This study presents a preliminary evaluation of the aggregate potential of representative sedimentary rocks from the Voltaian Supergroup in northern Ghana. Fifteen rock samples were collected from Gambaga, Pigu and Tamale, representing the Bombouaka, Oti-Pendjari and Obosum Groups. They were analysed using petrography, SEM–EDX and standard physico-mechanical tests conducted in accordance with BS 812 and ASTM procedures. Petrographic and microanalytical results indicate that the Bombouaka and Obosum samples are quartz-rich sandstones, whereas the Oti-Pendjari sample is a fine-grained calcareous rock with a micritic carbonate matrix and subordinate siliciclastic constituents. The physico-mechanical results reveal clear lithological contrasts in engineering performance. The Oti-Pendjari rock records the lowest aggregate impact, crushing and Los Angeles abrasion values (16%, 18% and 25%, respectively), indicating superior resistance to impact, crushing and wear. The Obosum sandstone shows moderate performance, whereas the Bombouaka sandstone performs poorly despite its high quartz content. These results demonstrate that aggregate quality in the Voltaian Supergroup is governed not only by mineralogical maturity, but also by textural and diagenetic controls, including grain support, matrix content and cementation. The study provides the first integrated preliminary dataset linking petrographic characteristics with engineering behaviour for selected Voltaian sedimentary rocks, and highlights the need to evaluate sedimentary aggregate resources based on fabric and rock quality rather than quartz abundance alone.
The upper mantle part of the Bela Ophiolite Complex in western Pakistan comprises mainly depleted harzburgites and dunites with associated podiform chromitites. This study analyzes the mineral compositions and whole-rock chemistry of these rocks, including major, trace and platinum group elements as well as Re-Os isotopic data, to provide constraints on their mantle melt evolution and petrogenesis. Cr-spinels in the harzburgites have lower Cr# values (42.7-44.6) than the Cr-spinels in the dunites (69.3-71.7) and chromitites (79.1-79.9). The harzburgites contain substantial Al2O3 (1.22 wt%), and CaO (1.63 wt%) but are depleted in ∑REE (0.521 ppm), which, together with their 187Os/188Os (0.11364 to 0.12582) and 187Re/188Os ratios (0.0139 to 0.2816), suggest a depleted residual mantle origin. Comparatively, the dunites have lower average Al2O3 (0.35 wt%) and CaO (0.38 wt%) as well as ∑REE (0.174 ppm) contents, although their 187Os/188Os (0.12979 to 0.14422) and 187Re/188Os ratios (0.0457 to 1.2179) are higher than those of the harzburgites. The chromitites also display higher 187Os/188Os (0.12611 to 0.13114) and 187Re/188Os ratios (0.0107 to 1.1102) than those of the harzburgites. These results indicate that the Bela dunites underwent modification due to interaction and/or equilibrium with melts. The mantle-normalized trace-element data of the harzburgites imply a lesser degree of partial melting (∼15.7 %) compared to that of the dunites (∼20.5 %). The data further demonstrate two distinct stages in the genesis of the Bela peridotites and chromitites. In the first stage, the harzburgites formed as a mantle residual product after low-degree partial melting in a mid-ocean ridge (MOR) environment. In the second stage, the dunites and chromitites formed after high-degree partial melting of the depleted mantle, and refertilization of dunites occurred in the forearc mantle in a supra-subduction zone (SSZ) environment. The dunites and chromitites crystallized as a result of interactions between boninitic melts and residual peridotites within the mantle wedge. This two-stage history highlights the transition from MOR to SSZ environments in the formation of the Bela Ophiolite Complex. The remarkable heterogeneity of Os isotopic compositions in this region of the Neo-Tethyan upper mantle reflects diverse processes of melt generation and extraction during its tectonic evolution.
