Intense Weathering Research Articles

Matese Mts. and Caserta District Karst Bauxites (Campania Region, Southern Italy): Insights on Geochemistry, Paleoclimate, Paleoenvironment, and Parental Affinity

In the Campania region (Southern Italy), in the Matese Mts. (Albian to Turonian/Coniacian) and Caserta district (Albian to Cenomanian), two karst bauxite deposits outcrop, consisting of flat lenses over shallow karst carbonate. Although the mineralogy and geochemistry of Campania bauxite deposits have been widely studied in recent years, new major and trace elements relationships were provided to highlight paleoclimatic and paleoenvironmental conditions that occurred during their formation. The purpose of this research is to provide for the first time information on the paleoclimatic and paleoenvironmental conditions that affected the bauxites of Campania. These deposits formed during different periods since the Matese deposit formed during intense weathering processes with more abundant precipitation while the Caserta district deposit experienced a more long-lasting exposure event. During the formation of the studied bauxites, the drier conditions favored the replacement of kaolinite by boehmite. R-mode factor analysis showed geochemical affinity among Al2O3, TiO2, and Nb. REEs minerals are mainly associated with the bauxite matrix while Zr, Hf, and V were mainly concentrated in detrital minerals during the later stages of bauxitization. Parental affinity indices (Eu/Eu* vs. Sm/Nd; Eu/Eu* vs. TiO2/Al2O3) assessed the origin of the protolith of the Campania bauxites by rejecting the hypothesis of the dissolution of the bedrock carbonate. The results confirmed the eolian transport of parental material with an Upper Continental Crust and an intermediate to mafic magmatic composition.

Sorting and Weathering Trends of Soil at Gale Crater, Mars: Implications for Regional Pedological Processes

AbstractDetailed soil characterization at Gale crater based on in situ observations has revealed compositional trends within soils, while the physical and chemical processes underlying the compositional trends remain to be evaluated. Here we use the grain‐morphometrical and geochemical trends across the Wentworth‐classes of 48 in situ soil targets at Gale crater to evaluate underlying pedological processes and potential chemical weathering signatures. The concentration of olivine minerals within the ∼250 to ∼500 μm size range indicates the prevalence of heavy mineral sorting in a granulometric sense in Gale soils that surpasses the possible effect of the cratering‐induced mixing processes. The extent of olivine sorting in soils varies spatially and is influenced by the targets' aeolian setting. The finest portion of Gale soils (<125 μm) is likely a mixture of allochthonous sediment, globally sourced from atmospheric suspension, and autochthonous counterparts from the weathering of local rocks, while the coarser soils (>125 μm) are mostly sourced from local rocks, with possible inputs from both the unaltered parent rock of the Stimson formation and the bedrocks that have undergone diagenetic alteration. If applicable globally, this would reinforce prior inferences that even dust‐mantled regions are geochemically heterogeneous owing to a substantial fraction of soils derived from underlying lithology. The low chemical weathering intensity and coupling of mobile elements in soils suggest localized, low pH and low water‐to‐rock ratio aqueous weathering conditions under predominantly cold and arid climates, which may occur either during post‐pedogenetic alteration in soils or during the acidic alteration of source rocks.

Global cooling controls Eocene environmental change in the Lunpola Basin, central Tibetan Plateau: Evidence from salinity and weathering reconstructions

