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This study investigates the influence of the Changbaishan mantle plume, formed by dehydration of stagnant slab, on Cenozoic intraplate magmatism in Northeast China, focusing on the plume's dominant influence zone. Compared to prior research, this paper includes a more extensive published dataset of major and trace element compositions of basalts and adopts machine learning algorithms with better generalization capabilities for the data being analyzed. This approach measures the geochemical similarity of basalts in Northeast China to training data from different geological backgrounds, determining their degree of influence by subduction-derived fluids. Global ocean island basalts (OIBs) and East African continental rift basalts (CRBs) serve as training data for subduction-distal basalts, while global island arc basalts (IABs) represent subduction-proximal basalts. A binary classification model is constructed through ridge logistic regression and support vector machine to establish a hyperplane in high-dimensional space. The greater the positive distance of the basalt data from the hyperplane, the closer it is to subduction-proximal basalts, and vice versa. Model feature importances correlate with their enrichment capacity in fluids, and the application of well-trained models to basalts with known water content shows a positive correlation between model results and H 2 O/Ce ratios, collectively demonstrating the models' ability to capture fluid signals. Model results of all Cenozoic basalts in Northeast China reveal that within a 600-km range centered on Changbaishan, fluid signals attenuate radially outward, rather than a continuous decrease along the subduction direction of the Pacific plate. This indicates a fluid-rich upwelling centered around Changbaishan, with fluid distribution decreasing from the center to the periphery. This upwelling plays a primary role in controlling the generation of Cenozoic basalts within a specific geographic range. • Big data methods investigate the origin of Cenozoic basalts in Northeast China. • Machine learning models detect fluid signals in the mantle source of Cenozoic basalts. • Fluid signals of Cenozoic basalts diminish radially from Changbaishan. [ABSTRACT FROM AUTHOR]

Adakites formed at the oceanic subduction zones are sodic, whereas adakitic rocks in continental collision zones are generally potassic. Many orogenic belts also contain sodic adakitic rocks which formed during continental collision. The source and petrogenesis of these sodic adakitic rocks are debated. In this paper, we present whole-rock geochemical and Sr Nd isotope, and zircon U–Pb–Hf–O isotope and trace element data for the newly identified Early Devonian granitic pluton from the Balong area in the East Kunlun Orogen (EKO), China. The Balong granites are characterized by low K 2 O/Na 2 O (0.40–0.84), high Sr/Y (33–53), and variable (La/Yb) N (6–40) ratios coupled with low Yb (0.71–1.05 ppm) and Y (7.80–12.8 ppm) concentrations. They display low MgO contents (0.60–1.23 wt%) and Mg# values (38–45), as well as low Cr (2.57–5.08 ppm) and Ni (1.10–1.90 ppm) concentrations. They have whole-rock (87Sr/86Sr) i = 0.7101–0.7123 and ε Nd (t = 418 Ma) = −6.8 to −5.8. Autocrystic zircon rims yield U Pb ages of 420–417 Ma, whereas relict zircon cores have Neoproterozoic ages of 918–909 Ma. The zircon rims have low P contents, variable ε Hf (t = 418 Ma) values of −6.4 to +2.2, and δ18O values of 5.4‰–7.5‰, whereas the zircon cores have elevated P contents, variable ε Hf (t) values of −5.5 to +5.3, and relatively high δ18O values of 8.2‰–9.8‰. These whole-rock and zircon geochemical characteristics suggest a genetic link with the Neoproterozoic S-type orthogneisses and MORB-like (mid-ocean ridge basalt) eclogites in the EKO. Two end-member mixing calculations show that the whole-rock Sr Nd and autocrystic zircon Hf isotopic compositions of the Balong granites can be produced by mixing 60–50 wt% orthogneiss-derived melt and 40–50 wt% eclogite-derived melt. Given that the P–T paths of the exhumed continental eclogites did not intersect the wet solidus of mafic rocks, we suggest the Balong granites formed by partial melting of ultrahigh-pressure metamorphic rocks of the subducted plate trapped beneath the lower crust of the overlying plate. These results, combined with existing data from adjacent regions, suggest the partial melting of ultrahigh-pressure metamorphic terranes was related to slab breakoff at the terminal stage of continental collision. This study provides a novel model for the origin of sodic adakitic rocks in the continental collision zones. [ABSTRACT FROM AUTHOR]

Cryogenic cave carbonates (CCCs) genetically related to permafrost are of special interest in paleoclimate research. Their 230Th/U ages provide unique information about the former presence and depth of permafrost in presently permafrost-free areas. Details of CCC formation processes and their diagnostic features, however, remain incompletely understood. In this paper, we report the results of a study of CCCs from two northern Eurasian caves, currently located in permafrost-free rocks. CCCs in the caves occur in a wide range of grain sizes (micrometers to several centimeters). Stable isotope values of different CCC morphotypes (size range of 0.1 to 4 mm) plot within relatively tight clusters in δ18O-δ13C space, regardless of their grain size, indicating that CCCs of the same morphotype, but of different size, formed simultaneously at certain freezing stages. The clusters conform to an overall negative "freezing trend" in δ18O-δ13C space. The position on the trend indicates the relative age of individual morphotypes; scatter of the data in δ18O-δ13C space suggests multiple episodes of freezing (permafrost formation). The systematic characterization of CCC morphologies and the study of fine-size fractions of CCCs provide important insights into the processes involved in CCC formation in caves located in permafrost. [ABSTRACT FROM AUTHOR]

Carbon capture and storage (CCS) is a promising technology for reducing greenhouse gas emissions, however, leakage of CO 2 constitutes a major concern for aquifers. Despite abundant literature on petrophysical and geochemical changes at storage conditions, few studies address the impact of CO 2 leakage on petrophysical and at aquifer-like pressures, flow rates and temperatures. The aim of the paper is to study and quantify at the core scale, the effects of various factors, including flow rates, fluid salinities, CO 2 concentrations and limestone carbonate facies, on the petrophysical and geochemical parameters of a carbonate freshwater aquifer during an experimental CO 2 leakage. To achieve this, successive CO 2 -rich water percolation experiments were performed at the core scale, while monitoring changes in petrophysical parameters and water chemistry. During our experiments, initial permeability increments were observed for both rock samples, followed by decreases in later experiments. Evidence of pore clogging and wormholes was also observed. It was found that the transport of particles led to significant porosity creation. The water monitoring sensors were sensible to the experimental leakage conditions, particularly electrical conductivity. The results of this study contribute to the understanding of petrophysical changes in carbonate aquifer systems by anticipating which type of aquifers are more vulnerable to dissolution and to what extent the CO 2 leakage conditions modify the petrophysical parameters. • Water-rich CO 2 percolation experiments on limestones at different conditions. • Transport of fine particles led to pore clogging and porosity increase. • Increasing the CO 2 concentrations, salinities and flow rates encouraged dissolution. • Significant difference in porosity increase depending on sedimentary facies. [ABSTRACT FROM AUTHOR]

