Ba Concentrations Research Articles

South Mid-Atlantic Ridge 25.3–27.7°S segment basalts: Implications for entrainment of the Tristan plume material in the mid-ocean ridge system

We present new major and trace element and Sr-Nd-Pb isotope data for basalts from the 25.3–27.7°S segments of the South Mid-Atlantic Ridge (SMAR). A fractional crystallization model shows that olivine, plagioclase, and clinopyroxene crystals crystallized in the magmatic chamber underlying the SMAR 27.1°S and 27.7°S segments, while the SMAR 25.3°S segment basaltic lavas are dominated by fractional crystallization of olivine and plagioclase. Their Ce/Yb, (Tb/Yb)N, and Fe/Mn ratios suggest a mantle source lithology dominated by spinel-lherzolite. The linear correlations between Mg# and TiO2, Ba, and Zr/Nb indicate that SMAR basalts in this study have primary mantle melts with similar chemical compositions and partial melting extents. The along-ridge variations in the fractionation-corrected incompatible element (Ba, Zr/Nb, (La/Sm)N) and Sr-Nd-Pb isotope compositions of the SMAR 20–40°S basalts show that Tristan mantle plume materials exist in the SMAR asthenosphere and gradually decrease from the southern SMAR 35°S segment in the vicinity of Tristan Island to the northern SMAR 25.3–27.7°S segments. The mixing models of the fractionation-corrected Ba contents, (La/Sm)N ratios and radiogenic Sr-Nd-Pb isotope ratios show that variable degrees of contamination by the Tristan mantle plume contribute to the heterogeneous SMAR 20–40°S mantle source. The proportion of Tristan plume-related materials retained in the SMAR 20–40°S asthenosphere is <10%, which gradually decreases from south to north. By integrating the evolution of the South Atlantic and the historical interaction between the SMAR system and the Tristan mantle plume, we demonstrate that the systematic variations in the geochemical compositions of the SMAR 25.3–27.7°S basalts are induced by the presence of the Tristan mantle plume materials in the southern SMAR asthenosphere.

First-principles calculations of equilibrium barium isotope fractionation among silicate minerals

Barium isotopes have been increasingly applied to trace igneous processes, but the applications are hindered by the lack of equilibrium Ba isotope fractionation factors between silicate minerals. In this study, the reduced partition function ratios (RPFRs) of the major Ba-hosting silicate minerals, including muscovite, phlogopite, tremolite, richterite, microcline, albite, and epidote, as well as witherite and barite, are obtained using first-principles calculations. The effect of Ba concentration on the RPFR of those silicate minerals was examined, and no significant effect was observed in the natural range of Ba concentrations. Our results show a heavy Ba isotope enrichment order of tremolite > epidote > albite > witherite ∼ richterite ∼ microcline ∼ barite ∼ muscovite ∼ phlogopite. The RPFRs are controlled by the force constant of Ba and affected by the BaO bond length. The lattice environment of substituted ions controls the equilibrium Ba isotope fractionation factors of trace elements. For instance, the replacement of Ba2+ with Mg2+ or K+ in phlogopite introduces an approximately 0.16‰ offset of Ba isotope ratios (138Ba/134Ba) at 1000 K. In general, light Ba isotopes are preferentially enriched in crystalline positions with larger ion radii. Equilibrium Ba isotope fractionation among silicate minerals is up to 0.08‰ at 1000 K, which can be well resolved by the current analytical precision (∼0.05‰ for δ138/134Ba). This study provides the calculated equilibrium fractionation factors, which are the key to understanding Ba isotope fractionation in natural rocks.

Water contents and hydrogen isotope compositions of amphibole in aillikites from the Tarim large igneous province, NW China: Insight into Earth’s deep water cycle

Water is known to play a crucial role in the generation of many large igneous provinces (LIP) worldwide, but the amount and origin of the water in their sources is still under debate. To address this question, this paper presents in situ major-, trace-element, and Sr isotope data coupled with bulk-mineral O-H-He isotope analyses of amphibole in a suite of aillikites from the Tarim LIP (NW China). The cores of zoned macrocrysts and microcrysts display partially overlapping compositions ranging between edenite and pargasite (75−83 versus 75−80 Mg#), which suggest a common origin from an evolving magma. The rims (Mg# = 75−80) of both macrocrysts and microcrysts are very similar to their cores for many elements, except for higher Sr and Ba contents. All the amphibole zones show similar primitive mantle−normalized trace element patterns, suggesting that they crystallized at different stages during magmatic evolution. This interpretation is confirmed by the homogenous Sr isotope compositions (87Sr/86Sr(i) = 0.70298−0.70394) of these amphiboles, which overlap with those of magmatic apatites and perovskites in these aillikites. The hydrogen isotope compositions (δD = −120‰ to −140‰) of the amphiboles are significantly lower than average mantle values. Given the low water contents (&amp;lt;0.66 wt%) of these minerals, the low H isotope signatures of the amphiboles might be caused by variable H2O loss during magma ascent. However, open-system Rayleigh fractionation modeling suggests that the hydrogen isotope compositions of these amphibole phenocrysts cannot be fully reproduced by crystallization following magmatic degassing. These low δD values require incorporation of recycled altered oceanic crust containing hydrous components in the plume source of these aillikites, which is consistent with the previously published moderately radiogenic He isotope ratios of olivine separates and bulk-rock Os and Pb isotope data for these same samples. We conclude that water in these magmas was derived from a plume source containing recycled water-bearing oceanic crust.

