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The Araba and Naqus formations in Ras Milan, Sinai, constitute part of the major continuous Paleozoic clastic belt stretching across northern Gondwana. They are sandstone-dominated successions, resting on Precambrian granitic basement, with lowermost thin basal polymictic conglomerate deposits (1–2 m), marking the unconformity. The Araba Formation section is composed mainly of varicoloured violet to reddish brown, fine to coarse-grained laminated and planner and overturned cross-bedded sandstones, while the overlying Naqus Formation is characterized by chaotically distributed poorly sorted quartz pebbles to cobbles within a moderately-sorted coarse- to medium-grained quartz arenite and by abundance and variety of large-scale tabular and trough cross bedding. Modal QFL classification of Araba and Naqus formation sandstones revealed that they are merely quartzose sandstones (quartz arenites). Geochemistry of the succession shows extremely wide compositional ranges for almost all major elements, but the Araba Formation is relatively enriched in SiO2, TiO2, Fe2O3*, Na2O, P2O5, and depleted in Al2O3, MgO, CaO and K2O relative to Naqus Formation. Only the Araba Formation samples are depleted in the transition elements Ni, Cr and Co and oppositely possess extreme enrichment in the HFSEs (i.e. Zr, Hf, Y, Nb, Ta, Th, U), whereas both formations show variable depletion in the LILE Rb, K and Ba, and excessive REE abundances relative to the PAAS and UCC, and LREE-enriched patterns with marked negative Eu anomalies. The provenance of the Naqus and Araba formations could be an earlier felsic magmatic source, which has undergone extensive sedimentary recycling. They possess high compositional maturity and were subjected to intensive to moderate weathering during humid climatic conditions. Passive margin tectonic setting is implied which denotes the derivation of Araba and Naqus formation siliciclastics from stable continental regions or plate interiors and deposition in intracratonic basins. [ABSTRACT FROM AUTHOR]

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Many scientific studies have been conducted to constrain present and past source‐to‐sink processes and their controlling factors. The role of typhoon and monsoon rainfall on chemical weathering and soils erosion in east Asia is still not well established. Clay minerals and major elements, combined with Nd and Sr isotopic compositions were analyzed on sediments from Core MD18‐3569 located on the Taiwan margin in the northeastern South China Sea. The aim was to reconstruct the weathering history of small river basins of southwest Taiwan and to establish the impact of East Asian summer monsoon and typhoon rainfall on source to sink processes since the last glacial period. 87Sr/86Sr and ɛNd values and predominant illite‐chlorite indicate that the rivers of southwest Taiwan is the sole source of sediments to Core MD18‐3569 since last deglaciation. Variations in clay mineral assemblages and major elements allowed us to evaluate the intensity of past weathering in the rivers of southwest Taiwan. We demonstrated that long‐term changes of chemical weathering intensity record from Taiwan are driven by changes in the summer monsoon rainfall. The deglaciation is characterized by a progressive increase in the intensity of chemical weathering, which peaked at the beginning of the Holocene. The chemical weathering degree of sediments from Taiwan decreases during the Holocene concurrently with a weakening of the summer monsoon, increase in typhoon activity, and changes in the vegetation cover. All these processes induce soil erosion, regressive pedogenesis, due to shorter residence time of minerals in the soils of southwest Taiwan. Plain Language Summary: East Asian summer monsoon and typhoon rainfall are important controls on the sediment transfer from land‐sea. It is important to understand their impacts on chemical weathering and soil erosion. We analyzed the clay mineralogy and geochemistry of sediments from Core MD18‐3569, from the Taiwan margin in the South China Sea, to trace the provenance of the sediments and reconstruct the chemical weathering history of soils of southwestern Taiwan since last glacial period. Clay minerals and Nd and Sr isotopic compositions determine that the rivers of southwest Taiwan are the sources of sediments to Core MD18‐3569. Changes in chemical weathering intensity from Taiwan, recorded by clay mineral assemblages and major elements, are controlled by the East Asian summer monsoon precipitation and temperature changes from the last glacial period to the early Holocene. Chemical weathering intensity in southwestern Taiwan reaches its maximum in the early Holocene, which is associated with the increase in monsoon precipitation and temperature. During the Holocene, the weakening of the summer monsoon rainfall is accompanied by changes in vegetation cover and an increase extreme typhoon rainfall, resulting in significant soil erosion, shortening of sediment residence time, and reducing chemical weathering intensity in the southwestern of Taiwan. Key Points: Penghu Canyon levee sediments have been derived from southwest Taiwan rivers since last deglaciationEast Asian summer monsoon and typhoons control the chemical weathering intensity and soil erosion of southwest Taiwan river basinsSediment to Taiwan margin is less chemically weathered during the middle and late Holocene due to short residence time induced by typhoons [ABSTRACT FROM AUTHOR]

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With the increasing demand for lithium (Li) resources in industry, there has been new attention on clay-type lithium-rich deposits recently. In this study, a Li-rich clay deposit with a Li2O content up to 0.3% in the Liangshan Formation in the upper Yangtze, South China Block was demonstrated. We analysed the mineralogy and element geochemistry of the samples from the Liangshan Formation and its underlying and overlying layers. Kaolinite (average 53%, up to 93%) was the major mineral in the samples from the Liangshan Formation. The Li concentrations increased with increasing kaolinite compositions and Al2O3 concentrations. Furthermore, based on the geochemical indicators, it was suggested that the clay formation and Li enrichment were related to the weathering processes of the bottom impure limestone under the hot and wet climate, and the sedimentary processes in the anoxic, still, and flat land–sea interaction area in the Upper Yangtze. The Li was probably sourced from the bottom impure limestone during the weathering stage. The samples from the Liangshan Formation also showed REE enrichment from 117 to 729 μg/g. [ABSTRACT FROM AUTHOR]

The paleoenvironment of shales can be reconstructed to some extent using the combinations or concentrations of elements that correlate strongly with environmental conditions. In this study, we analyzed rare earth elements (REEs), major elements, and trace elements in the marine-continental transitional shales (transitional shales for short) of the Shan 2³ submember of the Shanxi Formation in the southeastern Ordos Basin. The purpose is to deduce the paleoenvironmental conditions of the shales, encompassing paleoredox, paleoclimate, paleoproductivity, and paleo-provenance. The Shan 2³ submember comprises four sections, namely Shan 2³-1, Shan 2³-2, Shan 2³-3, and Shan 2³-4. The Ba/Al, P/Al, and Cu/Al ratios, along with biogenic barium (Babio), indicate that the paleoproductivity of the submember peaked during the Shan 2³-1 deposition and exhibited a downtrend upward in other sections. Trends in the Uau and the Ni/Co, V/Cr, U/Th, and V/Sc ratios suggest that suboxic conditions prevailed during the Shan 2³-1 deposition, with the oxidation level gradually increasing from Shan 2³-1 to Shan 2³- 4. C-value and the Sr/Cu vs. Ga/Rb cross-plot indicate a warm and arid paleoclimate during the Shan 2³-1 deposition, which transitioned to cooler, drier conditions during the deposition of other sections. Indicators sensitive to paleoclimate, such as the K/Rb and Th/U ratios, along with the ICV, PIA, and Chemical Index of Alteration (CIA), highlight elevated weathering from Shan 2³-2 to Shan 2³-4, with Shan 2³-1 exhibiting the weakest weathering during its deposition. As suggested by the REE data, the Zr/Sc vs. Th/Sr cross-plot, provenance discriminant functions, and the cross-plots of Hf vs. La/Th, Th vs. HfeCo, and PREE vs. La/Yb, the sedimentary provenance for the transitional shales of the Shan 2³ submember is of multiple origins, with significant contributions from the Upper Continental Crust (UCC). Discriminant diagrams, including those of TheCoeZr/10, TheSceZr/10, LaeTheSc, and K2O/Na2O vs. SiO2, suggest that the transitional shales of the Shan 2³ submember were primarily deposited under tectonic settings such as continental island arcs (CIAs) and passive continental margins (PCMs). [ABSTRACT FROM AUTHOR]

