Trace element zoning in dolomite: Proton microprobe data and thermodynamic constraints on fluid compositions

Petrography, trace elements and oxygen and carbon isotopes of Gordon Group carbonates (Ordovician), Florentine Valley, Tasmania, Australia

Mg isotopic geochemistry and origin of Early Ordovician dolomite and implications for the formation of high-quality reservoir in the Tabei area, Tarim Basin, NW China

Effects of selenium on agronomical characters of winter wheat exposed to enhanced ultraviolet-B

The Aptian shallow-water carbonate platform of the Benassal Formation in eastern Spain (Maestrat Basin) contains facies dominated by scleractinian corals. Corals and coral reefs are widely used as environmental archives; however, the effects of their complex diagenetic evolution are a major factor impacting reliable reconstructions of the environments. This study addresses the environmental signatures (i.e. relative sea-level changes) and burial conditions that controlled the various diagenetic minerals present in the Aptian coral facies. A multiproxy approach including petrographic and geochemical evaluation reveals the diagenetic pathways, fluid compositions and timing accounting for the syn- to post-depositional history of this ancient coral facies. Cc1, which shows low Fe and Mn content and high Na content, precipitated within the primary porosity, alongside the replacement of coral skeletons, in a mixing zone dominated by marine waters. Cement Cc2, characterized by its higher Fe and Mn content and low Na values, precipitated in the mixing zone dominated by meteoric waters related to a relative sea-level drop. Cement Cc3, distinguished by low Fe and Mn content and high Na content, reflects a subsequent phase of increased marine influence, likely associated with a relative sea-level rise. Silica and isolated rhombohedral dolomite crystals formed concurrently in this mixing zone. During intermediate burial, saddle dolomite and cement Cc4 precipitated from high-temperature formation brines. Finally, during uplift, meteoric fluids caused the calcitization of previously formed dolomite rhombohedra.

The complete and well-studied pelagic carbonate successions from the Umbria-Marche basin (Italy) permit the study of the event-rich stratigraphic interval around the Cretaceous-Paleogene boundary (e.g., Deccan volcanism, boundary impact, Paleocene recovery, and climate). To test the robustness of various proxy records (bulk carbonate δ13C, δ18O, 87Sr/86Sr, and Ca, Fe, Sr, and Mn concentrations) inside the Umbria-Marche basin, several stratigraphically equivalent sections were investigated (Bottaccione Gorge, Contessa Highway, Fornaci East quarry, Frontale, Morello, and Petriccio core). Besides the classical Gubbio sections of Bottaccione and Contessa, the new Morello section is put forward as an alternative location for this stratigraphic interval because it is less altered by burial diagenesis. Elemental profiles (Ca, Fe, Sr, Mn) acquired by handheld X-ray fluorescence (pXRF) efficiently provide regional chemostratigraphic and paleoenvironmental information. The Deccan volcanism, the Cretaceous-Paleogene boundary, the characteristic pattern of the Sr/Ca profile across the boundary driven by the extinction and recovery of coccolithophores, and the Dan-C2 hyperthermal event are examples of such recorded paleoenvironmental events. Moreover, cyclostratigraphic analyses of proxies of detrital input (magnetic susceptibility and Fe concentrations) show the imprint in the sedimentary record of a 2.4 m.y. eccentricity minimum around 66.45–66.25 Ma, and suggest that the occurrence of the Dan-C2 hyperthermal event was astronomically paced.

Assessment of Cd availability in rice cultivation (Oryza sativa): Effects of amendments and the spatiotemporal chemical changes in the rhizosphere and bulk soil.

