We present sulfur mineralogy and isotope geochemistry from the gabbro transect of the Oman Drilling Project to unravel the sulfur cycle during hydrothermal alteration of the plutonic oceanic crust. The sheeted dike-gabbro transition (Hole GT3A) shows low sulfide-sulfur concentrations (GT3A(median) = 178 ppm, sigma = 4873 ppm) but with great sulfur isotope variability (delta S-34 = -12.8 to 14.4 parts per thousand V-CDT, weighted average + 5.8 parts per thousand) and unusually heavy compositions relative to in-situ or ophiolitic crust. These features are consistent with abiogenic thermochemical sulfate reduction during intense hydrothermal alteration under greenschist facies conditions which formed a low-variance and relatively high-fS(2) assemblage of pyrite +/- chalcopyrite +/- bornite. The heaviest isotope compositions (+10 to +14 parts per thousand) occur within 10 m of the uppermost gabbro screen suggesting focused fluid-rock exchange with isotope enrichment relative to seawater due to closed-system reservoir effects. The change in isotope compositions from +5 to 0 parts per thousand in the overlying sheeted dike reflect fluids gradually buffered by magmatic sulfur to signatures similar to the Oman Volcanogenic Massive Sulfide deposits. Hole GT3A represents a deep hydrothermal reaction zone with extensive S and base metal losses and incorporation of up to similar to 80 % seawater-derived sulfate. The amount of Cu and Zn released in a 1 km(3) crustal section similar to Hole GT3A is similar to 3 times greater than the average contents of Omani VMS deposits. The mid to lower crustal section (Holes GT2A and GT1A) mostly preserves MORB sulfur isotope compositions but highly variable sulfide-sulfur contents (GT2A(median) = 454, sigma = 693 ppm, GT1A(median) = 114, sigma = 277 ppm). Away from fault zones, silicate microvein networks enabled variable sulfide and metal remobilization. Magmatic sulfides persist as remobilized remnants along with sulfidation reactions and mild isotopic enrichments (<+2.7 parts per thousand) in secondary sulfides (millerite + siegenite-polydimite(ss) + pyrite). The mid-lower crustal section experienced redistribution of magmatic sulfur mixed with minor inputs of seawater-derived sulfur (<10 %), under very low fluid/rock ratios and moderate sulfur fugacities, that chiefly preserved base metal abundances in secondary sulfides. The many faulted intervals present in Holes GT1A and GT2A record near complete sulfur and metal leaching of magmatic sulfides without the deposition of secondary sulfides, but preserve sulfate with a Cretaceous seawater sulfate-sulfur isotope signature (+16.1 to +17.3 parts per thousand). These structures are the expression of crustal scale channeled hydrothermal recharge fluid flow and record a previously unaccounted sulfur budget introduced in the deep crust.

Ceria (CeO2) is a candidate for arsenic removal, and characterizing its surface speciation is crucial for controlling its removal ability. Here, we focus on arsenates and exploit ab initio calculations to study their interaction with the three most stable surfaces of CeO2. The adsorption of arsenate is stronger on the {100} surface followed by the {110} and {111} surfaces. We find that arsenate can potentially adsorb to CeO2 surfaces, with a range of binding configurations. Interestingly, we discovered a 5-fold coordinated As(v) species in a trigonal bipyramidal coordination, which is stable and displays a strong interaction with the surfaces, pulling oxygen out of the surfaces, which should be a valuable model to address in As adsorption experiments such as EXAFS. We then predict the infrared (IR) and Raman spectral signatures, finding that adsorbed arsenates have a characteristic spectral fingerprint between 200 and 1200 cm-1. Characteristic peaks compared with experiments gives confidence in the modelling. The 5-fold coordinated As species in particular shows potential diagnostic As-O stretching modes between 635-756 cm-1 in IR spectra and 387-521 cm-1 in Raman spectra. While all binding modes for arsenate adsorption on ceria provide IR active modes, interestingly this is not the case for Raman active modes. Here, we provide a set of reference spectra and binding modes for arsenates on CeO2 that can further experimental characterization of arsenate speciation, and provide control of its impact on the removal performance of cerium dioxide.

