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 African–Apulian 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 Meso–Cenozoic 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 → smectite → 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 1214–1610 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

Trace and rare earth elements contents of a Sardinian sedimentary Mn-rich deposit: preliminary results.

Mn oxides are important scavengers of trace elements from waters. They often form deposits with high metals concentrations that sometimes have economic significance. Within a thick sedimentary deposits of northern Sardinia, Mn oxide mineralization was found as both matrix and coatings on clasts of a conglomeratic deposit, and subrounded nodules in residual clays. Lithiophorite and birnessite are the sole Mn phases that are also accompanied by variable amounts of Fe oxides and hydroxides, clay minerals, and phyllosilicates. Chemical analysis of the studied samples revealed high concentrations of most of trace metals (Co, Ni, Zn, Cu, Ba, Y, U and Pb) and all rare earth elements (REE). The latter were used to provide the first hypothesis regarding environmental conditions and chemical processes determining the precipitation of Mn oxides

REEs in the North Africa P‐Bearing Deposits, Paleoenvironments, and EconomicPerspectives: AReview

AreviewofthecompositionalfeaturesofTunisia,Algeria,andMoroccophosphoritesisproposedinordertoassessandcomparethepaleoenvironmentalconditionsthatpromotedthede‐positformationaswellasprovideinformationabouttheireconomicperspectiveinlightofgrowingworldwidedemand.Sincethesedepositsshareaverysimilarchemicalandmineralogicalcomposi‐tion,theattentionwasfocusedonthegeochemistryofrareearthelements(REEs)andmostlyonΣREEs,CeandEuanomalies,and(La/Yb)and(La/Gd)normalizedratios.TheREEsdistributionsrevealseveraldifferencesbetweendepositsfromdifferentlocations,suggestingmostlythattheTu‐nisianandAlgerianphosphoritesprobablywerepartofthesamedepositionalsystem.There,sub‐reducingtosub‐oxicconditionsandamajorREEsadsorptionbyearlydiagenesiswererecorded.Conversely,intheMoroccanbasins,sub‐oxictooxicenvironmentsandaminordiageneticalterationoccurred,whichwaslikelyduetoadifferentseawatersupply.Moreover,thedrasticenvironmentalchangesassociatedtothePaleocene–EoceneThermalMaximumeventprobablyinfluencedthecom‐positionofNorthernAfricanphosphoritesthataccumulatedthehighestREEsamountsduringthatspanoftime.BasedontheREEsconcentrations,andconsideringtheoutlookcoefficientofREEcomposition(Koutl)andthepercentageofcriticalelementsin ΣREEs(REEdef),thestudieddepositscanbeconsideredaspromisingtohighlypromisingREEoresandcouldrepresentaprofitableal‐ternativesourceforcriticalREEs

Hydrogeochemistry and Groundwater Quality Assessment in the High Agri Valley (Southern Italy)

The High Agri Valley (southern Italy) is one of the largest intermontane basin of the southern Apennines affected by intensive agricultural and industrial activities. The study of groundwater chemical features provides much important information useful in water resource management. In this study, hydrogeochemical investigations coupled with multivariate statistics, saturation indices, and stable isotope composition (δD and δ18O) were conducted in the High Agri Valley to determine the chemical composition of groundwater and to define the geogenic and anthropogenic influences on groundwater quality. Twenty-four sampling point ( including well and spring waters) have been examined. The isotopic data revealed that groundwater has a meteoric origin. Well waters, located on recent alluvial-lacustrine deposits in shallow porous aquifers at the valley floor, are influenced by seasonal rainfall events and show shallow circuits; conversely, spring waters from fissured and/or karstified aquifers are probably associated to deeper and longer hydrogeological circuits. The R -mode factor analysis shows that three factors explain 94% of the total variance, and F1 represents the combined effect of dolomite and silicate dissolution to explain most water chemistry. In addition, very low contents of trace elements were detected, and their distribution was principally related to natural input. Only two well waters, used for irrigation use, show critical issue for NO3- concentrations, whose values are linked to agricultural activities. Groundwater quality strongly affects the management of water resources, as well as their suitability for domestic, agricultural, and industrial uses. Overall, our results were considered fulfilling the requirements for the inorganic component of the Water Framework Directive and Italian legislation for drinking purposes. The water quality for irrigation is from "good to permissible" to "excellent to good" although salinity and relatively high content of Mg2+ can occasionally be critical

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 (Cenomanian–Turonian) 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 (ΣREE = 1006–2034 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 “economic importance” and “supply risk” parameters, indicate the ore contains large amounts of metals characterised by a “supply risk”, such as light and heavy REEs, and metals of “economic importance”, such as V and W. In this way, the Sardinian bauxite deposits could be reconsidered as a potential source of critical raw materials

Mn- and Fe-carbonate rich layers in Meso-Cenozoic shales as proxies of environmental conditions: A case study from the southern Apennine, Italy

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