Detailed investigations of sedimentary rocks from the Tibetan Plateau interior, which has been shaped by plateau development and climate change, will provide new insights into its uplift history. However, few continuous environmental records with clear climatic significance and precise age controls from the Tibetan Plateau hinterland exist, particularly in the early Cenozoic. This shortage hinders a full understanding of the impact of uplift on regional climate change. In this study, we present detailed mineralogical, micromorphological and geochemical investigations of the middle–upper Eocene (~39.6–35.3 Ma) lacustrine sediments from the well-dated Dayu section in the Lunpola Basin, central Tibetan Plateau, to explore the paleoenvironmental evolutionary history of the middle–late Eocene from paleoweathering and paleohydrological perspectives. The results reveal that the regional weathering process continuously weakened, as indicated by a long-term decrease in the (smectite + mixed-layer illite–smectite)/(illite + chlorite) ratio. The quantitative reconstruction of salinity variations via clay boron-based paleosalimeters reveals long-term salinization of paleolakes from freshwater–mesosaline conditions (averaging 9.0 psu) at ~39.6–37.8 Ma to freshwater–polysaline conditions (averaging 13.4 psu) at ~37.8–35.3 Ma. The long-term continuous weakening of the weathering intensity and lake salinization collectively suggests a secular drying trend in the central Tibetan Plateau. This drying was consistent with the climatic evolution of the southeastern and northern Tibetan Plateau, which is attributed primarily to global cooling, with secondary contributions from the increasing distance from moisture sources in the Paratethys and regional tectonics.

Micro-Topographic Controls on Rare Earth Element Accumulation and Fractionation in Weathering Profiles: Case Study of Ion-Adsorption Rare Earth Element Deposit in Hedi, Zhejiang Province, China

Ion-adsorption rare earth element (REE) deposits are a major source of REEs and are found mainly in China. The formation of such deposits is affected by a combination of endogenic and exogenic factors. This study investigated the effect of micro-topography on the REE distribution in four weathering profiles at different topographic sites on a knoll in Hedi, Zhejiang Province, China. The weathering profile and REE accumulation are both most developed at mid-slope positions of the knoll. The intensity of chemical weathering decreases in the order of mid-slope > base > summit. As weathering progressed, REE enrichment initially increased but later decreased, with a progressive increase in light/heavy REE fractionation. REE fractionation is more pronounced on the north-facing slope than on the south-facing slope. Weathering degrees and clay mineral characteristics are key factors influencing the varying REE distributions on the knoll. Water leaching and the evolution of clay minerals towards higher maturity reduce REE adsorption capacity. Clay minerals also play a significant role in REE fractionation; the abundance of these minerals and the presence of illite enable the retention of more HREEs with minimal desorption. Taking into account water content, it is inferred that hydrological conditions, modulated by the micro-topography, strongly affect the depth and extent of REE accumulation, as well as fractionation.

Late Miocene Uplift and Exhumation of the Lesser Himalaya Recorded by Clumped Isotope Compositions of Detrital Carbonate

AbstractThe Himalaya orogen evolved since the Eocene as the Tethyan‐, Greater‐, Lesser‐ and Sub‐Himalaya thrust sheets were uplifted and exhumed in sequence. Reconstructing the provenance of sediment in Himalayan River systems can inform on stages in the tectonic history of the orogen. Here, we analyze the oxygen, carbon and “clumped” isotope compositions of carbonate minerals from Himalayan bedrock, Ganga River sediments and Bengal Fan turbidite deposits. We demonstrate that river sediments consist of a mixture of Himalayan‐derived and authigenic calcite precipitated in the river system. The relative abundance and clumped isotope apparent temperatures of detrital calcite in turbidite deposits decreased between the Late Miocene and Pliocene, while chemical weathering intensity did not increase during this interval. Considered together, these results reflect the establishment of the Lesser Himalaya as an important carbonate sediment source for Himalayan rivers, driven by the uplift and exhumation of this thrust sheet.

Constraints on the continental weathering intensity through the Permian using lithium isotopes of well-preserved brachiopod shells