Phosphate and arsenate species provide challenging environmental problems necessitating the search for efficient removal mechanisms from natural waters. Arsenic and phosphorous compounds have a high affinity for metal (hydr)oxide surfaces, and since phosphate and arsenate are isostructural, they have similar adsorption behaviour. This study provides results on arsenate and phosphate adsorption onto cerium dioxide using density functional theory, which is a promising adsorbent for the removal of these species. Ceria was modelled as the {100}, {110}, and {111} faces representative of ceria nanoparticles, assuming compositions from fully oxidised to fully reduced surfaces. Phosphate is generally more stable than arsenate adsorption, in agreement with macroscopic experimental studies. However, in some of the probed surfaces and adsorption densities, the relative stability flipped, which is an important finding for the understanding of the competitive behaviour between the species, especially in systems controlled by fast initial adsorption kinetics. The strength of the adsorption is generally stronger as the concentration of surface Ce3+ increases, while remaining stable as the concentration of adsorbates increases. As the concentration of adsorbates increases, a complex hydrogen-bond network forms, but is not sufficient to stabilize the adsorption further as the adsorbates compete for surface anchoring sites disrupting the adsorption process.

A comprehensive geochemical survey was conducted in the western Yilgarn Craton, Western Australia, in 2007, collecting 3142 surface samples of regolith. Our study used this data to target potential sites for undiscovered buried or concealed Cu-Zn-Pb, and NiCu deposits. The core approach used the singularity mapping technique for detecting anomalies at the local scale. This work proposes a procedure to create a composite multi-element singularity map by linearly combining individual element singularity maps, using element-to-element correlation coefficients as weights for the linear combination process. Furthermore, the k-means clustering algorithm was applied to combinations of sub-sets of data and singularity values. Expert validation indicated that the k-means clustering approach yielded the best results when using 4 or 5 clusters, separating the distinct sites of the MINEDEX database. In either case, the incorporation of the singularity values provided the most accurate outcomes, with a dominant cluster correctly classifying up to 60 to 80 % of identified Cu and Ni deposits and mines, respectively. Based on these results and on the range of computed singularity values, simple rules were established to identify sampled data points satisfying the following criteria: (i) meeting the defined threshold singularity value and belonging to the k-means cluster that include the mines and (ii) not being in the neighbourhood of any known mineralization site from the MINEDEX database. These locations thus represent potential mineralization sites that warrant further investigation and exploration follow-up. The outcomes of this study strongly support the efficiency of anomaly detection and k-means clustering method applied on a regional surface geochemical dataset for mineral exploration to detect and target mineral systems.

The Samail ophiolite in Oman, represents one of the most well-preserved remnants of the Tethyan oceanic crust, and hosts numerous mafic-hosted volcanogenic massive sulfide (VMS) deposits. In this work we present Pb isotopic data from 13 VMS deposits in Oman, in different volcanostratigraphic positions, as well as pristine volcanic glasses from the ophiolite main volcanic units. Our data shows that the volcanic units and VMS deposits in Oman exhibit a wide range of Pb isotopic compositions. The volcanic glasses show an increasingly radiogenic Pb isotopic composition from the Geotimes lava unit (V1) into the uppermost Boninitic Alley unit (V2), supporting significant isotopic modification of the mantle source trough time. The VMS deposits isotopic composition generally reflects that of their host volcanic units, indicating that the footwall represents the major source of Pb for each deposit. Some deposits hosted in the uppermost Tholeiitic and Boninitic Alley units, however, show highly variable isotopic signatures, possibly due to leaching of Pb from different volcanic units at depth. These results demonstrate shallower metal sourcing than is typically considered for VMS deposits and highlights the importance of the footwall volcanic architecture in controlling the metal endowment of the VMS deposits.

