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Subduction of the Neotethys Ocean resulted in collisions of continental plates, with formation of Cenozoic orogens. The different shapes and structures of various segments of these young orogens, such the Zagros Collisional Zone, suppose a complex interplay of shallow and deep structures, producing different degrees and styles of deformation. As part of the PRIN 2017 project, we analyze several types of recently acquired data (e.g., seismic tomography models of the crust and upper mantle, Moho depth, seismicity distribution, and surface topography). We find that the NW and central Zagros is characterized by a zone of thickened crust of variable width and overlain by topography that exhibits large height variations over small distances, in the central part of the collisional zone. These variations are accompanied by sharp lateral changes in the number of seismic events and velocities/temperatures at depths of ~100 km. We attribute these observations to relamination processes (i.e., the detachment of Arabian crust from the subducting lithospheric mantle and its underthrusting beneath the crust of the overriding plate), which are controlled by the variable geometry and stiffness of the overriding and subducting plates. This hypothesis is tested by performing a series of numerical experiments, using the numerical code I2VIS [1], that simulates relamination processes, occurring during continental collision. The consistency of the results is also verified through forward models of the static gravity field of the modelled structures, which are compared with the present-day observed gravity.References[1] Gerya, T.V., 2019. Cambridge University Press. ISBN 978-0-521-88754-0., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The characterization of underground structures is crucial for explorative studies in geothermal systems. As recently demonstrated, analysis of the propagation of seismic waves provides information on physical rocks’ behavior and alternative assessments of the brittle-ductile transition (BDT) depth [1]. In particular, the decay of the amplitude of the seismic waves (i.e. seismic attenuation), which is usually described by a “quality factor” Q, depending on the seismic scale, could be used as an indicator of the subsurface heterogeneities. In this study, we investigate the sensitivity of the seismic velocity and attenuation to the crustal heterogeneities, by implementing a Q seismic tomography of the Krafla volcanic system, an area affected by young tectonics and hot thermal conditions. The applied method solves for Qp perturbations, using a combination of a spectral decay technique to retrieve the attenuation operator (t*) and tomographic inversion [2]. The distribution of seismic wave velocities is obtained from a 3D tomographic inversion, using 1453 earthquakes detected from a local seismic network (2009-2012) [2,3]. The obtained Qp variations up to a depth of 4 km are interpreted together with the seismic wave velocity values [3]. The joint interpretation helps discriminate between anomalies related to temperatures and compositional heterogeneities, defining the main structures of the area. We also try to define the BDT depth, based on the strong reduction of the Qp, related to hot temperatures/melt conditions.References[1] Natale Castillo et al., 2022. https://doi.org/10.1016/j.gloplacha.2022.103978.[2] Lanza et al., 2020. https://doi.org/10.1016/j.jvolgeores.2020.106804[3] Schuler et al., 2015. https://doi:10.1002/2015JB012350, The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Different hypotheses have attempted to explain the long-lasting subsidence of the intracratonic basins, characterized by prolonged intervals of low rate subsidence, alternating with episodic accelerations in subsidence rates. Among them, the Congo Basin (CB) occupies a large part of the Congo Craton, derived from the amalgamation of different cratons. Previous studies demonstrated that the CB formed from a rift phase, during the late Mesoproterozoic. This extensional phase could have been the effect of the action of a slow multi-directional extension on a cratonic lithosphere, which has induced the initial subsidence of the CB. We investigated this tectonic scenario with 3D numerical thermomechanical models, using bi-directional N-S/E-W intra-cratonic extension with uniform velocity applied for up to 200 Myr. We assumed that the amalgamation of several cratonic blocks left a rectangular region with warm and more fertile lithosphere in the model centre, having a size of 10 % or 20 % of the total model area. Numerical results show the formation of an almost circular subsided area in the central part of the model, due to the crustal and lithospheric thinning above the asthenosphere upwelling. We also observe series of topo-graphic highs and lows inside the subsided area and significant uplift at the transition zones towards the almost undeformed cratonic parts. At a later stage (>100 Myr), the topographic depression becomes inter-sected by two nearly orthogonal, elongated rift structures (quadruple junction), which tend to raise their surface topography. These features well represent the first order heterogeneity characterizing the CB basement, considering that its depth has been further modified by tectonic and climatic events. The formed structures are input for static and dynamic forward gravity models and the outputs compared with the present-day gravity field. In this way, the consistency between the modelled and observed main structures of the CB is demonstrated.(c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Recently, the continually increasing availability of seismic data has allowed high-resolution imaging of lithospheric structure beneath the African cratons. In this study, S-wave seismic tomography is combined with high resolution satellite gravity data in an integrated approach to investigate the structure of the cratonic lithosphere of Africa. A new model for the Moho depth and data on the crustal density structure are employed along with global dynamic models to calculate residual topography and mantle gravity residuals. Corrections for thermal effects of an initially juvenile mantle are estimated based on S-wave tomography and mineral physics. Joint inversion of the residuals yields necessary compositional adjustments that allow to recalculate the thermal effects. After several iterations, we obtain a consistent model of upper mantle temperature, thermal and compositional density variations, and Mg# as a measure of depletion, as well as an improved crustal density model. Our results show that thick and cold depleted lithosphere underlies West African, northern to central eastern Congo, and Zimbabwe Cratons. However, for most of these regions, the areal extent of their depleted lithosphere differs from the respective exposed Archean shields. Meanwhile, the lithosphere of Uganda, Tanzania, most of eastern and southern Congo, and the Kaapvaal Craton is thinner, warmer, and shows little or no depletion. Furthermore, the results allow to infer that the lithosphere of the exposed Archean shields of Congo and West African cratons was depleted before the single blocks were merged into their respective cratons.