Different discretizations methods applied to models of core/mantle segregations are tested (single stage, multistage accretion, results of N-body simulations) in order to test the sensitivity of the thermo-chemical coupling to the type of discretization used. We found that while single stage and large discretization of segregation steps yield very different core temperature, multistage models of accretion and core mantle segregation, at least for the model presented in this paper, tend to yield similar results, whether it is for the light element concentrations or the final temperature of the core. As long as a magma ocean existence throughout the entire process of core/mantle segregation is posited, and that only the impactor's masses of metal and silicate are re-equilibrated at each step, the degree of discretization of continuous model does not matter as long as it encompasses more than 10 steps of calculations. [ABSTRACT FROM AUTHOR]

Recent advancements in in situ analytical techniques have generated new interest in measuring strontium (Sr) isotopes in rock-forming apatite and apatite inclusions in zircon, because they can bring new insights into the primary signatures of magmatic sources. This paper introduces a novel approach based on laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS), which allows to achieve higher precision in situ analysis of Sr isotopes in small volumes of samples. The use of 1013 Ω current amplifiers for the acquisition of the signal on m/z 83, 83.5, 84, 85, 85.5, 86, 86.5, 87 and 88, along with a specific data reduction protocol, enhance both the internal precision and the external reproducibility of the 87Sr/86Sr ratio by a factor of four, presenting a significant improvement over the conventional use of 1011 Ω amplifiers. An internal precision better than 0.45‰ (i.e. 450 ppm; 2 s.e.) on the 87Sr/86Sr ratio can be achieved on the Durango apatite standard with a 13 μm square-shaped laser beam and a laser ablation pit of 60 μm depth. With a 5 μm beam, the precision is 2.2‰ on average with a 10 μm ablation pit depth for this standard. This analytical procedure was applied to investigate Sr isotopes in apatite and apatite inclusions within zircons from seven high Ba Sr magmatic rocks in the Northern Highland Terrane, Scotland. For these well-characterised, geochemically undisturbed samples, the data reveals similar Sr isotope compositions between apatite inclusions armoured in zircon, matrix apatites, and the bulk rock. This highlights the ability of apatite inclusions to faithfully record primary signatures of host magmas, elucidating their utility as reliable indicators in petrological studies of ancient samples. • 1013 Ω amplifiers improve the precision of Sr isotopes analysis by LA-MC-ICP-MS. • Precision on the 87Sr/86Sr ratio is ∼2.2 ‰ at 5 × 5 × 10 μm on Durango standard. • In Caledonian granites, bulk rocks and apatite inclusions have same 87Sr/86Sr. [ABSTRACT FROM AUTHOR]

Thermal history inverse modeling has become one of the primary platforms for interpreting thermochronometric data. This paper introduces new features in the HeFTy software, and compares them with both earlier HeFTy versions and other programs. The approach for combining multiple goodness-of-fit tests into a single probability has been changed to Fisher's method, improving both statistical accuracy and ease of plain-language interpretation. The mechanism and guidelines for setting up Monte Carlo inverse modeling in HeFTy are reviewed, with particular attention to the role of allowing complex but geologically realistic time-temperature (t-T) paths. A new implementation of the controlled random search algorithm for paths with variable time spacing greatly accelerates finding solutions that fit the data while trying to also map the solution space as effectively as an unbiased Monte Carlo approach, so as to avoid providing an unrealistic impression of resolving power. A new time-depth (t-Z) modeling mode uses a 1-D thermal model to make a first-order conversion between depth and temperature, with depth change corresponding to erosion or deposition at the Earth surface. This mode approximates the thermal buffering effects of the crust, and allows temperature relationships between samples and the Earth surface to evolve in a physically appropriate fashion. These improvements enable multi-sample modeling along an elevation transect, including testing and constraining the timing of deformation, expressed as tilting, and topography development. In most cases, adding geological constraints during the modeling process is crucial for achieving meaningful results, as the resolving power of the thermochronometric data alone is usually limited, and the best-fitting results are not necessarily geologically realistic. A crucial step in interpreting any modeling result is to ascertain how the data and assumptions, including those embedded in the software, lead to the outcome obtained. These principles are illustrated using recent examples of modeling thermal histories associated with the Great Unconformity. [ABSTRACT FROM AUTHOR]

Chemical and structural complexities in interstratified clay minerals arising from mineral transformations and evolving formation conditions should be recorded in their stable isotope signatures. This paper examines the controls on the stable hydrogen and oxygen isotope compositions of Fe3+-rich, glauconite-nontronite, talc-nontronite and talc-saponite from submarine hydrothermal sites, with a focus on the Red Sea Atlantis II Deep. Values of δ 18O became less positive in the order nontronite > glauconite-nontronite > talc-nontronite > talc-saponite, yielding oxygen isotope temperatures ranging from ∼40 °C for nontronite to ∼135–300 °C for talc-saponite. These clay minerals have low δ 2H, ranging from −145 to −127‰ for talc-nontronite, −135‰ for nontronite, −129 to −85‰ for glauconite-nontronite, and −95 to −59‰ for talc-saponite. The clay mineral-water hydrogen isotope fractionation is strongly affected by Fe3+ content, with increasing structural Fe3+ causing progressive weakening of O-H bonds. The large ionic radius and high charge of Fe3+ cause it to be more poorly shielded by surrounding oxygen from hydroxyl hydrogen relative to other octahedral or tetrahedral cations. The resulting lengthening of O-H bonds favours 1H over 2H. Our results confirm that Fe-rich phases, such as nontronite-glauconite, are produced at the lowest temperatures and Mg-rich phases, such as talc-saponite, are formed at the highest temperatures in seafloor hydrothermal environments. Evolving fluid chemistry and fluid pathways during clay mineral formation are also important. Glauconite layer formation from precursor nontronite likely occurred during diagenesis; redox changes causing Fe-reduction and an increase in layer charge facilitated interlayer K-fixation. Talc-saponite compositions vary with temperature and fluid chemistry, forming at variable sediment depths depending on access to the hottest hydrothermal fluids. • Fe3+ content controls δ 2H OH of seafloor Fe-rich hydrothermal, interstratified clay. • Large ionic radius and high charge of Fe3+ causes systematic decrease in clay δ 2H. • Seafloor clay δ 18O indicates lower temperature formation of Fe- versus Mg-rich phases. • Diagenetic glauconite-nontronite formed at ∼75 °C (Atlantis II Deep) from nontronite. • Talc-nontronite formed at ∼95 °C and talc-saponite at ∼240 °C (Atlantis II Deep). [ABSTRACT FROM AUTHOR]