Lithium isotopic compositions (δ7Li) in marine carbonates provide a powerful means to track continental weathering intensity through geological history and promote our understanding of how and why Earth remained habitable. However, δ7Li values in ancient carbonates can be affected by factors such as primary carbonate mineralogy (e.g., aragonite, high-Mg calcite, low-Mg calcite) and post-depositional diagenesis, which may alter their primary signals. Modern articulate brachiopod shells have shown a constant δ7Li offset compared to contemporary seawater, suggesting that fossil brachiopod shells could serve as robust archives for this geochemical proxy due to their diagenetically resistant low-Mg calcite composition. Despite this potential, few studies have explored this topic. In this study, we analyze and compare the geochemical compositions of fossil brachiopod shells and their enclosing carbonate rocks from Permian strata in South China to investigate whether brachiopod shells can reliably preserve the δ7Li values of ancient seawater and, if they do, to obtain new constraints on changes in the continental weathering regimes through the Permian. We used several diagenetic screening methods, including scanning electron microscopy, cathodoluminescence microscopy, and elemental concentrations to detect potential diagenetic alteration. Our results indicate that 32 out of 49 shells preserve primary δ7Li values. Notably, we observed that δ7Li offsets between brachiopod shells and their enclosing carbonate rocks vary across the studied sections, likely due to diagenetic alteration of the bulk carbonates. Using the δ7Li values from well-preserved brachiopod shells, we reconstructed δ7Li variations of Permian seawater. We identified three distinct intervals: (1) extremely low δ7Lisw values (as low as 6.7 ± 2.9‰, n = 12, 1sd) during the Asselian and Sakmarian stages, (2) high δ7Lisw values (32.6 ± 4.5‰, n = 3, 1sd) similar to modern seawater during the Kungurian stage, and (3) relatively low δ7Lisw values (13.6 ± 3.9‰, n = 14, 1sd) from the Capitanian to the Changhsingian stages. These significant changes in δ7Li values of Permian seawater indicate dramatic changes in continental weathering regimes during the Permian, possibly linked to major climate changes, such as the termination of the Late Paleozoic Ice Age and warming associated with the emplacement of the large igneous provinces.

Relating ten years of rock temperature monitoring to rockwall weathering processes in steep mountain valleys in western Norway

Most existing studies on rockwall frost regimes and frost weathering at rockwalls focus on permafrost-affected rockwalls. However, a high share of rockwall surface areas in Norway and in many other cold-climate environments is actually free of permafrost. It is therefore of interest how these permafrost-free rockwall systems will respond to future changes in air and rock temperatures. In this study, we report field measurements conducted at rockwalls beneath the current permafrost limit and investigate thermal regimes at rockwalls that include both rockwall areas with and without permafrost. We present a unique dataset of up to ten years of rockwall temperature measurements from ten temperatures sensors installed in two mountain valleys in western Norway. An analysis of the different rockwall thermal regimes with respect to rock weathering and associated rockfall supply for both, permafrost-affected and permafrost-free rockwalls is provided. The highest intensity of recent rockwall weathering including determined rockwall retreat rates and associated rockfall supply is detected for northeast-facing rockwalls followed by south-facing rockwalls in our study area. Frost cracking activity, probably in the form of segregation ice growth, seems to be an important factor particularly for the high weathering intensity on northeast-facing rockwalls whereas solar radiation-induced thermal stresses, which favour incremental subcritical crack growth, is assumed to play a relevant role in the moderate weathering intensity on south- and southwest-facing rockwalls. A mean annual and study area-wide rockwall retreat rate of 0.24 mm yr−1 is estimated for our ten-year investigation period (2010−2020) which is comparable to other published rates in similar lithologies and climates. As it can be assumed that seasonal frost regimes and permafrost will react differently to ongoing and future climate changes, more attention should be paid to analyse these two different thermal regimes with respect to possible varied implications for mechanical rockwall weathering and associated rockfall supply.

Mapping hydrothermal alteration in regolith using white micas and chlorite as vectors towards gold mineralization