During the COVID-19 public health emergency, an increasing number of studies reported the occurrence of SARS-CoV-2 in wastewaters worldwide, but little is known about the presence of the virus in surface freshwaters. The aim of the current study was to develop and validate an appropriate and scalable methodological approach for the concentration and detection of SARS-CoV-2 from surface freshwater samples, collected within the Milan rural network subjected to flood spillways activity. Overall, both surface water and distilled water samples spiked with inactivated SARS-CoV-2 were used to validate the concentration method for pathogens determination. Two pre-filtration systems, filter paper and Sartolab

The Congo basin is one of the largest intracratonic basins in the World, locating within a cold lithospheric plate. The structure of the thick sedimentary layer is investigated by seismic studies only in limited places. Here, we present a map of sedimentary thickness for the whole Congo basin, based on the inversion of the decompensative gravity anomalies. Contrary to the conventional Bouguer or isostatic gravity anomalies, the effect of the isostatic compensation of sediments is reduced in the decompensative anomalies, which provides a possibility to recover the full effect of low-density sediments. The calculated decompensative correction reaches ±70 mGal and exceeds the amplitude of the isostatic anomalies, especially in the long wavelengths. The final decompensative anomalies are negative over the whole basin and their patterns well correspond to its tectonic fragmentation. By inverting these anomalies with the predefined density-depth relationship we have obtained the sedimentary thickness map for the whole Congo basin. The maximum basement depth exceeding 10 km is found in the Lokoro basin and basins in the South. In the Lomami basin, thickness of sediments reaches about 6.5 km. It is important to note, that these deep depressions, are not covered by seismic studies. Furthermore, we found a new deep basin adjacent to the Lokonia High (on the SW side) that we propose to name as the Salonga basin.

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 Australian continent is composed of several geologic provinces, showing a general age progression from Archean in the west to Phanerozoic in the east. The lithospheric heterogeneity and complex tectonic history of this region make it a key area for studying the thermal and rheological structure of the geological provinces and testing the influence of different conditions, such as temperature, rheology, and strain rate on the plate strength. In a previous study, temperature and compositional variations of the Australian upper mantle have been determined based on a joint interpretation of the seismic tomography and gravity data. In this study, we further implement a thermal model of the crust, based on available surface heat flow data from regional and global database. The crustal and upper mantle thermal models show different anomalies distribution, indicating a significant variation of the thermal conditions with depth. The new thermal models are used to estimate strength and effective elastic thickness (Te) distribution in the lithosphere. For this aim, we assigned the rheology of the crust based on the seismic velocities provided by the AuSREM model and used the strain rate values obtained from a global mantle flow model, constrained by seismic and gravity data. The maximal strength and Te are found in the West Australian Craton, on account of the low temperatures in the lithospheric mantle. We found that locations of the intraplate earthquakes attend to sharp changes in the lithospheric strength. Comparison of the results with those obtained for uniform rheology and strain rate, indicate that in the Officer basin the variations of the crustal rheology enhance the effect of temperature changes, while in the Yilgarn craton they reduce it. On the other hand, the lower values of the strain rate in the cratons than in the Phanerozoic regions influence the strength/Te in the opposite way with respect to temperatures.

To discern temperature and compositional variations of the Australian upper mantle, we apply an integrative technique, which jointly interprets seismic tomography and gravity data. The final thermal model, obtained by changing the upper mantle composition according to the density variations, shows temperatures higher by 100–150°C in the Archean and Proterozoic upper mantle, with respect to the initial model based on a uniform “fertile” composition. In the North and West Australian cratons, the upper mantle is cold, with composition depleted in heavy constituents. This suggests the presence of an Archean lithosphere, which remained relatively undisturbed through the Proterozoic. Central Australia is predominantly characterized by a thick, low‐temperature lithosphere having a more fertile composition. Its shallow part is characterized by a thin layer of low‐velocity mantle, which is interpreted by our results as a thermal anomaly. However, this high‐temperature anomaly is hard to reconcile with the tectonic history of the region. A low‐density mineral phase, such as amphibole, may reduce the density relative to our assumed composition. Furthermore, we observe larger iron depletion in the Western Australian Craton than in the Proterozoic terranes. At the depths larger than 150 km, the depletion becomes negligible beneath the Proterozoic regions, while it also persists in the Western Australian Craton at the depths larger than 200 km.