The Yechangping Mo–W deposit in the East Qinling Orogen is a giant porphyry-skarn system, but the differences in genesis between its barren monzogranitic porphyry and mineralized granitic porphyry remain poorly defined. This study presents new zircon U–Pb ages, Hf isotopes, whole-rock geochemistry, Nd–Pb isotopes, and pyrite sulfur isotopes to elucidate the petrogenesis and key controls on Mo–W mineralization. Zircon U–Pb dating yields indistinguishable emplacement ages of 146.4 ± 2.3 Ma for the barren porphyry and 147.5 ± 2.0 Ma for the mineralized porphyry, indicating synchronous magmatism. Both intrusions are I-type granites, characterized by negative εHf(t) (−14.69 to −9.95) and εNd(t) (−15.22 to −12.33) values, Paleoproterozoic two-stage model ages (1.83–2.17 Ga), and Pb isotopic compositions similar to the Taihua Group basement, indicating a dominantly ancient crustal source from the Taihua Supergroup with a possible minor contribution from the North Qinling Accretionary Belt. The higher degree of fractional crystallization and moderately oxidized conditions (avg. logƒO2 = −13.11) of the mineralized porphyry are the key factors controlling Mo–W mineralization. Pyrite grains from both porphyry-type and skarn-type ore bodies yield δ34S values ranging from 3.16‰ to 5.35‰, indicating a common magmatic sulfur source. Furthermore, the restriction of scheelite to skarn orebodies highlights the fundamental role of carbonate wall–rock interaction in localizing tungsten mineralization.
Conventional data analysis in a complex deltaic system is typically constraints by heterogeneous nature of progradational sand-shale sequences, where independent analysis of individual data domains fails to capture uncertainty propagation across stratigraphic, geomechanical, and thermal interpretations. This study presents a machine learning (ML) framework that simultaneously addresses well log-based chemostratigraphy, geomechanical property, geothermal gradient and seismic correlation of attributes in the Niger Delta Basin, Nigeria, a gap that prior single-domain studies have not filled. A data set of 247 wells from Coastal Swamp, Central Swamp and Greater Ughelli Depobelts were analyzed, alongside with 3D seismic data (∼12,000 km2) and X-ray fluorescence (XRF) geochemical data from 1247 samples across 43 wells using Random Forest (RF), Support Vector Machine (SVM) and Deep Neural Network (DNN) algorithms with stratified 70/15/15 training-validation-test partitioning and blind well validation on 47 independent wells. RF achieved a lithofacies classification accuracy of 89.7% (95% CI: 87.2-92.1%), which is 23% higher than the baseline accuracy of rule-based classification (p < 0.001). The R2 for the blind test wells in the elastic moduli prediction is 0.87 and the RMSE is 2.1 GPa (Young's modulus R2 = 0.85 and RMSE = 2.1 GPa). A total of 47 marker horizons were identified in the Agbada Formation using chemostratigraphic integration, and improved inter-well correlation confidence by 31% (absolute). Three geothermal zones (18-45 °C/km) were identified, delineated, constraining the depths of hydrocarbon maturation to 2800–3500 m. The correlation between seismic and well data achieved a coefficient greater than 0.85, allowing for basin-wide prediction of reservoir properties while providing an estimated spatial uncertainty of 15–35%. The results in this study show that the ML integration across multiple domains significantly decreases the uncertainty in the subsurface in complex deltaic systems, and that provides a workflow applicable to other similar petroleum provinces globally.
Global correlations between upper-mantle seismic structure and shallow earthquake occurrence are commonly interpreted as evidence of mantle–lithosphere coupling. However, both seismicity and low shear-wave velocity anomalies are strongly concentrated near tectonic plate boundaries, raising the possibility that apparent coupling may arise from their shared geometric organization rather than from an independent physical relationship. Here, I quantitatively evaluate the extent to which global mantle–seismicity correlations are controlled by plate-boundary geometry. Using exclusively open-access datasets, I combine shallow seismicity from the USGS ANSS Comprehensive Catalog (2000–2025; M ≥ 5.5; z ≤ 70 km), upper-mantle shear-wave velocity perturbations from the SPani tomography model, PB2002 global plate boundaries, and GSRM strain-rate fields within a fully reproducible framework. Mantle structure and seismicity are compared on a common global grid using non-parametric rank statistics, bootstrap uncertainty quantification, depth-dependent analyses, and distance-to-boundary diagnostics. Significant negative correlations are observed between low-velocity mantle anomalies and shallow seismicity, particularly for upper-crustal earthquakes (0–30 km). However, both variables exhibit a strong dependence on proximity to plate boundaries. After explicitly removing the first-order distance-to-boundary trend, the residual global correlation is substantially reduced. However, an additional GCMT-based faulting-style analysis shows that statistically significant residual correlations persist in mechanically distinct tectonic regimes, particularly for strike-slip seismicity. These results indicate that a substantial fraction of the apparent global mantle–seismicity coupling reflects tectonic geometric organization rather than an independent mantle-controlled signal. The study highlights the importance of explicitly accounting for plate-boundary geometry before drawing causal geodynamic inferences from large-scale mantle–seismicity correlations.
