Search

The magmatic rocks from Jabuka, Brusnik, Vis Islands and the submerged Brusnik plateau have been investigated to define their age and genetic affinity, identifying their role in the geodynamics of the Adria Plate. The plutonic and lava flow samples have been characterized for their petrography, mineral chemistry, whole rock major and trace elements, and Sr and Nd isotopic compositions. The two samples with the freshest plagioclase crystals have been selected for 40Ar/39Ar analysis, which gave ages of 221.5 ± 2.5 Ma (Brusnik) and 227 ± 5 Ma (Jabuka), similar to those of the Triassic magmatism from the northern part of the Adria Plate and neighbouring territories. Geochemical and isotopic data suggest that the magmatism dominantly sourced from spinel peridotites variously metasomatized during pre-Mesozoic subduction events. Furthermore, the investigated rocks evidence interactions of the magmas with Mid-Late Triassic evaporites. The comparison with other coeval magmatic occurrences from the Adria Plate and its edges shows that the subduction signature of the Triassic within-plate magmatism is mainly related to the evolution of the upper mantle of the Adria Plate.

The occurrence of phlogopite and amphibole in mantle ultramafic rocks is widely accepted as the modal effect of metasomatism in the upper mantle. However, their simultaneous formation during metasomatic events and the related sub-solidus equilibrium with the peridotite has not been extensively studied. In this work, we discuss the geochemical conditions at which the pargasite-phlogopite assemblage becomes stable, through the investigation of two mantle xenoliths from Mount Leura (Victoria State, Australia) that bear phlogopite and the phlogopite + amphibole (pargasite) pair disseminated in a harzburgite matrix. Combining a mineralogical study and thermodynamic modelling, we predict that the P–T locus of the equilibrium reaction pargasite + forsterite = Na-phlogopite + 2 diopside + spinel, over the range 1.3–3.0 GPa/540–1500 K, yields a negative Clapeyron slope of -0.003 GPa K–1 (on average). The intersection of the P–T locus of supposed equilibrium with the new mantle geotherm calculated in this work allowed us to state that the Mount Leura xenoliths achieved equilibrium at 2.3 GPa /1190 K, that represents a plausible depth of ~ 70 km. Metasomatic K-Na-OH rich fluids stabilize hydrous phases. This has been modelled by the following equilibrium equation: 2 (K,Na)-phlogopite + forsterite = 7/2 enstatite + spinel + fluid (components: Na2O,K2O,H2O). Using quantum-mechanics, semi-empirical potentials, lattice dynamics and observed thermo-elastic data, we concluded that K-Na-OH rich fluids are not effective metasomatic agents to convey alkali species across the upper mantle, as the fluids are highly reactive with the ultramafic system and favour the rapid formation of phlogopite and amphibole. In addition, oxygen fugacity estimates of the Mount Leura mantle xenoliths [Δ(FMQ) = –1.97 ± 0.35; –1.83 ± 0.36] indicate a more reducing mantle environment than what is expected from the occurrence of phlogopite and amphibole in spinel-bearing peridotites. This is accounted for by our model of full molecular dissociation of the fluid and incorporation of the O-H-K-Na species into (OH)-K-Na-bearing mineral phases (phlogopite and amphibole), that leads to a peridotite metasomatized ambient characterized by reduced oxygen fugacity.