The Erlian Basin is a Mesozoic–Cenozoic rift basin with a large thick Pliocene sandstones deposit, which has important oil, gas, and uranium resources exploration potential. The paleo-sedimentary environment plays an important role in controlling the development of mineral resource. However, provenance and depositional environment of the Pliocene sandstones remain enigmatic. To address it, this study reports the whole rock geochemical compositions of sandstones from the Youqi and Siziwangqi regions to reflect the paleo-sedimentary environment. The Youqi sandstones are classified as litharenite-arkose, whereas the Siziwangqi sandstones exhibit a graywacke affinity. Furthermore, both the Youqi and Siziwangqi sandstones exhibit low CIA, PIA, ICV, and Th/U values, suggesting that their source rocks were of great maturation and experienced low to moderate chemical weathering processes. The Ni/Co, U/Th, and Ce/Ce* values in these sandstones range from 0.4 to 5.9, 0.20 to 0.37, and 0.80 to 1.09, respectively, indicating that these sandstones were formed in an oxygen-rich depositional environment. Additionally, interelement ratios such as Sr/Cu, SiO2/Al2O3, and Rb/Sr suggest a hot and arid paleoclimate during the deposition of these sandstones. Tectonic discrimination diagrams reveal a continental arc environment for the studied sandstones, Combining regional structural background, implying that the Erlian Basin was influenced by both Himalayan and the Pacific-Ocean-surrounding tectonism during the Pliocene period. [ABSTRACT FROM AUTHOR]

The rupture of an iron mining tailing dam in Brumadinho, Brazil, released around 10 million cubic meters of tailings, of which 1.6 Mm3 reached the Paraopeba River. In this work, a total of 30 samples from three bottom sediment cores were collected in the lower course of the Paraopeba River basin and analyzed for major, trace and rare earth elements by ICP-OES and ICP-MS. The sediments presented a range of compositions with different weathering histories, overall marked by depleted Ca2+, Na+ and K+ compared with the average UCC, PAAS and NASC and some advanced weathering trends. The samples presented a fractionation pattern characterized by a continuous depletion of light REEs from La to Sm and a regular decreased distribution of heavy REEs from Gd to Yb, and the Co/Th vs. La/Sc diagram indicates a predominant intermediate source. The upper samples presented the highest contents of REEs, probably due to the higher presence of iron and aluminum oxides and hydroxides, which can be related to more advanced weathering. The Al, Cu, Ni, V, Zn, Co, Mn, Ti, Fe and Si concentrations and the CF, EF and Igeo index values varied across the sediment core samples, demonstrating that there were long periods of geogenic or anthropogenic contributions. [ABSTRACT FROM AUTHOR]

Morphogenetic properties and geochemical compositions were analyzed and assessed to improve our understanding of pedogenesis and geochemistry of wetland soils on the Abeokuta formation of Ogun State, Nigeria. Three profiles were dug to a depth of 1.2 m except where the water table is high, and examined for their morphological, physical, chemical, and geochemical compositions using standard laboratory techniques. Gleying (mottles) were present in some of the subsurface horizons, and dark greyish colour dominates the soil matrix. The particle size is dominated by sand fractions and the clay fraction increases with depth. The soil pH was moderately acid to neutral (4.6–6.8) and the organic carbon contents were low to high (4.9–43.1 g/kg). The exchange site was dominated by Ca and Mg, while Fe and Mn contents were higher among the micronutrients. Kaolinite, quartz, and degraded mica were the dominant minerals in the clay fractions. The geochemical results reveal that the order of abundance of major oxides is SiO2 > Al2O3 > Fe2O3 > CaO > MgO > Na2O > TiO2 ≥ K2O. Geochemical indices point to a moderate degree of weathering and pedogenesis. Higher contents of SiO2 and Al2O3 and calcium in the surface layers indicate relative enrichment of minerals during weathering and nutrient cycling by vegetation. [ABSTRACT FROM AUTHOR]

Siliciclastic muds (clay-and silt-sized sediment) concentrate physical and chemical weathering products. However, both rock composition and climate can affect the mineralogy and geochemistry of these sediments. We quantitatively assessed the influence of provenance and climate on muds collected from end-member climates to test, which, if any, of these potential weathering signatures are indicative of climate in finegrained, fluvial sediments. Granulometry, mineralogy, and geochemistry of the studied muds indicated that provenance and mineral sorting hinder interpretation of (paleo)climate signals. These issues also affect chemical index of alteration (CIA) values, as well as mafic-felsic-weathering (MFW), Al2O3-(CaO* + Na2O)-K2O (A-CN-K), and Al2O3-(CaO* + Na2O + K2O)-(FeOT + MgO) (ACNK-FM) ternary plots, decreasing their utility as paleoclimate proxies. CaO content is heavily weighted within the calculations, resulting in even felsic-sourced sediment commonly plotting as mafic owing to the relative enrichment in CaO from preferential sorting of Ca-rich minerals into the mudsized fraction during transport. These results cast doubt on the indiscriminate use of CIA values and ternary plots for interpreting chemical weathering and paleoclimate within muds, particularly from glacial systems. Most notably, the positive correlations between CIA and climatic parameters (mean annual temperature and mean annual precipitation) diminished when sediments that had formed in nonglacial settings were filtered out from the data sets. This implies that CIA may only be applicable when used in nonglacial systems in which the composition of the primary source material is well constrained-such as soil/paleosol profiles. Within this end-member climate data set, CIA was only useful in discriminating hothumid climates. [ABSTRACT FROM AUTHOR]

Deciphering past climate variability in the Western Pacific Warm Pool (WPWP), the Earth's largest heat and moisture centre, is vital for understanding the global climate system. Nevertheless, its long-term evolution remains controversial, largely due to ambiguities in existing proxy interpretations and discrepancies between records. Here, we present a weathering and erosion reconstruction from the WPWP spanning the last 140,000 years, based on the mineralogy and geochemistry of a sediment core from offshore of northern New Guinea. The paleo-weathering reconstruction is consistent with the simulated precipitation evolution on nearby islands, thereby suggesting a close coupling between climate variability and island weathering in a tropical setting. In addition, our combined data-model interpretation of WPWP climate history shows many similarities to the East Asian Summer Monsoon (EASM) variability over orbital timescales. Overall, our study highlights the critical role of precession-paced interhemispheric energy redistribution, via the West Pacific meridional sea-surface pressure gradient, in linking orbital-scale WPWP climate and EASM variability. [ABSTRACT FROM AUTHOR]

The Santa Vitória Chalcolithic site (southern Portugal) prompts several questions related to the provenance and production technology of artefacts. Archaeological ceramics from two sections of Ditch 1 of the Santa Vitória site were studied by neutron activation analysis and X-ray diffraction for the first time, with the main goal of contributing to the contextualization of the artefacts and better understanding their production processes/technologies and the provenance of raw materials. The results point to a local production of ceramics, since their mineral phases reflect the geological contexts around the archaeological site. The mineralogical assemblage indicates a firing temperature below 850 °C. Iron is the better discriminator of ceramics from both sections, which could be related to the addition of different proportions of temper grains during the ceramics' production. Although trace elements do not serve as discriminating geochemical indicators for the analyzed samples, they do imply a slightly higher heterogeneity in the composition of the ceramic paste from section 2. The negative Eu anomaly found in two samples is in accordance with the lower contents of Na2O, related to plagioclase weathering. Detailed studies on ceramics and potential raw materials are foreseen to assist in discussing the role of this Chalcolithic archaeological site at a regional level. [ABSTRACT FROM AUTHOR]

Based on detrital monazite dating, mineral chemistry of tourmaline and rutile, bulk rock geochemistry, modal analysis of petrographic and palaeocurrent data, this study tracks the source of quartzose sandstone within the Cretaceous succession of the Cambay Basin primarily to rocks within the Aravalli‐Delhi Fold Belt. Monazite geochronology shows predominant peaks around 506 ± 11 Ma, 905 ± 12 Ma and a minor peak at 750 ± 20 Ma, 1485 ± 30 Ma relating sediment sources to the Aravalli‐Delhi orogeny and Pan‐African orogeny. The petrographic modal analysis of the moderate‐to‐well‐sorted Himmatnagar Sandstone indicates at least 91% quartz, with minor feldspar and rock fragments. The mineral chemistry of tourmalines in Himmatnagar Sandstone matches with Li‐ and Ca‐poor granitoid, pegmatites, metapelites and quartz tourmaline rocks. The trace element content of rutiles in sandstones corresponds to metapelitic sources. Detrital monazite dates and mineral chemistry of tourmalines and rutiles pinpoint the sediment source to the South Delhi Supergroup of rocks. The dominance of rounded zircons and tourmalines and abraded quartz overgrowth in the Himmatnagar Sandstone indicate the recycling of sediments, possibly from the Marwar Supergroup. Palaeoclimatic proxies based on mineralogy and geochemistry, particularly, the high value (93–97) of mineralogical index alteration, indicate intense chemical weathering of the source rocks under humid climatic conditions. Therefore, the combination of factors, including the quartzo‐feldspathic source rocks, intense chemical weathering under humid climatic conditions and the recycling of sediments facilitated the formation of quartzose sandstone within the Himmatngar Sandstone in the Cambay Basin. [ABSTRACT FROM AUTHOR]