The Arya Jonoub iron oxide–apatite (IOA) deposit, located in the southern part of the Kashmar–Kerman tectono-magmatic belt, Central Iran, is hosted by Lower Cambrian volcano–sedimentary sequences intruded by diorite, gabbro, and diabase dikes. This study integrates detailed field mapping, petrography, ore microscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and whole-rock geochemical analyses (ICP-OES1 and ICP-MS21 Inductively Coupled Plasma – Optical Emission Spectrometry.2 Inductively Coupled Plasma Mass Spectrometry.) to elucidate the mineralization processes. The principal Fe ore consists of magnetite–apatite mineralization, locally accompanied by titanomagnetite, ilmenite, and minor sulfides. Extensive alteration assemblages—including albitization, chloritization, silicification, and hematitization—are spatially and genetically associated with magnetite–apatite ore formation. Uranium mineralization occurs predominantly as uraninite and coffinite, closely associated with magnetite, pyrite, chalcopyrite, carbonates, chlorite, and REE-bearing phases such as monazite, allanite, and britholite. Geochemical data indicate uranium concentrations ranging from 369 to 3567 ppm, with strong positive correlations with Th and Y, and chondrite-normalized REE patterns characterized by LREE enrichment and pronounced negative Eu anomalies. These features support a multistage magmatic–hydrothermal evolution, in which primary Fe–P mineralization was subsequently overprinted by oxidizing, carbonate-rich fluids responsible for U and REE enrichment. Redox interactions between Fe2+ and U6+ played a critical role: oxidation of Fe2+ to Fe3+ (magnetite alteration to hematite) promoted the reduction of soluble uranyl species to insoluble U4+, resulting in uraninite precipitation. Collectively, these results provide new insights into uranium metallogeny in IOA systems and establish an exploration framework for U-bearing iron oxide–apatite deposits in Central Iran.
In the present study, we reconstruct depositional conditions and provenance changes across the PTB from Guryul Ravine (Kashmir) and Attargoo (Spiti) sections of the Tethys Himalaya. The Guryul section consists of shale, limestone, and calcareous sandstone from the Zewan and Khunamuh Formations. The Spiti section has organic-rich black shales from the Gungri Formation that are overlain by Tamba-Kukur (Mikin) Formation, separated by 8-10 cm ferruginous layer. Upper Permian sediments of the Zewan Formation (E1 unit) show stable euxinic conditions, with delta S-34 values of -22 parts per thousand to -9 parts per thousand and abundant syngenetic framboids (<10 mu m; similar to 60%). In contrast, Lower Triassic strata of the Khunamuh Formation (E3 unit) record more oxygenated conditions, characterized by larger framboids (30-35 mu m) and less negative delta S-34 values (-5.39 parts per thousand to +0.60 parts per thousand). This redox variability coincides with pronounced negative shifts in delta(13)Corg (-27 parts per thousand at Guryul Ravine and -26.8 parts per thousand at Attargoo) and elevated TOC values, reaching similar to 2% in the E1 unit of the Zewan Formation at Guryul and similar to 2-3% in the ferruginous layer at Attargoo section. Together, these changes show that the marine carbon and sulfur cycles were severely disrupted during the extinction period and was driven by multiple distinct pulses of environmental disturbance. Chemical weathering indices (CIA, alpha Ca-Al, alpha Na-Al, alpha Mg-Al) show an increase upward from Upper Permain to Lower Triassic sediments, suggesting increasing chemical weathering across the boundary. Upper Permian sediments with high Th/Sc (similar to 2), (La/Yb)(n) (similar to 14), Th/Yb-n (similar to 10), negative Eu anomalies, and enriched LREE patterns, point at felsic source rocks. In contrast, Lower Triassic strata display a sharp decrease in Th/Sc (similar to 0.39) and La-N/Yb-N (similar to 9), suggesting a change toward more mafic contributions. This transition is supported by isotopic data from the Guryul Ravine, where Upper Permian sediments of the Zewan Formation yield non-radiogenic epsilon Nd(0) values (-14.9 to -15.6), high Sr-87/Sr-86(0) ratios (0.718-0.724), and older TDM ages (1.71-1.76 Ga), whereas Lower Triassic sediments of Khunamuh Formation show more radiogenic epsilon Nd(0) values (-9.0 to -9.7), lower Sr-87/Sr-86 (0) ratios (0.718-0.721), and younger TDM ages (1.35-1.56 Ga). Geochemical proxies, delta S-34 values and framboid size distribution, carbon isotopes (delta(13)Corg) and total organic carbon, indicate persistent anoxia near the PTB. Overall, the our data reveal a noticeable provenance shift from felsic to mafic sources across the PTB and provide new constraints on marine redox evolution helping to improve global models of the end-Permian mass extinction.
