This study investigates the mechanisms of arsenic (As) and other naturally occurring contaminants (F−, U, V, B, and Mo) mobilization from Quaternary sedimentary aquifers of the Main Ethiopian Rift ...(MER) and their enrichment in the local groundwater. The study is based on systematic measurements of major and trace elements as well as stable oxygen and hydrogen isotopes in groundwater, coupled with geochemical and mineralogical analyses of the aquifer rocks. The Rift Valley aquifer is composed of rhyolitic volcanics and Quaternary lacustrine sediments. X-ray fluorescence (XRF) results revealed that MER rhyolites (ash, tuff, pumice and ignimbrite) and sediments contain on average 72 wt. % and 65 wt. % SiO2, respectively. Petrographic studies of the rhyolites indicate predominance of volcanic glass, sanidine, pyroxene, Fe-oxides and plagioclase. The As content in the lacustrine sediments (mean = 6.6 mg/kg) was higher than that of the rhyolites (mean: 2.5 mg/kg). The lacustrine aquifers of the Ziway-Shala basin in the northern part of MER were identified as high As risk zones, where mean As concentration in groundwater was 22.4 ± 33.5 (range of 0.60–190 μg/L) and 54% of samples had As above the WHO drinking water guideline value of 10 μg/L. Field As speciation measurements showed that most of the groundwater samples contain predominantly (∼80%) arsenate-As(V) over arsenite-As(III) species. The As speciation together with field data of redox potential (mean Eh = +73 ± 65 mV) and dissolved-O2 (6.6 ± 2.2 mg/L) suggest that the aquifer is predominantly oxidative. Water-rock interactions, including the dissolution of volcanic glass produces groundwater with near-neutral to alkaline pH (range 6.9–8.9), predominance of Na–HCO3 ions, and high concentration of SiO2 (mean: 85.8 ± 11.3 mg/L). The groundwater data show high positive correlation of As with Na, HCO3¯, U, B, V, and Mo (R2 > 0.5; p < 0.001). Chemical modeling of the groundwater indicates that Fe-oxides and oxyhydroxides minerals were saturated in the groundwater, suggesting that the As reactivity is controlled by adsorption/desorption processes with these minerals. The data show that As and other oxyanion-forming elements such as U, B, Mo, and V had typically higher concentrations at pH > ∼8, reflecting the pH-dependence of their mobilization. Based on the geochemical and stable isotope variations we have established a conceptual model for the occurrence of naturally occurring contaminants in MER groundwater: 1) regional groundwater recharge from the Highland, along the Rift margins, followed by lateral flow and water–rock interactions with the aquifer rocks resulted in a gradual increase of the salinity and naturally occurring contaminants towards the center of the valley; and (2) local δ18O-rich lake water recharge into adjacent shallow aquifers, followed by additional mobilization of As and other oxyanion-forming elements from the aquifer rocks. We posit that the combined physical-chemical conditions of the aquifers such as oxidizing state, Na–HCO3 composition, and pH>∼8 lead to enhanced mobilization of oxyanion-forming elements from Fe-oxides and consequently contamination of local groundwater. These geochemical conditions characterize groundwater resources along the Eastern African Rift and thus constitute a potential threat to the quality of groundwater in larger areas of Eastern Africa.
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•A model of arsenic mobilization mechanism was developed in sedimentary aquifers of the Main Ethiopian Rift.•Mineralogical and geochemical composition of the aquifer rocks were reconstructed.•Field-based As-species and total As and other toxic elements concentrations were measured in Main Ethiopian Rift groundwater.•Desorption of As from iron oxides and oxyhydroxides at pH > ∼8 under oxidizing condition controls As mobilization to the groundwater.•The study has important implications for other part of East Africa Rift with similar geology.
The Mesozoic southern branch of the Neo-Tethys Ocean was located between the Arabian shield and the Sanandaj–Sirjan continental block of Iran. The Kermanshah ophiolitic complex crops out in the Main ...Zagros Thrust Zone in Iran and consists of several rock associations, which record the geodynamic evolution of this ocean. In particular, the ophiolitic rocks that record the early stage of this oceanic evolution are represented by mantle metalherzolites, metagabbros and crosscutting metabasaltic dykes, as well as by basaltic pillow lavas and dykes. Mineral chemistry and whole-rock geochemistry of the metalherzolites show that they represent portions of exhumed sub-continental mantle. Four groups of rock can be recognized within the metagabbro and volcanic/subvolcanic sequences, based on many geochemical indicators and Sr–Nd isotopic data. They are: (1) metagabbros and metadykes with a N-MORB signature; (2) alkaline basalts and trachybasalts with ocean–island basalt (OIB) affinity; (3) rocks showing plume-type MORB (P-MORB) affinity; and (4) rocks showing enriched-type MORB (E-MORB) affinity. Metagabbros and metadykes show either low or high Sm/Yb ratios, which point to a genesis from partial melting of a pure depleted MORB mantle (DMM) source or a DMM source bearing garnet-pyroxenite relics, respectively.
