Contrasting Styles of Inter-Caldera Volcanism in a Peralkaline System: Case Studies from Pantelleria (Sicily Channel, Italy)

The recent (<190 ka) volcanic history of Pantelleria is characterized by the eruption of nine peralkaline ignimbrites, ranging in composition from comenditic trachyte to comendite to pantellerite. The ~46 ka Green Tuff (GT) was the last of these ignimbrites, which was followed by many effusive and explosive low-volume eruptions of pantellerite from vents within the caldera moat and along the caldera rim. Although recent studies have shed additional light on the age, petrochemistry, and volcanology of the older ignimbrites, there is very little knowledge of magmatism that occurred between these older ignimbrites, primarily due to the very scarce exposures. In this paper, we present new field descriptions and geochemical data for three local peralkaline centers never studied before, two pre-GT and one post-GT, which share a similar setting with respect to the caldera scarps but differ in terms of their age, composition, and eruptive style. These centers include: (i) the older (~125 ka) Giache center (comenditic trachyte), (ii) the ~67 ka Attalora center (comendite, pantellerite), and (iii) the younger (~14 ka) Patite center (pantellerite)

Late-Proterozoic to Paleozoic history of the peri-Gondwana Calabria–Peloritani Terrane inferred from a review of zircon chronology

U–Pb analyses of zircon from ten samples of augen gneisses, eight mafic and intermediate metaigneous rocks and six metasediments from some tectonic domains along the Calabria–Peloritani Terrane (Southern Italy) contribute to knowledge of peri-Gondwanan evolution from Late-Proterozoic to Paleozoic times. All samples were equilibrated under amphibolite to granulite facies metamorphism during the Variscan orogeny. The zircon grains of all considered samples preserve a Proterozoic memory suggestive of detrital, metamorphic and igneous origin. The available data fit a frame involving: (1) Neoproterozoic detrital input from cratonic areas of Gondwana; (2) Pan-African/Cadomian assemblage of blocks derived from East and West African Craton; (3) metamorphism and bimodal magmatism between 535 and 579 Ma, within an active margin setting; (4) rifting and opening of Ordovician basins fed by detrital input from the assembled Cadomian blocks. The Paleozoic basins evolved through sedimentation, metamorphism and magmatism during the Variscan orogeny involving Palaeozoic and pre-Paleozoic blocks. The Proterozoic zircon records decidedly decrease in the high grade metamorphic rocks affected by Variscan pervasive partial melting. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40064-016-1839-8) contains supplementary material, which is available to authorized users

Late-Hercynian post-collisional felsic and boninitic-like magmatism in central Calabria (Serre Massif, southern Italy)

Widespread late- to post-collisional magmatism occurred in the Calabria-Peloritani Orogen (Southern Italy) during the final stages of the Hercynian Orogeny. In the Serre Massif (central Calabria), medium- to high-K calcalkaline andesitic to dacitic-rhyodacitic dykes show typical geochemical features of subduction-related magmas (LILE and LREE enrichments, depletions in HFSE, peaks at Rb, Pb and Th, and troughs at Nb-Ta and Ti). The origin of late- to post-Hercynian calcalkaline rocks is usually interpreted in an extensional post-collisional framework, involving thinning of the continental lithosphere and progressive passive upwelling of asthenospheric mantle. In such a context, pure mantle, crustal and hybrid melt production likely can be generated. The andesitic dykes, with mineral chemical and geochemical composition resembling boninitic rock association, were produced by partial melting of an enriched mantle source metasomatized by crustal fluids/melts during former subduction and then suffered minor, if any, assimilation of lower crustal metapelites. Most dacite-rhyodacites were likely derived by hybridization in various proportions of crustal and mantle melts, whereas pure crustal metasedimentary sources, and more or less efficient restite unmixing processes, were involved in the generation of the most silica-rich rhyodacites

Late Triassic tholeiitic magmatism in Western Sicily: A possible extension of the Central Atlantic Magmatic Province (CAMP) in the Central Mediterranean area?

