To better constrain the age and composition of the sub-continental lithospheric mantle (SCLM) beneath the Cameroon Volcanic Line (CVL), we present Sr-Nd-Hf-Os isotopes of the Nyos mantle xenoliths ...(nine lherzolites and four harzburgites). The Nyos lherzolites have fertile compositions with 37.69–41.12wt.% MgO and 2.49–4.38wt.% Al2O3, whereas the harzburgites are more refractory containing 43.2–45.42wt.% MgO and 1.43–2.1wt.% Al2O3. The MgO contents of the Nyos xenoliths overall show negative correlations with CaO, Al2O3, Na2O and TiO2 contents, indicating that they represent mantle residues after melt depletion. Modal minerals like pargasitic amphibole have only been discovered in one Nyos lherzolite, suggesting modal metasomatism locally occurred. Clinopyroxenes in most Nyos xenoliths show enriched trace element compositions, indicating pervasive cryptic metasomatism within the SCLM. Clinopyroxenes in the Nyos lherzolites have less radiogenic Sr and more radiogenic Nd isotopes than the Nyos harzburgites. Clinopyroxene Hf isotopes of the harzburgites are comparable to those of the lherzolites. Although the CVL basalts have similar Sr-Nd isotopes with the Nyos harzburgites, they have different Hf isotopes. Therefore, the CVL basalts could not be sourced solely from the lithospheric mantle. The Nyos lherzolites show consistent HSE patterns, with slight depletion in both Re and Pt over Pd. The harzburgites are remarkably depleted in Pt, Pd and Re relative to Os, Ir and Ru. The Nyos lherzolites have variable 187Os/188Os ratios ranging from 0.11700 to 0.13129, yielding Os model ages (TMA) relative to the primitive upper mantle (PUM) of 0.27–2.18Ga and Re depletion ages (TRD) of 0.12–1.76Ga. In comparison, four harzburgites have more unradiogenic 187Os/188Os ratios of 0.11485–0.11705. Three of the four harzburgites with low Re/Os ratios yield similar TMA and TRD ages, i.e., 1.91–2.43Ga vs. 1.87–2.05Ga, respectively. The 187Os/188Os ratios of the Nyos xenoliths show a good correlation with bulk Al2O3 contents. An initial 187Os/188Os ratio of 0.11064 can be inferred from the 187Os/188Os-Al2O3 correlation, giving an Archean TRD age of ~2.6Ga. This suggests that the Nyos mantle xenoliths have been subjected to melt depletion events during the Paleoproterozoic convergence of the Congo and West Africa cratons, which formed the lithospheric mantle intruded by the CVL. The SCLM beneath the CVL is coeval with or slightly younger than the charnockite and tonalite-trondhjemite-granodiorite in the Ntem Complex of NW Congo Craton. We proposed that the old SCLM was a part of the Congo cratonic mantle. Therefore, our results suggest that old cratonic mantle beneath the CVL has not been completely removed during the Pan-African Orogeny, although the overlying crust might have been strongly deformed and reworked.
•Newly discovered volcanic rocks in Abushan Formation.•Zircon U–Pb dating constraints the volcanism during 102–96Ma.•Volcanics derived from partial melting of subducted ocean slab and ...sediments.•Bangong–Nujiang Ocean crust subducted beneath the Qiangtang Terrane.
The subduction of the Bangong–Nujiang Ocean is a long-standing problem in the study of the geological evolution of the Tibetan Plateau. Based on recent data acquired from the Abushan volcanic rocks in the Qiangtang Terrane, we will discuss the relationship between the Cretaceous volcanism and the evolution of the Bangong–Nujiang Ocean. The Abushan volcanic rocks are mainly composed of trachy-andesites, dacites, and rhyolites. Zircon U–Pb dating constrains the time of emplacement as the Middle Cretaceous (102.6±1.6–96.1±2.4Ma). Major element geochemistry shows that the volcanic rocks belong to the high-K calc-alkaline and calc-alkaline series. All of the volcanic rocks are enriched in light rare earth elements (LREE) and some large ion lithophile elements (LILE, Rb, Th, and U) and are depleted in heavy rare earth elements (HREE) and some high field strength elements (HFSE, Nb, Ta, and Ti). The geochemical characteristics of the Abushan volcanic rocks are correlated with those of the volcanic arc rocks in the subduction zone. The petrogenesis of the Abushan volcanic rocks suggests that they were derived from the partial melting of the relict subducted oceanic crust combined with the input of oceanic sediments. Oceanic crust will melt upon reaching its hydrous solidus in the amphibolite facies after plate collision; this induces the formation of the Abushan volcanic rocks. Our data, compared with the previous studies on volcanism in the Lhasa Terrane, leads us to propose that the Bangong–Nujiang Ocean crust was subducted beneath the Qiangtang Terrane and underwent bidirectional subduction during the Cretaceous.