Origin and mineralization processes of REE during magmatic-hydrothermal evolution: Insights from in-situ geochemistry of calcite from the Weishan REE deposit, eastern North China Craton

The Weishan REE deposit, hosting more than one million tons of light REE oxides (LREE2O3), is one of the largest LREE deposits in China. It has been considered to be a carbonatite-related REE deposit, but whether carbonatites occurred or not is still controversial, leading to the confusions of how the LREE originated and mineralized. Here, we conducted in-situ elemental and Sr-Nd isotopic analyses on different stages of calcite from the Weishan REE deposit, combined with petrographic and bulk C-O isotopic studies, with the aim to unravel the origin and mineralization processes of REE. Four stages of calcite (Cal-1, Cal-2, Cal-3 and Cal-4) were identified, of which the Cal-1 typically coexists with K-feldspar and quartz while the Cal-2 and Cal-3 coexist with sulfates and REE minerals (e.g., bastnäsite and parisite), respectively. The Cal-4 occurs in the post-ore veinlets and coexists with sulfides. The Cal-1 is characterized by exsolution of carbocernaite along its cleavage planes with highest Na, K, Sr, Ba and LREE contents. The other stages of calcite show continuous decrease of the above elements. Combined with petrographic features and elemental discrimination diagrams, it is concluded that the Cal-1 is magmatic while the others are hydrothermal. These calcites thus indicate a continuous magmatic-hydrothermal evolution. The four stages of calcite show similar isotopic compositions, which are consistent with those of the alkaline silicate rocks in the ore district, suggesting an uniform source or magma chamber for their derivation. Considering the magmatic features of Cal-1, it is inferred that carbonate melts coupled with abundant alkaline fluids were exsolved from the alkaline magmas. Alkalis (e. g., K and Na) were enriched in the magmatic-hydrothermal system with potassic metasomatism being more prevalent, which might play an important role in REE exsolution and transportation. Focused REE deposition occurred shortly after massive deposition of sulfates, indicating that REE-sulfate complexes might be the dominant transporting ligands of REE. The deposition of REE was mainly induced by fluid boiling, as indicated by the boiling/unmixing features of fluid inclusions. The Sr-Nd isotopic compositions of ores and associated alkaline rocks show affinities to the enriched lithospheric mantle (EM) beneath the study region, but are more depleted. Because subduction of the Paleo-Pacific oceanic plate beneath the eastern Asian occurred since the Jurassic, it is inferred that CO2- and REE-rich melts/fluids released from the subducted oceanic slab metasomatized the EM, leading to a REE-rich carbonated mantle. Rollback of the subducted slab occurred during the early Cretaceous, resulting in partial melting of the EM and thus generating the CO2- and REE-rich alkaline magmas. This deposit shows significant hydrothermal features with poorly-developed carbonatites, distinct from the typical carbonatite-related REE deposits in the other places. The REE mineralization is thus considered to be basically controlled by the alkaline magmas rather than the carbonatites.

Barium isotope fractionation during granitic magmatism and potential of δ138/134Ba for distinguishing magmatic-hydrothermal transition in granitic magma systems