This study investigates the geochemical characteristics and crystallization conditions of quartz and coexisting minerals from a high-purity quartz (HPQ) favorable pegmatite at the McKinney Mine, Spruce Pine district, USA, to elucidate crystal-scale processes responsible for quartz purification. Integrated petrography, cathodoluminescence (CL) imaging, LA-ICP-MS trace-element analysis of quartz, electron probe microanalysis (EPMA) of mica and feldspar, fluid-inclusion petrography, and whole-rock geochemistry were used to constrain quartz growth and late-stage modification. Quartz grains display five distinct CL-defined growth domains (Qtz Grn 1-5) characterized by heterogeneous trace-element concentrations (Ti = 3.54-17.55 ppm; Al = 70-258 ppm; Ge/Ti = 0.02-0.66), reflecting combined effects of magmatic differentiation and post-magmatic recrystallization, rather than melt evolution alone. TitaniQ thermometry, using a Ti activity of aTiO2 = 0.6 appropriate for low-Ti, rutile-absent systems, yields quartz crystallization temperatures of 519-563 degrees C. Coexisting muscovite (F = 0.18-0.47 wt%; 545-556 degrees C; 5.4-5.6 kbar) and biotite (Mg# = 0.21-0.23; 335-580 degrees C; 3.55-5.95 kbar) record evolving conditions during pegmatite crystallization. Feldspar compositions (Or89-96, Ab88-94), with low Ti contents in feldspar and micas, constrain crystallization from a Ti-depleted, strongly peraluminous melt. Wholerock geochemistry indicates peraluminous compositions (A/CNK approximate to 1.49), LREE enrichment (TLREE/ THREE = 1.8-6.96), and variable Eu anomalies (delta Eu = 0.17-2.95), consistent with crustal anatexis and plagioclase-controlled differentiation. CL textures, secondary fluid inclusions, and microstructural features indicate localized post-magmatic recrystallization with limited fluid ingress, which contributed to quartz purification. Collectively, the results support a two-stage model involving advanced magmatic differentiation followed by recrystallization-assisted purification, providing a geological framework of geochemical indicators for assessing HPQ potential in peraluminous pegmatite systems.
Non-silicate chromian spinel coexisting with the silicates like olivine and pyroxenes in the mantle-related rocks is nominally Si-free, but is expected to contain some Si due to chemical equilibrium. This anticipation has long been verified. How Si enters spinel, what the solubility is, what factors affect the Si-incorporation process, and what the implications are remain largely unexplored though. By performing high-P experiments in the system MgO-Al2O3-SiO2 and examining the literature data in other composition systems, we have found that (1) Si enters spinel via the substitution reaction Si4++ M2+= 2 M3+ (M2+: Mg2+, Fe2+, etc.; M3+: Al3+, Cr3+, etc.); (2) its solubility in spinel coexisting with olivine can reach the level of weight percent, and positively correlates with P, T, and compositional parameters Cr# and Mg# of the spinels; (3) the SiO2 contents of the chromian spinels from various mantle-related rocks of different petrological or tectonic origins can be very different. Interacting with Earth's major elements Mg, Fe, Al and Cr, attaining high levels of abundance for easy quantification, and possessing significantly different abundance variations among spinels from different types of mantle-related rocks, Si in nominally Si-free chromian spinel has the potential to be a powerful petrogenetic probe for the upper mantle.