Late Triassic basaltic rocks crop out in the Lercara area in Western Sicily. Major and trace element composition, as well as Sr-Nd isotopic ratios (87Sr/86Sri=0.7074-0.7076; εNdi=from -0.69 to -1.09) of the Lercara rocks shows many similarities with Large Ion Lithophile Elements (LILE)- and Light Rare Earth Elements (LREE)-rich tholeiitic basalts of the Central Atlantic Magmatic Province (CAMP), that erupted during the Mesozoic fragmentation of the Pangea supercontinent and subsequent opening of the Central Atlantic Ocean. The geochemical features of the Lercara igneous rocks, together with the spatial distribution of the ~200Ma old CAMP rocks are unlikely to be associated with the arrival of a thermal anomaly in the form of a mantle plume and are more compatible with adiabatic melting of passively upwelling sub-lithospheric mantle. The original melts variably interacted with lower crustal rocks before reaching the surface. AFC modeling suggests two distinct differentiation paths including either simple mixing or assimilation-fractional crystallization processes involving lower crustal rocks. These interactions with continental crust indicate that an ocean basement most probably had not yet formed. © 2013 Elsevier B.V

Thermodynamic modeling assisted by multivariate statistical image analysis as a tool for unraveling metamorphic P-T-d evolution: An example from ilmenite-garnet-bearing metapelite of the Peloritani Mountains, Southern Italy

An ilmenite-garnet-bearing schist from the medium-grade metapelite complex of the Mandanici Unit in the Peloritani Mountains has been investigated to constrain the P-Tconditions attained in this sector of the southern European Hercynian chain. Microprobe investigations assisted by sta- tistical handling of X-ray maps via principal component anal- ysis allowed us to better elucidate the porphyroblast-matrix relationships, the geometry of the elemental distribution in garnet porphyroblasts and the average volume percentage of the reactant garnet during retrograde metamorphic evolution. Selected microprobe data were then used to constrain, by means of P-T pseudosections, the main P-T stages of the metamorphic evolution, using the XRF bulk-rock chemistry as the equilibrium chemical composition for the prograde and peak stages and an effective bulk-rock composition for the retrograde one. Peak metamorphic P-T estimates (~530 \ub0C; 0.9 GPa) are consistent with a Hercynian crustal thickening stage at middle-lower crustal conditions, while subsequent evolution, constrained at 420 \u2013 460 \ub0C; 0.30 \u2013 0.60 GPa, depicts a retrograde clockwise P-T trajectory linked to exhumation under likely extensional shearing conditions. The results obtained in this paper lead to envisage a new scenario for the crustal evolution of the Peloritani Mountains and stimulate a revision of previous interpretations in the light of the new investigation techniques

Tectono-metamorphic evolution of the Calabria continental lower crust: the case of the Sila Piccola Massif

International audienceA combined structural and petrological study focuses on the Sila Piccola Massif to obtain new constraints on the exhumation history of a relic fragment of the intermediate to deep portion of the Variscan basement, which now belongs to the northern Calabria Peloritani Orogen. The timescale of the early (i.e. late-Variscan) shear-assisted exhumation stage is determined by diffusion-modelling and the strain rate of the latest (i.e. Alpine) shear event is determined by microstructurally derived paleopiezometry. The intermediate to deep portion of the Sila basement is characterised by a pervasive mylonitic horizon involving orthogneiss and, to a lesser extent, garnet paragneiss. Such a pervasive mylonitic foliation widely obliterated an older metamorphic fabric, which is preserved as relics in low-strain domains. The pre-mylonitic relics consist of plagioclase, biotite, white mica, sillimanite, quartz and the first generation of chemically homogeneous garnet. Our results show that the later mylonitization can be ascribed to two metamorphic stages. The first stage is associated with a late-Variscan extensional shearing, which shows a syn-kinematic growth of a second-generation garnet with plagioclase, biotite and quartz developed in the pressure shadows of garnet porphyroclasts likely during an early retrograde metamorphic stage. The second stage, characterised by a syn-shearing growth of chlorite, white mica, plagioclase and quartz, observed along the C-planes, is interpreted as a late Alpine mylonitic overprint in compressional regime