Regolith-hosted Ni-Cr prospects in the Nkonko serpentinized massif are located near Kananga city in the Democratic Republic of Congo (DRC). This serpentinized massif displays an underground regolith profile divided into three main layers: (1) unweathered serpentinite bedrock, (2) saprolite serpentinites, and (3) the pedozone top layer. The bedrock serpentinites consist of serpentine (including lizardite and antigorite "garnierite") as a major phase, with Cr-spinel and magnetite as a subsidiary phase. The rock contains rare pseudo-olivine relicts. Saprolite serpentinites contain serpentines (e.g., lizardite, chrysotile, antigorite "garnierite") and subordinate ferrochromite and Cr-magnetite. These saprolite serpentinites are crosscut by veins of "garnierite" phase, talc, brucite, magnetite, magnesite, and chlorite. The pedozone primarily consists of lateritic soils with red and yellow limonite. Saprolite serpentinites exhibit relatively higher Al2O3, FeO, Fe2O3, and volatiles (LOI: loss on ignition) compared to bedrock serpentinites, while maintaining similar SiO2 contents. For trace elements, saprolite serpentinites contain elevated Cr (up to 5.4 wt%) and Ni (up to 2.0 wt%) compared to bedrock samples (Cr up to 0.9 and Ni up to 0.3 wt%). The REE concentrations are low (total REE of about 2.0 ppm) and remain unchanged between the saprolites and bedrocks. Spinel is identified as the main host mineral for Cr, while secondary serpentine "garnierite" is the primary host phase for Ni. Plots of Al2O3/SiO2 versus MgO/SiO2 for bedrock and saprolite serpentinites, along with the REE patterns, suggest that the serpentine regolith originated from the alteration and weathering of harzburgite. [ABSTRACT FROM AUTHOR]

Detrital and volcanic-detrital rocks from the Ifni Buttonhole and Lakhssas Plateau were analyzed to determine their provenance, compositional maturity, and alteration source. Geochemically, the sediments were classified as arkoses, lithic arenites, grauwackes, sandstones, lithic arenites, and Fe-rich sands, indicating low compositional and mineralogical maturity. A high average SiO2 concentration and low Al2O3 were consistent with a low abundance of shale and clay components. The geochemical signatures of the detrital and volcano-detrital (RDVD) rocks indicate that they have undergone a moderate to low degree of chemical alteration. The CIA study also suggests that the granitic, granodioritic rocks represent the source provenance which, during weathering and transport, supplied the detritus to the supra-crustal units. The major trace element data suggest that these rocks are largely derived from felsic igneous rocks, namely granitoids, with a minor contribution from intermediate sources. The carbonate rocks do not represent a wide variety of facies: dolomitic limestone, calcareous limestone, and calcaro-dolomitic chert. Calcitic and dolomitic samples show a linear increase in SiO2, regardless of their CaO/LOI ratio values, which remain relatively constant. The highest SiO2 contents are observed in the calc-dolomitic chert. Geochemical analysis of RDVD from the Ifni buttonhole determined their origin, maturity, and alteration. Major oxides decreased with higher silica content, indicating quartz control. Samples, formed under semi-arid conditions, show maturity under stable deposition. They suggest a felsic, recycled source, with moderate alteration and zircon enrichment during recycling. In the study area, limestones and dolomites serve as materials applicable in the building sector, suitable for all types of concrete. The Taliwine Formation harbors Lower Cambrian dolomites and limestones, ideal for mosaic aggregates. Described as variable in color, compact, homogeneous, very hard, and resistant to alteration, the plutonic rocks form prominent peaks. They exhibit both subalkaline characteristics in granitoids and an alkaline trend in dolerite dykes. Most samples display minimal alteration, indicating the reliability of their major element compositions for geochemical analyses. These granitoids constitute valuable deposits for ornamental and building rock purposes.

The mid‐Proterozoic (∼1.8–0.8 Ga) ocean‐atmosphere system is hypothesized to have experienced fluctuations in redox conditions with transient oxygenation events. One of these happened at ∼1.4 Ga, and it is speculated that this event may link to the emplacement of large igneous province (LIP) at this time. However, direct evidence for this relationship remains to be proved. Here, we report Hg/TOC, P, and trace element concentrations across the ∼1.4 Ga oxygenation event in the Xiamaling Formation of North China. A prominent increase in Hg/TOC is slightly earlier than that of nutrient contents (especially P), pyrite and TOC abundances, suggesting that this distinct oxygenation event was likely the result of LIP activity at ∼1.4 Ga, which increased nutrient and sulfate supply from continental weathering to the ocean, sustaining elevated primary productivity, organic carbon and pyrite burial. This study indicates that LIP weathering could trigger transient oxygenation events during the mid‐Proterozoic. Plain Language Summary: The mid‐Proterozoic (∼1.8–0.8 Ga) retains persistent low oxygen concentrations in atmosphere and shallow seawater but is occasionally punctuated by transient oxygenation events. Multiple lines of evidence from sedimentary geochemistry have argued a global oxygenation event at ∼1.4 Ga, and speculated that this event was closely related to large igneous province (LIP) activity at this time. Direct link between LIP activity and the oxygenation event, however, has rarely been addressed yet. As mercury in sedimentary rocks has been widely used to trace volcanism, we therefore report Hg/TOC, P, and trace element concentrations across the ∼1.4 Ga oxygenation event. The result shows that a prominent increase in Hg/TOC is clearly recognized in the shales that stratigraphically just underly the layers recording the oxygenation event, suggesting a close causal link between LIP emplacement and the oxygenation event. Accompanied with this Hg/TOC ratio peak, increased nutrient contents (especially P), pyrite and TOC abundances are also observed. Based on these observations, we proposed a model that the Xiamaling oxygenation event was the result of the LIP's emplacement at ∼1.4–1.35 Ga, which increased nutrient and sulfate supply from continental weathering to the ocean, sustaining elevated primary productivity, organic carbon and pyrite burial. Key Points: High Hg/TOC ratios associated with large igneous province (LIP) emplacement were detected in the ∼1.4 Ga Xiamaling Formation shales of North ChinaHigh P content accompanied with this interval indicates enhanced phosphorous input from LIP weathering to the oceanA causal link between the LIP weathering and oxygenation event at ∼1.4 Ga was suggested [ABSTRACT FROM AUTHOR]

Rock weathering, an important geological process on the earth's surface, plays a key role in shaping surface morphology, providing nutrients needed by the ecosystem, and regulating the global climate. However, the regimes for controlling rock weathering in different regions are still controversial. In this respect, the heavy minerals, elements, Sr-Nd isotope, magnetic susceptibility, and chromaticity of the granite weathering profile in Harbin, a high latitude area of China, were analyzed for understanding the weathering characteristics and mechanisms of the granite weathering profile in the cold area. The results indicate that the profile underwent strengthened physical weathering (large volumes of cracks in the granite parent rock) and low–moderate chemical weathering (CIA = 56~68). However, the chemical weathering does not clearly affect the composition of the weathering products, making the weathering products a good inheritance from the parent rocks, as evidenced by the binary diagram (e.g., TiO2-Zr, and La/Sc-Co/Th) and geochemical genes (LG01 and LG03). The development process of the weathering profile has been affected by the input of external materials and biological activities, as evidenced by the Sr-Nd isotopic composition, Th/Zr values, chemical depletion fractions, ΔAl/Ti ratios, χfd%, and geochemical genes (LG03). Notably, a progressively decreasing weathering degree with a reduced depth is observed in the profile, which is likely to be related to an addition of external materials and/or effects of biological activities. In addition, the weathering regime of the profile does not vary in geology time, characterized by a kinetic-limited weathering regime with a limited supply. [ABSTRACT FROM AUTHOR]