This study contributes to the exploration and quantification of the weathering of organic-rich mudstones under temperate climatic conditions. Bowland Shales, exposed by a stream and slope, were sampled in order to develop a model for the effects of weathering on the mudstone geochemistry, including major and trace element geochemistry, Rock-Eval pyrolysis and δ 13 C org . Four weathering grades (I – IV) are defined using a visual classification scheme; visually fresh and unaltered (I), chemically altered (II, III) and ‘paper shale’ that typifies weathered mudstone on slopes (IV). Bedload abrasion in the stream exposes of visually fresh and geochemically unaltered mudstone. Natural fractures are conduits for oxidising meteoric waters that promote leaching at the millimetre scale and/or precipitation of iron oxide coatings along fracture surfaces. On the slope, bedding-parallel fractures formed (and may continue to form) in response to chemical and/or physical weathering processes. These fractures develop along planes of weakness, typically along laminae comprising detrital grains, and exhibit millimetre- and centimetre-scale leached layers and iron oxide coatings. Fracture surfaces are progressively exposed to physical weathering processes towards the outcrop surface, and results in disintegration of the altered material along fracture surfaces. Grade IV, ‘paper shale’ mudstone is chemically unaltered but represents a biased record driven by initial heterogeneity in the sedimentary fabric. Chemically weathered outcrop samples exhibit lower concentrations of both ‘free’ (S1) (up to 0.6 mgHC/g rock) and ‘bound’ (S2) (up to 3.2 mgHC/g rock) hydrocarbon, reduced total organic carbon content (up to 0.34 wt%), reduced hydrogen index (up to 58 mgHC/gTOC), increased oxygen index (up to 19 mgCO + CO 2 /gTOC) and increased T max (up to 11 °C) compared with unaltered samples. If analysis of chemically weathered samples is unavoidable, back-extrapolation of Rock-Eval parameters can assist in the estimation of pre-weathering organic compositions. Combining Cs/Cu with oxygen index is a proxy for identifying the weathering progression from fresh material (I) to ‘paper shale’ (IV). This study demonstrates that outcrop samples in temperate climates can provide information for assessing hydrocarbon potential of organic-rich mudstones. [ABSTRACT FROM AUTHOR]

The use of portable Energy Dispersive X-Ray Fluorescence (pXRF) spectrometers has exploded within the last decade for e.g., environmental, geological, and archaeological field research. Producing reliable geochemical data using a pXRF is a challenging process that requires the development of dedicated and matrix-matched empirical calibrations. Although a large field of applications, several research papers are still published using unquantified pXRF data, using manufacturers' built-in calibrations unsuitable for targeted rocks, or interpreting chemical concentrations without checking the limit of quantification of the pXRF spectrometer and its calibration model. In this paper, we present a general workflow for building an empirical calibration model for a pXRF spectrometer, from choosing reference materials to validating calibration's efficiency and quantifying its limit of quantification. We also compare the geochemical results on a sedimentary and an igneous rocks suite obtained from thirty-two calibration models that were built using different software available, including a simple homemade spreadsheet, the EasyCal calibration software, a free and open-source calibration app named CloudCal, and the built-in GeoMining and GeoExplorer calibrations provided by Bruker manufacturer on the Tracer 5 pXRF. This decoupled approach allows (i) to explore the pros and cons of each calibration model and determine which empirical calibration model brings the most accurate chemical concentration for a sedimentary and an igneous rock suite, (ii) to weigh the impact of each calibration parameter (type of regression line, spectral interferences, normalization, influence coefficients, multiple conditions of excitation and acquisition) on the accuracy of geochemical concentrations on rock samples and (iii) to bring innovative tools to assess the limits of quantification of a newly built calibration model. • Analysing the statistics on validation lines (not calibration lines) to quantify the accuracy of a pXRF calibration model. • Raw pXRF spectra normalization and the correction of matrix effect are the most important parameters to enhance the accuracy of chemical concentration. • The empirical determination of the lower limit of quantification of a pXRF calibration model is underused but crucial when users aim at discussing the significance of analytes' low concentrations and their relative variations. [ABSTRACT FROM AUTHOR]

Despite the conceptual elegance and simplicity of the External Detector Method (EDM) for fission track dating, an increasing number of laboratories are switching to LA-ICP-MS as a means of measuring the uranium content of apatite, zircon and sphene. LA-ICP-MS based fission track (LAFT) dating offers shorter turnaround times, removes the need to handle radioactive materials and hydrofluoric acid, and facilitates double-dating with the U-Pb method. This paper aims to bring the statistical treatment of LAFT data on an equal footing with the EDM by formulating four different analytical protocols, depending on the accuracy and reproducibility of the uranium measurements. Under the ‘absolute’ dating approach, the spontaneous track densities and uranium concentrations are directly plugged into the fundamental fission track age equation, assuming that both of these measured quantities have been determined accurately, and that the fission decay constant and equivalent isotopic track length are known. The ‘zeta calibration’ approach avoids making these assumptions by normalisation to a reference material of known age. Uranium zoning has a detrimental effect on the accuracy of LAFT ages. This effect can be removed by counting only those fission tracks located within the laser ablation pit. Alternatively, the uranium heterogeneity may be quantified by fitting multiple ablation spots in some or all the analysed grains, using a (lognormal) distributional assumption for the uranium concentration. LAFT dating is arguably less well suited than the EDM to young and U-poor samples that lack sufficient spontaneous fission tracks to reveal visual evidence for uranium zoning. Such samples occasionally contain no fission tracks at all, resulting in infinite analytical uncertainties. This paper introduces a pragmatic solution to this problem, in which the uranium measurement are converted to ‘virtual’ induced fission track counts to produce strictly positive ages with finite standard errors. With the age equation and zero-track strategy in place, LAFT ages can be subjected to more sophisticated statistical analysis. Using a logarithmic transformation, these ages can be visualised on radial plots and deconvolved into finite and continuous mixtures. The methods introduced in this paper have been implemented in a software package called IsoplotR that is available free of charge at http://isoplotr.london-geochron.com . [ABSTRACT FROM AUTHOR]

The recently developed TULIP methodology for determining Initial lead , based on the measured Pb isotopic compositions of rocks, was applied to four terrestrial terrains, and the results are shown and discussed in this report. Particular emphasis was given to the determination of initial Pb of the South Of Isua (SOI) terrain, because of the availability of a large high-quality database on its rocks and feldspar separates. The initial Pb results for SOI, are: 206 Pb/ 204 Pb = 11.088 ± 0.024, 207 Pb/ 204 Pb = 12.983 ± 0.002, and 208 Pb/ 204 Pb = 31.196 ± 0.014. Initial Pb was also precisely determined for the Beartooth Mountains, and the results are: 206/204 = 13.571 ± 0.071, 207/204 = 14.891 ± 0.003, and 208/204 = 32.41 ± 0.08. These results demonstrate the feasibility of routine determination of initial Pb by the developed methodology, once large databases for the terrains are established. Extending the methodology to terrains of other planets should be possible. Projection of initial Pb by a database is caused by Th-U-Pb fractionation, in disturbing events superimposed on the rocks of a terrain. As demonstrated mathematically (in a companion paper), elemental fractionation can induce alignments of the data in linear trends of false ‘ages,’ which together with the rocks' isochron, converge (on various Pb plots) on a point that yields initial Pb. This may result in two counter effects: (1) precise determination of initial Pb, and (2) ambiguity in the exact meaning of an isochron (because of the possibility it was affected by fractionation, like the other lines). Consequently associating a Pb/Pb age with the determined initial may not always be meaningful. For SOI, the rocks' age is 3.84 ± 0.05 Ga. The ability to determine initial Pb opens the possibility for eventual unfolding of details of the evolutionary history of the Earth and other planets. However, that cannot be satisfactorily achieved without additionally developing a methodology for resolving initial Pb to its multi-stages. Because such methodology is still lacking, a procedure of Congruently Associated Profiles ( CAPs ), for resolving initial Pb to a maximum of three stages was developed and outlined in a companion paper (C, P, # 1, 2016). For SOI, only a two-stage CAP solution is possible. It indicates a U-Pb fractionation event at 67.5 Ma after the Earth's accretion (that is a first stage lasting from 4.563 to 4.496 Ga), with μ = 238 U/ 204 Pb = 0.45 ± 0.25. For the second stage, extending from 4.496 to 3.8 Ga, I obtain μ = 9.25 ± 0.02. The stated duration of 67.5 Ma for the first stage is an upper limit, and in a multi- stage solution, if and when it becomes possible, the first stage duration would be shorter, and its meaning may be elucidated. For now it remains subject to qualitative speculations including the possibility of being ‘associated’ with core formation, or an early impact (resulting in formation of the moon?), or …or. This ambiguity underlines a crucial need for a methodology to resolve initial Pb to more of its multi stages. [ABSTRACT FROM AUTHOR]