The geochemistry of Ba is commonly used to study igneous processes and fluid-melt interaction in subduction zone and granitic environments. Recent advances in analytical techniques have also indicated that Ba isotope geochemistry has the potential to significantly augment these studies. Understanding the Ba isotope fractionation mechanisms is thus critical if this potential is to be fully realized. Hence, we have used the first-principles calculations based on the density functional theory (DFT) and long-time ab initio molecular dynamics (AIMD) simulation to calculate Ba isotope fractionation during felsic magma evolution. In fluids, the reduced partition function ratio (β factor) of aqueous Ba2+ is highly variable, depending on the coordination number (n) of H2O in the first hydration shell. At ambient surface conditions on the Earth, n = 8 best represents the aqueous Ba2+ species in natural fluid, and the temperature-dependent equilibrium Ba isotope fractionation between barite/witherite and fluids can be described by the relationships: 103lnαwitherite-fluid = −0.00009×(106/T2)2 + 0.0603×(106/T2) + 0.0003 and 103lnαbarite-fluid = −0.0001×(106/T2)2 + 0.0648×(106/T2) + 0.0004, which is consistent with previous theoretical and experimental studies. In hydrothermal fluids, the hydration number of Ba2+ varies from 4 to 6 at high P-T, and the cumulative average of 103lnβ is derived to be 0.0798 ± 0.005‰ in 923.15 K and 0.2 GPa. In silicate minerals, the enrichment of heavy Ba isotopes decreases in the sequence of muscovite > microcline ≈ celsian ≈ sanbornite > barylite > phlogopite. Variations in Ba concentrations and the degree of Al-Si disordering only induce limited Ba isotope fractionation, which would be hard to distinguish analytically. At high temperatures (> 600 °C), the melt phase is enriched in heavy Ba isotopes relative to any coexisting aqueous fluid and crystallizing minerals. During the early stages of felsic magma differentiation involving plagioclase crystallization as the main mineral, the δ138/134Ba and concentration in the residual melt remain close to their initial values, but any fluid exsolved from the melt will have light δ138/134Ba values. The high Ba distribution coefficient of K-feldspar means that the resultant K-feldspar granite inherits > 90% of the Ba contained in the initial magma reservoir. Hence, the δ138/134Ba of K-feldspar is close to that of the initial melt. During the final stage of felsic magma evolution, mixing of exsolved fluids from deeper reservoirs may significantly reduce the δ138/134Ba of the now Ba-depleted melt, and can account for the low δ138/134Ba values measured in highly differentiated leucogranites and pegmatites.

In vitro establishment of cell suspension culture of Ceropegia bulbosa for improved production of cerpegin content through elicitation of engineered carbon and ZnO nanoparticles.

The present investigations aimed to conserve C. bulbosa a threatened plant species and for production of cerpegin through cell culture technology using ENP elicitation. Leaf explants were aseptically cultured with normal MS medium-supplemented PGRs BA and NAA various concentrations, and the best callus induction response was recorded on 4.5 + 4.5 μM. The prospective special effects of the ENPs on plant cell cultures are the key part of our study and used to evaluate leaf callus culture proliferation with the reduction of browning, establishment, biomass, and metabolite formation. The CNP concentrations (0, 2, 4, 8, 12 mg/l) are used for the callus proliferation and browning reduction. The cell suspension cultures are also established, and they were elicited with EZnONPs (0, 25, 50, 100, 150 mg/l) for evaluation of biomass, antioxidant, non-antioxidant enzyme activation, toxicity, ROS defense activation, and metabolite development in cell cultures. The metabolite extraction, UV, and NMR characterization confirm that the toxic and nontoxic effect of ENPs on leaf cell cultures varies with high to low concentration.

Seawater–Groundwater Interaction Governs Trace Metal Zonation in a Coastal Sandy Aquifer

AbstractTrace metals in the groundwater of coastal sandy aquifers significantly influence the coastal ecosystem, yet the spatiotemporal controls of these metals remain unclear. In this paper, we comprehensively revealed the distribution patterns, key controlling factors, potential ecological risks, and fluxes to the ocean of groundwater trace metals (As, Ba, Cr, Cd, Fe, Mn, Pb, and Zn) in a coastal deep sandy aquifer. The results showed a clear zonation of trace metals in the groundwater in relation to the mixing extent between seawater and terrestrial freshwater. The freshwater zone exhibited a relatively low concentration of trace metals, whereas the freshwater‐seawater transition zone showed a substantial quantity of dissolved Fe, Mn, As, and Ba. Seawater‐groundwater interactions significantly affected the Fe, Mn, As, and Ba concentrations through redox potential and pH gradients. The tide‐driven saline water zone was vulnerable to oceanic environments and anthropogenic activities, resulting in the enrichment of trace metals such as Zn and Cd. Driven by recirculated submarine groundwater discharge (SGD), the concentrations of trace metals in the density‐driven saline circulation zone were found to be higher than those in the surrounding areas. The ecological risk index suggested that the freshwater‐seawater transition zone posted the highest ecological risks. Trace metal fluxes (i.e., Fe, Mn, and As) via SGD significantly contributed to the total input into the sea, which may have potential impacts on the coastal environments. Our study highlighted the importance of seawater‐groundwater interactions on trace element cycling in coastal sandy aquifers.