The Duxiushan deposit in the Anqing ore district is a newly discovered granite-pegmatite system hosting significant Li-Rb-Nb-Sn mineralization, representing a style markedly different from those previously recognized in the Middle-Lower Yangtze River Metallogenic Belt, yet its genetic mechanism remains unclear. In this study, we integrate geochronology, geochemistry, and isotopes to constrain its petrogenesis and rare metal enrichment. Zircon U-Pb dating of the two-mica granite (138.3 +/- 1.7 Ma) and barren pegmatite (136.7 +/- 1.6 Ma), together with cassiterite U-Pb dating of the mineralized pegmatite (136.6 +/- 1.9 Ma), indicate that magmatism and coeval Li-Rb-Sn mineralization occurred during the Early Cretaceous. The Duxiushan two-mica granite is classified as a highly fractionated, peraluminous S-type granite. Consistent isotopic compositions of zircon Hf, apatite Sr-Nd, and tourmaline delta 11B across all three lithologies indicate a cogenetic origin, involving partial melting of Neoproterozoic juvenile crust followed by assimilation of ancient continental crustal components within an extensional tectonic setting. Systematic geochemical trends from granite through barren pegmatite to mineralized pegmatite, including increasing SiO2 and Rb, decreasing TiO2, MgO, total REE, Ba, Th, Nd, and extreme depletion of Zr/Hf and Nb/Ta, record progressive fractional crystallization. The positive correlation between Fe and Al in tourmaline, combined with zircon Ce4+/Ce3+ ratios, indicates a reduced magmatic system. Tourmaline exhibits significantly higher F contents in mineralized pegmatite, indicating F enrichment during magma evolution. Collectively, these processes efficiently concentrated incompatible elements (Li, Rb, Sn, Nb, Ta) into the residual melt, leading to the formation of the mineralized pegmatite in the Duxiushan deposit.
Earthquake stress drop is a key parameter linking fault strength, rupture dynamics, and high-frequency ground motion, yet global observations exhibit variability spanning more than two orders of magnitude. This study reassesses the primary controls on stress-drop variability using a harmonized global database of 1748 earthquakes (Mw ≥ 5.5). Each event is classified by tectonic environment, focal depth, and faulting style, enabling a systematic evaluation of how these factors jointly influence stress drop. We find that intraplate earthquakes systematically exhibit higher stress drops than plate-boundary events across nearly all depth ranges. Depth exerts a strong control on stress-drop distributions: median values increase from the upper crust to the lithospheric mantle, and magnitude scaling becomes increasingly negative with depth. A multivariate regression incorporating Mw, depth, tectonic setting, and mechanism explains ∼4% of total variance, indicating substantial intrinsic variability but confirming that tectonic environment and depth contribute significant, though modest, systematic effects. Global kernel-smoothed maps reveal coherent regional patterns, including elevated stress drops within continental and oceanic intraplate domains and localized high-Δσ patches near subduction interfaces. K-means regionalization shows that ∼11% of the global variance in stress drop is attributable to large-scale tectonic domains. Faulting style produces weaker effects: reverse and strike-slip earthquakes show broadly similar distributions and magnitude scaling once depth and tectonic setting are accounted for. Collectively, these results demonstrate that tectonic environment and lithospheric depth are first-order controls on global stress-drop variability, providing new observational constraints on earthquake rupture physics and seismic hazard in intraplate regions.
To evaluate the resource potential and suitability for high-purity quartz production of the granitic pegmatite-type quartz deposit in the Huoqiu Group on the southern margin of the North China Craton, the quartz deposit in the Caolou area of Huoqiu County, Anhui Province, was selected for study. Optical microscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES), and related analytical methods were employed to systematically investigate the mineralogical characteristics, inclusion features, and geochemical properties of the quartz ore. A combined purification process including calcination-water quenching pretreatment, gravity separation, high-gradient magnetic separation, HF-activated flotation, mixed-acid leaching, and high-temperature HCl chlorination was adopted for quartz purification, and the impurity removal behavior at each stage was analyzed. The results show that sample I from the Caolou granitic pegmatite has a massive structure and contains mediumto fine-grained quartz with high crystallinity, closely associated with plagioclase and biotite. Quartz inclusions are dominated by secondary fluid inclusions with directional distribution, and most are smaller than 10 mu m with relatively low abundance, indicating favorable characteristics for high-purity quartz production. After systematic purification, the SiO2 purity increased from 99.921 wt% to 99.996 wt%, while the total impurity content decreased from 793.44 ppm to 39.27 ppm, corresponding to an overall impurity removal rate of 95.05% and meeting the technical standard for 4N6-grade high-purity quartz. Al, Ca, K, and Fe were efficiently removed because they mainly occur in gangue minerals or discrete oxide phases, whereas Li, Na, and Ti mainly occur in lattice-bound or inclusion-hosted forms and remain the main constraints on further purity improvement. These results indicate that the Huoqiu Group granitic pegmatite-type quartz deposit has good potential for high-purity quartz production, and that the purification process established in this study can provide a practical reference for the development and utilization of similar quartz resources.
