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Garnet zonation provides an unparalleled record of the pressure-temperature-time-fluid evolution of metamorphic rocks. At extreme temperature conditions >900 °C, however, most elements preserve little zonation due to intracrystalline diffusional relaxation. Under these conditions, slowly diffusing trace elements including P, Na, and Ti have the best chance of recording metamorphic histories. Here we map dramatic zoning patterns of these elements in subducted high-pressure felsic granulite (Saxon Granulite Massif) and ultrahigh-pressure diamondiferous \"saidenbachite\" (Saxonian Erzgebirge, Bohemian Massif). The results show that garnet replacement via interface coupled dissolution-reprecipitation can strongly affect garnet compositions in subduction zones and that P, Na, and Ti record burial and exhumation histories that are otherwise lost to diffusion. In these samples, P diffuses the slowest, and Ti the fastest.

Paleoenvironmental conditions significantly influence the distribution patterns and organic matter enrichment of shale. This study investigated the vertical variations of major elements, trace elements, and total organic carbon (TOC) in the Lower Carboniferous marine shale from the Yaziluo Rift Trough, South China, to understand the paleoenvironmental conditions, including redox conditions, terrigenous detrital input, paleoproductivity, and paleo-seawater depth. The Lower Carboniferous formation consists of three sedimentary facies: basin facies, lower slope facies, and upper slope facies. From the basin to the lower slope and then to the upper slope facies, TOC, quartz, and pyrite contents gradually decrease, whereas the carbonate mineral content shows an increasing trend. A continuous decline in paleo-seawater depth transformed a deep-water anoxic environment with high paleoproductivity and low detrital input in the basin facies into a semi-deep-water environment with dysoxic-oxic conditions and moderate detrital influx in the lower slope facies, evolving further into a suboxic environment with high detrital flux in the upper slope facies. The geochemistry results suggest that anoxic conditions and high paleoproductivity were the primary controls on organic matter enrichment in the siliceous shale of the basin facies. In contrast, redox conditions significantly influenced organic matter accumulation in the mixed shale of the lower slope facies, attributed to relatively low paleoproductivity in a more restricted marine setting. Additionally, the adsorption of carbon components by clay minerals facilitated the preservation of organic matter in the calcareous shale of the upper slope facies.

PurposeSurveillance monitoring programs can provide fast, relatively low-cost, synoptic information on key water quality drivers and help inform land management decisions. Here, we evaluate longitudinal changes in the geochemical composition and metal speciation of deposited sediment over a 967 km reach of a large glacier-fed river and its key tributaries in central Alberta, Canada. In particular, the work provides a basis to understand how a major urban conurbation influences the geochemical composition and trace element properties of deposited sediment.MethodsThe concentrations and spatial distribution of major elements and sediment-associated metals (As, Cd, Cr, Cu, Pb, Hg, Ni, Zn) were determined and compared to consensus-based threshold effect concentrations (TEC). Metal partitioning to geochemical properties of sediment was evaluated by sequential extraction.ResultsLevels of Cr exceeded the TEC in 28% and 20% of the samples in the North Saskatchewan River and tributary samples, respectively. One Ni sample (3%) also exceeds the TEC on the main stem of the North Saskatchewan River. No consistent downstream increase in major element or trace metal concentrations was observed. The majority of Cr was bound to the largely non-bioavailable silicate phase thus highlighting the importance of parent geology as a source of metals to receiving streams.ConclusionThe results of this surveillance monitoring provide preliminary data on the distribution and speciation of sediment-associated metals in the North Saskatchewan River and thereby address an evidence gap common to many large river basins in Canada.

The Fulu iron formation (IF) is an iron-rich unit in the Neoproterozoic glacial successions, South China. The major element data suggest that the iron sources of the Fulu IF are derived from binary mixing from hydrothermal and detrital loads. The Fulu IF is characterized by slightly positive Eu anomalies similar to other Neoproterozoic IFs, indicating that a high-temperature hydrothermal input may contribute little to Neoproterozoic IFs. A shift from non-existent to slightly negative Ce anomalies of the Fulu IF indicates that the IF precipitated across an iron chemocline separating a weakly oxic surface ocean from an oxygen-depleted deep ocean.