Abundant off-axis hydrothermal activity in the 29–30 ridge segment of the Southwest Indian Ridge: evidence from ferromanganese crusts

In the ultra-slow spreading mid-ocean ridge, seafloor hydrothermal ventings mostly occur in the off-axis region. The plume of hydrothermal venting provides Fe, Mn and other metal materials for the growth of ferromanganese crust in the surrounding seamounts, showing unique geochemical characteristics that are different from that of hydrogenetic crust. Based on five samples of ferromanganese crusts, major, trace and rare earth element analysis was carried out to identify their material sources. Combined with the investigation data of water column and seafloor camera photos by deep towed hydrothermal detection system, the potential of hydrothermal activity in the 29–30 ridge segment of the Southwest Indian ridge was evaluated. The results showed that the ferromanganese crust in the study area had significantly higher Fe/Mn value (average 1.9), relatively higher Si and Al contents, and significantly higher Ca/P value (average 9.3),without significant phosphorylation. ferromanganese crust in the study area have significantly lower Co and Ni contents (about 1600 mg/kg on average), and relatively lower Sr, Ba, Pb, Cu, Zr and Mo contents (between 100-1000 mg/kg on average). The contents of W, Th and Te are also relatively low (average content between 10–50 mg/kg); The total rare earth element content of the crust in the study area is relatively low (about 928 mg/kg on average), and the light rare earth is relatively enriched. The standardized rare earth curve of the shale shows a left-leaning pattern as a whole, showing the enrichment of heavy rare earth relative to the shale. The Co content and rare earth element content of the ferromanganese crusts in this area are significantly lower than those of hydrogenetic crusts. The discrimination diagrams of ternary and bivariate material sources reveal that they have mixed hydrothermal and hydrogenetic origins. The three crust samples of S1, S2, and S5 are located within 2 km of the known hydrothermal fields, indicating a correlation between ferromanganese crust and the location of hydrothermal activity. There is no known hydrothermal field near the S3 and S4 stations. Altered rocks and water column turbidity anomalies were found near S3 station, and large areas of altered rocks and suspected hydrothermal biological remains were also found near S4 station, indicating that hydrothermal activity may exist in both areas. In addition to the two new hydrothermal fields identified in this article, the spatial frequency of hydrothermal activity in the study area reaches 15 sites/100 km, which is significantly higher than other well investigated oceanic ridges. Out of the eight hydrothermal fields in the study area, seven are located in the off axis region, mainly because the hydrothermal activity in this area is controlled by high angle and large offset normal faults and one-way detachment faults. This also indicates that the off-axis region of the Southwest Indian Ridge has high potential for hydrothermal activity.

Patterns of trace element deposition in beluga whale teeth reflect early life history

Determination of trace element concentrations in continuously growing biological structures such as otoliths, whiskers, and teeth can provide important insight into physiological and ontogenetic processes. We examined concentrations of 11 trace elements (Li, Mg, Mn, Cu, Zn, Se, Rb, Sr, Cs, Ba, Pb) in the annual dentine growth layer groups (GLGs) of teeth of 66 Eastern Canadian Arctic belugas (Delphinapterus leucas). Several of these trace elements displayed clear and consistent patterns in early life, though few longer term trends or signals were present in trace element data for either females or males. Large changes in Sr and Ba concentrations in fetal dentine reflected in utero shifts in element deposition in the teeth of developing belugas. Marked changes in these elements during the first years after birth were likely associated with the onset of nursing and subsequent weaning. Mg, Mn, and Zn also displayed clear and consistent patterns in early life that correlated strongly with dentine stable nitrogen isotope (δ15N) data, suggesting these elements merit further study as potential tools for studying nursing and weaning. Depositional patterns of Zn and Pb, which have been linked to sexual maturation in female Pacific walruses (Odobenus rosmarus divergens), were inconsistent in beluga teeth. Some individuals (including males) displayed patterns strongly resembling those observed in female walruses, whereas many animals did not, perhaps because they had not yet reached sexual maturity. The lack of clear patterns in trace element deposition after the first few years of life may have resulted from pooling samples from multiple populations/regions collected across more than two decades, but may also indicate that elemental concentrations are primarily driven by other, extrinsic processes later in life, and might be useful as biomonitors of environmental element concentrations or tools for delineating population structure.

Effects of dietary standardized ileal digestible lysine to net energy ratio and wheat level on growth performance, meat quality, intestinal microbiota and body metabolism of finishing pigs

