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Correction: Trua, T.; Marani, M.P. Clinopyroxene Crystals in Basic Lavas of the Marsili Volcano Chronicle Early Magmatic Stages in a Back-Arc Transcrustal Mush System. <i>Geosciences</i> 2021, <i>11</i>, 159
No full textThe authors would like to make the following corrections to this paper [...
Comment on Gennaro et al., 2023, Lithos 456-457, 107325, Large silicic magma chambers at the Moho depth characterize the multi-level plumbing system of back-arc spreading ridges
No full textAn article (Gennaro et al., 2023, 456–457, 107325) recently published in Lithos proposes a model for the transcrustal magmatic plumbing system at the Marsili Seamount, a massive and still active volcanic centre at the Southern Tyrrhenian back-arc spreading ridge. Their model is based on a combination of geophysical and petrochemical data, the former confined to the axial zone of the Marsili volcano while the latter mostly refer to literature data dealing with samples collected from various sectors of the volcano. This comment questions the rationality of the proposed model, documenting that it is poorly constrained and, at places, incorrect
New geochemical constraints on the nature of the carbonatite signature in Ionian slab-edge magmatism (Southern Italy)
No full textThe Cenozoic basaltic volcanism in the Hyblean Plateau, southern Sicily, plays a role in the investigation of the complex Southern Tyrrhenian tectono-magmatic scenario. The geochemical features of new Hyblean rock samples presented in this study identify a hitherto overlooked variability in the carbonatitic metasomatism experienced by the continental lithospheric mantle that sourced the Hyblean magmas. Indeed, a subset of the samples exhibits a distinctive trace element signature with respect to the known Hyblean magmatism that requires significant input from a carbon-rich agent. This finding further supports the tectono-magmatic model in which fragments of the Hyblean carbonatitic metasomatized lithospheric roots were recycled in the slab-tear magmatism of the nearby Etna volcano, contributing to its anomalous high CO2 emission. Notably, the spatial variability in the carbonatitic metasomatism documented by the newly analysed Hyblean volcanic rocks suggests the idea that such variability could be a consequence of ancient metasomatic events driven by deep-mantle CO2 remobilization at the contact between the continental and oceanic lithospheric domains presently located in the Southern Tyrrhenian area. A similar scenario may have contributed to the origin of the carbonatitic signature exhibited by slab-tear volcanic sites elsewhere in this geodynamically complex area
Thermal constriction and slab tearing at the origin of a superinflated spreading ridge: Marsili volcano (Tyrrhenian Sea)
No full textRecently acquired swath bathymetry of the Marsili basin has offered an unprecedented opportunity to study the processes of back arc ocean basin development in the Tyrrhenian Sea. In particular, the detailed morphology of Marsili seamount, a large, strongly elongated volcano located in an axial position within the <2 Ma ocean crust floored Marsili basin, is a key to understanding the mechanisms governing lithosphere formation in this young basin. The basin is near circular in shape with diameter on the order of 120 km and is positioned in the southern Tyrrhenian Sea, above the steeply dipping Ionian oceanic slab of Mesozoic age. It is bounded southward by the Aeolian volcanic arc and the Calabrian accretionary wedge, surface evidence of the northwesterly directed subduction. The most outstanding feature of the basin is the elongated, 3000-m- high Marsili volcano which reveals distinctive morphology strikingly akin to the high-order segmentation and volcanic landforms described in mid-ocean slow spreading ridges. On the basis of its distinctive morphology and incremental growth relationship we propose that Marsili volcano represents a superinflated spreading ridge resulting from a distinct thermal pulse of increased melt production occuring within the young and immature Marsili basin. Surrounding cooler continental lithosphere thermally constricts ridge propagation and crust production in Marsili basin to the finite scale of Marsili volcano. Increased melt production to feed the superinflated Marsili ridge is generated by deep, lateral asthenospheric mantle flow produced at the edges of tears that bound the subducting ocean crust of the Ionian plate. Slow spreading plate separation, outpaced by the increase in magma generation, results in vertical accretion to produce the superinflated ridge. The existence of dip-directed tears delimiting the narrow Ionian slab is supported by the geological evolution of the surrounding foreland and Apennine/Maghrebid mountain belt during early/middle Pleistocene, i.e., the time of formation of the Marsili volcano. Present-day structure and volcanism furnish direct and indirect surface evidence of the presence and location of the slab tears
Coexistence of IAB-Type and OIB-type magmas in the southern Tyrrhenian back-arc basin : evidence from recent seafloor sampling and geodynamic implications
No full textThe evolution of the lithospheric mantle along the N. African Plate: Geochemical and isotopic evidence from the tholeiitic and alkaline volcanic rocks of the Hyblean plateau, Italy