The Samail ophiolite in Oman was sampled by scientific drilling targeting crucial sections of the oceanic crust and mantle during the Oman Drilling Project- OmanDP [1]. Drillhole CM1A aimed at characterizing the transition from the lower crust to the mantle Moho Transition Zone (MTZ), where both magmatic and hydrothermal exchanges took place. Four magmatic sequences were defined: SI- Layered Gabbro, with thin wehrlite and dunite layers (1.5-160.2 m); SII- fully serpentinized Dunite (160.2-250.0 m); SIII- Dunite with rodingitized gabbro (250.0-311.0 m) and; SIV- Mantle, harzburgite with opx-dunite levels (311.0-404.2 m). We present a sulfur and Sr isotope profile to characterize the sulfur cycling during hydrothermal alteration within the MTZ (SI-SIII). Acid Volatile Sulfides (AVS), Cr-Reducible Sulfur (CRS) and acid-soluble sulfate (SO4) were sequentially extracted and analyzed for δ34S on the same whole-rock powders analyzed for Sr isotopes. The crust-mantle transition records extreme and often decoupled variations in sulfur (δ34S=-25.8 to +56.9‰) and 87Sr/86Sr (0.703088-0.711688) signatures. Total extracted sulfur from sulfide (TS=AVS+CRS) contents increase gradually from the top to the bottom of SI from ca ~65-2820 ppm, to maximum of 5043 ppm in a Cpx-Pl-dunite layer ca. 16 m above SII. Sulfide assemblages comprises magmatic pyrrhotite+pentlandite+chalcopyrite and secondary pyrrhotite (in Fe-serpentine pseudomorphs)+bornite+cubanite+millerite+sphalerite±haezlewoodite. Excluding one dunite layer with δ34SAVS=+11.4‰, the δ34SAVS,CRS (-0.6 to +3.3‰) for SI are close to slightly elevated relative to mantle values. Scarce sulfates have identical δ34S relative to coexisting sulfides implying formation via abiotic oxidation of precursor sulfides. Despite widespread background alteration, olivine gabbros preserve primitive 87Sr/86Sr ratios (0.703088-0.703332) whereas serpentinised ultramafic layers have significantly more radiogenic signatures (0.707817-0.711688), close to or above Cretaceous seawater (87Sr/86Sr=0.70745). Gradual enrichment in sulfides by magmatic processes in SI, towards the MTZ, was followed by hydrothermal alteration with minor incorporation of seawater sulfate, leading to highly decoupled Sr-34S enrichment in the ultramafic layers due to their Sr-depleted nature. Narrow pegmatoid dikelets (amphibole+zoisite+prehnite+titanite) within SI have low TS (<80 ppm), mildly radiogenic 87Sr/86Sr (<0.704923) and a fracture-hosted, higher fS2sulfide assemblage (pyrite+Co-pentlandite+siegenite) with δ34SCRS down to -25.8‰ implying low-T (<110 C), open-system bacterial sulfate reduction (BSR) processes. The Dunite Sequence-SII has decreasing TS towards its interior (2-1253 ppm), consistent with extensive desulfurization producing an assemblage (awaruite+pentlandite+Co-pentlandite+magnetite, coexisting with brucite), during extremely low oxygen and sulfur fugacities typical of early serpentinization stages. SIII is highly heterogenous and S-depleted (3-623 ppm), with a heazlewoodite-bearing assemblage and lower 87Sr/86Sr (0.703952) relative to SII dunites (0.707065). The MTZ upper limit (SII) marks the onset of large shifts in S-isotopic composition, tendentially increasing downward throughout SII (δ34SCRS=-2.5, +15.6‰; δ34SSO4=+19.2, +32.4‰) and SIII (δ34SCRS=+1.4, +56.9‰; δ34SSO4=+19.4, +36.5‰). The occurrence of both sulfides and sulfates with δ34S above Cretaceous seawater sulfate (~18‰) can be explained by input of fluids at the top of SII which composition progressed towards extreme heavy values via closed system BSR during multi-staged serpentinization events. AJ acknowledges WWU International Visiting Scholars and EU-H2020 Marie Sklodowska-Curie #894599 Fellowships, FCT-project UIDB/GEO/50019/2020 [1] Kelemen PB, Matter JM, Teagle DAH, Coggon JA, OmanDP Science Team (2020) Proceedings of the OmanDP: College Station, TX (IODP).

Lithium (Li) was recently added to the list of critical raw materials by the European Union due to its significance for the green energy transition. Thus, the development of new toolchains to make Li exploration more economic and more effective is needed. Stream sediment analysis can play an important part in these new tool chains. In this work, two historical stream sediment datasets covering parts of the Fregeneda-Almendra pegmatite field in the Douro region (Portugal) were reprocessed considering two distinct approaches: spatial interpolation through inverse distance weighting (IDW) and the catchment basin approach using the concentration area (C-A) fractal analysis. The following objectives were delineated: (i) determine pathfinder elements for Li, considering relevant associations in the mineralization sources; (ii) compare the performance of both approaches; (iii) identify new target areas for Li. In the case of spatial interpolation, the highest Li values were associated to granites although the use of key elements allowed lithological discrimination and the delineation of target areas. In the catchment basin approach, fractal analysis proved to be effective in decreasing the number of areas of interest with high accuracy (>75%) when considering the previously mapped Li-pegmatites. One of the limitations identified was the number of anomalous basins related to the granites, despite the use of pathfinder elements allowing discriminating granite- from pegmatite-related Li anomalies. Comparing the two approaches, the spatial interpolation method is more adequate for the early stages of exploration (reconnaissance), while the catchment basin approach is more suited for prospect-scale exploration. Field validation of the results identified one pegmatite containing Li mineralization and three others with favorable signs for Li mineralization in the Douro region.