The toxicity, persistence, and propensity for accumulation of metals in aquatic environments have raised significant concerns globally. Expansion of urbanization with the growth of industrial and agricultural sectors in Miri City results in a high concentration of pollutants that flow directly into the Miri River. Hence, this study provides a comprehensive analysis of the Miri River water quality, focusing on spatial and temporal variations. River water samples were collected in two different time periods and analysed for physico-chemical parameters includes major ions, nutrients, metals and isotopes. Particularly, the metals were analysed in different size fractions (particulate and colloid) of the suspended solids. Geochemical plots, pollution index, geochemical modelling and factor analysis were used for the data analysis. Interpretation of data reveals that the mean concentration of metals in river water were increased from downstream to the upstream of the river irrespective of the seasons. Major ions were mostly derived from the chemical weathering of source rocks, which was supported by the Gibbs plot. Piper plot indicates the seasonal shifting of water types from Ca-Mg to Na-Cl. Isotopic signatures reveal direct atmospheric precipitation and evaporation were the major origins of river water. Fe was the dominant metal concentration in river water irrespective of the seasons (mean concentration 1.05 mg/L). Fe and Zn were the dominant metal concentration observed in all the 3 size fractions of suspended solids. Industrial activities and seawater influx dominate in the downstream, whereas weathering and agricultural inputs are significant in the upstream of the river. Particulate and colloidal fractions are the major contributors for the metal transport in the midstream and downstream of the river. The outcome of this study offer a thorough understanding of the seasonal elemental distribution at different size fractions, geochemical behaviour and the pollution status of the Miri River. With this knowledge, sustainable management strategies can be developed for this crucial water resource to the benefit of Miri community. [ABSTRACT FROM AUTHOR]

Rare Earth Elements (REEs) are mobile during weathering and their distribution is susceptible to both natural and anthropogenic influences. Four major drainage points in the Makran and Lasbela areas were selected for sampling to examine their REE geochemistry. The mean values of ∑REE are highest in Dasht River (DR: 109.4) and lowest in Shadi River (SR: 84.4). The mean values of Eu/Eu* are highest in Rakhshan River (RR:0.95) and lowest in DR (0.70); these values are higher as compared to the Upper Continental Crust (UCC: 0.23) and Post-Archean Australian shale (PAAS: 0.21) in all drainage points. The mean values of (Gd/Yb)N are highest in RR (2.66) and lowest in DR (2.03), while the mean values of Ce/Ce*, (La/Sm)N, (La/Yb)N, and (La/Lu)N are highest in DR (1.01, 3.01, 9.86 and 9.66, respectively) and lowest in RR (0.93, 1.49, 5.75 and 5.93). DR and HR, covering the longest distances from headwater to mouth, pass through a variety of lithologies and convey a more diverse range of sediment compared to RR and SR. Noticeably depleted elemental concentrations relative to UCC (elemental ratios <1) are observed in the majority of sediments, implying the influence of weathered source rocks. Normalized chondrite distributions of the REEs exhibit consistent trends marked by an enrichment of LREEs and a depletion of HREEs, a characteristic pattern was found in upper crust materials exposed to weathering and erosion. The presence of a positive Eu anomaly in UCC and PAAS normalized patterns suggests the contribution of plagioclase minerals. However, leaching is insignificant for the studied sediments due to low average annual precipitation. [ABSTRACT FROM AUTHOR]

Tectonic setting of the Late Carboniferous Cameng Formation in the north of South Qiangtang terranes (SQT) remains controversial. Here, we report new geochemical results for clastic rocks from the Cameng Formation. Our results show that the Index of Compositional Variability (ICV) is greater than 1, indicating these sediments experienced limited recycling and were probably derived from acid to intermediate magmatic rocks. The extent of weathering, with the Index of CIA vary from 67 to 75 (mean = 71), ICV > 1 (mean = 1.25) and the Th/U ratios > 4, is moderate in the source area. These new findings show that the Cameng Formation was most likely deposited in an unstable environment (continental island arc or active continental margin). Combined with other evidence, we further infer that the Early Paleozoic rocks (206Pb/238U ages varying from 438 to 502 Ma) presently exposed in the South Qiangtang terrane are the potential source of the Late Carboniferous depositions in the northern SQT, and were most likely deposited in a forearc basin under the in situ suture model, that is, the southward subduction of the Longmu Co-Shuanghu Tethys Ocean beneath the SQT. [ABSTRACT FROM AUTHOR]

The preliminary results of geochemical analyses of the surface sediments from 4 lakes on Robert Island, South Shetland, Antarctica, are presented herein. The samples were collected during the Turkish Antarctic Expedition (TAE-II) in 2018. Sediment samples were obtained from the littoral zone (approximately 20 cm) of 4 different lakes exposed on the glacier-free land area on Robert Island. The lake sediments predominantly consist of fine-grained sand, clay, and silt particles. These particles include Fe-shale and graywacke geochemical characteristics. Their plagioclase index of alteration, chemical index of weathering, chemical index of alteration, and other weathering index values, suggest that the studied sediments have likely undergone low to moderate weathering and alteration processes. The Th/U ratios generally indicated a lower distribution relatively to the upper continental crust, and they displayed slight enrichment in alkali elements, indicating a low degree of chemical weathering that has slightly influenced the sediment chemistry. Moreover, the Gd/Yb, Zr/Y, and La/Yb ratios exhibited similarities with the surrounding volcanic rocks on Robert Island. Additionally, their chondrite-normalized rare earth element (REE) patterns exhibited a similar trend, implying that the REE composition of the sediments is predominantly controlled by the local source rocks. Nevertheless, there were slight differences in the Y/Ho ratios and heavy REE (HREE) contents, suggesting the presence of additional sources contributing to the REE supply in the lake basins. The Co/Th, La/Sc, Th/Sc, and Zr/Sc ratios mostly resembled those of basic volcanic rocks, while the Rb, K, HREE, and Ni values dominantly indicated basic rocks with a minor input from felsic magmatic or quartzose sedimentary rocks. Considering the geomorphology and location of the basins, which are mostly situated along the coast where foehn winds have a limited influence over ice-free areas, it is likely that locally resuspended materials have had a significant impact. This factor may mask any potential signals of modern dust fallout and accumulation. However, possible dust sources include nearby or distant areas, such as exposed rock and sediment within the immediate vicinity of the lakes, including dry lakebeds, glacial outwash plains, or exposed moraines. Based on multiproxy element analyses, including REEs, high field strength elements, and lithophile elements, the geochemistry of the studied sediments, the overall geochemical characteristics cannot be fully explained by the local sources, suggesting that weathering processes and minor contributions from dust materials have played a nonnegligible role in shaping their chemistry. [ABSTRACT FROM AUTHOR]

Pedogenesis of volcanic soils has been studied broadly in humid regions, but very little data are present regarding these soils in arid and semi-arid regions of Turkey. This research aimed to assess the pedological processes and investigate the physical, chemical, and mineralogical characteristics of soil profiles developed from volcanic parent material. The studied soils were not classified as Andisol because they lack andic properties. The results showed that sand and coarse silt fractions exceeded 30%. The bulk density was higher than 0.90 grcm-3 in all profiles. In general, phosphate retention was low, higher than 25% in profiles but lower than 85% in all profiles. The Al + 1/2 Fed percentages were lower than 2% in all profiles. Selective extraction (Na-Pyrophosphate, Ammonium Oxalate, Na-Dithionite) indicated that soils lack noncrystalline minerals, such as allophane, imogolite, and iron humus complexes. The only noncrystalline minerals in high quantities are Al-humus complexes and small amounts of ferrihydrite. X-ray diffraction indicated that smectite, kaolinite and illite were dominant minerals in the clay fraction. Among the studied profiles, profiles 1 and profile 4 are classified as vitrandic Haploxerept, profile 2 as vitrandic haploxerolls, and profile 3 as vitrandic Xerorthent. The results indicated that the dominant soil-forming processes include the following: 1. desilication and the eluviations of base cations and Al from the solum; and 2. transformation of iron and aluminum from the sand and silt-size fractions into secondary clay and crystalline Fe minerals. The major factors determining soil genesis on Mt. Karacadağ appear to be climate and topography affected by the leaching regime and weathering rates. [ABSTRACT FROM AUTHOR]