Lowing lysine (Lys): energy ratio based on corn-soybean diets could increase intramuscular fat (IMF) content, the effectiveness of it in enhancing IMF content when corn is partially substituted by wheat is unclear. This study aimed to determine the effects of dietary wheat levels and standardized ileal digestible (SID) Lys: net energy (NE) ratio on growth performance and meat quality, alteration in gut microbiota and body metabolism, as well as its correlation with meat quality are revealed via combined microbiome and metabolomic methods. A total of 72 pigs were randomly divided into four groups and fed with high SID Lys:NE ratio (HR) diets containing 25% wheat (W25HR), low SID Lys:NE ratio (LR) diets containing 25% wheat (W25LR), HR diets containing 55% wheat (W55HR) or LR diets containing 55% wheat (W55LR). Increasing dietary wheat level impaired feed utilization during 65–90 kg phase (P < 0.05) and enhanced meat color values (P < 0.05) of longissimus dorsi (LD) in finishing pigs. Enhancing dietary wheat level decreased relative abundance of Lactobacillus and Coprococcus (P < 0.05), and inhibited microbial carbohydrate metabolism capacity (P < 0.05) in colon of finishing pigs. Changes in microbial composition and carbohydrate metabolism capacity caused by wheat level led to alteration in meat color. LR diets improved feed utilization (P < 0.05), affected amino acid and lipid metabolism, and increased IMF content in LD (P < 0.05). Reducing SID Lys:NE ratio changed the concentrations of PA, delta-tocopherol, L-arginine, AzA, BA, and L-carnitine at the 25% wheat level and ARA, SDA, Glu, fructose-6-phosphate, and isorhamnetin at the 55% wheat level in the serum (P < 0.05, VIP > 1), which could serve as key biomarkers for predicting meat quality. LR diets upregulated mRNA expression levels of CCAAT/enhancer binding protein (C/EBP) α (P < 0.05), C/EBPβ (P < 0.01), sterol regulatory element-binding transcription factor 1c, fatty acid synthase (FAS) (P < 0.05), while downregulated mRNA abundance of adipose triglyceride lipase (ATGL) (P < 0.05) in liver at the 25% wheat level. The mRNA expression levels of C/EBPβ (P < 0.01), FAS, acetyl-coA carboxylase and fatty acid binding protein 1 (P < 0.05) were higher in the W55LR than W55HR groups, whereas mRNA abundance of ATGL was lower (P < 0.05). These results indicated that lowering SID Lys:NE ratio promoted lipogenesis, inhibited lipolysis and improved IMF deposition in LD via altering serum metabolism in different manner at two wheat level. LR diets containing 25% wheat was recommended to enhance the growth performance of finishing pigs, while concurrently achieving higher IMF content and improved meat color in the LD.

Geology and mineral assemblages of the early Cambrian black shales in the South Qinling: Implications for vanadium and barium mineralization

Early Cambrian black shales in the South Qinling (SQL) of China constitute one of the world's most important vanadium- and barium-metallogenic belts. It is controversial on the enrichment mechanics of vanadium (V) and barium (Ba) mineralization. The V and Ba mineralization in the Xichuan area from the northern SQL is mainly hosted by shales and chert of the early Cambrian black shales. We conducted mineralogy and geochemistry studies to reveal the mineralization process. Electron probe X-ray microanalysis (EPMA) studies show V is enriched in jarosite, illite and chlorite in shales. The jarosite develops as concretions or flakes and shows close affinity with apatite, with biogenic structures. EPMA and X-ray maps indicate a V heterogenetic distribution within illite and chlorite. Barite occurs as spots and veins in the dark chert and siliceous shale. K-feldspar in shales occurs as columns and flakes with inhomogeneous Ba concentrations. Calcite is intergrown with quartz and Ba-enriched K-feldspar closely in the shales recording the fluctuation of pH values in the diagenetic stage. An acidity environment favors silicification, and increased pH leads to silica dissolution and calcification along with illitization and chloritization. Slightly enriched heavy rare earth elements, positive Eu anomalies, and fluorite from the shales and chert suggest the hydrothermal fluid has existed. Compared with the representative V and Ba deposits associated with black shales worldwide, these deposits occurred synchronously with extinction or anoxic events as both V and Ba mineralization are redox-dependent and associated with organisms. These events could lead to the initial enrichment of V and Ba. Our study suggests that V and Ba mineralization is mainly associated with pH fluctuation in the diagenetic and biogenic processes.

Synergistic effects of Vermi-Co extracts mixture with cytokinins on shoot regeneration of Lindernia minima (Benth.) Mukerjee—An endangered medicinal plant

The present investigation illustrates the synergistic growth effect of Vermi-Co (Vermicast and Coconut-water) extracts mixture with cytokinins on in vitro shoot regeneration of Lindernia minima. Due to less distribution threat status, this plant species has been considered as an endangered plant by IUCN (International Union for Conservation of Nature). Hence, it is necessary to conserve and to develop an efficient plant regeneration protocol for the rapid multiplication of L. minima. The nodal explants were inoculated on (¼) quarter-strength MS (Murashige and Skoog) medium supplemented with different concentrations (0.5 – 2.5 mg L-1) of BA (6-Benzyladenine), KIN (Kinetin) and TDZ (Thidiazuron) combined with various percentages of (5%, 15%, and 25%) Vermi-Co extracts mixture. Among the concentrations tested, 1.5 mg L-1 TDZ with 15% of Vermi-Co extracts mixture produced the maximum percentage of response with the highest (19.5 ± 0.20 shoots/explant) number of shoots and (10.2 ± 0.14 cm) shoot length. Then, the well-elongated shoots were transferred to rooting medium (quarter-strength MS) supplemented with 0.5 – 3.0 mg L-1 of IBA (Indole -3- butyric acid) and IAA (Indole -3- acetic acid). The highest percentage of response (98%) and maximum number of roots were observed in 1.5 mg L-1 IBA with 11.5 ± 0.29 roots per shoot and 6.6 ± 0.28 cm root length. Finally, well-developed plants were successfully transferred to the natural field condition with a survival rate of 97%. The present research revealed that, the combined growth stimulating effect of Vermi-Co extracts mixture combined with cytokinins increased the number of shoots and shoot length on shoot regeneration of L. minima from nodal explants. Our findings will be very useful for regeneration of Lindernia minima through plant tissue culture.