All volcanic and subvolcanic rock-types have variable, but generally high La/Yb, Sm/Yb, Th/Yb, Ta/Yb and Zr/Y ratios, and low Zr/Nb ratios. These features coupled with relatively low 143Nd/144Nd ratios and high 87Sr/86Sr indicate that the alkaline rocks were generated from an enriched, OIB-type (plume-type?) mantle source, whereas P- and E-MORB rocks can be interpreted as the product of variable interaction between depleted MORB-type asthenosphere and OIB-type material.
We propose a tectono-magmatic model that can explain the different rock associations cropping out in the Kermanshah ophiolites involving a type of rifted margin that is intermediate between the amagmatic Iberia/Ligurian Tethys type and the magmatic, plume-influenced East Greenland type. This model presupposes that the Sanandaj–Sirjan block was rifted from the northern margin of Arabia through passive extension, which led to the exhumation of the sub-continental mantle now represented by the metalherzolites. Meanwhile, the asthenosphere upwelling associated with the partial melting of a heterogeneous mantle source locally bearing garnet-pyroxenite relics allowed the formation of both low and high Sm/Yb N-MORB-type metagabbros and metadykes at the continent–ocean transition zone. This model is similar to the model proposed for the Ligurian Tethys. But, in contrast with the Ligurian Tethys model, extension was also associated with volcanism characterized by a marked influence of OIB-type components linked to the uprising of MORB-type, depleted asthenospheric mantle. If so, the Kermanshah ophiolites represent a particular type of continental margin ophiolite, comprising a combination of continental margin- and plume-type ophiolites.
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► The sub-continental mantle is documented for the first time in the eastern Neo-Tethys. ► Plume-related volcanics are associated with asymmetrical passive extension. ► A new rifted-margin model is proposed for the eastern Neo-Tethys.
A comprehensive study including new field, petrological and geochemical data is reported on the Jacupiranga alkaline-carbonatite complex (133–131Ma) which, together with other alkaline complexes, ...occurs in southern Brazil and is coeval with the Paraná CFB province. It consists of a shallow intrusion (ca. 65km2) in the Precambrian crystalline basement, and can be subdivided in two main diachronous plutonic bodies: an older dunite-gabbro-syenite in the NW and a younger clinopyroxenite-ijolite (s.l.) in the SE, later injected by a carbonatitic core (ca. 1km2). An integrated petrogenetic model, based on bulk rock major and trace element analyses, mineral chemistry and Sr-Nd-Pb-C isotopic data, suggests that the two silicate intrusions generated from different mantle-derived magmas that evolved at shallow level (2–3km depth) in two zoned cup-shaped plutonic bodies growing incrementally from independent feeding systems. The first intrusion was generated by OIB-like alkaline to mildly alkaline parental basalts that initially led to the formation of a dunitic adcumulate core, discontinuously surrounded by gabbroic cumulates, in turn injected by subanular syenite intrusive and phonolite dykes. Nephelinitic (±melilite) melts – likely generated deep in the lithosphere at ≥3GPa – were the parental magmas of the second intrusion and gave rise to large coarse-grained clinopyroxenite ad- to meso-cumulates, in turn surrounded, and partially cut, by semi-annular fine-layered melteigite-ijolite-urtite ortho-cumulates. The available isotopic data do not evidence genetic links between carbonatites and the associated silicate intrusions, thus favouring an independent source from the mantle. Moreover, it may be suggested that, unlike gabbro-syenites and carbonatites, mostly generated from lithospheric mantle sources, the parental magmas of the ijolite-clinopyroxenite intrusion also record the influence of sublithospheric (plume-related?) geochemical components.