As the parent element in the U-Pb and Pb-Pb radiochronometers, uranium (U) was one of the first heavy elements whose isotopic composition was carefully determined. Thought to be constant until the end of the 20th century, the ratio of the long-lived isotopes of U (238U/235U) has since been shown to be variable at the permil to sub-permil levels in natural materials. Today, the study of U isotopes has found applications in a variety of fields including geo/cosmochronology, oceanic paleoredox reconstruction, magmatic differentiation, environmental remediation, and forensic studies. With thousands of newly reported U isotopic data each year, a real need exists for a comprehensive U isotope database. Here, we introduce a global, updatable, U isotope database (UID), which not only contains the most expansive, internally consistent U isotopic dataset to date (14,591 entries from more than 320 papers), but also includes all other sample data from the original publications, as well as the relevant metadata and sample information to facilitate further analysis. The UID is freely accessible and will be updated regularly. All data are normalized to the widely-used CRM-145 standard, and all assumptions used to convert the published data are explicitly detailed in the paper and the database itself. New data can be easily formatted and submitted for incorporation into the database. Using the UID we provide new recommended δ238U values for certified U standards and geostandards and discuss important applications and future directions for U isotope studies. • Introduce a comprehensive, freely accessible, updatable U isotope database • Already contains over 14,000 entries from more than 320 papers. • All data is consistently and transparently normalized to CRM-145. • Provide recommended δ238U for a wide range of standards and reference materials. • UID will be maintained and regularly updated. [ABSTRACT FROM AUTHOR]

Iron, Co and Ni are first row transition metals and are all able to combine with S, As, and Sb to form disulphides, sulpharsenides and sulphantimonides, respectively, all of which exhibit substitutions of metal and metalloid elements in their structures. As an important tracer in the geochemistry of ore deposits, S isotope fractionation in sulphides can be used to analyse the ore-forming process and the source of ore-forming elements. However, there have been few studies of S isotope fractionation in sulpharsenides and sulphantimonides. Studying the isotope fractionation of the various members of this structural group can provide systematic information regarding S isotope fractionation in transition metal disulphides, sulpharsenides and sulphantimonides. In this paper, the S isotope fractionation parameters for Fe, Co and Ni sulpharsenides and sulphantimonides were calculated using first-principles methods based on density functional theory in the temperature range of 0–1000 °C. Our calculations show that the order of heavy S isotope enrichment is arsenopyrite > cobaltite > gudmundite > costibite > gersdorffite > ullmannite. For sulphides with the same anion pair, the main factor affecting S isotope fractionation is the metal-sulphur bond strength. For most of the sulphides studied in this paper, S isotope fractionation arising from substitution of metalloid elements is much smaller than that of metal elements. [ABSTRACT FROM AUTHOR]

This paper is the first among two articles which aim at exploring the possible similarities between the well-known Liesegang banding phenomenon in precipitate systems, and the stripe formation observed in a large number of rocks. In the present (first) article, we review a comprehensive and long study wherein patterning experiments were performed in-situ (real rock systems), to simulate the band formation through the acidization of a ferruginous limestone rock, causing dissolution and precipitation reactions. The results are analyzed by microscopy, AA and XRD techniques. The correlation between the Liesegang gel experiment and the processes taking place inside the rock medium is established. In the second part (following paper), a theoretical model is set forth to support our experiments. The fractal nature of the contours of the various regions will be explored. [ABSTRACT FROM AUTHOR]

In mining and smelting sites, where diverse potentially toxic element-rich wastes (e.g., waste rocks and slags) are stored over a mineralized background, difficulties arise to decipher the influence of multiple sources in the contaminated compartments of the critical zone. This paper aimed at testing the coupling of Pb and Sb isotopes to distinguish the sources of an inherited anthropogenic contamination in a mining and smelting environment. To do so, a selection of contamination sources (ore-bearing rocks, n = 4; slags, n = 2; stack residues - matte, n = 2), mine dewatering gallery sediments (n = 3), river sediments (n = 3) and soil horizons (n = 31) were sampled at the Peisey-Nancroix mining and smelting site (Pb Ag, French Alps), which has been abandoned for >150 years. The contamination sources, the soils and some sediments display similar 206Pb/207Pb ratios (1.173 ± 0.003), but distinct Sb isotopic signature (δ123Sb). Slags and stack residues have similar high δ123Sb signature (+0.62 to +0.78 ‰), whereas the ore-bearing rocks display lower δ123Sb signatures (−0.28 to +0.10 ‰). Such a result indicates Sb isotopes fractionation during smelting, suggesting Sb may be used to distinguish the contribution of metallurgic wastes from that of ore-bearing rocks to the environmental contamination. However, our results indicate that Sb isotopes alone cannot be used to discuss the degree of anthropogenic contamination, and must be coupled to another isotopic system. Coupling Pb and Sb isotopic systems, makes it possible to determine the degree of anthropogenic contamination (Pb isotopes) and the contribution of local ore vs slags (Sb isotopes) to it. This multi-isotope approach provides an added advantage to identify mining and metallurgical sources of contamination more accurately than using a single isotopic system. [Display omitted] • Soils are locally affected by extreme Pb and moderate Sb contamination. • Anthropogenic soil contamination is restricted to the surface horizons. • Antimony isotopes allowed to discriminate Sb from mining vs metallurgical sources. • Pb Sb isotope coupling is a powerful tool to identify the anthropogenic sources. [ABSTRACT FROM AUTHOR]