How is carbonate crust digested by magma?

Magma’s volatile budget depends on deep magmatic sources, the degree of differentiation and degassing conditions, and volatile input from the assimilated crust. It is, therefore, important to know the exact mechanism by which the crust is assimilated into magma to understand volatile budgets and eruption behavior. To explore reactions between carbonate, calc–silicate, or skarn xenoliths and basaltic andesite magma, we studied ten calc–silicate xenoliths from the 1994, 1998, 2006, and 2010 Merapi eruptions and four sediment samples of local Javanese carbonate crust. An in situ electron probe microanalysis of the 1994–2010 calc–silicate xenolith minerals and glasses suggests that calcite is a minor and metastable mineral phase in association with wollastonite. In addition, carbonate melts quenched to calcic glasses (32 ± 7 wt% SiO2; 38 ± 3 wt% CaO), similar to experimental glasses produced by crust–melt interaction experiments. Thermodynamic modeling using rhyolite MELTS (version 1.2.0) predicts the production of highly silicic (up to ∼84 wt% of SiO2) and CaO-rich (up to ∼25 wt%) melts during partial melting of calc–silicate material. The observed mechanism of calc–silicate xenolith assimilation is the generation of highly silicic (77 ± 4 wt% of SiO2) melts in association with idiomorphic diopside [Wo49En29; 57 ± 3 Mg# = Mg/(Mg+Fe2+)] and other calcic pyroxenes (Wo54-82 En2-21; 16–43 Mg#) due to partial melting of xenolith and incongruent dissolution reactions. We hypothesize that the rate-limiting process is the subsequent mixing of the produced crustal melts with representative resident andesitic melt (average 65 wt% SiO2) through chemical diffusion, which explains major and volatile (Cl) element contents in the Merapi glass products. In addition to high Sr contents and radiogenic 87Sr/86Sr and elevated CO2, Ba, Co, Cr, Cu, V, Zn, and Zr contents in the magmatic minerals and associated glasses, the recrystallized and residual metamorphic sphene, quartz, garnet, and apatite predicted by rhyolite-MELTS or Magma Chamber Simulator modeling during wallrock melting and residual metastable calcite and wollastonite are important tracers of calc–silicate crust assimilation. The disequilibrium process of calc–silicate crustal assimilation can, thus, be well predicted by dissolution experiments and thermodynamic modeling using rhyolite-MELTS or Magma Chamber Simulator. The rate of calc–silicate crustal assimilation is still unconstrained without adequate high-temperature kinetic time-series experiments. We predict that the crustal assimilation rate is controlled by the Si–Al diffusion and associated convection in the hydrous silicate magma.

Petrogenesis of the Laoshan Suite in the Jiaodong Peninsula (Eastern China): An Oxidized Low Ba–Sr A1-Type Granite

The Jiaodong Peninsula is closely related to Mesozoic granites in terms of spatial and temporal aspects. However, the specific association between the genesis of gold mineralization and these granites remains unclear. It is also ambiguous why Laoshan-type granites, which are similar to Mesozoic granites, are not gold mineralized. In this study, we analyzed the Laoshan granites and compiled Mesozoic magmatic rock data (Linglong, Guojialing, and Weideshan suites) of the Jiaodong Peninsula. We performed whole-rock major and trace elements, LA–ICP–MS zircon U–Pb geochronology and geochemistry analyses. Our zircon U–Pb data denote that the Laoshan granite was emplaced during the 118 ± 1 Ma. The Laoshan granite is characterized by high SiO2 content (76.03–80.28 wt.%), high TFe2O3/MgO (11.1–27.1) and Ga/Al (3.0–3.5) ratios, high zircon saturation temperature (809–850 °C), and negative Eu (Eu/Eu* = 0.05–0.08) anomalies, showing A-type granite characteristics. Furthermore, the Laoshan granite is identified as an A1-type granite with low Ba (33.1–42.0 ppm) and Sr (14.1–21.0 ppm) contents. It was formed in an extensional tectonic environment induced by the subducting slab roll-back of the Paleo-Pacific Plate, mainly from the partial melting of lower crustal materials, mixed with a small amount of mantle components. Zircon trace elements indicate that the Laoshan suite had relatively high oxygen fugacity and temperature (ΔFMQ = + 2.43 to + 4.22, T-Ti in zircon (mean) = 796 °C) compared to the pre-mineralization and contemporaneous mineralization magma. We propose that oxidized adakitic magma (Weideshan suite) may contribute to the enrichment and mineralization of gold. Although Laoshan-type granite also has a high oxygen fugacity, its location is distant from the ore-controlling faults, which ultimately hinders the formation of gold mineralization. From the Jurassic to the Cretaceous, the tectonic and geochemical properties of magmatic rocks in the Jiaodong Peninsula have changed, and gold deposits are formed in such a transitional process (compression to extension, reduction to oxidation).