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•The Jacupiranga intrusions generated from alkali-basalt and nephelinitic parents•Mineral composition and phase equilibria indicate shallow level fractionation.•Zoned, cup shaped intrusions were fed independently and grown incrementally.•Carbonatites do not show genetic links with the associated silicate intrusions.•Sr-Nd-Pb isotopic composition reflects lithospheric and sublithospheric signatures.
The occurrence of rhyolite melts in the mantle has been predicted by high pressure-high temperature experiments but never observed in nature. Here we report natural quartz-bearing rhyolitic melt ...inclusions and interstitial glass within peridotite xenoliths. The oxygen isotope composition of quartz crystals shows the unequivocal continental crustal derivation of these melts, which approximate the minimum composition in the quartz-albite-orthoclase system. Thermodynamic modelling suggests rhyolite was originated from partial melting of near-anhydrous garnet-bearing metapelites at temperatures ~1000 °C and interacted with peridotite at pressure ~1 GPa. Reaction of rhyolite with olivine converted lherzolite rocks into orthopyroxene-domains and orthopyroxene + plagioclase veins. The recognition of rhyolitic melts in the mantle provides direct evidence for element cycling through earth's reservoirs, accommodated by dehydration and melting of crustal material, brought into the mantle by subduction, chemically modifying the mantle source, and ultimately returning to surface by arc magmatism.
In the Adriatic lagoons of northern Italy, manila clam (
) farming provides important socio-economic returns and local clams should be registered with the Protected Designations of Origin scheme. ...Therefore, there is a need for the development of rapid, cost-effective tests to guarantee the origin of the product and to prevent potential fraud. In this work, an elemental analysis (EA) coupled with isotope ratio mass spectrometry (IRMS) was employed to identify the isotopic fingerprints of clams directly collected onsite in three Adriatic lagoons and bought at a local supermarket, where they exhibited certification. In particular, a multivariate analysis of C/N, δ
C and δ
N in manila clam tissues as well as δ
C in shells and Δ
C (calculated as δ
C
-δ
C
) seems a promising approach for tracking the geographical origin of manila clams at the regional scale.
A comprehensive tectono-magmatic model based on new geochemical and field data is discussed in order to highlight the significance of the high-TiO
2 bimodal picrite basalt/rhyolite association in the ...north-eastern sector of the Ethiopian Plateau, which is considered to be the axial zone of the 30
Ma Continental Flood Basalt activity related to the Afar plume (Beccaluva et al., 2009). In this area the volcanic sequence consists of approximately 1700
m of high TiO
2 (4–6.5%) picrite basalts, covered by rhyolitic ignimbrites and lavas, with an average thickness of 300
m, which discontinuously extend over an area of nearly 13,500
km
2 (ca. 3600
km
3). Petrogenetic modelling, using rock and mineral chemical data and phase equilibria calculations by PELE and MELTS, indicates that: 1) picrite basalts could generate rhyolitic, sometimes peralkaline, residual melts with persistently high titanium contents (TiO
2 0.4–1.1%; Fluorine 0.2–0.3%; H
2O 2–3%; density ca. 2.4) corresponding to liquid fractions 9–16%; 2) closed system fractional crystallisation processes developed at 0.1–0.3
GPa pressure and 1390–750
°C temperature ranges, under QFM
fO
2 conditions; 3) the highest crystallisation rate – involving 10–13% of Fe–Ti oxide removal – in the temperature range 1070–950
°C, represents a transitory (short-lived) fractionation stage, which results in the absence of erupted silica intermediate products (Daly gap). The eruption of low aspect ratio fluorine-rich rhyolitic ignimbrites and lavas capping the basic volcanics implies a rapid change from open- to closed-system tectono-magmatic conditions, which favoured the trapping of parental picrite basalts and their fractionation in upwardly zoned magma chambers. This evolution resulted from the onset of continental rifting, which was accompanied by normal faulting and block tilting, and the formation of shallow – N–S elongated – fissural chambers parallel to the future Afar Escarpment. The eruption of large volumes of rhyolitic magmas generated from underlying picrite basalts appears to be a common geological process acting in most plume-related LIP, which in turn is related to the inversion of the stress regime from regional extension lithosphere doming to localised continental rifting.
► Rhyolites associated to Northern Ethiopian CFB at the Afar plume axis. ► Petrogenetic modelling of rhyolites using major, trace elements and phase equilibria. ► Inversion of the stress regime and incipient rifting. ► Tectono-magmatic conditions changed from “open” to “closed” system. ► Rhyolites fractionated from picrite basalts in upward zoned fissural magma chambers.
