U-Pb geochronology on zircon and columbite-group minerals of the Cap de Creus pegmatites, NE Spain

Abstract

Aquesta és una còpia de la versió author's accepted manuscrit d'un article publicat a la revista Mineralogy and petrology Abstract The Cap de Creus granitic pegmatites in the eastern Catalan Pyrenees were dated using in situ U-Pb geochronology by laser ablation ICP-MS on zircon and columbite-group minerals (CGM), which are present in the different types of pegmatites from type I (K-feldspar pegmatites, least evolved) to type IV (albite pegmatites, most evolved) and therefore allow dating the different ManuscriptClick here to download Manuscript publication_text_v9. doc 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 pegmatitic pulses. In a type III pegmatite where zircon and CGM are co-genetically associated in the same sample, both minerals were dated using zircon and tantalite reference materials, respectively, to avoid laser-induced matrix-dependent fractionation. In one sample, xenotime genetically associated with zircon was also dated. Two ages were obtained for type I and three ages for type III pegmatites. Three of these 5 ages range from 296.2 ± 2.5 to 301.9 ± 3.8 Ma and are allocated to the primary magmatic stage of crystallization and therefore to the emplacement event.Two younger ages (290.5 ± 2.5 and 292.9 ± 2.9 Ma) obtained on secondary zircon and xenotime, respectively, are interpreted as late post-solidus hydrothermal remobilization. There is no age difference between type I and type III pegmatites. The mean 299 Ma primary magmatic age allows the main late Carboniferous deformation event to be dated and is also synchronous with other peraluminous and calc-alkaline granites in the Pyrenees. However, the youngest ages around 292Ma imply that tectonics was still active in Early Permian times in the Cap de Creus area. IntroductionThe Cap de Creus peninsula (NE Spain) in the easternmost end of the Pyrenean Axial Zone is a remarkable center of interest for geologists because of its well-exposed outcrops that reveal a complex tectonic, metamorphic and magmatic history. Several episodes of deformation and regional metamorphism are accompanied by calc-alkaline and peraluminous magmatism and affected a late Proterozoic series of metasediments and metavolcanics during the Variscan orogeny. An important group of mineralized granitic pegmatites is associated with these tectonic events.The study of granitic pegmatites in Europe is gaining interest because these highly fractionated rocks are important sources of industrial minerals and strategic metals such as Li and the high field strength elements Nb-Ta and Sn (Linnen et al. 2012). In Europe rare-element granitic 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 ...

Multi-scale strainfield analysis using geostatistics: Investigating the rheological behavior of the hot Variscan crust of the Pyrenees (Axial Zone)

“…Therefore, we consider that these regional shear zones nucleated because of the emplacement of domes and plutons -themselves driven by mechanical instability during regional-scale shortening. Such an interpretation is further supported by geochronological and field structural studies arguing that steep shear zones were activated during and after the emplacement of gneiss domes and plutons (Vilà et al, 2007;Denèle et al, 2007;2009;Druguet et al, 2014;Cochelin et al, 2017;Van Lichtervelde et al, 2017).…”

Vertical strain partitioning in hot Variscan crust: Syn-convergence escape of the Pyrenees in the Iberian-Armorican syntax

“…4 and 13b) and were active until after ca. 290 Ma, i.e., the age of the youngest pegmatites they affect Van Lichtervelde et al, 2017). At least some of them must have been through-going during earlier (310-300 Ma) crustal flow of the infrastructure because they acted as magma channels at the time (Denèle et al, 2008, Fig.…”

Unusual LREE-rich, peraluminous, monazite- or allanite-bearing pegmatitic granite in the central Grenville Province, Québec

“…In granitic pegmatite fields reported in the literature, e.g. in Cap de Creus (northeastern Spain, Alfonso and Melgarejo, 2008;Druguet et al, 2014;Van Lichtervelde et al, 2016) or in Gatumba (central Rwanda, Hulsbosch et al, 2014;Melcher et al, 2015), the closest bodies from the sources (usually a granite) (i) are the least evolved, and (ii) contain biotite but no muscovite nor rare-element minerals (i.e. Li, B, Be, Rb, Sn, Nb-Ta… e.g.…”