Mississippi Valley-type (MVT) deposits contain about 20% of global zinc resources and host critical raw materials crucial to the development of green technologies. Despite their economic and strategic importance, there is a lack of consensus on the duration of mineralizing fluid flow events in MVT systems. This study couples in-situ U-Pb dating with Sr-isotope and trace element analysis of syn- and post-ore gangue carbonates to establish: (1) timing and duration, (2) redox evolution, and (3) flow rates of mineralizing fluids in the world-class San Vicente Zn-(Pb) deposit (Peru). New radiometric ages bracket the crystallization of syn-mineralization dolomite, characterized by high Fe and Mn contents and Sr isotopic values overlapping with that of host carbonates, between 103.2 ± 4.1 Ma and 70.6 ± 5.6 Ma. This age interval reveals a direct genetic relationship between flow of mineralizing fluids and late Cretaceous Andean compressional tectonics. Basinal fluid expulsion coeval with known tectonic events continues in the district until Pliocene times, driving episodic crystallization of post-ore hydrothermal carbonates between 61.6 ± 9.3 and 2.7 ± 0.2 Ma. The low Mn and Fe content and high 87Sr/86Sr values characteristic of these post-ore, bedding-parallel and cross-cutting carbonate veins indicate a colder, oxidized environment. Our findings highlight the contribution of paired carbonate geochemistry and U-Pb geochronology in drawing links between tectonic events, fluid expulsion and the waxing and waning of mineralization potential in foreland basins. The results of this study challenge our understanding of timescales in MVT systems and imply that anomalous metal enrichment in basinal fluids over a short temporal interval is not a necessary precondition to form economic-sized, sediment-hosted Zn-Pb deposits. Rather, it is the coexistence of a focused fluid flow in an interconnected aquifer with suitable metal depositional mechanisms over a prolonged period of time (106–107 yr) that allows precipitation of economic amount of base metals at a specific site in the upper crust.

The aim of the present study is to evaluate the status of plasma essential trace element selenium (Se), manganese (Mn), copper (Cu), zinc (Zn), and iron (Fe) concentrations and the effect of these elements on oxidative status in patients with childhood asthma. Plasma Se, Mn, Cu, and Zn concentrations were determined by atomic absorption spectrophotometry (AAS) and Fe concentrations, malondialdehyde (MDA), and total antioxidant capacity (TAC) were determined by the colorimetric method. The plasma MDA/TAC ratio was calculated as an index of oxidative status. Plasma albumin levels were measured to determine nutritional status. Plasma Fe concentrations, MDA levels and the MDA/TAC ratio were significantly higher (p<0.001, p<0.001, and p<0.01, respectively) and Se and Mn concentrations and TAC were lower (p<0.01, p<0.05, and p<0.01, respectively) in patients when compared to the healthy subjects. Plasma Zn, Cu, and albumin levels were not found to be significantly different in patients and controls (p>0.05). There were positive relationships between plasma MDA and Fe (r=0.545, p<0.001) and TAC and Se (r= 0.485, p<0.021), and a negative correlation between TAC and MDA values (r= -0.337, p<0.031) in patients with childhood asthma. However, there was no correlation between these trace elements and albumin content in patient groups. These observations suggest that increased Fe and decreased Se concentrations in patients with childhood asthma may be responsible for the oxidant/antioxidant imbalance.

Iron (Fe) toxicity is recognized as a widely observed nutritional disorder that lowers rice crop productivity worldwide. The high concentration of Fe in soil may also alter the uptake and accumulation of other mineral elements. However, the relative change in the accumulation of other mineral elements affected by Fe toxicity is largely unknown. Therefore, this experiment studied the mineral nutrition of two Fe-tolerant (Bw372 and Bw267-3) and Fe-susceptible (Bw272-6B and Bg359) rice varieties to variable Fe concentration in the growing medium. Four Fe concentrations were used; 7 mgL− 1(1.25 × 10− 4molL− 1), 100 mgL− 1 (1.79 × 10− 3molL− 1), 300 mgL− 1 (5.37 × 10− 3 molL− 1), and 500 mgL− 1 (8.95 × 10− 3 molL− 1). The experiment was conducted as a hydroponic system with 15 plants as replicates for each treatment combination. Results revealed that, when increasing Fe concentration in the growing medium, tissue Fe, Na, and Co concentrations increased while tissue Mn, Mg, Mo, Cu, Zn, and Cd concentrations decreased for all the varieties. When comparing varieties, the concentration of Fe in Bw372 was the lowest, and that in Bw272-6B was the highest. As a result, the reduction in shoot dry weight (SDW) and root length (RL) to increased Fe concentration was the lowest in Bw372 (33% for SDW and 40% for RL) and highest in Bw272-6B (64% for SDW and 52% for RL). Moreover, Bw372 and Bw267-3 did not show bronzing symptoms when grown in any of the tested Fe concentrations. These traits have contributed to Bw272-6B being susceptible and Bw372 being tolerant to Fe toxicity.