Western China experienced progressive aridification during the Late Cenozoic, yet the development of large lakes in the Tarim Basin indicates intervals of enhanced hydrological conditions, creating an apparent paradox. Here, we analyze carbonate mineralogy and oxygen isotope compositions from the LS2 drill core in Lop Nur to constrain the origin of lacustrine dolomite and the hydrological evolution between similar to 7 and 4.9 Ma. Dolomite abundance covaries with bulk carbonate delta O-18 values, with higher dolomite contents corresponding to isotopic enrichment. This relationship, together with pronounced stratigraphic variability, indicates that dolomite formed predominantly during deposition or early diagenesis under the control of lake-water chemistry, rather than through late-stage burial diagenesis. Although this pattern is consistent with evaporative concentration, the absence of a clear delta C-13-delta O-18 correlation and the lack of quantitative constraints on detrital carbonate input introduce uncertainty in attributing evaporation as the dominant control. Our results reveal a shallow saline lake system characterized by strong hydrological fluctuations superimposed on a persistently arid background. The environmental evolution can be divided into two stages: (1) 7.0-5.7 Ma, characterized by a shallow, reducing saline lake under generally warm and arid conditions, with intermittent cooling and humid episodes; and (2) 5.7-4.9 Ma, marked by continued shallow lacustrine conditions with higher-frequency hydrological variability, showing alternations between relatively warm-dry and cool-wet conditions, superimposed on an overall arid background with intensified evaporation and increasing salinity. Comparison with regional records suggests that Late Miocene lake expansion in Central Asia does not necessarily indicate sustained humid conditions, but instead reflects complex interactions among evaporation, basin hydrology, and climate forcing.
The spatiotemporal variations in land use/land cover (LULC) significantly affect groundwater movement. Therefore, assessing the impact of LULC changes on recharge is crucial for sustainable groundwater resource management. This study aims to monitor the influence of LULC alterations on groundwater recharge zones in a semi-arid region. This study integrated the ‘fixing-changing’ method with GIS and the Analytic Hierarchical Process (AHP) to delineate groundwater recharge areas. Satellite images were utilised to evaluate patterns from 2000 to 2022. Results showed that from 2000 to 2022, settlement, croplands, water bodies, and closed savannah increased by 164.94 %, 172.272 %, 102.94 %, and 25.43 %, respectively. The legitimacy of the outcome was trained and tested by applying receiver operating characteristic (ROC) curves, which revealed training and testing accuracies of 81.683% and 79.912%, respectively, indicating a very high correlation between the groundwater recharge potential zone (GWRPZ) and the well yields, which helped in the validation of the results. The changes in the 2022 LULC with reference to the 2000 LULC resulted in the excellent, very good and good recharge zones decreasing by 59.16 %, 73.75 % and 56.98 %, respectively. The findings produced essential facts about the groundwater network and its reaction to LULC changes. The outcomes also revealed the implementation of certain sustainable strategies. This information can serve as a valuable tool for sustainable groundwater resource management and development in semi-arid regions.
Migmatites can record the complex melting processes during crustal anatexis, and investigating their petrogenesis is crucial for deciphering the chemical differentiation processes of continental crust. This study conducted systematic geochronological, petrological, and geochemical analyses on melanosome and leucosome samples from migmatites exposed in the Guixi area, Jiangxi Province. The results indicate that the Guixi migmatites were formed through remelting of the Neoproterozoic Zhoutan Group during the Early Paleozoic (436 ± 2 Ma). The leucosome samples exhibit higher zircon δ18O values and whole-rock (87Sr/86Sr)i ratios than those of the melanosomes, suggesting a water-fluxed melting process with involvement of external fluids. Influx of fluid led to the preferential breakdown of plagioclase in the melanosome, while garnet in the source rock underwent limited melting. The melting processes imparted chemical characteristics of adakitic rocks to the leucosome samples, such as high Sr, low Y and Yb, and high Sr/Y and (La/Yb)N ratios. Biotite remained as a residual phase during water-fluxed melting and could react with the melt, resulting in elevated Nb contents in residual biotite and significant Nb enrichment in the source, which potentially favored Nb enrichment and mineralization in South China during the Mesozoic.