A first pass workflow for placing cover sequence materials into four broad lithological groups using A-CNK-FM (Al2O3-CaOþNa2OþK2O-Fe2O3þMgO) and A-CN-K (Al2O3-CaOþNa2O-K2O) ternary diagrams in conjunction with the SiO2 vs Al2O3, Fe2O3 and CaO plus the Ca versus Sr XY diagrams has been derived from lithological logging and laboratory whole-rock geochemistry of 2346 samples. These lithological groups include siliciclastics (quartz sands and clays), weathered material, carbonate lithologies (marine limestone, pedogenic carbonate and compositions intermediate between the two end members) and ferruginous lithologies (including ferricrete and ferruginous sediments). Depositional, weathering and groundwater processes influence sample geochemistry during or after the formation of the material and will influence where the sample will plot on the geochemical diagrams used in this study. Geochemical data for discrete lithologies targeted during sampling (e.g. carbonate lithologies) clusters on diagrams used in the geochemical workflow, whereas data from targeted stratigraphic horizons (e.g. basement-cover interface) are more variable. The ability to characterise rock types that are texturally defined using the geochemical workflow is limited. For instance, the geochemistry of diamictite/conglomerate samples is dependent on the matrix versus clast content and composition as well as the source rock and catchment area. This workflow has the potential to be applied in a mineral exploration environment for rapid interpretation of real-time geochemical (e.g. portable XRF) data to gain an understanding of background geochemistry and geochemical signatures that may be related to underlying mineralisation. [ABSTRACT FROM AUTHOR]

The shale samples from Uzebba, Ayoguiri, and Ugbenor within Edo State, Anambra basin, southern Nigeria, were geochemically analyzed for major oxides, trace elements, and mineral content. The trace element ratios from the paleoredox inferences revealed that the shale samples were deposited in an oxic environment (Ni/Co, V/Cr, and V/V+Ni) except for V/Ni which was deposited in a dysoxic - oxic environment. The ancient climate condition of the shale was a semi-arid climate with increasing chemical maturity and the bivariate relations (SiO2 vs. Al2O3) authenticating that the shale was terrestrially sourced. The Al2O3/TiO2 (13.48) indicates that the provenance of the shale is from a felsic source. The bivariate relationship of (SiO2 vs. Al2O3+Na2O+K2O) suggests a semi-arid paleoclimate with increasing chemical maturity in a phanerozoic shale environment. The data obtained from the study, showed that the average values of the following weathering indices: the Plagioclase Index of Alteration (PIA) with a value of 91.00% (73.58-98.43), the Chemical Index of Alteration (CIA) of value 74.33% (65.18-78.25), the Chemical Index of Weathering (CIW) with a value of 93.12% (73.58-98.43) and the Mineralogical Index of Alteration (MIA) valued at 48.67% (30.36-56.50) which indicates a substantial, moderate to intense chemical weathering with a PIA average indicating a phenerozoic ancient environment. The mineralogy of the shale from the diffractogram profiles were quartz, fluorapatite, calcite and montmorillonite. The predominance of quartz again confirms the resistance of quartz to weathering conditions while the other minerals that are in trace amounts are only indications that they are less resistant to weathering and have dissolved in the solution. [ABSTRACT FROM AUTHOR]

The Ni-laterite deposit at the San Felipe plateau, located 30 km northwest of Camagüey, in central Cuba, is the best example of a clay-type deposit in the Caribbean region. San Felipe resulted from the weathering of mantle peridotites of the Cretaceous Camagüey ophiolites. In this study, a geochemical and mineralogical characterization of two profiles (83 and 84) from the San Felipe deposit has been performed by XRF, ICP-MS, quantitative XRPD, oriented aggregate mount XRD, SEM, FE-SEM, and EMPA. Core 83, with a length of 23 m and drilled in the central part of the plateau, presents a notable concentration of cryptocrystalline quartz fragments and a rather poor content of NiO, averaging 0.87 wt.%. Core 84, which is 12 m long and drilled at the border of the plateau, lacks silica fragments and presents a higher NiO content, averaging 1.79 wt.%. The smectite structural formulae reveal that they evolve from trioctahedral to dioctahedral towards the top of the laterite profiles. Quantitative XRD analyses indicate that smectite is a dominant Ni-bearing phase, accompanied by serpentine and minor chlorite. Serpentine, as smectite, is enriched in the less soluble elements Fe3+, Al, and Ni towards the top of the profiles. Core 83 seems to have been affected by collapses and replenishments, whereas core 84 may have remained undisturbed. [ABSTRACT FROM AUTHOR]

The geochemical signatures of recent stream sediments in the study area revealed an old recycled sedimentary source and weak to moderate chemical weathering. The sediments exhibit a positive correlation of large ion lithophile elements (Ba, Sr, and Rb), transition trace elements (Co, Cr, Cu, Ni, Sc, and V), and REE with Al2O3 and associated immobile oxides, indicating affinity with phyllosilicate sedimentary rocks of Semri Group of Vindhyan basin. The La–Th–Sc and Th–Sc–Zr/10 ternary plots show mixed sediment sources of clays, silts, and sands. Positive correlations of LREE with Th, Zr, Al2O3, and TiO2 and negative correlations with Y and P2O5 suggests the cumulative influence of Ti-bearing minerals and clay minerals. The high Zr/Sc ratio (mean 30.8), strong LREE/HREE enrichment (mean 8.1), prominent negative Eu anomalies (mean 0.57) and flat HREE suggest input from the recycled sedimentary source. The mean chemical index of alteration (69.17), plagioclase index of alteration (74.94), chemical index of weathering (93.08), and ACNK indicate weak to moderate weathering with the presence of minor K-feldspar mixed in illite dominated mud. This is also supported by a high Rb/Sr ratio (mean 1.09) and K/Rb ratio (0.018). A higher K/Al than Na/Al ratio points to higher illite content. The presence of illite, minor feldspar, and less SiO2/Al2O3 ratio (mean 4.98) suggests low textural and compositional maturity, attributed to the mixing of sediments by significant physical weathering. The positive correlation between Th/Sc (mean 0.6) and Zr/Sc (30.8) indicates less fractionation, low to moderate hydraulic sorting, and sufficient sediment recycling in Kurheri sediments. [ABSTRACT FROM AUTHOR]

The chemical weathering of carbonate rocks is the main form of interaction between earth spheres in the karst critical zone. The karst weathering cover, which is composed by residua from carbonate rocks weathering, contains important information about the climate environment and material cycle. We present the chemical composition of weathering covers in karst area of Guilin, Guangxi province, analyze their weathering process and strength, and compare them with the other weathering covers in other karst area in China, including Yunnan, Guizhou, Hunan, and Qinghai Tibet Plateau. The results showed: (1) the chemical composition of Guilin weathering covers were similar to that of carbonate weathering covers in other areas of China, and had the common characteristics of uniform distribution of chemical composition in the profile and obvious enrichment of Fe, Al and trace elements. During the formation of carbonate weathering cover and the residua, the rapid dissolution of Ca and Mg had an important impact on the migration and enrichment of other elements. (2) The chemical index of alteration (CIA) of carbonate weathering covers in Guilin and other karst areas of China was much larger than that in the upper crust (UCC) (60.13), which showed strong chemical weathering characteristics of the humid and hot climate. (3) The weathering process of carbonate rock was different from that of silicate and loess. In the early stage of carbonate rock weathering, soluble components (calcite and dolomite) had been rapidly dissolved and leached. All the carbonate weathering residua was measured to be in the stage of K2O weathering and Al2O3 increasing. Therefore, the weathering degree of carbonate weathering cover was mainly determined by the leaching of K2O and the increase of Al2O3. As a result, there was no correlation between CIA and Na/K (molar ratio), but was a significant negative correlation between CIA and K/Al (molar ratio) in the carbonate weathering cover. (4) The CIA values of weathering residua and carbonate weathering cover in southern China were negatively correlated with latitude, reflecting the influence of climate factors. From the influence of lithology, the chemical compositions of parent rock can affect the CIA of weathering cover, and the content of insoluble matter in carbonate rock was negatively correlated with CIA. From the influence of topography, the CIA value of weathering residua decreased from the high to the low position and from the shallow to the deep part of the profile. [ABSTRACT FROM AUTHOR]