Caves are complex systems characterized by high variability in trace element signatures that simple geochemical analysis cannot detect since useful information hidden in the dataset may be lost. Sufficiently robust unsupervised statistical approaches may provide these significant signatures for cave hydro/geochemical profiling. The present study focused primarily on quantifying the relevant contributions of elements and their relationships to the variability of the hydro/geochemical profiles of speleothems, sediments and drip water within a cave using Principal Component Analysis (PCA) after Varimax rotation and two-way joining analysis as a clustering method. This prospective study was conducted on the Urșilor (Bears') show cave (Romania). The contents of Ca, Mg, Sr, Al, P, S, Fe and Zn in the mineral deposits were determined via X-ray fluorescence, while the content of these elements in drip water was determined via inductively coupled plasma–optical emission/mass spectrometry. The contents of HCO 3 −, Cl−, F−, NO 3 −, and SO 4 2−; pH; electrical conductivity; and organic and inorganic carbon fractions were also determined. In the case of speleothems, the determinations were performed on randomly selected spots, reflecting the composition at various growth times. The PCA revealed that the geochemical profile of speleothems can be described by four principal components (PCs), represented by 71% for stalactites and 82/92% by three PCs for stalagmites/sediments. The strong signatures of Ca, Mg/Ca, K, and detrital elements (Al, Si, P, S) in stalagmites/sediments in proportions of 41/46%; K, Fe and Zn 30/32%; and Sr and Sr/Ca 11/15% were retained by PCA. The geochemical profile of the stalactites was described by Mg (35%), P, Zn, and Sr (21%); Al and Si (15%); and S, Ca and Mg/Ca (10%). Reducing the dimensionality of the data matrix to alkaline earth elements, two PCs described 95% of the mineral deposits, including the strong signatures of Mg/Ca and Sr/Ca, exceeding 50% of the variability in the first PC. Stalactites and stalagmites were primarily grouped based on their geochemical profile and less so on location, yielding two clusters/four subclusters of stalagmites. The PCA plot did not show a separation between stalactites and stalagmites, as their geochemical profiles differ significantly only in terms of Fe concentration. The hydrochemical profile of drip water was described by 4 PCs at a percentage of 95%: (i) alkaline elements, alkaline earth elements, anions and organic carbon and (ii) trace elements and DOC. The profile of Ca2+–HCO 3 − imprint drip water was described by two PCs at proportions of 66% (Ca, Mg, Na, K, Mg/Ca, Sr/Ca, Ba/Ca ratios, HCO 3 − and organic carbon) and 74% by trace elements (Co, Ni, Ti, Fe, Mn, V and Si). The transition trace elements have very complex chemical behaviour and appear in drip water as Ca-/Si-rich inorganic/organic colloids and simple ions. Although complementary to the PCA, the two-way joining analysis in a heatmap did not offer relevant information in the description of the hydro/geochemical profile of the karst system compared to PCA. A study of a farmed calcite sample highlighted its difference in composition compared with stalagmites in terms of Mg, Si, K, Zn, Sr and Sr/ Ca. Future development could include the application of PCA to seasonally collected farmed calcite and drip water samples to obtain hydro/geochemical profiles of stalagmites in the making to determine the seasonal leaching of metals from bedrock/soil by drip water, inclusion in stalagmites, and seasonal growth. The practical significance of this paper for trace element research is of great concern because it allows these recorded indicators to be connected to the ancient climate and environment of stalagmites. • Element signatures in the hydro/geochemical profile of a cave highlighted by PCA. • Geochemical pattern of the mineral deposits was described as a proportion of 80–90%. • The Ca2+-HCO 3 − imprint drip water profile is described as a proportion of 95%. • The speleothems were primarily grouped by geochemical profile and then by location. • Stalactites and stalagmites differed significantly only in terms of Fe content. [ABSTRACT FROM AUTHOR]

The Ediacaran period witnessed events that were of significance to the evolution of Earth's environment and early life, especially the Neoproterozoic Oxygenation Event during the Shuram Event (ca. 570–562 Ma) that was followed by the rise of animal life. However, the nature of the climate change that followed the Shuram Event in South China remains unclear. Black shale-hosted Mn‑carbonate deposits have the potential to reveal valuable information about paleo-seawater conditions and paleoclimate. This paper presents results of an investigation of the unique Ediacaran mudstone succession of South China, especially black shale-hosted Mn‑carbonate deposits, and offers a new perspective of the interconnected nature of paleoclimate and Ediacaran deposits. Relying on detailed petrological, sedimentological, and geochemical data, we posit that Ediacaran Mn‑carbonates accumulated in a semi-enclosed basin that experienced oscillating water column redox conditions and enhanced primary productivity. Chemical index of alteration (CIA) values, Rb/Sr ratios, and δ13C − δ15N stratigraphy of the analyzed deposits provide evidence of episodic warming during an otherwise protracted cooling trend following the Shuram Event (ca. 562–551 Ma). This study highlights the significant utility of black shale-hosted Mn‑carbonate strata in reconstructing Earth's paleoclimate during transitions. • New chemostratigraphic data of the Late Ediacaran in northern Yangtze margin. • Genesis of the late Ediacaran black shale-hosted Mn-carbonates in South China. • Climate fluctuation events during the Late Ediacaran in South China. • Climate-controlled "episodic ventilation" model of the black shale-hosted Mn-deposit. [ABSTRACT FROM AUTHOR]

Global peatlands are a valuable but vulnerable resource. They represent a significant carbon and energy reservoir and play major roles in water and biogeochemical cycles. Peat soils are highly complex porous media with distinct characteristic physical and hydraulic properties. Pore sizes in undecomposed peat can exceed 5 mm, but significant shrinkage occurs during dewatering, compression and decomposition, reducing pore-sizes. The structure of peat soil consists of pores that are open and connected, dead-ended or isolated. The resulting dual-porosity nature of peat soils affects water flow and solute migration, which influence reactive transport processes and biogeochemical functions. Advective movement of aqueous and colloidal species is restricted to the hydrologically active (or mobile) fraction of the total porosity, i.e. the open and connected pores. Peat may attenuate solute migration through molecular diffusion into the closed and dead-end pores, and for reactive species, also through sorption and degradation reactions. Slow, diffusion-limited solute exchanges between the mobile and immobile regions may give rise to pore-scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils. While new information on the diversity and functionalities of peat microbial communities is rapidly accumulating, the significance of the geochemical and geomicrobial study on peat stands to benefit from a basic understanding of the physical structure of peat soils. In this paper, we review the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and briefly discuss their implications for water storage, flow and the migration of solutes. This paper is intended to narrow the gap between the ecohydrological and biogeochemical research communities working on peat soils. [ABSTRACT FROM AUTHOR]

This paper investigates the origin of solutes within the groundwaters of the Monturaqui–Negrillar–Tilopozo (MNT) aquifer system within the high Andes of the Atacama Desert that discharges into the Salar de Atacama. Key questions include the relative significance of volcanic hydrothermal processes and evaporitic brine recycling over solute supply as well as the pathways of solute ingress to the MNT aquifer system. Groundwaters were analysed for elemental (major, minor and trace) and isotopic (δ 18 O/δ 2 H; δ 13 C–DIC; δ 34 S–SO 4 ; 87 Sr/ 86 Sr) constituents to which various hydrochemical and multivariate statistical methods have been applied. Groundwaters are all classified as thermal and show increasing temperatures (27–35 °C) and concentrations of HCO 3 (4.4–10.4 mmol L − 1 dissolved inorganic carbon [DIC]) with increasing proximity to Volcano Socompa resulting from an increasing mass flux of steam and magmatic CO 2 ( p CO 2 = 0.016 to 0.10 atm; δ 13 C–CO 2 = − 9.3 to − 3.6‰ (V-PDB)) boiled off a deep hydrothermal reservoir. Superimposed upon this gradational and relatively smooth spatial increase in heat and mass flow is a sharp, structurally controlled, increase in TDS (826–3632 mg l − 1 ) and a concomitant change in δ 34 S–SO 4 (+ 0.79 to 4.9‰ (V-CDT)) and 87 Sr/ 86 Sr values (0.707375–0.706859) associated with the inflow of evaporitic solutes. Evaporitic inputs are chemically and isotopically distinct from localised secondary hydrothermally derived solutes with major, minor and trace element data suggesting an origin within a highly oxidising, alkaline, evaporitic lake receiving dilute inflows enriched in volcanic/fumarolic sulfur mineralisation probably from volcanoes Socompa, Salín or Pular that delimit the eastern topographic extent of the aquifer system. The conceptual model presented in this paper proposes that basal leakage of evaporitic brines from active salar(s), within the high altiplano/volcanic arc, are actively entrained by sub-regional groundwater flow and conveyed to the MNT aquifer system where they mix with solutes derived from localised secondary hydrothermal gas–water–rock interaction. This work provides detail on the origin and processes controlling the solute composition of groundwater inflows to the Salar de Atacama within the volcanically active and hyperarid Atacama Desert and may be of significance to conceptual models of evaporitic brine evolution, recycling of evaporitic brines and hydrothermalism in arid regions. [ABSTRACT FROM AUTHOR]