With the rapid advancement of low-temperature thermochronology, the (U–Th)/He dating technique has become indispensable for reconstructing shallow crustal thermal histories. A key obstacle to the broader application of (U–Th)/He thermochronology is the limited availability of thoroughly validated analytical protocols that demonstrate a laboratory's ability to produce internationally comparable data. This work overcomes this obstacle by establishing and rigorously validating a complete analytical workflow for single-grain apatite and zircon (U–Th)/He dating through long-term (>1 year) replicated analysis of four diverse international reference materials, encompassing both apatite (Durango, MK) and zircon (Fish Canyon Tuff, Penglai) standards with distinct ages and chemical characteristics. The derived weighted mean ages (Durango: 31.22 ± 0.35 Ma; MK: 18.95 ± 0.35 Ma; FCT: 27.91 ± 0.44 Ma; Penglai: 4.29 ± 0.11 Ma) are statistically indistinguishable from their globally accepted reference values. This multi-standard calibration confirms the exceptional accuracy and long-term reproducibility of our protocols and demonstrates their robustness across different mineral types and age ranges. By providing a transparent, thoroughly validated methodological framework and establishing direct comparability with international standards, this work transitions our laboratory into a certified source of high-fidelity (U–Th)/He data. It thereby lowers the technical barrier for high-quality thermochronology within the region and provides a solid foundation for resolving nuanced shallow crustal thermal histories in future tectonic studies.
Thallium (Tl) isotopes are valuable geochemical tracers widely applied in planetary evolution, redox history of ancient oceans, pollution source tracing, and crustal recycling. Contemporary Tl isotope analyses generally rely on either the standard-sample bracketing or element-doping approach to correct for mass bias. However, complex matrices and residual Pb can introduce correction artifacts, making efficient Tl purification a prerequisite for obtaining accurate isotope data. In this study, we developed an improved dual-column purification system composed of AG 1-X8 anion-exchange resin (200–400 mesh) and AG 50W-X12 cation-exchange resin (200–400 mesh), enabling highly efficient separation and purification of Tl from natural samples. Isotopic measurements were performed on a Nu Plasma II multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS), using Pb as an internal standard for mass-bias correction. The optimized protocol yields Tl procedural blanks <1 pg and Pb blanks <13 pg. Long-term monitoring of the NIST SRM 997 Tl standard produced ε205Tl = 0.0 ± 0.7 (2SD, n = 214). The measured ε205Tl values for the ferromanganese nodule reference materials NOD-A-1 and NOD-P-1 are 10.8 ± 0.8 (2SD, n = 8) and 3.6 ± 0.8 (2SD, n = 5), respectively, both in excellent agreement with published data. These findings confirm that the method achieves effective matrix removal and Pb elimination, ensuring analytical accuracy and reliability. The developed purification and analytical protocol offer a solid foundation for future Tl isotope investigations of soil and related terrestrial materials.
Stable isotopic composition of Cerium (Ce), a refractory, incompatible, and redox-sensitive element, provides a powerful tracer for continental weathering processes. However, the average δ142/140Ce value of the upper continental crust (UCC) remains poorly constrained. Here, we report Ce isotopic data of characterized upper crustal samples, including granitic rocks with distinct sources (I, A, and S-type) and loess, to constrain the Ce isotopic composition (expressed as δ142/140Ce relative to the NIST SRM 3110 standard) of the UCC. Despite SiO2 contents varying from 64 % to 77 %, I and S-type granites in SE China show indistinguishable δ142/140Ce values (−0.018 ‰–0.057 ‰ and 0.008 ‰–0.045 ‰), while A-type granites exhibit a small but detectable variation relative to the analytical precision (±0.040 ‰). These granites have experienced fractional crystallization, but the δ142/140Ce values show no correlation with geochemical indices (CaO/Al2O3, Eu/Eu∗, P2O5), and without correlation was observed with La/Sm(N), Nb/Y, Isr and εNd(t), indicating that the influences of source heterogeneity, partial melting, and magmatic crystallization are negligible. The δ142/140Ce values in loess range from −0.027 ‰ to 0.073 ‰, showing limited variations. Moreover, the δ142/140Ce of loess shows no correlation with chemical weathering, mineral sorting, and sample locations, confirming its representativeness of the average UCC. These results show that the stable Ce isotopic composition of UCC is relatively uniform. Based on the lithology-weighted average method, the δ142/140Ce value of UCC is 0.017 ± 0.026 ‰.
