Petrogenesis of late Hercynian calc-alkaline dykes of mid-eastern Sardinia: petrographical and geochemical data constraining hybridization process

Structure and tectonic setting of the SE Sardinia mafic dyke swarm. Insights for the stress state during magma emplacement in the upper crust

“…1a). They represent around the 25% of the volume of the Sardinia batholith (Secchi and Lorrai, 2001;Vaccaro, 1990Vaccaro, , 1991, ranging in thickness between ≈1 and 15 m (Atzori et al, 2000). The contrast in dyke strike between SE and NE Sardinia was interpreted by Helbing et al (2006) to correspond with a bending structure attributed to the Alpine event.…”

“…1a), configuring the so-called Corsica-Sardinia batholith (Rossi and Cocherie, 1991;Atzori et al, 2000;Gaggero et al, 2007). Three magmatic suites can be distinguished: (i) early Mg-K calc-alkaline monzo-diorites and monzonites, (ii) peraluminous calc-alkaline granodiorites and monzogranites with subordinate tholeiitic gabbros; and (iii) metaluminous calc-alkaline to calcic gabbros and alkaline volcanic complexes.…”

Petrogenesis of post – orogenic Lower Permian andesites in southern Europe: insights into the collapse of the Variscan range

“…In a 87 Sr/ 86 Sr vs. 87 Rb/ 86 Sr diagram, the best fit line of the seven andesite samples has a slope corresponding to 275 Ma, though with a large scatter (MSWD = 644), and an initial 87 Sr/ 86 Sr = 0.7085 ± 0.0043. Without claiming that this is a reliable estimate of the andesite age, its similarity to the published ages [17,26,[68][69] indicates that the Rb-Sr isotope system has not been deeply perturbed since the crystallization of the magmas. Initial 87 Sr/ 86 Sr ratios are significantly different in the three Ligurian Alps, Southern Alps and Sardinia domains (Table 2, Fig.…”

“…The following evolution to Pangaea A along an intra-Pangaea dextral megashear system was located at the Mid Permian as a process lasting about 20 Ma. The andesite magmatism occurred in Sardinia between 291 ± 3 Ma (Rb-Sr on Bt; [68]) and 259 ± 3 Ma (Rb-Sr on Bt; [69]), between 284-274 Ma in the Ligurian Alps (U/Pb on zircon, LAM-ICP-MS; [17]) and between 283-280 Ma in the Southern Alps (U/Pb on zircon; [26]) evidencing a substantial temporal overlap, though a broad N-S diachronism. In the addressed volcano-sedimentary successions, the andesite episode should represent I) the proxy of incipient major delamination at depth, II) the tapping of deeper melts after the early rhyolite volcanism as effect of the re-equilibration of isotherms through the lower and middle crust and II) an agent of plasticization in the lithosphere rheology, precursor of the widespread dacite activity between 280 Ma (Collio basin) and 272.7±1.1 Ma (Liguria; [17]).…”

Le magmatisme basique hercynien et post-hercynien du Système central espagnol : essai de caractérisation des sources mantelliques

“…Les donnees isotopiques Sr-Nd des materiaux basiques calco-alcalins Gb2 et Gb3 se reportent dans le meme quadrant representatif des reservoirs emichis du diagramme SSr-SNd, mais leurs rapports 87Sr!86Sr sont sensiblement plus radiogeniques (de 0,7067 a 0,7087) que ceux des gabbros Gb 1. Ces suites Gb2 et Gb3 occupent un domaine trios semblable a celui de fini par d'autres roches basiques calco-alcalines tardi- hercyniennes [2,21] ou par les lamprophyres d'Europe occidentale [25]. Le second cornposant est d6fini par les larnpro phyres (camptonites) ultrabasiques alcalins (Gb4), qui se situent le long du mantle array, dans la partie ap pauvrie du champ des OIB (Fig.…”