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This paper deals with the evaluation of geo- and bioavailability of trace elements, including heavy metals, present in a typical serpentinite-derived soil of the Pollino Massif (Southern Italy). Precisely, the research was aimed to (1) assess processes and factors controlling the mobility of metals in the soil in order to identify the elements "potentially harmful" for the human health, (2) estimate possible metals accumulation in horticultural crops, and (3) evaluate phyto- and genotoxicity of Cr naturally present in soils and water. The studied profile has a homogeneous mineralogical composition consisting of metal-rich phases as prevailing minerals. The three-step sequential extraction was performed on soil samples from which four fractions (exchangeable, reducible, oxidizable, and residual) were obtained and analysed by ICP-MS. The lowest contents of metals are in the exchangeable and oxidizable fractions suggesting a metal contamination is unlikely for the studied soil. Conversely, the residual and reducible fractions are the more metal enriched fractions. Among heavy metals, mainly Pb and Cd and subordinately Ni, Cr, Cu, and Zn are associated with Fe- and Mn-oxi/hydroxides that, under acidic conditions, may release the adsorbed metals in circulating water. The high contents of heavy metals, including Cr and Ni, of analysed vegetables suggest a metal transfer from soil to plant. However, no significant effects on Vicia faba seeds were observed by in vivo phyto- and genotoxicity tests. Conversely in vitro genotoxicity tests, performed on HepG2 human cell line, showed that DNA damage and cytotoxic effect depending on Cr concentration may occur.

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). [ABSTRACT FROM AUTHOR]

Supergene concentrations of lithiophorite found in alluvial conglomerates and residual sandy clay deposits of Messinian age in northern Sardinia, were investigated for minero-chemical composition and fractionation processes. The Mn concentration occurs as cement in conglomerate, coatings on pebbles and as concretions in clays. In the mineralisation, some transition metals including Ni, Cu, and Zn along with Ba, U, Pb, and REEs, are enriched relative to the composition of the upper continental crust. Zn and Ni co-vary with Mn, suggesting that they are hosted in lithiophorite. Also the REEs, with the exception of Ce, co-vary with Mn. Ce, due to its redox chemistry, fractionates relative to the other REEs and precipitates as cerianite during Mn 4 + reduction. Mn mineralisation has a different Ce signature as expressed by the Ce anomaly, which varies between 0.22 and 11.75. A two-stage model was proposed for explaining the Ce anomaly fluctuations. Precipitation of the samples with positive Ce anomalies occurred in the first stage from organic matter-free fluids which favored the oxidation of cerium on the Mn phase surface; in the second stage, instead, Ce-depleted solutions, resulting from the first stage, were responsible for the precipitation of samples with negative Ce anomalies. [ABSTRACT FROM AUTHOR]

The Mt Vulture carbonatites are the only carbonatite occurrence in the southern Apennines. We present new trace element data for these rocks in order to evaluate the factors influencing rare earth element (REE) and other trace element fractionations and their REE grade. This study focuses on massive hyalo-alvikites from two lava flows and one dike, which have different relative abundances of silicate and carbonate (i.e. Si/Ca). These differences are also evident from CaO/(CaO + MgO + FeO(T) + MnO) and Sr/Ba ratios. The REE grade of the Mt Vulture carbonatites is very similar to that of the global average for calcio-carbonatites. R-mode factor analysis shows that most of the trace element variance reflects the relative roles of carbonate and silicate minerals in influencing trace element distributions. Silicates largely control heavy rare earth element (HREE), transition metal, Zr, and Th abundances, whereas carbonate minerals control light rare earth element (LREE), Ba, and Pb abundances. In addition, apatite influences LREE concentrations. Increasing silica contents are accompanied by decreases in (La/Yb)N and (La/Sm)N ratios and less marked LREE enrichment. In contrast, higher carbonate contents are associated with increases in (La/Yb)N and (La/Sm)N. The Si/Ca ratio has little influence on Eu anomalies and middle rare earth element (MREE) to HREE fractionations. Apatite has a negligible effect on inter-REE fractionations amongst the carbonatites. [ABSTRACT FROM AUTHOR]

In the Tethyan realm, leucocratic rocks were recognized as dikes and layers outcropping in the ophiolitic rocks of the Western Alps, in Corsica, and in the Northern Apennines. Several authors have suggested that the origin of leucocratic rocks is associated with partial melting of cumulate gabbro. Major and trace elements composition and paragenesis provided information about the leucocratic rocks genetic processes. This research aims at disclosing, for the first time, the petrographical and geochemical features of Timpa delle Murge leucocratic rocks, Pollino Massif (southern Italy), in order to discuss their origin and geodynamic significance through a comparison with other Tethyan leucocratic rocks. These rocks are characterized by high amounts of silica with moderate alumina and iron-magnesium contents showing higher potassium contents than plagiogranites, due to plagioclase alteration to sericite. Plagioclase fractionation reflects negative Eu anomalies indicating its derivation from gabbroic crystal mushes. The chondrite normalized REEs patterns suggest the participation of partial melts derived from a metasomatized mantle in a subduction environment. The results reveal some similarities in composition with other Tethyan leucocratic rocks, especially those concerning Corsica and the Northern Alps. These new data provide further clues on the origin of these leucocratic rocks and the Tethyan area geodynamic evolution. [ABSTRACT FROM AUTHOR]