Mineral exploration through regolith-dominated terrains poses a significant challenge to cost-effective exploration techniques. Due to missing surface expression, undercover mineral exploration relies on understanding ore-forming processes and characterizing alteration regimes to decipher suitable vectors towards ore deposits. The work presented focuses on the Archean granite-greenstones of the Yilgarn Craton, east of the Meekatharra area in Western Australia, and characterizes the weathering profiles by understanding metal dispersion mechanisms and identifying mineralogical vectors towards gold mineralization within regolith. Mineral mapping of gold mineralization using TESCAN Integrated Mineral Analyzer and laser ablation ICP-MS shows gold is associated with multiple generations of pyrite, and base metal sulfides and sulfosalts hosted in felsic to intermediate volcanics and volcaniclastics. Intensive weathering generated a thick regolith profile dominated by a leached zone of kaolinitic and micaceous saprolite underlain by a supergene Au-Cu deposit blanket at the base. The supergene deposit is dominated by colloform and framboidal pyrite, with pure microcrystalline Au, chalcocite, bornite, malachite, and alunite. Hyperspectral analyses were used to trace the composition and abundance of chlorite and white mica variations in the host rock and the weathering profile. The mineral assemblage in the hydrothermal alteration halo proximal to and intersecting gold mineralization is dominated by Fe-rich chlorite and Na-rich white mica (paragonite). Fe-rich chlorite and paragonite are spatially tied to elevated Au concentration and trends to Fe-Mg-rich chlorite and K-rich white mica (muscovite) distal to the alteration. The variations in chlorite chemistry were detected mainly in bedrock and saprock. Conversely, the white mica chemistry variations were detected in bedrock and the regolith profile, in which white micas resist intensive weathering. The spectral signatures identified through short-wave and thermal infrared data are verified through X-ray diffraction, mineral chemistry, and bulk geochemical analyses. This distinctive spectral signature of white mica and chlorite is a cost-effective exploration method for regional mapping of mineral systems to identify hydrothermal alteration footprints in the regolith developed over felsic and intermediate rocks.

Astronomical Calibration of the Ocean Anoxic Event 1b and Its Implications for the Cause of Mid‐Cretaceous Events: A Multiproxy Record

AbstractThe timing and duration of oceanic disturbances linked to Oceanic Anoxic Event (OAE) 1b, as well as the mechanisms driving anoxia and carbon burial during this period, remain subjects of debate. We conducted cyclostratigraphic analyses on magnetic susceptibility (MS) and elemental Ti and Fe series within the upper Aptian‐lower Albian interval of the Poggio le Guaine core in the Umbria‐Marche Basin, Italy. This interval provides a detailed sedimentary record, supported by variations in magnetic mineral content, Ti, Fe, and significant global shifts in the δ13C curve. Orbital control of MS, Ti, and Fe suggests a duration of 2.84 Myr for the OAE 1b event. Our chronostratigraphic analysis reveals ages of 114.07 ± 0.12 Ma for 113/Jacob, 113.28 ± 0.12 Ma for Kilian, 112.49 ± 0.12 Ma for the central age of the Monte Nerone cluster, 111.70 ± 0.12 Ma for Urbino, and 111.28 ± 0.12 Ma for Leenhardt sub‐events. Stable δ13C chemostratigraphy correlations enable the transfer of tiepoints across various sedimentary basins. Key features of the carbon isotope curves were identified, named, and dated using astrochronology. Our findings suggest that the organic‐rich layers associated with the OAE 1b event exhibit distinct characteristics influenced by several factors, including a warm climate driven by volcanic CO2 emissions, heightened precipitation, intense weathering, and marine transgressions. These factors amplify orbital forcings on paleoclimate changes, leading to oceanic‐atmospheric disturbances that promote deoxygenation and carbon burial during OAE 1b.

Frost weathering in contemporary active-layer deposits—micro-scale records from Kaffiøyra Plain (NW Spitsbergen)

Frost weathering serves a critical role under cold, nonglacial (i.e., periglacial) conditions. Within a contemporaneous active layer, the progressive development of microscale frost-weathering features may be recorded on the surface of sand-fraction quartz grains (0.5–0.8 mm). The purpose of this study is to identify the factors responsible for the effects of this type of frost weathering. Sediments from four profiles were tested from the Kaffiøyra Plain (NW Spitsbergen) in 2011. These profiles represent sediments of various origins and ages, ranging from 11 to 9 ka B.P., and on to the Little Ice Age. Scanning electron microscopy, grain-size distribution, CaCO3 content, pH, and deposit geochemistry were used to determine the intensity of frost weathering on study sediments. The results from sand-sized quartz-grain microtexture analysis indicates that a low degree of micro-scale frost weathering had occurred regardless of sediment age. Most of the micro-scale frost-weathering effects were recorded in the active layer's top and base. Quartz-sand-grain microtextures predominate in these two locations, their extant providing insight into the initial development of such weathering. Microtexture's predominance signifies an inception of weathering development, manifested as large and small conchoidal fractures (>10 μm and <10 μm, respectively). Small and large breakage blocks (>10 μm and <10 μm, respectively) are recorded as accessory microtextures, requiring more freeze–thaw cycles and longer operating times. Of note, frost-weathering effects are dependent on grain-size composition; the finer the sediment, the more intense is the grain-weathering development.

