628 research outputs found
Geochemistry as a Clue for Paleoweathering and Provenance of Southern Apennines Shales (Italy): A Review
The southern Apennines (Italy) chain is a fold-and-thrust belt mainly derived from the deformation of the AfricanâApulian passive margin where shallow-water, basinal, and shelf-margin facies successions, including fine-grained sediments, occur. Here, we provide a review of the geochemistry of MesoâCenozoic shales from the Lagonegro basin to elucidate provenance and paleoweathering. The different suites of these shales are dominated by 2:1 clay minerals and are Fe shales and shales. An R-mode factor analysis suggests Ti, Al, and LREE (F1) and K2O-MgO (F2) covariance, likely related to the illite â smectite â kaolinite evolution during weathering. HREE and Y are distributed by phosphate minerals, suggesting LREE/HREE fractionation. The CIA paleoweathering proxy rules out non-steady-state weathering conditions and indicates that the source area was affected by moderate to intense weathering. The paleoprecipitation values derived from the CIA-K and CALMAG indices show median values in the 1214â1610 mm/y range. The Eu/Eu*, Sm/Nd, and Ti/Al provenance ratios point toward a UCC-like source excluding any mafic supply and suggest that the Lagonegro basin was connected, through a southern area, with the African cratonic area. However, the Eu/Eu* median value of the southern Apennine shales is quite similar to the value of the Archean shales, possibly indicating a less differentiated component. This is consistent, in many samples, with the value of the (Gd/Yb)ch ratio, suggesting that the shales likely incorporated ancient sediments derived from African Archean terranes through a cannibalistic proces
Geochemistry and Geometrical Features of the Upper Cretaceous Vitulano Para-Autochthonous Karst Bauxites (Campania Region, Southern Italy): Constraints on Genesis and Deposition
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Formation of atypical podosomes in extravillous trophoblasts regulates extracellular matrix degradation
Throughout pregnancy the cytotrophoblast, the stem cell of the placenta, gives rise to the differentiated forms of trophoblasts. The two main cell lineages are the syncytiotrophoblast and the invading extravillous trophoblast. A successful pregnancy requires extravillous trophoblasts to migrate and invade through the decidua and then remodel the maternal spiral arteries. Many invasive cells use specialised cellular structures called invadopodia or podosomes in order to degrade extracellular matrix. Despite being highly invasive cells, the presence of invadapodia or podosomes has not previously been investigated in trophoblasts. In this study these structures have been identified and characterised in extravillous trophoblasts. The role of specialised invasive structures in trophoblasts in the degradation of the extracellular matrix was compared with well characterised podosomes and invadopodia in other invasive cells and the trophoblast specific structures were characterised by using a sensitive matrix degradation assay which enabled visualisation of the structures and their dynamics. We show trophoblasts form actin rich protrusive structures which have the ability to degrade the extracellular matrix during invasion. The degradation ability and dynamics of the structures closely resemble podosomes, but have unique characteristics that have not previously been described in other cell types. The composition of these structures does not conform to the classic podosome structure, with no distinct ring of plaque proteins such as paxillin or vinculin. In addition, trophoblast podosomes protrude more deeply into the extracellular matrix than established podosomes, resembling invadopodia in this regard. We also show several significant pathways such as Src kinase, MAPK kinase and PKC along with MMP-2 and 9 as key regulators of extracellular matrix degradation activity in trophoblasts, while podosome activity was regulated by the rigidity of the extracellular matrix
Gut mesenchymal stromal cells in immunity
