Basalt Research Articles

The fate of solid-phase transfer in subduction zones: Evidence from Ti-oxides in Luobusa ophiolitic chromitite

The transport of hydrous components from a subducting oceanic plate to the supra-subduction lithospheric mantle and their influence on arc magmas is well-documented. Yet the transfer of solid-phase materials remains enigmatic, despite an increasing body of literature regarding inherited rutile in well-characterized arc magmas and ophiolitic chromitites. The mechanism governing the introduction of solid phases into the overlying mantle wedge as well as the duration of their residence are poorly understood. This study investigates mineralogical and geochemical characteristics of rutile inclusions in the Luobusa chromitite of southern Tibet.In the investigated chromitite, rutile, associated with ilmenite, corundum, ulvöspinel, zircon, and melt silicate inclusions, exhibits geochemical characteristics indicative of derivation from crustal mafic rocks. Estimated formation or recrystallization temperatures of rutile range from 570 to 675 °C at approximately 1.2 GPa. These temperature estimates illustrate the challenges of obtaining accurate dating, as the rutile UPb system resets near 600 °C. The Fe/Zr ratios in Luobusa rutile serve as indicators of H2O/Zr ratios, suggesting a significant role for hydrous components in the behavior of high field strength elements (HFSE) during subduction processes.A fluid-assisted transport mechanism likely facilitated the movement of HFSE, such as Ti, V, Zr, Nb, and Ta, within accessory mineral phases into the supra-subduction mantle wedge. The presence of rutile and polymorphs of TiO₂, including Ti0.82Si0.18O2 and TiO2-II, within chromite crystals underscores the extensive recycling and recrystallization processes occurring under diverse mantle conditions during the genesis and evolution of the Luobusa ophiolites.

Integrated geophysical and remote sensing/GIS interpretation for delineating the structural elements and groundwater aquifers of the Foumban locality, Western Highlands of Cameroon (WHC)

This study was conducted in the Foumban locality, in the Western Highlands of Cameroon (WHC) where a majority of the population is suffering from scarcity of water for domestic purposes and many other related uses. Thus, it aims at investigating the structural and geo-electrical characteristics of the aquifer system of the locality, based on an integrated approach (Geophysics and GIS). For this purpose, the Landsat 8 image with 30 × 30 m resolution and 20 vertical electrical sounding (VES) data were analysed with ArcGIS, ENVI version 5.3, Stereonet v9.3.2 and QWSELN software, coupled with the principal component analysis (PCA). Based on the structural aspect, a total of 224 fractures with lengths higher than 1 km have been identified and drawn. They are mainly grouped in the Centre, North-East and South-East of the study area. Five main families within linear directions have been identified: N10-20 (13.84%), N20-30 (17.86%), N50-60 (9.82%), N80-90 (5.90%) and N140-150 (7.59%). They are mostly oriented NE-SW, following the Cameroon Volcanic Line (CVL). These fractures which play an important role in the capacitive and drainage function of the fractured aquifer result from the tectonic movements and decompression of rock masses. According to the geoelectrical characteristics, different VES curve types have been identified, corresponding to various alternate layers of conductive, semi resistive and resistive formations; with thickness ranging between 0.41 to 47 m and resistivity values between 82 to 3410 Ωm. The three cross-section realised (A-A’, B-B’ and C-C’) show that those alternate materials (topsoil, laterite, weathered layer, fractured basement and fresh basement rock) are discontinuous both vertically and horizontally, highlighting the geometry and hydrogeological complexity of these areas. This study is a contribution to a better understanding of the basement aquifers milieu; it could be used by the water supply departments and decision makers for locating appropriate positions of new productive wells in the study area.

Hidden Archaean basement beneath the southwestern Yangtze Craton: Evidence from 2.8 Ga xenocrystic zircons in an early Cretaceous dolerite dyke

The distribution of Archaean basement rocks in the southwestern Yangtze Craton, China, is not well documented due to the scarcity of outcrops. In this study, we identified Meso–Neoarchaean zircons in a dolerite dyke that was emplaced in the Meso–Neoproterozoic Dongchuan Group in the southwestern Yangtze Craton. Ninety-seven analyses of zircons from the dolerite yielded two distinct U–Pb age groups. The younger group of zircons, characterised by euhedral crystals and relatively high Th/U ratios (0.15–2.03), has a weighted-mean age of 109.4 ± 3.0 Ma (n = 27), which is considered to be the emplacement age of the dolerite. The older group of zircons, with a weighted-mean age of 2831 ± 18 Ma (n = 33), crystallised during the Meso–Neoarchaean. These zircons might be xenocrysts captured during magma emplacement. Moreover, the zircons have εHf(t) values of −24.59 to −4.16 for the young population and −9.80 to −3.86 for the old population, indicating the dolerite was derived by melting of Archaean crustal igneous rocks. These results demonstrate the existence of Archaean rocks in the southwestern Yangtze Craton and provide new evidence for the spatial distribution of Archaean basement.