&amp;lt;p&amp;gt;The deep subseafloor biosphere represents one of the Earth&amp;amp;#8217;s largest, but also least understood ecosystems with diverse species and mostly uncharacterized microbial communities. International Ocean Discovery Program (IODP) Expedition 370 (Temperature Limit of the Deep Biosphere off Muroto) established Site C0023 down to 1180 mbsf in the Nankai Trough off Japan to explore the upper temperature limit of microbial life in the deep sedimentary biosphere [1]. Site C0023 is characterized by a complex lithostratigraphic and depositional history with strongly changing sedimentation rates. Volcanic ash layers are ubiquitous in all lithological units. However, the highest abundance of ash layers could be observed between 400 and 700 mbsf. Previous studies have shown that volcanic ashes represent hotspots for microbial life [2] and are commonly characterized by high Fe(III) and Mn(IV) contents [3]. Onboard measurements show a release of dissolved Fe in the depth interval associated with the highest abundance of ash layers [1]. Therefore, we hypothesized that the release is related to microbial Fe reduction fueled by the mineralogy of the volcanic ash. In order to identify the source and reaction pathway of the liberated Fe, we applied sequential extractions of differently reactive Fe oxide pools on mud rock and ash layer samples as well as stable iron isotope (&amp;amp;#948;&amp;lt;sup&amp;gt;56&amp;lt;/sup&amp;gt;Fe) analyses on pore-water and solid-phase samples. Microbial Fe reduction leads to Fe isotope fractionation with an enrichment of light isotopes in the released Fe and a respective enrichment of heavy isotopes in the residual ferric substrate. Therefore, the &amp;amp;#948;&amp;lt;sup&amp;gt;56&amp;lt;/sup&amp;gt;Fe signals of different reactive Fe pools and the pore water are used to identify the pools actually involved in microbial respiration processes. Our results show that the total Fe content in mud rock of Site C0023 is relatively constant at ~4.2 wt%. Reactive Fe oxides represent 25% of the total Fe. The bulk Fe content in the ash layers varies between 1.4 and 6.8 wt%. Surprisingly, most ash samples contain less total Fe (3.35 wt% on average) compared to the surrounding mud rock. Similarly, the contents of the reactive Fe oxides are significantly lower. This indicates that either (1) ash layers do not represent the energy substrate for microbial Fe reduction, or (2) reactive Fe in ash samples has already been used up by microbes. The bulk Fe content in recent volcanic material from an active volcano on the Japanese island arc is ~4.4 wt% [4]. The higher Fe content in fresh volcanic material compared to ash samples at Site C0023 might suggest that reactive Fe in ash layers is already reduced. Alternatively, the dissolved Fe release might be related to microbial reduction of structural Fe(III) in smectite promoting the smectite-to-illite transition, which has previously been proposed for Site C0023 [5].&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;