This study aims to assess the specific PM2.5-bound metallic elements that contribute to asthma emergency department visits by using a case-crossover study design.
This study analyzed data from 11,410 ...asthma emergency department visits as case group and 22,820 non-asthma onset dates occurring one week and two weeks preceding the case day as controls from 2017 to 2020. PM2.5 monitoring data and 35 PM.2.5-bound metallic elements from six different regions in Taiwan were collected. Conditional logistic regression models were used to assess the relationship between asthma and PM2.5-bound metallic elements.
Our investigation revealed a statistically significant risk of asthma emergency department visits associated with PM2.5 exposure at lag 0, 1, 2, and 3 during autumn. Additionally, PM2.5-bound hafnium (Hf), thallium (Tl), rubidium (Rb), and aluminum (Al) exhibited a consistently significant positive correlation with asthma emergency department visits at lags 1, 2, and 3. In stratified analyses by area, age, and sex, PM2.5-bound Hf showed a significant and consistent correlation.
This study provides evidence of PM2.5-bound metallic elements effects in asthma exacerbations, particularly for Hf. It emphasizes the importance of understanding the origins of these metallic elements and pursuing emission reductions to mitigate regional health risks.
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Understanding the behavior of elements under highly reduced conditions is fundamental to explain the differentiation, crust formation, and volatile budget of Mercury. Here we report experiments on a ...synthetic composition representative of the bulk silicate Mercury (BSM), at pressure up to 3 GPa, temperature up to 1720 °C, and under highly reduced conditions (∼IW − 8 to ∼IW − 1, with IW the iron-wüstite oxygen fugacity buffer). We determined partition coefficients for >30 minor and trace elements between silicate melt, metal melt (FeSi), sulfide melt (FeS), and MgS solid sulfides. Based on these results and published literature, we modeled the behavior of heat-producing elements (HPE: U, Th, and K) during Mercury's early differentiation and mantle partial melting and estimated their concentrations in the mantle and crust. We found that U, K and especially Th are principally concentrated in the BSM and did not partition into the core because they are not siderophile elements. Uranium is chalcophile under highly reduced conditions, and so our model suggests that an FeS layer at the core-mantle boundary formed during Mercury's primordial differentiation would likely have incorporated large amounts of U, significantly increasing the Th/U ratio of the BSM. However, this is inconsistent with the chondritic or slightly sub-chondritic Th/U ratios of Mercury's lavas. In addition, the likely presence of mantle sulfides, such as MgS, would have also fractionated U and Th, increasing the mantle Th/U. It is possible to have an FeS layer if Mercury formed under less reduced conditions, or if the building blocks of Mercury had Th/U ratios close to the lower end of chondritic data. If, as suggested by our model, no FeS layer formed during differentiation, it means that the majority of HPE are concentrated in Mercury's thin silicate part. Based on the compatibility of U, Th and K, we also show that surface K/Th and K/U ratios are respectively 2–4 times and 3–6 times lower than expected for initial K/Th and K/U ratios similar to enstatite chondrites, implying that the planet suffered an important volatile loss via mechanisms that remain undetermined.
•FeS, metal and MgS/silicate partition coefficients for ∼30 minor and trace elements.•U, Th and K are largely concentrated in the silicate part of Mercury.•An FeS layer formed in equilibrium with the magma ocean is improbable.•Surface K/Th is lower than predicted, supporting bulk K loss for Mercury.