The Western Indonesia Bauxite Province in Kalimantan is a lateritic bauxite region with a complex history and poorly known sustainable metal contents within the bauxite residue. Bauxite residue produced using the Bayer process contains, notably, scandium. We present new geochemical, mineralogical and geological data from the lateritic bauxite and red mud from the active mine and deposit, which allow us to investigate the behaviour of critical elements during weathering. The geochemical analysis and translated isocon results have shown that the content of scandium in red mud is higher than the average concentration of crustal rocks and is concentrated in the ferrite layer and bauxite residue. A positive correlation between the existence of iron oxyhydroxide mineral in the residual iron-rich layer and red muds with the rare earth elements (REEs) and scandium concentrations may be interpreted as a scavenging effect of mobile REEs. The weathering and leaching processes in bauxite allows the adsorption of the trivalent scandium cation (Sc3+) on goethite and are followed by ionic substitution with other trivalent cations in crystals of hematite. The study illustrates the importance of understanding processes during weathering and laterization for geochemical processes and REE exploration in tropical areas. Supplementary material: Material A, (A) Mineralogical profile of the bauxite, ferrite, and tonalite in Tayan and Mempawah, (B) Ternary diagram of bauxite and their parent rocks, (C) Trace element ratios in bauxite; Material B, Spearman's correlation rank of bauxite and associated rocks from Tayan mine (n = 35); Material C, (A) XRD patterns of representative samples from the Tayan mine and Mempawah deposit, West Kalimantan, (B) Typical normal (left) and continuum (right) removed reflectance spectral curves of samples are available at https://doi.org/10.6084/m9.figshare.c.6689139 Thematic collection: This article is part of the Geochemical processes related to mined, milled, or natural metal deposits collection available at: https://www.lyellcollection.org/topic/collections/geochemical-processes-related-to-mined-milled-or-natural-metal-deposits [ABSTRACT FROM AUTHOR]

This paper reports the results of the geochemical study of the Jutogh metasedimentary rocks that occur as a tectonic window between the Lesser and the Higher Himalaya. The Jutogh Group of rocks are mostly mica-schists of different metamorphic grade. The weathering intensity parameters, such as chemical index of alteration (CIA), plagioclase index of alteration (PIA), and index of compositional variability (ICV), range from 81 to 65 (mean = 72), 97 to 68 (mean = 84), and 1.9 to 0.6 (mean = 1.2), respectively indicating low to moderate degrees of weathering. Transition element ratios [Ni/Co (6.98 to 2.88), and V/Ni (2.32 to 1.27)], and major and trace element geochemistry imply recycled, felsic to intermediate, Archean to post-Archean are the sources for Jutogh rocks. The tectonic discrimination diagram implies an active continental margin setting for the deposition of the Jutogh metasediments. The geochemical data from the Jutogh rocks, when combined with the S-type Paleoproterozoic granite magmatism, imply the existence of an active tectonic setting during the deposition of the Jutogh sediments at the northern margin of the Indian continent during Nuna assembly. [ABSTRACT FROM AUTHOR]

The potential of river Mg isotope systems to trace continental chemical weathering processes has been emphasized in recent years. The geochemical behavior of Mg isotopes in the surface process of the watershed was summarized. The results show that river Mg is mainly derived from mineral chemical weathering, atmospheric precipitation, groundwater and plant debris. Mg isotopic composition of the world's major runoff shows great variability, which is difficult to fully explain by the conservative mixing of Mg reservoirs in the basin alone, because the differential weathering of bedrock and Mg isotope fractionation during continental chemical weathering is important influencing factor of Mg isotopic composition in river water. The main fractionation processes affecting Mg isotopic composition in river water include primary mineral decomposition, secondary mineral formation, adsorption-desorption of exchangeable states, plant uptake and debris release. At present, the primary control process of river Mg isotope system is still not well understood. On a global scale, Mg isotopic composition of large rivers correlates well with the chemical weathering strength of carbonate minerals. In addition, multi-isotopic systems such as Mg-Sr, Mg-Li, Mg-Ca and Mg-O also provide powerful tracing tools for the study of surface environment evolution. In the future, the discussion on Mg isotope fractionation factors, special chemical weathering types, multi-isotope coupling combination and quantitative tracing of Mg isotopes in key processes in river basins should be strengthened, and the application of river Mg isotopes in chemical weathering in river basins should be promoted. [ABSTRACT FROM AUTHOR]

Selected Malaysian black shale sequences of the Permo-Triassic and Devonian ages that crop out in the Central Belt were investigated to discuss their chemical composition, provenance, tectonic setting, and weathering history. X-ray fluorescence (XRF) analysis shows that the BRSZ Unit 1 black shale has elevated SiO2, TiO2, and K2O contents compared to the Semantan and Gua Musang black shale. In terms of trace elements, the BRSZ Unit 1 black shale has elevated trace element contents compared to the Semantan and Gua Musang black shales. The BRSZ Unit 1 has the highest V, U, Pb, and Mo contents relative to the other two formations. The Mo content is significant in the BRSZ Unit 1 and is thought to be associated with the elevated total organic carbon (TOC) in the BRSZ Unit 1 black shale. Compared to Post-Archean Australian Shale (PAAS), the BRSZ Unit 1 and Gua Musang black shales are low in Fe2O3, MnO, CaO, Na2O, and P2O5. The Semantan black shales are deficient in CaO, K2O, and P2O5 and enriched in MnO. The black shales of BRSZ Unit 1 are enriched in V, Cu, Ga, Rb, Mo, Sn, Pb, and U. Except for Pb (mean: 32.3 ppm), the Gua Musang black shales are largely depleted in trace elements. Similar to the Semantan black shales, all trace element concentrations are largely depleted with the exception of Sc (mean: 22.3 ppm), which is slightly higher. Provenance analysis shows that the BRSZ Unit 1, Semantan, and Gua Musang black shales derived from felsic and intermediate parental source rocks. The BRSZ Unit 1 and Gua Musang black shales indicate a collision setting, whereas the Semantan black shales show affinity to a continental arc setting. The CIA values for all the samples analyzed in this study range between 79.4 and 95.8, indicating an intense chemical weathering in warm and wet paleoclimatic conditions. The average CIW values of samples from the BRSZ Unit 1, Semantan, and Gua Musang are 99.4, 94.5, and 98.6, respectively, implying an intense degree of weathering of the source rocks. [ABSTRACT FROM AUTHOR]

The Permian Lucaogou oil shales in the eastern Junggar Basin have long been regarded as important source rocks and reservoirs for tight oil exploration. The oil shales can also be used to assess the provenance and tectonic setting of the East Junggar region using major, trace and rare earth element geochemistry. The low chemical index of alteration ratios (37.36–64.18, 45.54 on average), low plagioclase index of alteration ratios (26.99–62.95, 42.99 on average), and high index of compositional variability ratios (0.64–1.66, 1.10 on average) suggest that the Permian Lucaogou oil shales mostly consist of immature sediments that have experienced a weak weathering intensity. The samples have low TiO2/Al2O3 and TiO2/Zr ratios that indicate a felsic origin with minor intermediate igneous rocks. The high Th/Sc and Zr/Sc ratios suggest a felsic origin without sediment recycling. The samples show fractionated light rare earth elements and relatively flat heavy rare earth elements patterns with weak negative Eu anomalies, which implies that the main provenance is lower Carboniferous intermediate–acid volcanic rocks. In addition, multiple major- and trace-element‐based discrimination diagrams show that the parent rock of clastic sediments formed mainly in a continental island arc and active continental margin environment, consistent with previous studies on the tectonic background of the East Junggar region during the late early Carboniferous. Immature sediments are present in the Permian Lucaogou oil shales and have a weak weathering intensity. The provenance of the clastic sediments of the Permian Lucaogou oil shales was predominantly early Carboniferous intermediate–acid volcanic rocks. The clastic sediments of the Permian Lucaogou oil shales were developed in a continental island arc and active continental margin environments. The Permian Lucaogou oil shales provide crucial information for tectonic setting and evolution of the northern Xinjiang during the Carboniferous–Permian. [ABSTRACT FROM AUTHOR]

As part of paleogeographic studies on the Curonian Spit (geological section GS 024), a coastal section was studied from the sea in the area of the village of Lesnoy in the place where relict lagoon oozes come out. The granulometric, chemical, and mineral compositions of slope sands were studied for the first time. Heterogeneous conditions for the formation of sand strata were confirmed. A high probability of a secondary change in the composition of sediments as a result of weathering processes was revealed. The results of the study indicate a gradual advance of sand deposits on the coastal part of the lagoon, which began about 10 ka ago. Differentiation of the sand stratum into lower and upper parts with respect to an interlayer marker of coarse-grained sand identified in the section may reflect different stages of generation of the sand stratum: from an alleged shallow-water swell formed during sea level rise to beach and eolian sands. [ABSTRACT FROM AUTHOR]