The influence of weathering and pedogenesis on the geochemical record of Miocene marls and Plio-Quaternary sediments, Medvednica Mt., Croatia

The geochemical signature of weathering and pedogenesis in a temperate humid climate on two parent material types in the foothills of Medvednica Mt. was studied. Five soil profiles on Miocene marls and three sections of Plio-Quaternary (PlQ) proluvial sediments with overlying soil and weathered material were analyzed. The (clay) mineralogy of all profiles and sections had been determined in previous studies. The chemical composition of the samples was determined by inductively coupled plasma emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectroscopy (ICP-MS). Poorly ordered Fe and Mn oxides were determined in the PlQ sediment and overlying soil samples by atomic absorption spectroscopy (AAS), after oxalate dissolution in the dark. The concentrations and element ratios were used to determine element enrichment/mobility and intensity of chemical weathering, material provenance, and to compare the geochemical signatures with previously obtained clay mineralogy results. Trace elements in the Miocene marls, including rare earth elements (REE), indicate the continental origin of the marl siliciclastic component, while more scattered geochemical data of the PlQ sediments reflect their proluvial/torrential nature. The mass transfer coefficient (τ) for major elements and element ratios of the Miocene marl profiles indicate chemical weathering and pedogenesis of lower intensity. The geochemistry of these samples shows homogeneity within the profiles. In the geochemical signature of the PlQ sections, a chaotic proluvial deposition of the material is visible, as well as the heterogeneity with the overlying soil and weathered material. Overall, the geochemistry results largely support the clay mineralogy of the samples and demonstrate how a multiproxy approach can help test hypotheses about past environments and provide valuable additional information for complex paleoenvironmental studies.

Correlations between the increase in atmospheric CO2 and temperature, and the subsequent increase in silica, and groundwater organisms

Rising atmospheric temperature and CO2 impact all freshwater systems. In groundwater, one such impact is CO2- and temperature-induced weathering, which leads to more intense weathering of silicate rocks. Here, we tested whether the increased CO2 levels, the weathering, or rather the increasing temperature, impacted on fauna and prokaryotes in the groundwater ecosystem. We also conducted the analyses separately for two groups of wells, one of which contained wells that were secluded from the surface (and often rather deep), and wells tapping the quaternary aquifers (often rather shallow) which exchange with the surface more intensely. Organism abundances and relative composition did not correlate with temperature or CO2 levels. While many organisms rely on silica, in contrast, we found negative correlations between silica concentrations and fauna. The increases in silica concentrations over time, i.e. temporal trends, also partly correlated negatively with organisms. We hypothesize that the unexpected negative correlations are not direct effects, but indirectly indicate that groundwater communities do not adapt rapidly enough to changes in silica concentrations, but also more generally to changes for which silica might only be a proxy. Groundwater fauna take part in the ecosystem service of water self-cleaning and are thus considered beneficial for sustainable raw water for drinking water production. The propensity of groundwater fauna to decrease with increases in silica, jeopardizes future drinking water production.

Ironing out complexities in karst chronology: (U-Th)/He ferricrete ages reveal wet MIS 5c.