The complex European–Adria geodynamic framework, which led to the formation of the Alpine belt, is considered responsible for the orogenic magmatism that occurred in the Central Alps along the Periadriatic/Insubric Line (late Eocene–early Oligocene) and the anorogenic magmatism that occurred in the Southeastern Alps (late Paleocene–early Miocene). While the subduction-related magmatic activities are, as expected, near convergent margins, the occurrence of the intraplate-related magmatism is still puzzling. Therefore, in this work new geochemical and geochronological data of magmatic products from the Veneto Volcanic Province (VVP, north–east Italy) are provided to constrain the Cenozoic intraplate magmatism of the Southeastern Alps. The VVP is formed by dominant basic–ultrabasic (from nephelinites to tholeiites) magmatic products and by localized acid (latitic, trachytic, and rhyolitic) volcanic and subvolcanic bodies. Trace element patterns and ratios suggest that the mantle source of the alkaline magma types was a garnet lherzolite possibly metasomatised by carbonatitic melts and with residual phlogopite. According to the biostratigraphic records and our new 40Ar/39Ar ages, VVP eruptions occurred in several pulses, reflecting the extensional phases experienced by the Eastern Alpine domain. The volcanism started in the late Paleocene in the western sector of the VVP where activity was widespread also during the Eocene (45.21 ± 0.11 Ma – 38.73 ± 0.44 Ma). In the eastern sector eruptions took place in the early Oligocene (32.35 ± 0.09 Ma – 32.09 ± 0.29 Ma) and in the early Miocene (~23–22 Ma). From the studies so far undertaken, the anorogenic magmatic activity of the VVP was interpreted as resulting from mantle upwellings through slab window(s) following the European slab break-off, which occurred at ~ 35 Ma. However, considering (i) new tomographic images evidencing a continuous subvertical (~ 500 km in depth) slab beneath the Central Alps, and (ii) the onset of magmatic activity in the VVP in the late Paleocene (i.e., before the slab break-off) and its continuation until the Miocene, a better suited geodynamic scenario is required to explain the anorogenic magmatism. The westward rollback of the European slab caused the retreat and steepening of the subducting plate. As a consequence, sub-slab mantle material escaped and upwelled from the front of the slab and created a poloidal mantle flow. The latter induced the breakdown of carbonates in calcareous metasediments and carbonated metabasics within the subducting oceanic slab, providing carbonatitic melts, which could be responsible for the metasomatism of the VVP mantle sources. After that, the poloidal mantle flow also induced (i) the extensional deformation in the overriding Adria microplate, (ii) the decompressional melting of VVP mantle sources, and (iii) the intraplate affinity of the VVP magmatism. During these processes, the Adria microplate also rotated counterclockwise, forming sedimentary basins, and allowing the poloidal mantle flow to affect different portions of the overlying lithosphere, generating syn-estensional magmatism within the VVP.

The effects of peat burning on organic‐rich agricultural soils of the Mezzano Lowland (NE Italy) were evaluated on soil profiles variously affected by smoldering. Profiles were investigated for pH, electrical conductivity, bulk density, elemental and isotopic composition of distinct carbon (and nitrogen) fractions. The results suggest that the horizons affected by carbon loss lie at depths 10–70 cm, where the highest temperatures are developed. We suggest that the exothermal oxidation of methane (mediated by biological activity) plays a significant role in the triggering mechanism. In the interested soils we estimated a potential loss of Soil Organic Carbon of approximately 110 kg m −2 within the first meter, corresponding to 580 kg CO2 m −3. The released greenhouse gas is coupled with a loss of soil structure and nutrients. Moreover, the process plausibly triggers mobility of metals bound in organometallic complexes. All these consequences negatively affect the environment, the agricultural activities and possibly also health of the local people., Key Points Peat burning in the Mezzano Lowland is a process active since wetland reclamation and variously affects the soil structure and carbon contentThe main carbon loss occurs in the depth interval 10–70 cm, where temperature up to 750°C is recordedThe process induces negative effects to surrounding environment, agriculture activities and possibly also human health

Sustainable agricultural management is needed to promote carbon (C) sequestration in soil, prevent loss of soil fertility, and reduce the release of greenhouse gases. However, the influence of agronomic practices on soil C sequestration depends on the existing pedoclimatic features. We characterized the soils of three farms far away each other in the Emilia-Romagna region (Northern Italy): an organic farm in the Northern Apennines, a biodynamic farm, and a conventional farm on the Po Plain. The total, inorganic, and organic carbon in soil, as well as the distinct humic fractions were investigated, analyzing both the elemental and isotopic (13C/12C) composition. In soils, organic matter appears to be variously affected by mineralization processes induced by microorganisms that consume organic carbon. In particular, organic carbon declined in farms located in the plain (e.g., organic carbon down to 0.75 wt%, carbon stock0-30 cm down to 33 Mg/ha), because of the warmer climate and moderately alkaline environment that enhance soil microbial activity. On the other hand, at the mountain farm, the minimum soil disturbance, the cold climate, and the neutral conditions favored soil C sequestration (organic carbon up to 4.42 wt%, carbon stock0-30 cm up to 160 Mg/ha) in humified organic compounds with long turnover, which can limit greenhouse gas emissions into the atmosphere. This work shows the need for thorough soil investigations, to propose tailored best-practices that can reconcile productivity and soil sustainability.