This paper aims to determine the geochemical provenance, source area weathering, and tectonic setting of the Bida sandstone exposed at Doko and Jima in the Northern Bida Basin, Northcentral Nigeria. Geological fieldwork was carried out and sandstone samples were collected and analyzed for major element concentrations using X-Ray Fluorescence (XRF) method. Major element abundance shows that the studied sandstone samples consist of SiO2 (average 71.42%), Al2O3 (average 15.16%), and CaO (average 0.26%) constituting about 90% of the bulk rock composition. While P2O5, Na2O, K2O, MgO, TiO2, MnO, and Fe2O3 constitute about 10% of the composition. The results obtained using the Al2O3/TiO2 ratios show that the sandstones derived from intermediate to felsic igneous rocks. The A-CN-K triangular diagram shows that majority of the analyzed samples plotted on the aluminum zone towards kaolinite shows predominantly intermediate degree of weathering except for one sample which falls towards the CN-K line, indicating the different degree of weathering (perhaps an existence of differential weathering in the area). The source area weathering indices which include CIA (68.6%), CIW (71.20%), and PIA (54.66%) further confirms that the sediments have been subjected to intermediate weathering. The K2O/Na2O versus SiO2 tectonic setting discriminant plot shows that the samples are dominantly deposited in the passive margin setting. It is, therefore, concluded that the Bida sandstone analyzed was sourced from predominantly felsic igneous rocks where the degree of chemical weathering was intermediate and in the passive margin setting. [ABSTRACT FROM AUTHOR]

Chemical weathering indices (CWIs) based on bulk chemical rock composition can potentially provide an objective tool for estimation of weathering intensity and classification of weathering products. However, despite their long history and the large number of indices that have now been developed, their applicability still has serious limitations. To overcome most of the limitations, this paper proposes a new weathering index based on the review of geochemical and mineral rock evolution during weathering and analysis of the existing CWIs. The new index, the alumina + ferric oxide to bases ratio (AFB), is expressed as AFB = AFBw/AFBp where AFB = (Al2O3+Fe2O3)/(K2O + Na2O + CaO + MgO); w, weathered rock and p, parent rock, with all elements in molecular proportions. The index provides a basis for comparison of weathering intensities between different lithologies by linking the chemical and mineral transformations that characterise the regolith profile. It is sensitive to all stages of weathering, including lateritisation by using the ratio of the stable (relatively immobile) to mobile metals expressed as oxides. An extensive, worldwide chemical database on 40 well-documented regolith profiles developed on felsic, mafic and ultramafic substrate was used for testing the proposed index and its comparison with the most common indices. The rocks were mostly weathered under tropical or subtropical conditions. The results confirmed consistent increase in the AFB value with intensifying weathering. The index is applicable to all silicate rock types including Al-poor ultramafic rocks. Use of parent rock normalisation allows a more accurate comparison of weathering intensities between different lithologies. At the expense of these benefits, the parent normalised index AFB requires data for the unweathered protolith that is commonly difficult to obtain. The index is also sensitive to inhomogeneity of the original rocks. The unreferenced to parent rock AFBu index has potentially broader applications including provenance and the weathering history of sediments, soil and engineering studies, although collection of more data is required for understanding the index constraints for various conditions and rock types. A new chemical weathering index, expressed as the alumina+ferric oxide to bases ratio normalised to parent rock provides reasonable results for all major types of silicate lithologies. The index is applicable for all types of weathering including the lateritic environment. On the downside, the index is sensitive to inhomogeneity of the original substrate and to later epigenetic modifications of the residual regolith. [ABSTRACT FROM AUTHOR]

We report two experiments using 13 mineral and rock samples exposed to a complex synthetic Venus atmosphere composed of nine gases for durations of 30 and 11 days conducted using the NASA Glenn Extreme Environments Rig (GEER). Examination of our run products using a scanning electron microscope equipped with an energy dispersive spectrometer reveals secondary minerals predominantly formed from reactions of Fe and Ca in the solid samples with sulfur in the atmospheric gas, results largely predicted in the literature, and indicating that such reactions between rocks and the atmosphere at the Venus surface may occur rapidly. Samples that displayed larger degrees of reaction include calcite (forming Ca‐sulfate), Fe‐Ti oxide (forming an Fe,S phase), biotite (forming an Fe,S phase), chalcopyrite (forming a new Cu,Fe‐sulfide and a Ag,Cl phase), and Mid‐Ocean Ridge Basalt glass (forming a Ca‐ and S‐bearing phase, Fe‐ and S‐bearing phase, and an Fe‐oxide); pyrite was observed to be stable in our 30‐day experiment. These reactions indicate that the fS2 of the experiments was above or at the high end of what is thermodynamically predicted for the Venus surface. Apatite, feldspars, actinolite, and quartz did not change in this time frame. The presence of multiple S species in the GEER atmosphere may explain the dissimilarities to the style of reactions seen in previous experiments with simpler gas mixtures. Plain Language Summary: The surface conditions of Venus are unique in our solar system, where rocks are exposed to a sulfur‐rich atmosphere at 460°C and pressures ∼90× that of the surface of the Earth. The Glenn Extreme Environments Rig (GEER), located at NASA Glenn Research Center, is the world's first laboratory vessel to mimic Venus surface conditions (including 9 atmospheric gases) over durations of weeks to months. We placed 13 rock and mineral samples in GEER for 11 and 30 days to observe changes in the samples due to reactions with the simulated Venus atmosphere. We find that Fe‐ and Ca‐bearing minerals react with S and Cl in the gas, to produce discrete secondary minerals. We find that sulfur gas is the dominant driver of mineral reactions in this experiment and that the mixture of gases in GEER may account for some of the differences in the reaction products seen here as compared to previous experiments. Some mineral surface compositions change significantly, suggesting that these changes will be rapid on Venus. The style and rate of these reactions will help us better understand the climate history recorded in Venus surface rocks from remote sensing measurements from spacecraft at the end of this decade. Key Points: Mineral weathering experiments were conducted for up to 30 days under Venus surface conditions, including a nine‐gas atmospheric mixtureCalcite, biotite, basaltic glass, chalcopyrite, and Fe‐Ti oxide all reacted to produce secondary minerals dominated by Ca, Fe, and SOur results indicate the fS2 of the experiments was above or at the high end of what is thermodynamically predicted for the Venus surface [ABSTRACT FROM AUTHOR]

The shale units of the Late Devonian to Early Carboniferous successions of the Kaista and Ora formations from extreme northern Iraq have been studied for their geochemical and mineralogical features to reconstruct paleoenvironmental conditions. The Chemical Index of Alteration (CIA; high values ~93-99), high, Plagioclase Index of Alteration (PIA ~92-98), and the A-CN-K plot indicate the studied shales have undergone intense weathering at the source area. Also, high kaolinite content and predominance of kaolinite over illite in the studied shale support this conclusion. The Rb/K and Sr/Ba ratios of the Kaista and Ora formations indicate freshwater to brackish water during deposition. Geochemical investigations, using redox-sensitive trace elements ratios such as V/(V + Ni), Th/U, and U index suggest deposition of the Ora black shales under anoxic marine conditions, thus recording an ocean anoxic event in the region. Geochemical variations in the concentrations of some major and trace elements and their elemental ratios such as an increase in the Rb, K2O, Th, K/Al, and TOC values and a decrease in the Zr/Al, Ti/Al, Mo, P, Zn, and Zr, from the Kiasta upward to the Ora Formation indicate the transgressive systems tract (TST) of the Kaista-Ora sequence. Paleo-productivity indicators (P content, P/Ti, and P/Al ratios) suggest lower productivity and the paleoredox conditions in the Ora shales play an important role in the preservation of organic matter. The ternary diagram of Co-Zn-Ni, Co/Zn, U/Th, and Ba/Sr ratios indicates that there was hydrothermal activity in the basin during the deposition. [ABSTRACT FROM AUTHOR]