The Cambrian period holds a crucial position in the history of life evolution. The Cambrian strata in the Yangtze Plate is a research hotspot in multiple disciplines and it of great significance for the study of the “Cambrian Explosion”. However, the research on the provenance and the degree of weathering of the sedimentary rocks in the Wulongqing (WLQ) Formation remains insufficient. This study focuses on the Cambrian WLQ Formation in the Yangtze Plate. A total of 26 samples, including sandstone and mudstone, were collected and analyzed using petrographic and geochemical analysis (including major elements, trace elements and rare earth elements) to constraint provenance and paleoweathering. The results show that SiO2, Al2O3, and total Fe2O3 (Fe2O3T) are the main components. The average total concentration of rare earth elements is higher than the average value of the Upper Continental Crust. Through a variety of discrimination methods, such as the ratios of w(SiO2)/w(Al2O3) and w(Al2O3)/w(TiO2), the Zr–TiO2 and Th/Sc–Zr/Sc diagrams, it is indicated that sedimentary rocks and felsic igneous rocks are the main provenances. The paleoweathering was evaluated by Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA). The CIA value ranges from 56.08 to 75.92, with average value 68.03, indicating a moderate chemical weathering. After correcting for the K metasomatism during diagenesis, the CIAcorr value indicates that deposition took place various climatic conditions ranging from warm and humid to hot and humid. The CIAcorr value indicated a moderate to strong chemical weathering. These findings provide critical geochemical evidence for deciphering the evolution of the Cambrian paleoenvironment. This study establishes connections to biological events through the disclosure of felsic provenance characteristics within the WLQ Formation and the interpretation of paleoclimatic shifts as evidenced by chemical weathering patterns.

The organic matter content of sludge can improve the physical, chemical and biological properties of the soil ensuring better cultivation and good agricultural productivity. The objective of this study is to evaluate the effect of sewage sludge on the main physicochemical and biological properties of the soil. The sludge was spread in an agricultural field in Ain defla (Algeria) cultivated with a tomato crop (‘Panikra’) in four treatments: (T): soil without sewage sludge and without mineral fertilization, (B): soil with sewage sludge, (E): soil with mineral fertilization, (B + E): soil with sewage sludge and mineral fertilization. For this, several physical, chemical and microbiological properties were analyzed on the residual sludge used and the soils collected in the studied plots. The results show that the sludge used does not exhibit any toxicity and that the treatment with the sewage sludge with the fertilizer used on the agricultural soil forms a better compost for improving the physicochemical quality of the soil compared to the other treatments. The application of sewage sludge also can accelerate microbial activity by increasing the number of bacteria, fungi and azotobacter.

The compositions of soils and their parent materials were studied within one of the most northern land areas of the world — the island of Alexandra Land of the Franz Josef Land archipelago. Contents of 65 trace and major elements were determined using atomic emission spectrometry (ICP-AES) and inductively coupled plasma spectrometry (ICP-MS). Other analyzed characteristics included soil pH, particle-size distribution and contents of carbon and nitrogen. The bedrock had an alkaline pH, whereas the soil pH ranged from weakly acid to alkaline. The textural class of the soils predominantly corresponded to sandy loam. The contents of clay and silt increased with depth due to the migration of these fractions with groundwater. The studied soils were formed on basalts with high contents of MgO, Fe2O3, TiO2, Cu, Co, V, Ni, Cr, Zn, and low contents of Pb and Hg. The present study confirms that the FJL basalts are similar to the Siberian Platform basalts in composition and belong to the continental basalt series. The composition of soils was generally similar to that of the bedrock. Compared to other Arctic archipelagos (i.e., Svalbard, Severnaya Zemlya), the soils of Alexandra Land are characterized by increased contents of Cu, Mn, Co, and Fe and reduced contents of Hg, Pb, and Cd. The median concentrations (mg kg−1) of trace elements in the soils were as follows: Cu—142, Zn—100, Ni—72, Pb—2.4, Cd—0.1, and Hg—0.0052. The low contents of Hg, Pb, and Cd in the soils are indicative of low inputs of these elements from both long-range transport and local sources of pollutants.

In this study, we investigated the spatial characteristics of the rate of soil distribution and the mechanism of major element migration in a typical karst hillslope in Guangxi Province, Southwestern China. Soil redistribution was examined using 137 Cs technique under different hillslope components. With the combination of geochemical methods, the migration characteristics of major elements in soils of three hillslope components in both the horizontal and vertical directions were determined. Thirty-seven soil samples were collected and analyzed for 137 Cs and the major elements were determined. By using the profile distribution model the mean soil redistribution rates were found to be -17.01, 0.40 and -23.30 t ha -1 yr -1 in the summit (BYSD), shoulder (BYSY) and toeslope (BYSJ) components of the studied hillslope, respectively. In comparison to BYSD, the sesquioxides of Fe 2 O 3 and TiO 2 tend to be enriched, whereas the alkalis (CaO, MgO, Na 2 O and K 2 O) tend to be depleted, both in the shoulder and toeslope components. Due to human and animal activities, the contents of CaO, MgO, K2O and Na 2 O have somewhat increased within the topsoil. The results indicated that 137 Cs activities are significantly correlated with clay particles and organic matter, and are affected by the pedogenic process and vegatation. Overall, it maybe necessary to use techniques such as 137 Cs to investigate soil erosion with the combination of geochemical methods.