The economic and strategic importance of tungsten is widely recognized, but several concerns exist on its stable future supply. Portugal is one of the main tungsten producers in Europe, having generated ≈121 kt of contained tungsten in mineral concentrates from 1910 to 2020, i.e., ≈3.3% of the global production documented for the same time period. Since the early nineties, tungsten mining in Portugal is confined to the Panasqueira deposit which accounts for 79% of the country reserves (≈5.4 kt). However, according to the performed Generalized Verhulst and Richards curve-fitting forecasts, there is a significant future potential for increasing production in Portugal due to the low (<2%) depletion rates of the remaining known tungsten resources (≈141 kt). This projected growth is not necessarily guaranteed, depending on many unpredictable economic, technological, and political factors, besides appropriate social consents. Even so, a prudent land-use planning oriented to long-term needs should avoid the sterilization of the most relevant tungsten resources so far identified in the country. These are resources of “public importance”, as objectively demonstrated with a weighed multi-dimensional (geological, economic, environmental, and social) approach. Safeguarding the access to these resources does not implicate more than ≈6% of the Portugal mainland territory. The joint interpretation of results independently gathered for tungsten production forecasts and for the definition of areas hosting tungsten resources of public importance, provides additional support to political decisions on the urgent need to reconcile mineral exploration surveys and mining with other land uses.

The chestnut trees are well adaptated to temperate and humid climates, with moderate annual thermal contrast and without long and severe summer droughts. Bioclimatic studies suggest that chestnut trees have special needs, including at least six months with average monthly air temperature above 10 ⁰C, total annual precipitation of 800 – 900 mm, and 25% of annual precipitation in summer. Weather is also determinant in the phenology of the species. For example, the suitable average air temperature range is: 13 – 15⁰C to initiate the phenological activity, 18 – 20⁰C for flowering, and 20 – 22⁰C for maturation. Therefore chestnut production is highly affected by adverse weather conditions and can be severely reduced by the occurrence of extreme weather/climate extremes: late frosts, heat waves, heavy rainfall, wind gusts, maximum air temperature lower than 25⁰C during flowering or above 32⁰C, which cause thermoinhibition of vegetative activity. Thus, it is important to characterize the chestnut producing regions in present and future climate and estimate how, when and where the weather conditions will be maintained or changed. For this study we used meteorological data from ERA5 for the 1981 – 2010 period and several GCM-RCM simulations from CORDEX Bias-adjusted RCM data for 2011 – 2100 period to assess the climate for current and two future scenarios (RCP 4.5 and RCP 8.5). The meteorological variables selected for this study have been identified in previous studies as having the greatest influence in the phenological activity of the chestnut tree and on the chestnut productivity. The results include the identification of the regions where: (i) the variables will have significantly different statistical distributions in the future; (ii) will be necessary to adopt hazard risk management and climate adaptation measures, including substitution by other varieties more adapted to future conditions or the development of genetic improvement programs; and, (iii) the identification of new production areas.

Carbonate rocks in sedimentary basins are reactive and can record complex histories of events associated with fluid flow in these basins. These include processes of dolomitization and dedolomitization. In this work we provide some preliminary data where distinct calcite and dolomite generations in the Jurassic Lusitanian Basin were analysed by LA-ICP-MS for trace elements in order to characterize chemical signatures of fluid-mineral interaction. It was observed that different carbonate generations can preserve the range of certain trace metal concentrations, but later calcites have distinctly higher contents in REE, Th and U, and Ba. Dolomites also show distinct chemical signatures but lack of analytical and spatial resolution does not allow quantification of the precursor calcite relicts. However, these processes point to the action of basinal fluids triggered by distinct tectonic episodes and associated volcanic activity.