Climatic variability and silicate weathering are remarkable features throughout the Late Cretaceous period. Late Campanian black shale is considered the most significant silicate source rock in the southern Tethys. Here, we used mineralogical and geochemical data to evaluate the continental weathering intensity and climatic changes as well as their impact on the deposition of the Late Campanian black shale in the Western Desert of Egypt. The studied black shale has a relatively high concentration of Al, Fe, Mg, Ca, Sr, Ga, Co, Cr, and V when compared to the average Post-Archean Australian Shales (PAAS). The studied samples have elevated values of Ga/Rb, and low values of Rb/Sr, Sr/Cu, and K2O/Al2O3, supporting the deposition of Late Campanian shale under warm/humid conditions. Furthermore, the average chemical index of alteration (CIA, 78.6%), chemical index of weathering (CIW; 83.8%), C-value (1.26), Fe/Mn (408), and Mg/Ca (1.54) reveal the predominance of warm/humid climate. The chemical weathering proxies (CIA, CIW, PIA, LnAl2O3/Na2O) and ACNK diagram imply that the Late Campanian samples were exposed to a moderate grade of chemical alteration. The deposition of black shale occurred under high seawater salinity conditions based on Sr/Ba (Avg = 3.6). Additionally, the weathering indices are well correlated with paleoclimatic proxies, suggesting that weathering intensity is strongly affected by paleoclimate. However, chemical weathering during the Late Campanian has a weak influence on oceanic nutrient fluxes. No substantial impact of the paleoclimate during the deposition of Late Campanian black shale on water salinity was reported. [ABSTRACT FROM AUTHOR]

To ascertain weathering, provenance, and paleoclimate of the last ca. 29 ka in mainland Gujarat, western India, a sedimentary profile of ~7.5 m was measured, described, and sampled at Pratappura and a multiproxy analysis was conducted. To determine weathering, siltysand and sandy-silt facies were analyzed, and log Na2O/K2O versus log SiO2/Al2O3 was plotted, which shows clustering in the quartz arenite and sub-litharenite categories, indicating low to moderate weathering. The chemical index of alteration (CIA) is 55-74, and was plotted versus the index of chemical variability (ICV) of 1.50, with samples clustered mainly between subalkali basalt and picrite, indicating the dominance of a mafic component. While depleted chondrite normalized light rare earth element (REE) (La/Yb <1) levels suggest the prevalence of a mafic source in the catchment, identical chondrite normalized REE patterns indicate that sediments were well homogenized. Using multiple proxies, the measured profile was subdivided into five paleoclimatic zones. Zone-I (29-18 ka) exhibits decreasing moisture, Corg, χlf, Al2O3, TiO2, and Fe2O3 trends, while higher values of CO3-2 and δ13C indicate a change from a warm-humid to semiarid climate. Zone-II (18-11 ka) shows signs of the beginning of aridity ca. 18 ka during the Last Glacial Maximum (LGM). Several proxies in zone-III show wetter climatic conditions from the early Holocene (ca. 11-4 ka) due to the onset of the SW monsoon, with the trend continuing in zone-IV (4-2 ka). In zone-V, the climate appears to have been similar to the modern conditions in the area from 2 ka-present. [ABSTRACT FROM AUTHOR]

The geochemical characteristics of stream/slopewash sediments, modal composition and petrography of the clastic units from the Siwalik Group has been investigated to determine the provenance and tectonic setting of these rocks, as well as to appraise the influence of the weathering and recycling processes upon source rock signatures. The higher CIA index indicates that the source area underwent moderate to intense chemical weathering processes, possibly due to climatic and/or tectonic variations. Alternatively, modal analyses show that the source area of the Siwalik rocks may have been composed of recycled sedimentary materials. The La/Th ratios and Hf discriminant plot show that they originally come from a differentiated silicic source. This has been further supported by Hiscott Diagram (Cr/V vs. Y/Ni) and Th–Hf–Co discrimination diagram which supports a primitive silicic source for these rocks indicating a higher proportion of felsic material in their primitive source area. The Eu/Eu* versus (Gd/Yb)N diagram for the samples of the Siwalik sediments indicates that the source rocks are mainly influenced by post-Archean felsic rocks. [ABSTRACT FROM AUTHOR]

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The geochemical and petrological studies were carried out to deduce the chemical composition, provenance, and intensity of chemical weathering of the source rocks in the Middle Cambrian sandstone of Spiti Basin. The petrographical studies of sandstones show texturally immature with fine to medium, angular to sub-rounded, and moderately sorted grains. The major constituent of the framework components is quartz which is majorly monocrystalline, undulatory in nature, followed by feldspar and mica with matrix. The presence of quartz grains classifies it under quartz intermediate greywacke. The studies reveal that sandstone was derived from a nearby mixed source and reflects low degree of weathering. Various weathering indices such as Chemical Index of Alteration (CIA avg. 67.24%), Plagioclase Index of Alteration (PIA avg. 75.20%), and Index of Compositional Variability (ICV avg. 1.21%) suggest low to moderate chemical weathering of the source area. The provenance discrimination based on major element concentrations indicates an intermediate and a felsic provenance for the Middle Cambrian sediments. Chondrite-normalized rare earth element (REE) patterns show enriched light rare earth element (LREE) and relatively flat heavy rare earth element (HREE) pattern with negative Eu anomaly and conclude that the sediments were derived from felsic source. The major element–based discrimination diagrams suggest active marginal setting to the studied sediments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Clay mineralogy reflects climatic conditions before, during and after the Sturtian Snowball Earth glaciation. • Detrital and diagenetic illite is common across all three climatic intervals. • Predominance of detrital chlorite in the glaciogenic tillites plus weak chemical weathering of source rocks is consistent with strong continental erosion by melting ice sheets. • Detrital clay minerals modulated nutrient supply to marginal seawater across the Sturtian Snowball Earth glaciation. Recent evidence from marine sedimentary rocks suggests that clay minerals were important in the supply of bioessential nutrients to seawater at the end of the Sturtian Snowball Earth glaciation that occurred ∼ 717–660 million years ago. However, little is known about the identity of these clay minerals, their abundance and distribution in the pre-glacial, glacial and post-glacial deposits. Here, high resolution petrographic scanning electron microscopy-energy dispersive x-ray spectroscopy, combined with bulk and < 2µ clay-size fraction X-ray diffraction mineralogical analysis and trace and major element geochemistry, point to dominant enrichment of illite in shallow marine platform sediments preserved across Sturtian Snowball Earth facies on Islay and the Garvellachs Island, Scotland. The glacial till is enriched with detrital chlorite, while pore-filling authigenic kaolinite is observed in the pre-glacial and post-glacial greenhouse facies, but scarce in the glaciogenic tillites. Discriminant binary plots of Th/Sc vs Zr/Sc ratios, indicative of insignificant modification of primary sediment composition by hydraulic sorting and recycling processes, together with chemical weathering indices, point to moderate to intense chemical weathering of the pre-glacial and post-glacial source rocks. Low Chemical Index of Alternation (CIA) values, coupled to the distinct chlorite composition of the glacial till, is consistent with mechanical tillage of continental landmass by the terminal Snowball melting ice sheets. The moderate to intense chemical weathering indices in the pre- and post-glacial deposits correspond with greenhouse conditions of elevated atmospheric CO 2 content and temperature. Overall, the predominantly detrital origin of the clay minerals implies enhanced post-glacial nutrient supply bound to clay minerals in lower pH river water during transportation, followed by release in higher pH saline seawater. [ABSTRACT FROM AUTHOR]

The black shales of the Koushk series in the Bafq metallogenic zone, which are part of the upper Neoproterozoic shales of Central Iran, are typically comparable with the Proterozoic Shale signature but comprehensive information about formational conditions and geochemical characteristics is scarce. In this study, the chemical composition, provenance, tectonic setting, climatic conditions during the weathering of source rocks and paleoredox depositional environments for Koushk shales are investigated. Compared with 'Post Archean Average Shale', the samples are depleted in Fe2O3, MgO, TiO2, K2O, Na2O, Sc, Co, Th, V and Cr, owing to the chemical composition and degree of weathering of the source rocks. The provenance study implies that the sediments originated from felsic igneous rocks with a moderate degree of weathering in a semiarid to arid climate. The ratios of redox-sensitive elements [e.g. V/Cr, V/(V + Ni)] revealed that the studied black shales were deposited under moderately anoxic conditions. Furthermore, trace-element ratios (e.g. La–Th–Sc) suggest a continental arc setting for the provenance, which is consistent with the tectonic evolutionary history of Central Iran throughout the late Neoproterozoic. Neoproterozoic black shales of the Koushk series in the Bafq metallogenic zone host a Zn–Pb SEDEX deposit with 13 Mt, averaging 7 wt% Zn and 3 wt%. The provenance discrimination diagram of the black shales suggests their derivation from felsic source rocks. The black shales were deposited under a moderately anoxic environment. Trace-element ratios reveal a continental arc setting for the source rocks. [ABSTRACT FROM AUTHOR]