A New Albite Microanalytical Reference Material from Piz Beverin for Na, Al and Si Determination, and the Potential for New K‐Feldspar Reference Materials

Determination of alkali elements is important to Earth scientists, yet suitable and reliable microanalytical reference materials are lacking. This paper proposes a new albite reference material and evaluates the potential for future K‐feldspar reference materials. The proposed Piz Beverin albite reference material from Switzerland yields a homogeneous composition at the centimetre‐ to micrometre‐scale for Si, Al and Na with &lt; 2000 μg g‐1 total trace elements (mostly heterogeneously distributed Ca, K and Sr). EPMA and LA‐ICP‐MS measurements confirm a composition of 99.5(2)% albite component, which is supported further by bulk XRF measurements. A round robin evaluation involving nine independent EPMA laboratories confirms its composition and homogeneity for Si, Al and Na. In addition, a set of five distinct clear K‐feldspar samples was evaluated as possible reference materials. The first two crystals of adular and orthoclase yield unacceptable inhomogeneities with &gt; 2% relative local variations of Na, K and Ba contents. The three other investigated sets of K‐feldspar crystals are yellow sanidine crystals from Itrongay (Madagascar). Despite distinct compositions, EPMA confirms they are each homogeneous at the centimetre to micrometre scale for Si, Al and K and have no apparent inclusions; further investigation to find larger amounts of these materials is therefore justified.

Nano structural engineering of Ba-substituted Sr-hexaferrites for viable microwave absorbance and magnetic data storage

This work focuses on optimization of magnetic attributes of Sr hexaferrites using Ba as a substituent at Sr-site, for viable utilization in magnetic data storage devices and as microwave attenuation media. In this context, a series of Sr1-xBaxFe12O19 samples was prepared using a facile hydrothermal route. X-ray diffraction confirmed the hexagonal structure with space group P63/mmc. The morphological analysis revealed that the samples had hexagonal nanorod-like morphology which was quite suitable for microwave-absorbing devices and data storage. The analysis demonstrated that the particle sizes were decreased while the width of particles increased with increasing Ba contents. The dielectric parameters were suitably tuned as a function of frequency and Ba contents. The saturation magnetization, coercivity, remanent magnetization, and squareness ratio of all the sample compositions showed an increasing behavior with Ba contents, revealing that the prepared samples were favorable for use as microwave absorbers, data storage devices, and magnetic recording media.

Giant magnetothermal anomalies and direct measurements of the magnetocaloric effect in Pr0.7Sr0.3−xBaxMnO3 manganites

The paper presents the results of a study of magnetization, specific heat (CP), thermal diffusivity (η), thermal conductivity (κ) and direct measurements magnetocaloric effect of polycrystalline samples Pr0.7Sr0.3−xBaxMnO3 (x = 0–0.3). An increase in the Ba concentration leads to a decrease in the Curie temperature (TC), an increase in the disorder parameter (σ2) and a noticeable increase in thermal conductivity of the ferromagnetic phase (FM). The κ(Т) data near ТС revealed small minima and a sharp jump-like change in thermal conductivity upon transition to the FM phase. These results suggest that the anomalies in the temperature dependences of η(Т) and κ(Т) are associated with the scattering of thermal phonons both from distortions of the crystal lattice and from spin fluctuations. The giant change of η (Δη/η ∼ 67%) and κ (Δκ/κ ∼ 33%) was found in a magnetic field of 1.8 T for the x = 0 (Pr0.7Sr0.3MnO3) sample. The maximum values of ∆T, ∆S and relative cooling power (RCP), observed for this sample in a field of 1.8 T, are equal to 1.81 K, 3.38 J/kg K and 74.02 J/kg, respectively. In the studied Pr0.7Sr0.3−xBaxMnO3 samples, the specific cooling power value at f = 0.2 Hz is 0.35, 0.29, 0.21, and 0.11 W/g for x = 0, 0.1, 0.2, and 0.3 sample, respectively.