Determination of the 14 C content of dissolved inorganic carbon (DIC) is useful for dating of groundwater. However, in addition to radioactive decay, the 14 C content in DIC ( 14 C DIC ) can be affected by many geochemical and physical processes and numerous models have been proposed to refine radiocarbon ages of DIC in groundwater systems. Changes in the δ 13 C content of DIC (δ 13 C DIC ) often can be used to deduce the processes that affect the carbon isotopic composition of DIC and the 14 C value during the chemical evolution of groundwater. This paper shows that a curved relationship of 14 C DIC vs. δ 13 C DIC will be observed for groundwater systems if (1) the change in δ 13 C value in DIC is caused by a first-order or pseudo-first-order process, e.g. isotopic exchange between DIC and solid carbonate, (2) the reaction/process progresses with the ageing of the groundwater, i.e. with decay of 14 C in DIC, and (3) the magnitude of the rate of change in δ 13 C of DIC is comparable with that of 14 C decay. In this paper, we use a lumped parameter method to derive a model based on the curved relationship between 14 C DIC and δ 13 C DIC . The derived model, if used for isotopic exchange between DIC and solid carbonate, is identical to that derived by Gonfiantini and Zuppi (2003). The curved relationship of 14 C DIC vs. δ 13 C DIC can be applied to interpret the age of the DIC in groundwater. Results of age calculations using the method discussed in this paper are compared with those obtained by using other methods that calculate the age of DIC based on adjusted initial radiocarbon values for individual samples. This paper shows that in addition to groundwater age interpretation, the lumped parameter method presented here also provides a useful tool for geochemical interpretations, e.g. estimation of apparent rates of geochemical reactions and revealing the complexity of the geochemical environment. [ABSTRACT FROM AUTHOR]

Combined shell growth pattern and oxygen isotope analysis has become a powerful approach in palaeoclimate and archaeological studies for reconstructing palaeoclimate conditions and littoral exploitation patterns, respectively. Recent investigations have shown that the gastropod Phorcus lineatus (da Costa, 1778) forms its shell in conditions of near equilibrium with the oxygen isotope signature of the seawater environment, demonstrating the utility of this species for reconstruction of sea surface temperature and determination of the season of harvest in archaeological studies. In contrast, the shell growth patterns of this species have received virtually no attention despite providing information on the rate and timing of shell growth that is crucial for correctly interpreting environmental proxies derived from shell geochemistry. In this paper, we compare microgrowth patterns and isotopic profiles of four modern individuals of the gastropod P. lineatus from northern Iberia to determine the timing and periodicity of subannual growth markers within the shells. Results of this sclerochronological study showed the presence of two types of growth lines/increments: i) large-scale accretionary units formed with variable periodicity, and ii) small-scale accretionary units formed by micro growth lines and increments determined by semidiurnal tidal cycles. Results suggest that shells grew uninterruptedly during early ontogeny. However, older specimens exhibited growth cessation/slowdown during summer and winter/spring. Therefore, shell growth rate is not only controlled by environmental conditions, but also by ontogenetic age and/or endogenous rhythms. A high correlation was found between seawater temperature derived from shell oxygen isotopes and instrumental seawater temperature (r2 = 0.88–0.98; p-values < 0.0001). This study shows that establishing accurate growth patterns of the topshell P. lineatus is essential for correctly reconstructing past seawater temperature conditions in palaeoclimate studies and for determining with higher precision the season(s) when the subfossil shells were collected by humans. [ABSTRACT FROM AUTHOR]

Laser ablation inductively coupled plasma mass spectrometry is a unique technique designated for in situ analysis of a wide variety of solid samples. Nowadays, LA-ICP-MS is almost routinely used to study chemical and isotopic composition of geological materials. This paper reviews our experience with the analysis of tin in geological samples and comprehensively summarizes the limitations that may lead to inaccurate and imprecise outcomes. Experimental results show the extent of cross-contamination given by the ablation of materials containing tenths and tens of % m/m of Sn, and elucidate the impact of contamination on a background progress. Moreover, an analysis is also jeopardized by the occurrence of doubly charged ions of uranium as well as by the matrix effect amplified with operating conditions. Finally, the inhomogeneity of NIST SRM 614 is highlighted via 2D mapping especially within the rim area where tin content reaches up to 8 mg kg−1. Furthermore, a real quartz sample is subjected to LA-ICP-MS analysis to demonstrate the manifestation of discussed negative effects. The true tin content in quartz sample and NIST 614 is verified via GF-AAS. The result of NIST 614 bulk analysis is in a good agreement with GeoReM value. • Background intensity leads to tenfold overestimation of tin content. • Tin analysis is jeopardized by the occurrence of doubly charged ions of uranium. • Spatial inhomogeneity of tin in NIST SRM 614 reachs up to 8 mg kg−1. [ABSTRACT FROM AUTHOR]

The positive correlation between total organic carbon and specific surface area in sediments and mudstones implies the association between sedimentary organic matter (OM) and clay minerals. However, the traditional classification of OM, including insoluble kerogen and soluble OM (SOM), ignores the role of minerals, significantly limiting the understanding of the role of mineral-OM interactions in OM preservation and evolution. This paper reviews the mineral and OM characteristics and their relationship in argillaceous sediments and rocks and classifies sedimentary OM into three forms of occurrence, namely free SOM (FSOM), mineral-bound OM (MOM), and particulate OM (POM). FSOM, dominated by non-polar compounds, is physically adsorbed on the external surface of minerals or free in pores of different sizes, so it is susceptible to oxidation. MOM includes polar SOM and insoluble amorphous OM. The former is chemically adsorbed on the external surface, sheet edge and intercalated into interlayer space, and the latter is encapsulated in the clay microfabric. MOM is preserved by mineral adsorption, physical encapsulation, and degradation-recondensation, so it is very stable. POM is predominantly insoluble structured OM in the form of discrete particles and is preserved by selective preservation at the expense of chemical reactivity. The three forms of OM occurrence result from the synergistic operation of multiple preservation mechanisms, in which mineral-OM interactions dominate long-term OM preservation. Depending on environmental conditions, the change of mineral-OM interaction leads to the OM release or cracking, thereby promoting carbon cycling. Compared to traditional OM classifications, the new model of OM occurrence incorporates mineral protection mechanisms and provides a unifying principle linking inorganic and organic processes in OM preservation and evolution. OM preservation and evolution is essentially the process of mutual transformation of OM between different forms of occurrence, so this model is very useful for understanding carbon cycling and hydrocarbon generation and should be valued. • Sedimentary organic matter is divided into three forms of occurrence. • Mineral-organic matter interaction leads to the fractionation of organic matter. • The role of mineral-organic matter interactions in carbon cycling is discussed. [ABSTRACT FROM AUTHOR]

