Geochemistry and petrology of lamprophyres from the Hellenides and the European Variscides

The enriched Variscan lithosphere of NE Iberia: data from postcollisional Permian calc-alkaline lamprophyre dykes of Les Guilleries

“…Integrating the above results, major, trace-and rare-earth-element ratios suggest that the LGL magma source was probably an enriched SCLM with the composition of an amphibole-bearing spinel-garnet lherzolite that underwent low degrees of partial melting. Similar sources have been proposed for post-collisional spessartites across the Variscan Belt in the Bohemian Massif, Vosges and Black Forest (Soder, 2017). However, lamprophyre dyke swarms related to the inner parts of the orogenic belt show a wide variety of lamprophyre types with higher LILE, HSFE, REE enrichments (Fig.…”

“…Lamprophyres from Vosges and Black Forest show even lower ɛNd i values that overlap with LGL between -4 and -6, as well as the highest 87 Sr/ 86 Sr i enrichments between 0.708 and 0.712. Soder (2017) found a boundary between Saxo-thuringian granitoids and lamprophyres with higher ɛNd i and lower 87 Sr/ 86 Sr i , and the Moldanubian granitoids and lamprophyres with lower ɛNd i and higher 87 Sr/ 86 Sr i that cluster together with LGL dykes (Fig. 8B).…”

“…The calc-alkaline mafic dyke swarms of the first cycle include, in some locations, potassium-rich varieties, such as lamproites, and calc-alkaline lamprophyres (spessartites, vosgesites, kersantites and minettes), that suggest the Variscan Subcontinental Lithospheric Mantle (SCLM) sources contained enriched domains in LILE (Large Ion Lithophile Elements: Ba, K, Rb, Sr, Th, U and Pb), HFSE (High Field Strength Elements: Hf, Nb, Ta, Ti, Zr and P) and REE (Rare Earth Elements), with high 87 Sr/ 86 Sr i and low εNd i (Perini et al, 2004;Seifert, 2008;Soder, 2017). The general consensus is that these enriched domains are formed by metasomatism of the SCLM in suprasubduction zones when silica-rich, carbonatite-rich and/or asthenospheric melts penetrate mantle peridotite as vein networks (Foley, 1992;Prelević et al, 2004;Seifert, 2008;Soder, 2017). Then, when the enriched mantle domains are affected by low degree melting, potassium-rich mafic magmas with a hybrid crustal and mantle signature may form; this magma can differentiate during ascent and may emplace at different crustal levels (Awdankiewicz, 2007;Elter et al, 2004;Prelević et al, 2004;Soder, 2017).…”

“…The general consensus is that these enriched domains are formed by metasomatism of the SCLM in suprasubduction zones when silica-rich, carbonatite-rich and/or asthenospheric melts penetrate mantle peridotite as vein networks (Foley, 1992;Prelević et al, 2004;Seifert, 2008;Soder, 2017). Then, when the enriched mantle domains are affected by low degree melting, potassium-rich mafic magmas with a hybrid crustal and mantle signature may form; this magma can differentiate during ascent and may emplace at different crustal levels (Awdankiewicz, 2007;Elter et al, 2004;Prelević et al, 2004;Soder, 2017).…”

“…However, lamprophyre dyke swarms related to the inner parts of the orogenic belt show a wide variety of lamprophyre types with higher LILE, HSFE, REE enrichments (Fig. 3; 6), being the most extreme examples the lamproites and peralkaline minnetes from the Bohemian Massif and Black Forest, respectively, that formed from very low degree melting of enriched domains (Krmíček et al, 2015;Soder, 2017), not observed in the CCR. Figure 11 shows there is a compositional continuum between high-K lamproites and low-K gabbros revealing different degrees of metasomatism in Variscan SCLM, variable melting conditions and complex differentiation stories.…”