This study was carried out over a 7-month period at two active clam fishing locations, Ada and Aveglo at the Volta estuary in Ghana, to assess the levels of some heavy metals: Mn, Zn, Fe and Hg in whole soft tissue of Galatea paradoxa and their suitability for human consumption. The clam, Galatea paradoxa (Born 1778) is a commercially important bivalve species exploited mainly for its flesh. In Ghana, it constitutes an important and affordable protein source and is consumed by the riparian communities and beyond the Volta estuary. For each sampling location 30 clams were obtained and grouped into three size classes of 10 individuals, each based on shell lengths. The categorization was as follows: small (25–40 mm), medium (41–55 mm), and large (above 55 mm). The groupings were chosen based on the three dominant size groups in the natural population to give a broad and representative range of metal concentrations in the clams. The concentrations of zinc, iron and manganese were determined using a flame Atomic Absorption Spectrophotometer (AAS) and mercury concentrations were determined using an Atomic Mercury Analyzer. The results were expressed as total concentrations (μg/g dry weight (dw)). There were no significant differences (p>0.05) in Mn, Fe and Zn concentrations among the different size classes except for Hg concentration in clams from Ada, indicating a similar bioavailability of Mn, Fe, Zn at both locations and, possibly, an efficient metabolism to keep the concentrations of Mn, Fe and Zn relatively similar in the tissues of the different clam sizes. Spatial variations in metal concentrations (i.e., Ada small vs. Aveglo small, Ada medium vs. Aveglo medium, and Ada large vs. Aveglo large) were not significant for Mn, Zn and Hg for all the size classes. However, variations in Fe concentration in the large-sized clams was significant (p<0.05).

The influence of diagenesis on carbon and oxygen isotope values in shallow water carbonates from the Atlantic and Pacific: Implications for the interpretation of the global carbon cycle

Four single‐cross corn hybrids (Zea mays L.) which differ with respect to their accumulations of Ca, Sr, Mg, and K were grown under greenhouse conditions in soil treated with 0, 100, 200, and 400 ppm of Sr as SrNO3. The investigation was conducted to determine if these hybrids would exhibit variable selectivity for Sr compared with Ca and Mg.All hybrids responded substantially to Sr additions to the soil. The concentrations of Sr in hybrids I and IV increased more with increasing rates of Sr than was observed for the other two hybrids. Relative to concentrations of Ca plus Mg in the plants, hybrid IV accumulated more Sr than did hybrid III with the other two hybrids being intermediate. Results for selectivity ratios indicated that Sr was removed as readily by hybrid IV as were Ca and Mg, while other hybrids were selective for Ca and Mg in preference to Sr. It was concluded that although variable selectivity was evident among the hybrids, the concentrations of Sr accumulated by the hybrids were predominantly a function of the availability of Sr in the soil and the Sr and Ca accumulation characteristics of the hybrids. It is not likely that hybrids can be developed which accumulate high concentrations of Ca and low concentrations of Sr.

Sr isotope tracing of multiple water sources in a complex river system, Noteć River, central Poland

Estudou-se o efeito do composto de lixo urbano na fertilidade e nos teores totais e extraídos com solução de DTPA 0,005 mol L-1 pH 7,3 dos elementos Fe, Mn, Zn e Ni em um Podzólico Vermelho-Amarelo textura arenosa, em casa de vegetação. Empregou-se sorgo como planta-teste, avaliando-se perfilhamento, produção de matéria seca e quantidade acumulada dos elementos P, K, Ca, Mg, Fe, Mn, Zn e Ni em função de doses de composto equivalentes a 0, 12,5, 25, 50 e 100 t ha-1, na ausência e na presença de adubação mineral. O composto aumentou a produção de matéria seca do sorgo na ausência de adubação mineral; esta, contudo, promoveu maior aumento de produção e perfilhamento das plantas. Na parte aérea de sorgo, não foi detectado Ni, enquanto as quantidades acumuladas de Fe, Mn e Zn relacionaram-se com os teores no solo extraídos com DTPA. A aplicação do composto de lixo promoveu aumento dos valores de pH, matéria orgânica, bases trocáveis, P resina e CTC do solo, reduzindo a acidez potencial (H + Al). Os teores totais de Fe, Mn e Zn no solo aumentaram com as doses do composto, enquanto o de Ni aumentou somente na ausência de adubação mineral. Os teores de Zn e Ni no solo, extraídos com DTPA, aumentaram com as doses do composto tanto na ausência como na presença de adubação mineral; já os de Mn e Fe diminuíram na presença de adubação mineral e não foram alterados na sua ausência. Apesar de não ter ocorrido acúmulo dos metais pesados no tecido vegetal, houve incremento no solo de alguns dos elementos; portanto, deve-se atentar para aplicações sucessivas de composto de lixo domiciliar.