This paper presents the results of the geochemical and mineralogical investigation of siderite in the Late Permian coal-bearing strata from western Guizhou, SW China. Siderite occurs as fine-grained ooids, as recrystallized stellate-like forms, as ellipsoidal, rhombohedral, and oolitic aggregates, indicating their authigenic origin. In contrast, pore filling and veinlet siderite are of epigenetic origin. The low sulfur contents, absence of pyrite, and Sr/Ba ratios indicate that the siderite was deposited in a freshwater (non-marine) environment. The V/(V + Ni) values of studied samples, ranging from 0.68 to 0.86, indicate that the siderite developed under anoxic conditions. The presence of authigenic kaolinite and epigenetic siderite in the same samplesuggests that the chemical conditions changed from acidic to alkaline conditions during early diagenesis. Iron in the siderite was not only derived from silicate weathering of high-Ti basalts in the sediment source regions followed by transport as ions by ground and surface waters, but was also generated from in situ alteration of the Fe-bearing minerals within the peat itself. In addition, ascending hydrothermal solutions would also contribute some Fe, with the Fe probably sourced from the leaching of the basaltic basement. The presence of siderite-rich layers indicates enhanced chemical weathering rates in the sediment source regions. The δ 13C PDB , δ 18O PDB , and δ 18O SMOW values of siderite in claystones and mudstones vary within the ranges of −7.7 to 5.8‰, −12.1 to −6.6‰, and 18.4 to 24.1‰, respectively, indicating that carbon and oxygen primarily originated from marine carbonate, dehydroxylation of organic matter, carbonate dissolution, and hydrothermal fluids. The released CO 2 invoked the alteration of reactive silicate minerals in the sediments, and ultimately the formation of siderite. Circulating pore fluids dissolving iron, which is derived from the silicate weathering of high-Ti basalts in the sediment source regions and from in situ alteration of the Fe-bearing minerals within the peat, would transport some iron from the overlying peat into the underlying sediments, and the flow of fluids would be diminished or stopped at the base of the peat due to the mechanical barrier of the impervious claystone or mudstone layers. The ferrous iron was precipitated due to the alkaline environment conditions of the peat, by reaction with HCO 3 − dissolved in the waters to form siderite. [ABSTRACT FROM AUTHOR]

This paper describes the creation of a consistent database of the far-from-equilibrium dissolution rates of secondary silicate minerals including clays, zeolites, serpentines, chlorites, prehnite, wollastonite, epidotes, garnets, kyanite, staurolite, cordierite, tourmaline, and feldspathoids. This work, based on the regression of available dissolution rate data normalized to their BET surface area as a function of pH and temperature, was performed using equations described in Heřmanská et al. (2022a) using a least-squares algorithm. The average difference between calculated and measured rates ranged from 0.18 to 0.66 log units depending on the mineral. Where relevant data were lacking, rate parameters are proposed based upon the rate behaviors of minerals with similar structures. All obtained rate equations and parameters have been incorporated into the KINEC.v1.dat database for direct use in geochemical fluid reactive transport software. The far-from-equilibrium dissolution rates of most naturally forming silicate minerals are notably similar to one another at neutral conditions. More than 65% of the silicate minerals considered in this study and that of Heřmanská et al. (2022a) range in value from 10-11.8 to 10-12.5 mol m-2 s-2 at 25 oC and pH 7; this range is within the uncertainties associated with these rates. This similarity in rates is attributed to the likelyhood that breaking Si-O bonds is the rate limiting step of the dissolution of each of these minerals. Faster rates are observed for minerals that can be dissolved without breaking Si-O bonds. Retrieved apparent activation energies for the silicate minerals are found to be similar over all pH conditions and average ∼55 kJ mol-1. This apparent activation energy suggests that rates at 100, 200 and 300 °C will be approximately 86, 3,600 and 42,000 times higher, respectively, than corresponding rates at 25 oC. [ABSTRACT FROM AUTHOR]

Mineral dissolution rates control the temporal evolution of many natural processes on the surface and upper crust of the Earth. This is the first of a series of papers describing the development and implementation of a comprehensive and internally consistent database of the dissolution rates of the major rock-forming minerals. In this paper, we describe the retrieval and regression of the dissolution rates of the primary rock-forming silicates, including quartz and other SiO 2 polymorphs, feldspars, pyroxenes, amphiboles, micas, volcanic glass, and olivines. Owing to the limited fluid chemistry data available for many of the published experimental studies, BET surface area normalized mineral and most glass dissolution rates (r) were regressed using r = ∑ i A i a H + n i e E a i RT 1 − exp − A σRT where A i stands for pre-exponential factors, a H + corresponds to the hydrogen ion activity, n i refers to reaction orders, T designates absolute temperature, R denotes the gas constant, E ai represents activation energies, σ stands for Temkin's average stoichiometric number, and A denotes the chemical affinity of the dissolution reaction. Where relevant data were lacking, rates were extrapolated assuming that mineral dissolution follows similar trends within the same mineral group. Regression was performed using least-squares algorithms. The average difference between calculated and measured rates ranged from 0.1 to 0.7 log units depending on the mineral. The obtained rate equations were implemented into the carbfix.dat database for direct use in the PHREEQC software but can be extended to other geochemical modeling software, such as TOUGHREACT. [ABSTRACT FROM AUTHOR]

Invited Technical Paper: High quality analytical data are essential for the development of sound scientific interpretations. To ensure the quality of the data published in Chemical Geology, a new type of contribution has been introduced - the "Invited Technical Paper". When a particular technical issue needing discussion or clarification is identified, specialists in the technique will be invited to share their expertise. As is true for all articles published in the journal, these contributions will be subject to peer review before publication. The first topic to be treated concerns in situ Hf isotopic measurements in zircon by laser ablation inductively coupled plasma mass spectrometry. This is an extremely powerful and promising technique that has been adopted by many laboratories throughout the world. However, if insufficient care is taken during analysis and data processing, inaccurate results can be obtained, notably because of the existence of very large isobaric interferences on the isotope of interest. To address this issue, we have asked Christopher Fisher, Jeffery Vervoort and John Hanchar to provide a set of guidelines that can be adopted to assure that reliable Hf isotopic data are obtained by this technique. Abstract Over the past decade, the Hf isotope composition of zircon, as determined in situ by laser ablation-multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS), has been applied increasingly to a wide range of geological problems and has proven to be a valuable analytical tool. There has been no uniformity, however, in the reporting of in situ Hf isotopic data and, quite often, reviewers and readers of papers are not provided with sufficient information to assess data quality. The goal of this invited contribution is to provide the non-specialist with a brief outline and explanation of what is required for proper presentation and documentation of in situ Hf isotopic data from zircon, including details of how the challenging large isobaric interference corrections have been made. In addition, we discuss a number of potential pitfalls vis-à-vis the assignment of the incorrect age to the measured Hf isotope composition. Non-specialists should be aware of these important issues when doing their own analyses and evaluating the analyses done by others. [ABSTRACT FROM AUTHOR]