Karst landforms provide insights into landscape evolution and paleoclimate but are inherently challenging to date. An ancient interval of particularly intense weathering of Western Australian Pleistocene aeolianites is recorded in a spectacular pinnacle karst landscape with associated ferricrete nodules. (U-Th)/He dating of the ferricrete nodules revealed an age of 102.8 + 10.6/-11.4 thousand years, corresponding to marine isotope stage 5c. The (U-Th)/He age thus directly dates the wettest interglacial period in the region over the last 500 thousand years, which was responsible for the dissolution that formed the pinnacles. The reliability of the ferricrete (U-Th)/He age is supported by bounding optically stimulated luminescence and U-Th dates on associated aeolianites and carbonate precipitates, respectively. A (U-Th)/He approach is globally applicable to aeolianites with associated ferricretes, allowing more accurate dating of the environmental changes affecting these lithologies, and temporally constraining rapid Pleistocene climatic oscillations to better contextualize the associated evolution of the biosphere.

Lithium isotopes track changes in continental weathering regimes across the end-Permian mass extinction in Southwest China

It has been assumed there was a massive amount of volcanic CO2 injection into the Permian-Triassic atmosphere and ocean systems, leading to rapid climatic warming and expansion of marine anoxia. However, it remains intriguing how Earth recovered from such a CO2-driven hyperthermal condition. One potential mechanism involves the negative feedback between continental silicate weathering and atmospheric CO2, which could have helped maintain habitability across the end-Permian mass extinction (EPME) interval. This process can be examined using lithium isotopes (δ7Li), which reflect the balance of physical erosion and chemical weathering, and chemical weathering indices such as the Chemical Index of Alteration (CIA), which indicates the chemical alteration of parent materials during weathering. In this study, we analyze siliciclastic sedimentary rocks from the Lopingian to Lower Triassic depositional sequences in the HK-1 drill core at the Lengqinggou section, a terrestrial coastal depositional environment in Southwest China, to reconstruct changes in continental chemical weathering intensity across the EPME. We observed a significant ∼4 ‰ positive shift in δ7Li, accompanied by a marked decrease in Li content from 26 ppm to 6 ppm. Our corrected CIA data (CIAcorr) also exhibits a considerable decrease from 94 to 59 across the EPME. The new δ7Li and CIAcorr data from the terrestrial section indicate a decrease in overall chemical weathering intensity in Southwest China, alongside an increase in physical erosion rates, suggesting a shift from a transport-limited to a kinetically limited weathering regime across the EPME. These changes in the continental weathering regime appear to be linked to active volcanic activity near the South China Block, which led to massive deforestation and the collapse of soil systems. Dramatic reductions in chemical weathering intensity may result in inefficient atmospheric CO2 consumption through silicate weathering if other climatic and tectonic conditions remain constant, potentially contribute to maintaining high global surface temperatures and prolonged marine anoxia into the Early Triassic.

Evolution process of chemical weathering and sediment sources in the Makran Continental margin since the Younger Dryas

The chemical weathering processes and sedimentary source evolution since the Younger Dryas (YD) in the low-latitude arid continental margin have been investigated. Two sediment cores, MK07G and MK09G, were retrieved from the Makran continental margin in the northern Arabian Sea and subjected to analyses of major and trace elements, along with AMS14C dating. The results show that since the YD, the weathered parent rocks of Makran sediments have remained relatively stable, predominantly consisting of felsic rocks, with some contributions from mafic rocks. The Makran sediments exhibit initial to moderate weathering, with no discernible effects from grain size sorting or disturbances from sediment recycling, indicating primary deposition. Significant contributions of terrigenous eolian dust from surrounding continents (e.g., the Indian subcontinent, Arabian Peninsula, and northeastern Africa) were identified, along with riverine inputs from the Dasht River and fine-grained components from the Late Pleistocene Indus delta sediment, as well as proximal basin sedimentation. The evolution of sediment sources in the study area is significantly influenced by the Indian Monsoon and westerly wind systems, with intensified monsoon phases and westerly conditions correlating with increased fluvial input. Furthermore, chemical weathering processes since the YD are closely linked to local precipitation patterns, where intensified rainfall enhances weathering intensity. Records from the Makran continental margin indicate a teleconnection between chemical weathering and sedimentary processes in the Arabian Sea and Bond events in the North Atlantic, highlighting the extensive influence of Northern Hemisphere climate fluctuations.