G-protein coupled receptors 40 and 120 (GPR40 and GPR120) are increasingly emerging as potential therapeutic targets for the treatment of altered glucose homeostasis, and their agonists are under ...evaluation for their glucagon-like peptide-1 (GLP-1)-mediated therapeutic effects on insulin production and sensitivity. Here, we characterized a new dual GPR40 and GPR120 agonist (DFL23916) and demonstrated that it can induce GLP-1 secretion and improve glucose homeostasis.
Resulting from a rational drug design approach aimed at identifying new dual GPR120/40 agonists able to delay receptor internalization, DFL23916 had a good activity and a very high selectivity towards human GPR120 (long and short isoforms) and GPR40, as well as towards their mouse orthologous, by which it induced both Gαq/11-initiated signal transduction pathways with subsequent Ca2+ intracellular spikes and G protein-independent signaling via β-arrestin with the same activity. Compared to the endogenous ligand alpha-linolenic acid (ALA), a selective GPR120 agonist (TUG-891) and a well-known dual GPR40 and GPR120 agonist (GW9508), DFL23916 was the most effective in inducing GLP-1 secretion in human and murine enteroendocrine cells, and this could be due to the delayed internalization of the receptor (up to 3 h) that we observed after treatment with DFL23916. With a good pharmacokinetic/ADME profile, DFL23916 significantly increased GLP-1 portal vein levels in healthy mice, demonstrating that it can efficiently induce GLP-1 secretion in vivo. Contrary to the selective GPR120 agonist (TUG-891), DFL23916 significantly improved also glucose homeostasis in mice undergoing an oral glucose tolerance test (OGTT).
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•DFL23916 is a new dual agonist of human and mouse GPR40 and GPR120.•DFL23916 significantly delayed receptor endocytosis compared to other known GPR120 agonists.•DFL23916 efficiently induced GLP-1 secretion in vitro and in vivo.•DFL23916 significantly improved glucose homeostasis in mice following glucose load.
High-MgO ultrapotassic rocks are found in four different areas of the Western Mediterranean basin associated in space and time with shoshonitic and calc-alkaline rocks. They represent different ...magmatic events at the active continental plate margin from Oligocene to Pleistocene. These rocks are found within the Western Alps (Northern Italy), in Corsica (France), in Murcia-Almeria (South-Eastern Spain), and in Southern Tuscany (Central Italy). Ultrapotassic terms are mostly lamprophyres, but olivine latitic lavas with a clear lamproitic affinity are also found. Lamproite-like rocks range from slightly silica under-saturated to silica over-saturated, and they are characterised by low Al
2O
3, CaO, and Na
2O contents. They are plagioclase-free rocks, but K-feldspar is abundant beside other K-bearing phases. Shoshonitic and calc-alkaline rocks are invariably space associated to lamproites, and they either precede or follow them. High-Mg ultrapotassic rocks are characterised by strong enrichment of incompatible elements, which prevent further enrichment due to shallow level crustal contamination. K
2O and incompatible element contents decrease passing from high-Mg ultrapotassic to high-Mg shoshonitic and calc-alkaline rocks suggesting that K and incompatible trace elements enrichments are a primary characteristic. Ultrapotassic to calc-alkaline rocks from Western Mediterranean regions, in spite of their different age of emplacement, are characterised by similar incompatible trace elements distribution. Depletion of High Field Strength elements with respect to Large Ion Lithophile elements is observed. Positive spikes at Th, U, and Pb, with negative spikes at Ba, Nb, Ta, Sr, P, and Ti, are common characteristics of ultrapotassic (lamproitic) to high-K calc-alkaline rocks. Ultrapotassic rocks are extremely enriched in radiogenic Sr and unradiogenic Nd with respect to the associated shoshonitic and calc-alkaline rocks. Different isotopic values are distinctive of the different magmatic provinces irrespective of magmatic affinities.
87Sr/
86Sr
i ranges between 0.71645 and 0.71759 for Western Alps lamproites, between 0.71226 and 0.71230 for Corsica lamproite, between 0.71642 and 0.72259 for Murcia-Almeria lamproites, and between 0.71578 and 0.71672 for Tuscany lamproites. Radiogenic Sr decreases along with K
2O through shoshonitic to calc-alkaline rocks. Conversely
143Nd/
144Nd
i values increase with decreasing K
2O, with the highest value of 0.51243 found for the one samples from Murcia-Almeria. Contrasting trends are observed among initial values of lead isotopes, but all falling well within the field of upper crustal rocks. Different trends of
207Pb/
204Pb
i and
208Pb/
204Pb
i vs.
