in the Palaeozoic samples studied here to those published for the Upper Proterozoic, Lower Cambrian and Lower Ordovician sediments of NW Iberia argues against the separation of Armorica, and points to a common source area for all of the Palaeozoic detrital formations of NW Iberia, the West African craton and the surrounding Pan-African belts. LA-ICP-MS U-Pb dating of zircons from a synorogenic flysch preserved in klippen in the core of a syncline establishes a maximum depositional age for this deposit as Early Namurian. This age is also a maximum age limit for thrusting and refolding in this part of the Iberian Massif. Correlation of the zircon age populations with published ages confirms the link between the emplacement of the allochthonous complexes of NW Iberia and synorogenic sedimentation.

Heavy-mineral, mineral-chemical and zircon-age constraints on the provenance of Triassic sandstones from the Devon coast, southern Britain

“…The origin of the late Mesoproterozoic to early Neoproterozoic group is less certain, since the Brioverian metasediments do not contain this group (Miller et al, 2001;Samson et al, 2005), and crystalline rocks of this age do not appear to be present in the Armorican Massif (Roach et al, 1990). However, such zircons are found as detrital components of sediments in other parts of the Armorican Massif (Catalán et al, 2004;Dinis et al, 2012), and recycling from pre-existing sediment is therefore considered their most likely origin.…”

Detrital zircon and tectonostratigraphy of the Parautochthon under the Morais Complex (NE Portugal): implications for the Variscan accretionary history of the Iberian Massif

“…These allochthonous units have been interpreted as forming a Variscan accretionary prism (Ribeiro et al 1990;Martínez Catalán et al 1997) composed of units reflecting different pre-Variscan tectonic settings: a passive continental margin (including evidence of continental rifting), oceanic lithosphere, and pieces of a continental magmatic arc (Martínez Catalán et al 2009). Their relative autochthon is the Central Iberian Zone (Julivert et al 1972), regarded as a part of the Gondwana continental margin (Martínez Catalán et al 2004aNance et al 2008). This contribution deals with the geology of the southeastern end of the Galicia-Trás-os-Montes Zone, and describes the tectonostratigraphic unit occurring between the Morais Allochthonous Complex (Pereira et al 2006a;Ribeiro et al 2006) and the Central Iberian Zone, known as the Schistose Domain (Farias et al 1987), the Parautochthon (Ribeiro et al 1990), or the Parautochthonous Thrust Complex (Rodrigues et al 2006;Rodrigues 2008).…”

“…This record is marked by two regional unconformities that are the result of the stepped, yet continuous, evolution of the northern Gondwana passive margin (Gutiérrez Marco et al 1990;Martínez Catalán et al 1992;Sá et al 2005; Dias da Silva 2014). The zircon age populations of the autochthonous detrital rocks show four main age clusters (Fernández-Suárez et al 2000, 2013Gutiérrez-Alonso et al 2003;Martínez Catalán et al 2004a;Ábalos et al 2012;Pereira et al 2012;Talvera et al 2012;Teixeira et al 2012Teixeira et al , 2013Shaw et al 2014), namely Neoproterozoic-Cambrian (500-850 Ma), Stenian-Tonian (0.9-1.1 Ga), Palaeoproterozoic (1.8-2.15 Ga) and Archaean (2.5-2.7 Ga).…”

Dating cassiterite using laser ablation ICP-MS

“…In this case, multi-collector ICP-MS does not have significant advantage over ICP-MS. LA-ICP-MS is much cheaper than LA-MC-ICP-MS, which has been widely used on U-Pb dating of zircon (Allen and Campbell, 2012;Black et al, 2004;Bryan et al, 2004;Catalan et al, 2004;Liang et al, 2006;Simonetti and Neal, 2010), monazite (Kohn and Vervoort, 2008), perovskite (Cox and Wilton, 2006), baddeleyite (Horn et al, 2000), titanite and rutile (Kooijman et al, 2010;Storey et al, 2007;Zack et al, 2011), loparite (Mitchell et al, 2011) and eudialyte (Wu et al, 2010). Our results in this contribution show that LA-ICP-MS can provide cassiterite U-Pb ages comparable to those obtained using LA-MC-ICP-MS.…”