Abstract Geochemical models are considered an abstract representation of natural processes of a system, usually, but not exclusively, represented by a set of master variables and described by mathematical equations. The output data of these models is a quantitative representation of an outcome that can be either observable in the natural system or subject to experimental confirmation. From this definition, the importance of defining proper boundary conditions and using reliable experimental data on models is discussed. Geochemical models may have distinct components such as chemical reactions (inorganic and/or biological), transport of chemical elements by advection and dispersion, fluid flow, and heat transport. These are the building blocks of geochemical models, which can be divided as speciation‐solubility, reaction‐path, inverse mass balance, and coupled reaction‐transport models. Finally, model validation and usefulness is briefly discussed.

The Iberian Pyrite Belt (IPB) is a world-class province of Upper Paleozoic age for volcanic- and shale-hosted massive sulfides that includes 5 of the 10 supergiant (> 150 Mt) deposits of their kind in the World. The volcano; sedimentary sequences hosting the ores are locally exposed, commonly covered by flysch-type successions of variable thickness (the Baixo Alentejo Flysch Group, BAFG) as a result of primary (sedimentary) features and superimposed effects due to Variscan folding and tectonic stacking. In addition and when affected by late developed geomorphic depressions, the exhumed Paleozoic basement is also capped by Meso-Cenozoic sediments. The total thickness of cover sequences on top of the litho-stratigraphic sequence of interest can reach 100's of meters, creating problems for mineral exploration. A large stream sediment (multi-element) geochemical database for the IPB was done in the 90's during a wide-ranging regional survey. This database was reassessed by means of multifractal methods in view of their faculty to enhance the detection of faint geochemical anomalies and provide geochemical indicators to deep buried ore-systems. Several anomalies were detected, namely for Cu, Zn, and Co along NW-SE to WNW-ESE trends. The main anomalous geochemical trends identified include zones that: (i) extend along the Mira Formation of BAFG, opening for the first time two non-traditional areas for further exploration studies; (ii) run along the boundary between the Mira and Mertola Formations of BAFG, probably related to different geochemical signatures and late-developed, fault-controlled, epigenetic ore systems; and (iii) overlap windows of volcanic-sedimentary sequences within the Cenozoic detrital cover and the site below which the deep buried deposit of Lagoa Salgada is located.

The Nisa deposit is the largest known uranium reserve in the country, and is hosted by metasediments of the Beiras Group, in the Alto Alentejo region, central Portugal. After almost two decades without significant studies, the current trend to seek improved knowledge of raw materials motivated the application of different surface geophysical and geochemical characterization methods, which proved to be a valuable exploration approach for this type of deposit. Detailed mapping in the experimental open pit showed the structural aspects controlling the mineralization. A radiometric survey of the deposit was carried out, providing a map of the main sites of mineralization. The U mineralization is of secondary origin, formed exclusively by uranyl phosphates that were formed during the development of a weathering profile. The mineralization occurs along schistosity planes, quartz veinlets and alteration zones, along a general trend N60°–80°W (approximately the same as S0) in association with iron oxyhydroxides, as demonstrated by both petrographic and geochemical data. These hydroxides, in addition to the geochemical characteristics of the host rocks, were key factors in the precipitation and trapping of dissolved uranyl ions.

This work presents two novel climate‐related time series for the northwest of Portugal. The first is anAD1626–1820 triennial‐resolved wine production series, based on the Benedictine accounts from six monasteries of the Entre‐Douro‐e‐Minho (EDM) region. The second, anAD1654–2010 benthic foraminiferal record from the Caminha salt marsh, located in the lower estuary of the Minho River. The series were analysed together for the common period to outline how both palaeoclimatic proxies respond to the most likely natural environmental drivers of temporal variability, solar forcing included. Singular spectral analysis revealed a common significant multidecadal periodicity agreeing with recognized long‐term changes in solar activity, i.e. the Lower Gleissberg cycle (50–80 years). The application of wavelet analysis allowed the detection of high coherence at this time scale (centred atc. 64 years) between marsh foraminifera and both total solar irradiance and the North Atlantic Oscillation index. This relationship persists throughout thec. AD1730–1875 period. The continuous wavelet transform results for wine production were inconclusive. As the time‐span analysed is recognized as one of high socio‐economic and political distress, the main human‐driven impacts on wine production, particularly in the two periods of greatly reduced solar activity – the Maunder and Dalton Minima – are reviewed in the light of the available historical records. In addition to a documented climate‐related agricultural crisis in Portugal, damage and losses to wine production may have been triggered by several local and international conflicts in which the country was involved. But to what extent the two influences contributed to the wine production variations observed in theEDMregion during both periods remains an open question.