Determination of concentrations of Sr and Ba in coal and coal combustion by-products: A comparison between results by ICP-MS and XRF techniques

Concentrations of trace elements in coal and coal combustion products are commonly analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) due to large number of elements detected and the relatively the low detection limits of this technique. Like other geological samples, complete dissolution of coal and coal combustion products is also essential for accurate ICP-MS results. In this study, Sr and Ba in coal and coal combustion products (fly and bottom ashes) from two coal-combustion power plants from North China analyzed by XRF and ICP-MS were comparatively studied. The concentrations of Sr and Ba analyzed by ICP-MS, when a mixture of acids (2 ml HF + 5 ml HNO3 for each 50 mg coal sample and 5 ml HF + 2 ml HNO3 for each 50 mg ash sample) was used for microwave-assisted digestion, do not fit well with the their relative XRF results. This is most probably due to the formation of the fluorides during microwave digestion, and this assumption is supported by the presence of various fluoride compounds, NaMgAl(F, OH)6·H2O, NH4MgAlF6, AlF3, and K2SiF6, in the residues of all the coal and ash samples in our sequential extraction experiment. Cations of Sr and Ba were probably trapped into the divalent cation sites of the fluorides. Concentrations of Sr and Ba analyzed by ICP-MS using increased HF and HF/HNO3 ratio (7 ml HF and 2 ml HNO3 for each 50 mg coal/ash sample) are in better agreement with the XRF results. Our results indicate that excess amount of HF probably has led to the suppression of these elements due to fluoride precipitation. The results indicate that the modified digestion method is capable of achieving complete digestion of coal samples and results in a reliable analysis of Sr and Ba concentrations in coal samples and most fly ashes by ICP-MS. However, the formation of insoluble fluorides is probably not completely suppressed for some bottom ash samples, which can result in underestimation of Sr and Ba concentrations. Nevertheless, XRF analysis can serve as a reliable cross-check method to assist in the evaluation of the accuracy of ICP-MS results.

Trace Elemental and Heavy Metal Levels in Frequently Consumed Local Vegetables of Three Chronic Kidney Disease-Prevalent Villages.

The present study reports the trace elemental and heavy metal (24 elements) levels in six (Capsicum frutescence L., Carica papaya L., Momordica charantia L., Moringa oleifera Lam., Musa sapientum L., and Solanum melongena L.) vegetables. The vegetable samples are collected from the three villages and are subjected to ICP-MS analysis, to test a group of 24 elements, viz., Li, Be, Al, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Ag, Cd, Cs, Ba, TI, Rb, and U, for their levels. The obtained levels of each element were compared with the WHO/FAO permissible values. Out of the tested 24 elements, 16 elements may cause kidney problems and the remaining 8 (Mn, Co, Ni, Cu, Zn, Se, Sr, and TI) may cause other health problems when they are in high concentration (FAO/WHO, 18; ATSDR, 19; Drake and Hazelwood in Ann Occup Hyg 49:575-585, 20; US EPA, 21; FAO/WHO, 22; Choudhury et al., 23; Food Safety and Standards, 24). The results reveal that Ba is in high concentration (2.51 times) in all the tested vegetable samples and Pb is in high concentration (1.28 times) in 11 vegetable samples; Ag and Fe are high in one vegetable sample each. Among the three locations highest Ba concentration is observed in S1 (Capsicum) of L2 followed by S5 (Musa) and S1 (Capsicum) of L1. The higher Pb concentration is present in S1 (Capsicum) of L3 followed by S1 (Capsicum) of L2. The results reveal that out of the six vegetables tested, Capsicum shows high concentrations of Ba and Pb. The variation in the levels of trace elements and heavy metals with regard to location and vegetable samples may be due to soil and or due to groundwater.

Revealing the link between A-type granites and hottest melts from residual metasedimentary crust

Abstract Among S-, I-, and A-type granites, the latter are the most debated in terms of origin, and metasedimentary crust is usually discarded as a potential source. Here we tackle this issue by adopting an in-source perspective, rather than focusing on the final product (granite), documenting the occurrence of pristine melt inclusions (MIs) in garnet from residual metapelitic ultrahigh-temperature (UHT) granulite from East Antarctica. Coexistence of sapphirine + quartz, phase equilibria calculations, and Zr-in-rutile thermometry indicate that MIs trapped UHT melts formed at peak conditions (930–1000 °C) from a residual metapelitic source. MIs are granitic with weakly peraluminous to weakly peralkaline affinity, ferroan character, high alkali contents, high K/Na and Ga/Al, and low Ca, Ba, Sr, and H2O concentrations. These features and geochemical modeling indicate that MIs represent primary melts for high-SiO2 A-type granites. Therefore, MIs reveal the missing link between A-type granites and the hottest metasedimentary crust. Voluminous amounts of slightly peraluminous, high-SiO2 A-type granites can be produced in large, residual UHT terranes such as those of eastern Gondwana. Our results provide a wider view of processes responsible for granite formation and show that a larger variety of granites must be considered in models of the effects of UHT anatexis on crustal differentiation.