Reconstructing the past environmental conditions of southwestern India using estuarine sediment core

Geological archives can be examined via multiple proxies to uncover significant information about historical environmental changes. In comparison to single proxy approach, the use of multiple proxies can provide better resolution of the paleoenvironmental record. Thus, in the present study, to understand the paleoenvironmental conditions in the Kali coast in southwestern India, sedimentological, geochemical and isotopic (210Pb, 137Cs) proxies were used. The findings demonstrated that, in previous decades, the sedimentation rate varied from 0.5 to 1.0 cm/year under conditions with relatively higher hydrodynamic energy that were more common and fluctuating, allowing for larger sand particle deposition. However, in more recent years, finer particle deposition towards the surface has been observed under conditions with lower and more stable hydrodynamic energy, with a sedimentation rate of 1.87 cm/year. Additionally, the finer fractions displayed a strong correlation with the metal distribution, which was mostly governed by Fe-Mn oxides. Furthermore, it can be revealed that the environment was warm, humid, and marine-like between 1995 and 2000 based on chemical weathering intensity values and Rb/K ratios. A subtle shift to a freshwater habitat with relatively less warm, less humid climate occurred between 2000 and 2020. Therefore, similar research with longer depositional histories coupled with multiple proxies can help predict the future climatic shifts in decadal time scales.

Rare earth elements enrichment and extraction potential of bauxite deposits in Samar, Philippines

Abstract Rare earth elements (REE) play an integral part of modern life, from smartphones to satellites. Dubbed ‘critical metals’, the demand for REE has significantly increased, driven by the growth in global production for green technologies such as e-vehicles, solar panels, wind turbines, and other energy-economic infrastructure. Therefore, there is a need to explore alternative REE sources to ensure continued development of emerging green technologies. A possible alternative REE source is bauxite, which is soil that forms from intense weathering of aluminum oxide-rich rocks exposed to tropical climate. This paper investigates the REE enrichment and extraction potential from bauxite deposits in Paranas, Samar, Philippines. The sampling survey included collection of rock and soil on surface exposures, test pits, and drill cores from accessible portions of the bauxite mineral reservation site. The soil and parent rock samples collected were then subjected to various geochemical and mineralogical analyses. The main ore minerals of aluminum are gibbsite and boehmite; with minor goethite, hematite, and magnetite. Investigation of the geochemical composition of the bauxite reveals a total REE content of up to ~300 ppm, which is one of the highest REE and critical metal content among geological deposits in the country. These results will provide inputs in the design of a green and economical process to recover REE from bauxites. If the bauxite deposits prove to be a valuable REE resource, this study will help maximize the economic potential of the mineral resource in the Philippines and contribute to an economically efficient and environment-friendly way to produce e-tech elements for the country.

Investment in Plant Protection with an Initial Copper Deposit

The impact and influence of copper fungicides is large and as durable as their deposits against the most intense weathering pressures planet earth has to offer. Copper fungicide has been at the forefront of plant disease control since the establishment of copper’s activity as a biocide in 1885. Several supreme ironies surround discovery of copper as a highly effective broad-spectrum fungicide. Like many other major discoveries, including Penicillin by Sir Alexander Fleming, it was an accidental milestone in science and technology. In the late nineteenth century vineyard owners in the M??doc region of southern France were splashing grapevines alongside public footpaths with a concoction of copper sulphate and slaked lime ‐ CuS04 .5H2 O + Ca(OH)2. The unsightly water resistant deposits left on the foliage and bunches deterred the pilfering of grapes.