Abstract: The petrography and geochronology of detrital minerals form rich archives of information pertaining to the provenance of siliclastic sediments. The composition and age spectra of multi-sample datasets can be used to trace the flow of sediments through modern and ancient sediment routing systems. Such studies often involve dozens of samples comprising thousands of measurements. Objective interpretation of such large datasets can be challenging and greatly benefits from dimension-reducing exploratory data analysis tools. Principal components analysis (PCA) is a proven method that has been widely used in the context of compositional data analysis and traditional heavy mineral studies. Unfortunately, PCA cannot be readily applied to geochronological data, which are rapidly overtaking petrographic techniques as the method of choice for large scale provenance studies. This paper proposes another standard statistical technique called multidimensional scaling (MDS) as an appropriate tool to fill this void. MDS is a robust and flexible superset of PCA which makes fewer assumptions about the data. Given a table of pairwise ‘dissimilarities’ between samples, MDS produces a ‘map’ of points on which ‘similar’ samples cluster closely together, and ‘dissimilar’ samples plot far apart. It is shown that the statistical effect size of the Kolmogorov–Smirnov test is a viable dissimilarity measure. This is not the case for the p-values of this and other tests. To aid in the adoption of the method by the geochronological community, this paper includes some simple code using the statistical programming language R. More extensive software tools are provided on http://mudisc.london-geochron.com. [Copyright &y& Elsevier]

Abstract: Isotope geochemistry is now a tool for shale gas exploration, largely due to the association of isotope reversals with mature, highly productive shale gas. Its utility, however, depends on an understanding of the isotope systematics for the particular region of interest, as well as for shale gas maturation in general. This paper reviews and re-examines isotope data from four published papers that include shale gas from the Barnett and Fayetteville Shales (Rodrigez and Philp, 2010; Zumberge et al., 2012), and gas from fractured reservoirs in the Appalachians (Burruss and Laughrey, 2010) and the Foothills of the Western Canada Sedimentary Basin (WCSB) (Tilley et al., 2011). New shale and tight sandstone gas data are also presented for the WCSB. Comparisons of these data show that the progression through three stages of gas maturation (pre-rollover zone, rollover zone and post-rollover zone) is universal in sealed, self-contained petroleum systems and that each zone has characteristic isotopic relationships and trends that are seen in all areas examined. Gases in the pre-rollover zone are isotopically normal (δ13Cmethane <δ13Cethane <δ13Cpropane) unless mixing of gases from different sources has occurred. In the rollover zone, δ13Cethane and δ13Cpropane become progressively more negative as δ13Cmethane becomes less negative, and ethane and methane are reversed (δ13Cethane <δ13Cmethane) only towards the most mature portion of the rollover zone. At the beginning of the post-rollover zone, δ13Cethane <δ13Cmethane, but as δ13Cethane and δ13Cpropane become increasingly less negative at varying rates, ethane and propane may or may not be reversed with respect to each other at the highest maturities. δ2Hmethane in gases of the post-rollover zone approaches isotopic equilibrium with local formation water, generally becoming more negative with increasing maturity. Correct assignment of maturity stage could be of importance because the rollover zone may represent the peak of high productivity shale gas whereas the post-rollover zone may represent a decline in productivity (Burruss and Laughrey, 2010). [Copyright &y& Elsevier]

The wolframite series may contain relatively high U and low common Pb contents, and thus has been used for direct U-Pb dating of hydrothermal W mineralization. In this paper, we present in-situ laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) analysis of U–Pb isotopes and trace elements of wolframite crystals from the giant Yaogangxian and Piaotang W deposits in the extensive Nanling metallogenic belt, South China. The objective of this work is to directly constrain the timing of hydrothermal W mineralization in these two deposits. Wolframite crystals from both deposits show textural evidence for two generations. Early wolframite (Wol-1) has higher Fe and lower Mn contents relative to those in the late wolframite (Wol-2). Uranium is correlated positively with Nb5+, tetravalent (Ti, Sn, Zr, Hf), and trivalent (Sc, V, Y, REEs) cations in all wolframite samples, suggesting that the incorporation of U into wolframite is controlled by the coupled substitution mechanisms. The early and late wolframite domains from the Yaogangxian deposit yielded U–Pb ages of 159.1 ± 2.0 Ma (2σ; MSWD = 0.7) and 153.7 ± 0.7 Ma (2σ; MSWD = 0.5), respectively. Similarly, two wolframite generations from the Piaotang deposits yielded U–Pb ages of 159.5 ± 1.3 Ma (2σ; MSWD = 0.3) and 152.1 ± 0.9 Ma (2σ; MSWD = 0.5). The obtained U–Pb ages confirm two successive episodes of hydrothermal W mineralization at ~159 Ma and ~153 Ma in the Yaogangxian and Piaotang deposits. This study demonstrates the potential of U–Pb dating of wolframite by LA-ICPMS and highlights its importance for directly dating hydrothermal ore-forming processes. • In situ LA-ICPMS analysis of wolframite yielded accurate U-Pb dates. • Uranium in wolframite is dominantly structure-bound. • In situ LA-ICPMS U-Pb dating of wolframite provides a useful method for direct dating hydrothermal mineralization. [ABSTRACT FROM AUTHOR]

The economically important platinum-group elements (PGE) are known to be mobile in the surface weathering environment, but their mobility in the presence of soil organic matter under surficial conditions has been poorly constrained so far. In this paper, the behavior of synthetic platinum-group minerals (PGM) placed in solutions containing humic acids is described. In order to approximate the natural weathering environment in the area of the Bushveld Igneous Complex, South Africa, humic acid solutions were prepared at concentrations of 0.1, 1, and 10 mg/l, and allowed to react with synthetic palladium monotelluride (PdTe), palladium ditelluride (PdTe 2), palladium sulfide (PdS) and platinum disulfide (PtS 2). The solutions remained stationary for a period of up to 306–308 days, with aliquots being taken at various intervals. The solutions were then analyzed by inductively coupled plasma mass spectrometry (ICP-MS). With both telluride minerals, Pd was not mobilized above concentrations of about 4 μg/l, but tellurium proved to be more mobile, reaching concentrations of several thousand μg/l. In these experiments, tellurium oxide crystals formed on the substrate of the humic-acid leached palladium tellurides. The palladium content of the initial palladium tellurides increased relative to tellurium, possibly approximating the structure of extant naturally forming palladium telluride minerals. The PdS and PtS 2 solutions appear to have undergone hydrolysis of sulfur, producing sulfurous/sulfuric acid, which lowered the pH of these solutions from 7 to 8 to about 3. Due to this lowering of the pH, Pt was observed to precipitate out of solution between days 50–150. Meanwhile, Pd steadily increased in the 10 mg/l humic acid solution, reaching a final value of 162 μg/l. The increase in Pd in this solution matches a linear equation of y = 0.5× + 4.9, where x = time in days and y = concentration of Pd in μg/l, corresponding to a rate of mobilization for Pd of 0.5 μg/l per day. [ABSTRACT FROM AUTHOR]