Mesenchymal stromal cells (MSCs), first found in bone marrow (BM), are the structural architects of all organs, participating in most biological functions. MSCs possess tissue-specific signatures that allow their discrimination according to their origin and location. Among their multiple functions, MSCs closely interact with immune cells, orchestrating their activity to maintain overall homeostasis. The phenotype of tissue MSCs residing in the bowel overlaps with myofibroblasts, lining the bottom walls of intestinal crypts (pericryptal) or interspersed within intestinal submucosa (intercryptal). In Crohnâs disease, intestinal MSCs are tightly stacked in a chronic inflammatory milieu, which causes their enforced expression of Class II major histocompatibility complex (MHC). The absence of Class II MHC is a hallmark for immune-modulator and tolerogenic properties of normal MSCs and, vice versa, the expression of HLA-DR is peculiar to antigen presenting cells, that is, immune-activator cells. Interferon gamma (IFN) is responsible for induction of Class II MHC expression on intestinal MSCs. The reversal of myofibroblasts/MSCs from an immune-modulator to an activator phenotype in Crohnâs disease results in the formation of a fibrotic tube subverting the intestinal structure. Epithelial metaplastic areas in this context can progress to dysplasia and cancer
REEs in the North Africa PâBearing Deposits, Paleoenvironments, and EconomicPerspectives: AReview
AreviewofthecompositionalfeaturesofTunisia,Algeria,andMoroccophosphoritesisproposedinordertoassessandcomparethepaleoenvironmentalconditionsthatpromotedthedeâpositformationaswellasprovideinformationabouttheireconomicperspectiveinlightofgrowingworldwidedemand.Sincethesedepositsshareaverysimilarchemicalandmineralogicalcomposiâtion,theattentionwasfocusedonthegeochemistryofrareearthelements(REEs)andmostlyonÎŁREEs,CeandEuanomalies,and(La/Yb)and(La/Gd)normalizedratios.TheREEsdistributionsrevealseveraldifferencesbetweendepositsfromdifferentlocations,suggestingmostlythattheTuânisianandAlgerianphosphoritesprobablywerepartofthesamedepositionalsystem.There,subâreducingtosubâoxicconditionsandamajorREEsadsorptionbyearlydiagenesiswererecorded.Conversely,intheMoroccanbasins,subâoxictooxicenvironmentsandaminordiageneticalterationoccurred,whichwaslikelyduetoadifferentseawatersupply.Moreover,thedrasticenvironmentalchangesassociatedtothePaleoceneâEoceneThermalMaximumeventprobablyinfluencedthecomâpositionofNorthernAfricanphosphoritesthataccumulatedthehighestREEsamountsduringthatspanoftime.BasedontheREEsconcentrations,andconsideringtheoutlookcoefficientofREEcomposition(Koutl)andthepercentageofcriticalelementsin ÎŁREEs(REEdef),thestudieddepositscanbeconsideredaspromisingtohighlypromisingREEoresandcouldrepresentaprofitablealâternativesourceforcriticalREEs
REEs and other critical raw materials in Cretaceous Mediterranean-type bauxite: the case of the Sardinian ore (Italy)
Mediterranean-type bauxite deposits in Sardinia formed during the Upper Cretaceous (CenomanianâTuronian) due to the emergence of the south European margin of the Alpine Tethys in an area affected by monsoonal climate. The deposits were controlled by the structural frame formed in a transpressive tectonic regime and unconformably overlie carbonate rocks of different age and composition, which led to the formation of different bauxite types. In general, in the Sardinian bauxite deposits, boehmite is the main Al-phase, kaolinite is the main Si-rich mineral, and hematite as well as goethite are the Fe-rich phases. Secondary authigenic anatase and detrital rutile control the Ti contents. Eu/Eu* anomalies show that the bauxite types were derived from the Variscan basement. However, there are differences in Al2O3 and SiO2 contents, which suggest there was localised variability in the extent of epigenetic replacement of kaolinite by boehmite. R-mode factor analysis suggests that most critical raw materials (as defined by the devoted European Union working group), such as Sc, Ga, Nb, Hf, Ta, and W, covary with Al2O3 contents. In the Si-poor bauxite, these metals of economic interest are likely controlled by boehmite, whereas in the Si-rich bauxite they are mostly controlled by weathering-resistant minerals. Rare earth element (REE)-rich minerals, including fluorocarbonates and cerianite, are concentrated in the basal, illuvial horizon, especially in the silica-rich bauxite (ÎŁREE = 1006â2034 ppm). Cerianite formation required Ce oxidation, whereas fluorocarbonate formation involved mobilisation of trivalent REEs and further fluoride complexation. Both REE-rich mineral phases precipitated under alkaline pH conditions near to the carbonate bedrock. Our evaluation of the critical raw materials distribution in the Sardinian bauxite, coupled with the âeconomic importanceâ and âsupply riskâ parameters, indicate the ore contains large amounts of metals characterised by a âsupply riskâ, such as light and heavy REEs, and metals of âeconomic importanceâ, such as V and W. In this way, the Sardinian bauxite deposits could be reconsidered as a potential source of critical raw materials
Petrography, Geochemistry and Mineralogy of Serpentinite Rocks Exploited in the Ophiolite Units at the Calabria-Basilicata Boundary, Southern Apennine (Italy)