Chemical weathering in the Mekong River Basin: Clay mineralogy and element geochemistry of lower-reach river sediments

Chemical weathering of parent rocks in river basins plays a significant role in controlling the global geochemical cycle and climate change, especially in the world's largest river basins such as the Mekong River Basin in tropical regions. However, the chemical weathering process of the Mekong River Basin is still not well understood. In this study, clay mineralogy and major/trace-element geochemistry of fluvial sediments (clay, silt, and sand fractions) collected from the lower Mekong River Basin (Cambodia and Vietnam) were utilized to investigate the sediment provenance and chemical weathering process. The major-element compositions of the clay, silt, and sand fraction sediments from both the mainstream and tributaries consist of dominant SiO2, Al2O3, and Fe2O3, (84 wt%, 89 wt%, and 95 wt%, respectively) and minor K2O, Na2O, MgO, CaO, TiO2, P2O5, and MnO. The clay mineral assemblages in mainstream sediments are high in illite (36 wt%), moderate in kaolinite (28 wt%) and chlorite (26 wt%), and low in smectite (10 wt%), whereas those in tributary sediments are high in smectite (37 wt%), moderate in kaolinite (26 wt%) and chlorite (22 wt%), and low in illite (15 wt%). The different clay mineral assemblages between mainstream and tributary sediments can be significantly related to the parent rock lithology and/or the weathering process in the source region. On the basis of clay mineralogy and elemental geochemistry, river sediments of the mainstream in the lower reach may be derived mainly from felsic rocks in the lower part of the middle reach of this basin, with secondary contributions from the upper and lower reaches as well as the upper part of the middle reach. Sediments in the Kampi and Speu tributaries highly originate from felsic rocks, whereas sediments in the Srepok, Ter, and Chhiong tributaries can be mostly weathering products of mafic rocks. The clay mineral proxies (smectite/(illite + chlorite) and kaolinite/(illite + chlorite)) combined with the elemental geochemistry (CIA, αAlE values, and weathering trends) of the clay fraction sediments indicate intensive chemical weathering in the lower and middle reaches. The high-relief topography and cold and dry climatic conditions in the upper reach result in high illite and chlorite contents in the soil and moderate chemical weathering. The chemical weathering intensity increases from the upper to middle reaches and further to the lower reach. Tectonics in the middle and upper reaches of the Mekong River Basin play the most important role in controlling weathering and erosion processes, whereas East Asian–Indian monsoon climate conditions with warm temperature and predominant rainfall throughout the year and lithology are the main forcing factors for the intensity of chemical weathering in the lower reach.

Origin and composition of dissolved and particulate matter in mountain rivers of the Nepal Himalayas: Insights from Sr and Nd isotopes and elemental ratios

The Ganga River exhibits elevated concentrations of dissolved strontium (Sr) and a higher radiogenic Sr (87Sr/86Sr) among global rivers, which impacts oceanic Sr composition. This has implications for understanding weathering and sediment flux into open oceans. The Nepal Himalayan section is a significant part of the upstream Ganga River catchment. We analyzed Sr and Nd isotopes and major element concentrations in water and sediments to trace compositional and seasonal variability in dissolved and particulate matter. The Sr and Nd isotopes, in particular, are crucial in this study as they provide unique signatures that can be used to trace the origin and composition of the dissolved and particulate matter. Representative rivers draining monolithological terrains were selected to investigate the isotopic and elemental provenance and weathering intensity. The elemental ratios (Ca/Na, Mg/Na) indicate the watersheds are carbonate-rich terrains. The Lesser Himalaya (LH) rivers transport radiogenic Sr with high values compared to rivers draining the Tethyan Sedimentary Series (TSS), Higher Himalayan Crystalline (HHC), Mahabharat, and Siwalik Hills. The dry season records a higher 87Sr/86Sr ratio than the monsoon. Due to the faster dissolution of carbonates compared to silicates, monsoon waters transport less radiogenic Sr. The significant correlation of 87Sr/86Sr in dissolved and particulate phases signifies that short-term interactions between sediment and water may alter the 87Sr/86Sr composition. Notably, sediments originating from continental rocks exhibit an inverse correlation between 87Sr/86Sr and εNd. In conclusion, the Sr and Nd isotopic records in this study categorize the fluvial catchments into geological clusters aligned with the TSS, LH, and Siwaliks, which advance our understanding regarding the provenance besides providing crucial insights into geological processes, weathering, landscape evolution, and sediment flux.