Garnet is one of the most robust and ubiquitous minerals that record element zoning during crustal metamorphism. In addition to major elements, zoning in trace elements can provide a wealth of information to document the changing conditions of garnet growth and modification. However, mapping trace elements at low concentrations, over large areas and with high resolution has remained a major challenge. We present a comprehensive investigation of the TE distribution in garnet from three Alpine samples that underwent a complex evolution at different metamorphic conditions. The TE distribution in garnet grains is mapped in 2D in thin section with a novel approach using laser ablation inductively coupled plasma time of flight mass spectrometry (LA-ICP-TOFMS) to achieve a lateral resolution of 5 µm and limits of detection for the heavy rare earth elements (REE) down to 0.2 µg/g. Comparison with major element zoning measured by electron probe microanalysis and trace elements measured by conventional LA-ICPMS spot analysis testifies to the accuracy of the measurements. Garnet in an amphibolite-facies metapelite from Campolungo, Central Alps, that recorded metamorphism to 600 °C preserves Y + REE trace element zoning that closely matches that of Ca. In this sample, there is no notable diffusive modification for trace elements. Y + REE zoning is dominated by Rayleigh fractionation in the core and by the sporadic breakdown of accessory phases producing annuli in the rim of the garnet. A granulite-facies garnet from Malenco, Eastern Central Alps, formed during subsolidus heating, followed by peritectic melting reactions up to temperatures of 800–850 °C. Major and trace element zoning are decoupled indicating diffusional resetting of major elements, whereas trace elements still largely document the growth history. Enrichment of trace elements in the garnet mantle may be related to the consumption of biotite (V, Cr) and the dissolution of zircon (Zr) and monazite (Y + REE) in the melt. Diffusion of Y + HREE at the core–mantle boundary occurred over a length scale of ~ 200 µm. Garnet in an eclogite from the Sesia Zone, Western Alps (P ~ 2 GPa, T ~ 600 °C), displays pronounced fluid-related veinlets, visible in FeO, MgO and MnO, which cross-cut the primary growth zoning. Surprisingly, complex Y + REE and Cr zoning is not affected by the veinlets, indicating that they did not form by a crack-seal mechanism but are rather related to a selective replacement process. The trace element maps provide a detailed insight into the growth and modification of garnet and thus allow assessment of equilibrium versus disequilibrium processes, and assist in determination of P–T conditions, garnet dating, diffusion modelling as well as documenting fluid-induced modifications.

By coordinating the design and distribution of global climate model simulations of the past, current, and future climate, the Coupled Model Intercomparison Project (CMIP) has become one of the foundational elements of climate science. However, the need to address an ever-expanding range of scientific questions arising from more and more research communities has made it necessary to revise the organization of CMIP. After a long and wide community consultation, a new and more federated structure has been put in place. It consists of three major elements: (1) a handful of common experiments, the DECK (Diagnostic, Evaluation and Characterization of Klima) and CMIP historical simulations (1850-near present) that will maintain continuity and help document basic characteristics of models across different phases of CMIP; (2) common standards, coordination, infrastructure, and documentation that will facilitate the distribution of model outputs and the characterization of the model ensemble; and (3) an ensemble of CMIP-Endorsed Model Intercomparison Projects (MIPs) that will be specific to a particular phase of CMIP (now CMIP6) and that will build on the DECK and CMIP historical simulations to address a large range of specific questions and fill the scientific gaps of the previous CMIP phases. The DECK and CMIP historical simulations, together with the use of CMIP data standards, will be the entry cards for models participating in CMIP. Participation in CMIP6-Endorsed MIPs by individual modelling groups will be at their own discretion and will depend on their scientific interests and priorities. With the Grand Science Challenges of the World Climate Research Programme (WCRP) as its scientific backdrop, CMIP6 will address three broad questions: - How does the Earth system respond to forcing? - What are the origins and consequences of systematic model biases? - How can we assess future climate changes given internal climate variability, predictability, and uncertainties in scenarios? This CMIP6 overview paper presents the background and rationale for the new structure of CMIP, provides a detailed description of the DECK and CMIP6 historical simulations, and includes a brief introduction to the 21 CMIP6-Endorsed MIPs.