• The Chah-Gheib Nickel laterites is formed on the Neyriz serpentinized ultramafic rocks. • Iron oxy-hydroxides dominantly is hosted Ni, and other transition metals. • Alkaline pH condition control enrichment of transition metals and depletion of copper. • Alternating wet-dry climate allows lateritization during the Late Cretaceous-Late Paleocene period. Nickel laterites are supergene deposits derived from the weathering of ± serpentinized ultramafic rocks and they commonly accounts for over 70% of world land-based Ni resources. Serpentinized ultramafic rocks outcrop extensively in Iran as result of collision between Afro-Arabian and Iranian micro-plate during the Late Cretaceous. Two Ni-bearing laterite belts developed on the ultramafic rocks of the Neyriz ophiolite have been recently discovered in the Bavanat region (South Iran). The Chah-Gheib deposit, as the biggest Ni-bearing laterite in the Bavanat area, hosts a total estimated reserve mineralization of about 102,000 tons of ore at 0.92% Ni and 180,000 tons at 1.63% Cr. This study focuses on elemental fractionation and mineralogical control of major, trace and rare earth elements in a selected profile from the Chah-Gheib Ni-laterite, in order to assess the conditions of ore formation and its paleo-environmental significance. Four distinct horizons, including saprolite, lower limonite, upper limonite, and lateritic duricrust, have been recognized from the bottom to the top of the studied profile. Iron oxy-hydroxides are the dominant phases found in the laterite profile. Overall, Fe and other first raw transition metals (i.e. Cr, Ni, V, Co, Cu, and Zn) show abundances higher than those of the bedrock. The main Fe and Cr carriers in the laterite deposit are Fe oxy-hydroxides and chromite, respectively, although authigenic Ni- and Cr-bearing palygorskite is also common throughout the profile. Elemental mobility, estimated using Th as immobile element, showed that the major oxides are largely depleted with the exception of Fe 2 O 3 and CaO. Among trace elements, Cr is the element resulting strongly enriched in those levels where large chromite crystals occurs while V, Co, Ni, and Zn are enriched only in some levels of the upper limonite horizon and in the lateritic duricrust, likely as adsorbed cations onto iron oxy-hydroxides and as a consequence of an alkaline pH environment. Alkaline pH conditions can also explain the Cu depletion observed throughout the profile. Such a condition during lateritization appears further supported by both the occurrence of carbonates and palygorskite and by the distribution of the Ba/Sr ratio. Carbonates and palygorskite, as well as secondary quartz, require dry climate to form and alternating wet-dry climate may allow lateritization. This study suggests that the Chah-Gheib laterite formed in a subtropical climate, possibly during the Late Cretaceous-Late Paleocene period, in a roughly 25°–35° latitude range, promoting Si and Mg mobilization during the wet season and carbonates, quartz, and Mg-rich silicate precipitation during the drier periods. [ABSTRACT FROM AUTHOR]

• We studied the middle–late Permian bauxite deposits in the northwestern Iran. • Large compositional fluctuations characterize both major and trace elements. • Paleo-weathering proxies indicate climatic conditions as the Permian global warming. • Eu/Eu* and Sm/Nd indicate that deposits were mainly derived from a mafic protolith. • U/Th ratio does not necessarily reflect the protolith of karst bauxite deposits. This study focuses on the middle–late Permian bauxite deposits found within karstic depressions and sinkholes of carbonates of the Ruteh and Nessen Formations, northwestern Iran. Data concerning five karst bauxite deposits, each related to a different stratigraphic position within the bedrock, were selected to address the chemical distribution and inter-elemental relationships, especially for critical elements, factors that control bauxite formation, and the parental affinity. The analyzed samples, mainly clayey bauxite and bauxitic clay, are characterized by large compositional fluctuations involving both major and trace elements. The major element composition is dominated by SiO 2 , TiO 2 , Al 2 O 3 , and Fe 2 O 3. Among the critical elements, compositional fluctuations induce the occurrence of outliers for Co, Nb, Ta, LREE, and HREE, similar to other trace elements, such as Ba, Sr, Cr, U, and Zr. Elemental mobility indicates that most of elements are generally depleted. Among the critical elements, Co is enriched only in several samples of the older deposits, and ΣREE are enriched in some samples of the younger deposits. Factor analysis suggests that, due to the observed Al–Ga covariance, fairly acidic conditions were never attained during bauxitization, and that detrital resistant minerals concentrated during a bauxitization stage, promoting Al–Ti accumulation. Furthermore, the U co-variance with low soluble elements (Nb, Ta, and Th) suggests that U was mostly conservative during the formation of deposits. Cobalt co-varies with Cr, and these elements accumulated during later bauxitization stages, when the massive leaching of silica occurred. The CIA, CIW, and PIA paleo-weathering proxies indicate an upward weathering increase, which suggests a trend toward more extreme weathering conditions in a wetter and warmer climate, according to the Permian global warming. This is consistent with an upward increasing Ba/Sr ratio and the inspection of the A–CN–K plot, where the younger deposits fall close to the A–K edge, involving a clayey precursor requires a rainfall increase. Interestingly, the upward trend toward a warmer and wetter climate was also coupled with paleo-redox conditions promoting cerium oxidation, as depicted by the Ce/Ce* values. Finally, the Eu anomaly and the Sm/Nd ratio indicate that the studied bauxite deposits were mainly derived from a mafic protolith that formed in the middle–late Permian, as a consequence of the volcanism that affected the entire Iranian platform. A cluster of karst bauxites, however, has Eu/Eu* values lower than the average-standard deviation range of the mafic rocks, suggesting a possible contribution of a more differentiated and less mafic protolith. Similarly, the U/Th ratio, at large, supports the hypothesis of a mafic protolith for the middle–late Permian bauxite deposits, although some samples show the U/Th values well above the average-standard deviation range of the mafic rocks, likely indicating that processes promoting the accumulation of resistant minerals with high U/Th ratios cannot be excluded. This means that, in this case, the U/Th ratio does not necessarily reflect the protolith of karst bauxites and that, more in general, this proxy needs to be carefully interpreted when used to assess the parental affinity of residual rocks. [ABSTRACT FROM AUTHOR]