In diabetes, increased oxidative stress and impaired trace element metabolism play an important role in the pathogenesis of diabetic nephropathy. The objective of this research was to examine the ...outcomes of blocking the renin-angiotensin system, using either the angiotensin-converting enzyme inhibitor (ACEI), perindopril, or the angiotensin II type 1 (AT1) receptor blocker, irbesartan, on oxidative stress and trace element levels such as Zn, Mg, Cu, and Fe in the kidneys of diabetic rats that had been induced with streptozotocin. Thirty-two Wistar albino male rats were equally divided into four groups. The first group was used as a control. The second group of rats developed diabetes after receiving a single intraperitoneal dose of STZ. The third and fourth groups of rats had STZ-induced diabetes and received daily dosages of irbesartan (15 mg/kg b.w/day) and perindopril (6 mg/kg b.w/day) treatment, respectively. Biochemical analysis of the kidneys showed a distinct increase in oxidative stress, indicated by heightened levels of malondialdehyde (MDA) and decreased superoxide dismutase (SOD) activities, as well as reduced glutathione (GSH) levels in the kidneys of diabetic rats. In the kidneys of diabetic rats, the mean levels of Fe and Cu were found to be significantly higher than those of the control group. Additionally, the mean levels of Zn and Mg were significantly lower in the diabetic rats compared to the control rats. Both perindopril and irbesartan decreased significantly MDA content and increased SOD activities and GSH levels in the kidneys of rats with diabetes. The Zn and Mg concentrations in the kidneys of diabetic rats treated with perindopril and irbesartan were markedly higher than in untreated STZ-diabetic rats, while the Cu and Fe concentrations were significantly lower. The urinary excretion of rats treated with perindopril and irbesartan showed a pronounced increase in Cu levels, along with a significant reduction in Zn and Mg levels. Although diabetic rats demonstrated degenerative morphological alterations in their kidneys, both therapies also improved diabetes-induced histopathological modifications in the kidneys. Finally, the present results suggest that manipulating the levels of Zn, Mg, Cu, and Fe - either through ACE inhibition or by blocking AT1 receptors - could be advantageous in reducing lipid peroxidation and increasing antioxidant concentration in the kidneys of diabetic rats.
Shallow aquifers are the most accessible reservoirs of potable groundwater; nevertheless, they are also prone to various sources of pollution and it is usually difficult to distinguish between human ...and natural sources at the watershed scale. The area chosen for this study (the Campania Plain) is characterized by high spatial heterogeneities both in geochemical features and in hydraulic properties. Groundwater mineralization is driven by many processes such as, geothermal activity, weathering of volcanic products and intense human activities. In such a landscape, multivariate statistical analysis has been used to differentiate among the main hydrochemical processes occurring in the area, using three different approaches of factor analysis: (i) major elements, (ii) trace elements, (iii) both major and trace elements. The elaboration of the factor analysis approaches has revealed seven distinct hydrogeochemical processes: i) Salinization (Cl−, Na+); ii) Carbonate rocks dissolution; iii) Anthropogenic inputs (NO3−, SO42−, U, V); iv) Reducing conditions (Fe2+, Mn2+); v) Heavy metals contamination (Cr and Ni); vi) Geothermal fluids influence (Li+); and vii) Volcanic products contribution (As, Rb). Results from this study highlight the need to separately apply factor analysis when a large data set of trace elements is available. In fact, the impact of geothermal fluids in the shallow aquifer was identified from the application of the factor analysis using only trace elements. This study also reveals that the factor analysis of major and trace elements can differentiate between anthropogenic and geogenic sources of pollution in intensively exploited aquifers.
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•Multivariate statistical analysis used to determine hydrogeochemical processes.•Different runs of Factor Analysis were applied using separate trace elements.•7 factors were extracted including Trace and major elements.•U and V originate from Anthropogenic activities.•As related to volcanic sediments and Li to geothermal activity.
The lack of magmatic records with high-quality geochronological and geochemical data in the central segment of the southern Qiangtang subterrane in central Tibet inhibits a complete understanding of ...the subduction polarity of the Bangong–Nujiang Ocean lithosphere during the Mesozoic. In this study, we present the zircon U–Pb age as well as geochemical and Sr–Nd–Pb isotopic data for the Late Jurassic pluton from the Kangqiong area in the central segment of the southern Qiangtang subterrane. The Kangqiong pluton primarily consists of granodiorites (SiO2=62.87–65.17wt.%) and was emplaced in the Late Jurassic (147.6±2.4–149.9±2.1Ma). The granodiorites display high Na2O numbers (Na2O/K2O=1.75–2.24) as well as high MgO (2.21–3.14wt.%) and Mg-numbers (53–58), are characterized by a low abundance of heavy rare earth elements (e.g., Yb=1.05–1.92ppm) and Y (12.63–17.52ppm), and high Sr/Y (29–61) and La/Yb (14–18) ratios, which are comparable in composition to those of slab-derived adakitic rocks. The Kangqiong adakitic granodiorites have initial (87Sr/86Sr)i ratios of 0.70611 to 0.70669, negative εNd(t) values (−1.06 to −0.25), (206Pb/204Pb)t ratios of 18.42 to 18.47, (207Pb/204Pb)t ratios of 15.62 to 15.63, and (208Pb/204Pb)t ratios of 38.50 to 38.60. These geochemical signatures indicate that the magmas were most likely derived from the partial melting of the subducted Bangong–Nujiang oceanic crust and minor contaminants from the accretionary complex. Our results, in combination with the coeval magmatism in the western segment of the southern Qiangtang subterrane, indicate that the Bangong–Nujiang oceanic lithosphere was subducted northward beneath the Qiangtang Terrane, forming a west-east magmatic arc over 800km during the Late Jurassic.