Mineralogy and heavy metal assessment of the Pietra del Pertusillo reservoir sediments (Southern Italy)
The Pietra del Pertusillo freshwater reservoir is a major artificial lake of environmental, biological, and ecological importance
located in the Basilicata region, southern Italy. The reservoir arch-gravity dam was completed in 1963 for producing hydroelectric
energy and providing water for human use, and nearby there are potential sources of anthropogenic pollution such as urban
and industrial activities. For the first time, the minero-chemistry of the lake and fluvio-lacustrine sediments of the reservoir have
been evaluated to assess the environmental quality. Moreover, the composition of fluvial sediments derived from the peri-lacual
zone of the reservoir and of local outcropping bedrock were also studied to understand the factors affecting the behavior of
elements in the freshwater reservoir, with particular attention paid to heavy metals. In Italy, specific regulatory values concerning
the element threshold concentration for lake and river sediments do not exist, and for this reason, soil threshold values are
considered the standard for sediments of internal waters. The evaluation of the environmental quality of reservoir sediments has
been performed using enrichment factors obtained with respect to the average composition of a reconstructed local upper
continental crust. We suggest this method as an innovative standard in similar conditions worldwide. In the studied reservoir
sediments, the trace elements that may be of some environmental concern are Cr, Cu, Zn, As, and Pb although, at this stage, the
distribution of these elements appears to be mostly driven by geogenic processes. However, within the frame of the assessment
and the preservation of the quality of aquatic environments, particular attention has to be paid to As (which shows median value
of 10 ppm, reaching a maximum value of 26 ppm in Quaternary sediments), constantly enriched in the lacustrine samples and
especially in the fine-grained fraction (median = 8.5 ppm)
U-Pb detrital zircon ages and Hf isotope from Sardinia and Adria Cretaceous bauxite (Italy): Constraints on the Alpine Tethys paleogeography and tectonic evolution
Bauxite deposits in Italy mainly distribute in Sardinia and Adria regions within Cretaceous carbonate sequences. Parental affinity of Italian bauxite deposits has long been a controversial problem. At least four potential sources have been proposed: (1) Cretaceous debris and autochthonous marlstones; (2) alluvial sheets from the weathered Variscan basement; (3) weathering materials from North Africa and (4) Cretaceous bimodal volcanism in the Dinaric and Carpatho-Balkan orogenic belts. In this study, a total of 374 detrital zircon U-Pb ages and 86 Hf isotope values have been acquired from Cretaceous bauxites of Sardinia and Adria regions. Combining with the published geochemical data, provenances of Cretaceous bauxite deposits in Sardinia and Adria regions have been discussed. In bauxite deposits of Sardinia, dominant Early Paleozoic aged zircon grains (main age peaks at 291 â 295 Ma, 454 â 465 Ma, and 582 â 639 Ma) and their various Hf isotope compositions (ΔHf(t) = +9.61 to â5.66) indicate a parental affinity of Variscan metasedimentary basement. As a contrast, bauxite deposits in Adria show abundant Jurassic â Cretaceous (93 â 178 Ma) zircon grains with negative ΔHf(t) values (-13.75 to â4.61), demonstrating significant supply from coeval volcanic materials. Cretaceous bauxite samples from Sardinia and Adria shed light on paleogeographic restoration and tectonic evolution of Alpine Tethys. Began in Early Cretaceous, Sardinia was affected by uplift due to the subduction between Ligurian oceanic crust and the Iberia plate. The Mesozoic carbonate sequence were eroded and the underlying Variscan basement was exposed in the area from Sardinia to the Massif Meridional, provided weathering materials for bauxitization. Late Cretaceous witnessed the further NNE-trending subduction of the Adria Plate to the West Vardar oceanic plate, where calcalkaline igneous rocks and volcanic ashes from Dinarides supplied windborne weathering materials to carbonate platforms in Adria. Particularly, provenance difference between the bauxite of central-southern Apennine and Sardinian reveals that the hosting carbonate sequence in Apennine was not located on the Sardinia shelf before the Cenozoic tectonism in the south Mediterranean realm. Diversity of provenances in bauxite deposits from Sardinia and Adria may cause differences in geochemical composition and further influence qualities of bauxite ore in two regions
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