No full textThe geochemical characteristics of primitive tholeiitic and alkaline volcanic rocks that erupted in the Plio-Pleistocene along fissures on the Hyblean plateau in Sicily (Italy) were used to constrain the mantle sources involved in the volcanic activity of this area of the Mediterranean. It is shown that some of the Hyblean plateau magmas with the most extreme isotopic compositions have combined radiogenic Nd, Sr and Pb, a feature that is distinct from the mixing end-members of the oceanic array. In addition, alkalinity in the basalts is found to be positively correlated with an increase in some HFSE ratios (e.g. Nb/Ta, Zr/Hf) and negatively correlated with ratios between HFSE and MREE (e.g. Ti/Eu), a characteristic that is attributed to a mantle source that has been modified by a carbonatitic metasomatic agent. This metasomatic enrichment had the effect of increasing the U/Pb of portions of the lower lithosphere, possibly by adding phases such as sodic pyroxene and apatite to the basalt-depleted lithosphere. It is suggested that rock types that formed by melting metasomatized portions of lithosphere-asthenosphere boundary affected by this recent enrichment in U/Pb fall along a trend with a shallow slope in a plot of 206pb/204pb versus 207Pb/204Pb, and have Nd isotopic compositions that are as radiogenic as present day MORB. The isotopic compositions and trace-element concentrations of the Hyblean plateau basalts are, therefore, mostly consistent with the interaction of a MORB-type mantle source with a young lithosphere that was probably formed in the Phanerozoic and metasomatized by CO2-rich fluids, possibly during the Jurassic. The absence of a geochemical component indicative of involvement of older Proterozoic lithosphere and continental crust in the evolution of these magmas distinguishes them from those erupted along the margins of the Tyrrhenian sea, and supports the suggestion that at least portions of the lithosphere underneath Sicily have oceanic affinity and may be genetically related to the adjacent Ionian abyssal plain. © Springer-Verlag 1998
Lithospheric versus crustal contamination in a bimodal basalt-rhyolite association in the central sector of Main Ethiopian Rift (MER): Sr, Nd, Pb isotopes and trace element evidence
No full textClinopyroxene crystals in basic lavas of the marsili volcano chronicle early magmatic stages in a back-arc transcrustal mush system
No full textConstraining the pre-eruptive processes that modulate the chemical evolution of erupted magmas is a challenge. An opportunity to investigate this issue is offered by the interrogation of the crystals carried in lavas. Here, we employ clinopyroxene crystals from back-arc lavas in order to identify the processes driving basalt to andesite magma evolution within a transcrustal plumbing system. The assembled clinopyroxene archive reveals that mantle melts injected at the crust-mantle transition cool and crystalize, generating a clinopyroxene-dominated mush capped by a melt-rich domain. Magma extracted from this deep storage zone fed the eruption of basalt to basaltic andesite lavas. In addition, chemically evolved melts rapidly rising from this zone briefly stalled at shallow crustal levels, sourcing crystal-poor andesite lavas. Over time, hot ascending primitive magmas intercepted and mixed with shallower cooling magma bodies forming hybrid basic lavas. The blended clinopyroxene cargoes of these lavas provide evidence for the hybridization, which is undetectable from a whole-rock chemical perspective, as mixing involved chemically similar basic magmas. The heterogeneity we found within the clinopyroxene archive is unusual since it provides, for the first time, a complete set of mush-related scenarios by which mantle melts evolve from basalt to andesite compositions. Neither the whole-rock chemistry alone nor the record of the mineral phases crystallizing subsequent to clinopyroxene can provide insights on such early magmatic processes. The obtained clinopyroxene archive can be used as a template for interpretation of the record preserved in the clinopyroxene cargoes of basalt to andesite lavas elsewhere, giving insights into the magma dynamics of the feeding plumbing system that are lost when using whole-rock chemistry
Volcanological and petrological evolution of Marsili seamount (southern Tyrrhenian Sea).
No full textNew petrological data for the Mt Iblei volcanic rocks, southeast Sicily: genetic and geotectonic implications)
No full textDuring the Cretaceous, Miocene and Plio-Quaternary time the SE Sicily was affected by widespread volcanism. Cretaceous volcanic rocks outcrop in the southern part of Sicily. They consist of basaltic flows, sometimes subaqueous, with a dominant alkaline character. Upper Miocene volcanism is characterized by numerous subaqueous eruptive centres, comprising volcaniclastic deposits interbedded with carbonate sediments. Alkaline and subalkaline magmas were contemporaneously erupted. In the Middle Upper Pliocene sequence alkaline and tholeiitic basalts are interbedded in a thick sequence of subaereal lava flows. Geochemical data suggest that the alkaline rocks could be derived by 4% and 10% of partial melting, whereas higher degrees of partial melting (35%) are necessary for the tholeiitic basalts. The association between alkaline and tholeiitic basalts can be related to the tectonics of eastern Sicily. -English summar
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