206Pb/
204Pb
i for samples from the different provinces are observed. Several evidences indicate that most of the magmas of the different provinces have been generated in a depleted upper mantle (i.e., lithospheric) modified by metasomatism, but an asthenospheric component is also recognised in Corsica. At least two different subduction-related metasomatic agents re-fertilised the depleted original upper mantle source. Carbonate-free siliciclastic sediments and carbonate-rich sediments have been recycled within the upper mantle through subduction and partial melting. Assuming that metasomatic component is concentrated in a vein network, in Tuscany and Corsica, time relationships indicate that low degree of partial melting of the pure vein produced lamproitic-like magmas, whereas an increase in the partial melting involve the surrounding upper mantle, then diluting the alkaline component and produced the entire spectra of magma observed. In South-Eastern Spain calc-alkaline magmatism preceded lamproitic ones, and might be generated by partial melting of mantle wedge metasomatised by fluids from oceanic slab prior to collision. Lamproitic magmas followed after melt-dominated metasomatic agents invaded the lithospheric upper mantle domain. Migration of the magmatism with time is the result of eastward migration of subduction with subsequent opening of Balearic, Ligure-Provençal, and Tyrrhenian basins.
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•Isotope ratio mass spectrometry (IRMS) was used to trace the orchard of provenance of apples.•The δ13C, δ15N, and δ34S values of apple parts were measured rather than the whole ...fruit.•The inner part of the seed is the most practical subfraction to be analyzed using IRMS.•Sulfur in seed is the best isotopic marker for tracing the regions of provenance of apples.•Linear discrimination analysis with the δ13C and δ34S of apple parts traced zones of production.
Isotope ratio mass spectrometry is a well-known technique used to trace the origin of agri-food products from different countries. Here this method was tested to trace the exact orchard of provenance of Italian apples harvested at sites close to each other. We measured the δ13C, δ15N, and δ34S values of apple subfractions (peel, petiole, pulp, seed) from two orchards in Ferrara and one orchard in Trento. Sulfur represents the best marker for tracing the regions of provenance of samples because it is linked to the presence of sulfate (Ferrara1: +9.0 ‰; Ferrara 2: +7.3 ‰) and sulfide (Trento: −1.3 ‰) minerals in soils. However, the δ13C of apple subfractions combined with the δ34S of seed in a linear discrimination analysis better discriminated the three orchards. The isotopic fingerprint of apples is thus significantly affected by the relative terroir, and it can be used as “isotopic identity card” to certify “protected designations of origin”.
The year 2017 was anomalously warm and dry across the whole Italian Peninsula, and the paucity of precipitation was emphasized during the extreme summer drought of the main Italian river, i.e., the ...Po river, which was characterized by a discharge persistently below 600 m3/s (in spite of the average discharge of 1500 m3/s). During these extreme conditions, the Po river oxygen and hydrogen stable isotopes (δD, δ18O) displayed a relation (δD = 6.1*δ18O − 6.6) significantly different from that recorded in the previous investigation of the years 2012–2014 (δD = 7.5*δ18O + 6.5). The lowering of the slope and the negative intercept clearly reflect the transition toward arid conditions that characterized the investigated period. The difference is expressed by the derivative parameter Line-Conditioned excess (LC-exc), which better describes the compositional difference of Po river water in the year 2017 with respect to that of the period 2012–2014, when the system was less affected by warm or dry conditions and the river discharge was more similar to the historical trends. The isotopic anomaly observed in 2017 throughout the river is even greater in the terminal part of the river, where in the meanders of the deltaic branches, the river flow progressively slows down, suffering significant evaporation. The isotopic signature of the water appears, therefore, an appropriate tool to monitor the watershed response to evolving environmental conditions. These sensitive isotopic parameters could be interpreted as “essential climate variables” (ECV) that are physical, chemical, or biological geo-referenced parameters that critically contribute to the characterization of Earth’s climate. Future research needs to find relationships between ECV (including the water stable isotopes) and the evolution of ecosystems, which especially in the Mediterranean area, appear to be fragile and severely affected by natural and anthropogenic processes.
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