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•Newly discovered adakitic rocks in the southern Qiangtang subterrane•Adakitic rocks were generated in the Late Jurassic (148–150Ma).•Bangong–Nujiang Ocean subducted northward beneath the Qiangtang terrane.
In this paper, we first proposed mathematical model equations for wave propagation in a multi-functional transformation optical device, namely, an electromagnetic rotation concentrator. This device ...can concentrate electromagnetic energy while rotating electromagnetic waves. We also demonstrate the stability of the model equation in the continuous case. Next, we designed the multi-functional device with multiple layers. We then proposed a time-domain finite element method for simulating wave propagation in this device and conducted a stability analysis of the model equations in the discrete case. Finally, we implemented the proposed algorithm and obtained numerous numerical results that demonstrate the validity of our model equations. To the best of our knowledge, this is the first work on time-domain modeling and analysis of multi-functional electromagnetic devices.
•Palaeoproterozoic dykes in Bundelkhand are NW trending and at least of two geochemical groups.•The magmas are near primary melts and gabbro fractionated products from ~12% mantle melts.•Mantle ...potential temperature estimates of ~1550–1600 °C indicate thermal anomaly.•Indicated magma interaction with H2O-CO2 fluid metasomatised lithosphere mantle.•Dykes with same structural trend but represent more than one generation of intrusions.
NW-SE trending mafic dykes in the Bundelkhand Craton of the Indian shield manifest Palaeoproterozoic igneous activity. These dykes are Fe-rich tholeiitic basalts with compositions varying from near primary melts to more evolved magmas (Mg#: 0.64–0.35) and show enrichment of large-ion lithophile and light rare earth elements relative to primordial mantle values. Despite very subtle variations of elemental abundances and similar structural trend, at least two groups are identified, mainly based on incompatible element ratios and rare earth element patterns. Group 1 samples are characterized by relatively low Ti/Y (av. 222 ± 22) and Ti/Nb (av. 609 ± 108), high Zr/TiO2 (av. 117 ± 15), more light to heavy rare earth element fractionation (La/Yb)CN: 2.7–5.1) and mild negative Eu anomaly (Eu* = 0.77 ± 0.10). Group 2 samples possess high Ti/Y (av. 334 ± 46) and Ti/Nb (av. 1349 ± 198), low Zr/TiO2 (av. 70 ± 7) and minor light to heavy rare earth element fractionation ((La/Yb)CN: 1.5–2.7) without any Eu anomaly (Eu* = 0.97 ± 0.04). Both groups show relative depletions in Nb, Sr and P while the Group 1 also shows Ti depletion. A third group is apparent but is less certain. Group 2 dykes constitute the 1.98 Ga Jhansi swarm, whilst the Group 1 and unclassified samples are likely to be of older age (~2.18–2.20 Ga and ~2.37 Ga) based on available U-Pb ages and palaeomagnetic considerations. Despite the compositions indicate different batches of magma, the dykes have near similar petrogenetic evolutionary pattern as if the entire population constitutes a single clan. Samples of both groups (a) do not indicate significant crustal contamination (b) derived from two different batches of magmas formed by ~10–12% fractional melting of mantle near the spinel-garnet transition zone and (c) evolved through initial fractionation of olivine and thereafter clinopyroxene and plagioclase became important fractionation phases. The more primitive compositions of both groups indicate mantle potential temperatures of ~1550–1600 °C suggesting thermal anomaly. The dyke magmas inherited variably enriched compositions as a result of interaction of upwelling mantle melts with metasomatised subcontinental lithospheric mantle. Low H2O-CO2-rich silicate melts/fluids are likely the dominant metasomatic agents to develop the Indian subcontinental lithosphere in the Archaean (c. 3.0 Ga).
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