The Congo Basin (CB) occupies a large part of the Congo Craton, which formed from the amalgamation of different cratonic blocks of Archean age. It records the history of deposition of up to 1 Gyr of sediments, one of the longest geological records on Earth above a crystalline basement. It is considered as a typical intracratonic basin, with its slow and long-lived subsidence history and the largely unknown formation mechanisms. In this study, we analyze the gravity field in the central area of the CB, applying two different methodologies to investigate the depth of the crystalline rock basement and crustal structures. The crustal contribution to the gravity observations is determined in one case by a data driven approach, while in the other using an isostatic compensation model that includes the effect of the rigidity of the lithosphere. Both methods are constrained by density measurements from rock samples/boreholes and interpretations of the reflection seismic profiles, crossing the CB. The results obtained are quite consistent with the aeromagnetic anomalies, showing structural highs and lows, NW-SE trending, matching the axial magnetic zone. The maximum basement depth is between 10 and 18 km, depending on the gravity method and assumptions used. Furthermore, we could identify several small basins that from the interpolation of seismic profiles are not clearly resolved, such as Busira (7–9 km deep), Lokoro (10.5–12 km deep), and Salonga basins (10–11.5 km deep), in the northwestern, southeastern, and central sector of the CB, respectively. The analysis of the gravity anomalies mainly related to the crystalline crust supposes the presence of high-density bodies located in the southern part of the CB that we interpreted as related to the extensional phases that initiated the subsidence of the basin.

New seismic data on the crust and upper mantle of South America have recently become available and describe its deep structure with unprecedented resolution. Here, seismic data are combined with gravity data and mineral physics constraints to develop self‐consistent models of the temperature, composition and density of the South American lithospheric and sub‐lithospheric upper mantle. A new model of the crustal structure was developed, including sediment and average crustal density and depth to the Moho. This crustal model was used to correct the gravity field and obtain the residual topography. Then, an initial temperature model, derived from seismic tomography and mineral physics, was improved through an iterative process based on the joint inversion of gravity and residual topography. The results reveal deep cratonic roots present under wide parts of the Amazon, São Francisco and Paranapanema Cratons, but not under the Rio de la Plata and Parnaíba Cratons. These cratons probably never developed lithospheric roots or were rejuvenated during subsequent tectonic events. We hypothesize that the root of the northwestern Amazon craton was removed by upwelling of hot mantle material under the Guyana highlands. Temperature and density anomalies evident beneath the São Francisco Craton appear to be connected with those of the Paranapanema Craton, which could indicate a westward shift of its root. Depletion south of the Paranapanema Craton probably denotes remnants of a previously larger craton that was rejuvenated by the upwelling of hot mantle material leading to emplacement of the Paraná Flood Basalts.

In Finger et al. (2022), we created consistent three-dimensional models in terms of temperature, density and composition of the upper mantle of the cratonic part of the African continent by combining seismic [Celli et al., 2020] and gravity [Förste et al., 2014] data with mineral physics constraints in an iterative integrated inversion approach [Kaban et al., 2014; Tesauro et al., 2014]. Further, we calculated a new model of depth to the Moho to correct the gravity field for crustal effects and calculate the residual topography, and provide an update for the average crystalline crust density from Litho1.0 [Pasyanos et al., 2014]. To calculate depth to the Moho, data from the GSC [Global Seismic Catalog, Mooney, 2015 with updates up to 2019] were combined with those published by Globig et al. [2016]. Here, we share data used from the GSC, final models of the upper mantle and crust that are discussed in the article, as well as the test cases set up in the uncertainty assessment. The upper mantle models are given in six layers centered at 50, 100, 150, 200, 250 and 300 km. In addition, density variations determined for the crust are given in an additional layer at 15 km depth. All fields range from -40.5°N to 40.5°N and -20.5°E to 55.5°E with a 1° by 1° lateral resolution. The data is provided in binary format as three netCDF4 files, containing the final results discussed in the paper ("Results_AF"), and the two uncertainty assessment cases for an upwards/downwards shifted Moho ("Results_AF_Moho_up" / "Results_AF_Moho_down"), respectively. In addition, data extracted from "Results_AF" to create the six profiles shown in the main article, and measurements of depth to Moho from the GSC are provided as ASCII formatted .dat files.