Late Triassic Felsic and Mafic Magmatism in the South Qinling Orogen, Central China: Insights from the Petrology, Zircon U-Pb Geochronology, and Geochemistry of the Huoshaodian Pluton

The petrology, geochemistry, and zircon U-Pb chronology of the Huoshaodian pluton in the Liuba area of the western part of the South Qinling tectonic belt are investigated in this study. The Huoshaodian pluton consists of gabbro, quartz diorite, and granodiorite, and the dominated rock type is quartz diorite. The results indicate that the Huoshaodian pluton belongs to the calc-alkaline series. In the chondrite-normalized REE, all of the samples showed similar patterns, with an enrichment of light REEs and depletion of heavy REEs, but they showed slight differences in the degrees of Eu anomalies. The primitive mantle-normalized trace element diagram reveals an enrichment of large-ion lithophile elements (LILEs) and light rare earth elements (LREEs), as well as depleted high field strength elements (HFSEs). The zircon U-Pb dating results reveal that the gabbro, quartz diorite, and granodiorite have crystallization ages of 214.9 ± 0.58 Ma, 215.0 ± 1.2 Ma, and 215.4 ± 1.9 Ma, respectively, indicating that the Huoshaodian pluton was emplaced during the late Triassic period (214.9–215.4 Ma). In terms of petrogenesis, the gabbro of the Huoshaodian pluton originates from a transitional lithospheric mantle that has undergone fluid metasomatism and partial melting. Specifically, it originated through 1%–2% garnet spinel peridotite undergoing partial melting. In addition, the gabbro underwent a slight degree of contamination by crustal materials during its ascent and intrusion, with some continental crust material being incorporated. The quartz diorite and granodiorite of the Huoshaodian pluton are formed through partial melting processes occurring within the normal lower crust. Combined with the previous studies on the early Mesozoic tectonic evolution of the South Qinling, this study proposes that the formation mechanism of the Huoshaodian pluton may be as follows: in the early Triassic, the Mianlue Ocean subducted northward beneath the Qinling microblock, resulting in a large-scale continental-continental collision between the North China Block and the Yangtze Block; when the oceanic crust subducted to a certain depth, the detachment of the subducting slab triggered the upwelling of mantle material. The heat from mantle-derived magma caused the partial melting of the mafic lower crust, while the mafic magma entered into the upper granitic magma chamber and began to mix. Due to the high viscosity contrast and temperature difference between the two end-member magmas, incomplete mixing led to the formation of a melt with distinct adakitic characteristics and a mafic melt representing mantle-derived material.

Mapping Soil Contamination in Arid Regions: A GIS and Multivariate Analysis Approach

Heavy metal soil contamination is a global environmental issue that poses serious threats to human health, agricultural advancement, and ecosystem systems. Thirty-five soil samples from various parts of Jazan, Southwest Saudi Arabia, were collected. To create spatial pattern maps for nine potentially toxic elements (PTEs) (As, Co, Cr, Cu, Fe, Ni, Pb, V, and Zn), Ordinary Kriging (OK) was utilized. The variability of the soil metal concentration was estimated using multivariate analysis, including principal component analysis (PCA) and cluster analysis. In addition, the levels of soil contamination in the research area were assessed using contaminations indices, namely, Enrichment Factor (EF), Contamination Factor (CF), and geoaccumulation index (Igeo), and modified contamination degree (mCd). Normalized Difference Vegetation Index (NDVI) and land use/land cover (LULC) were assessed to evaluate vegetation density and identify different forms of land cover and land use. The results showed that the Gaussian model fitted As well, whereas the spherical model fitted Co, Cr, Cu, Ni, and Zn. An exponential model was fitted to Fe and V. Pb also suited the Stable model. In each of the selected metals, the root mean square standardized error (RMSSE) values were close to one, and the mean standardized error (MSE) values were almost zero for each fitted model. Moreover, the findings showed that there was a tendency for the concentration of heavy metals in the research area to rise from west to east. The cluster analysis divided the data in this investigation into two clusters. Significant alterations in Co, Cr, Cu, Fe, Ni, V, and Zn were revealed by the acquired data. However, the total As and Pb concentrations in the two clusters did not differ significantly. The mCd value of the research region often fell into one of three classes, with areas of 148.20 km2 (nil to very low degree of contamination), 26.16 km2 (low degree of contamination), and 0.495 km2 (moderate degree of contamination). The findings indicated that the minerals connected to the Arabian Shield’s basement rocks are the main source of these PTEs. It is crucial to monitor PTEs contamination because the research region is highly cultivated, as shown by the NDVI and LULC status. Given the potential for future pollution due to human activity, PTEsPTEs decision-makers may use the findings of the spatial distribution maps of pollutants and their concentrations as a basis for future monitoring of PTEs concentrations in the study area.

Geochronology and geochemistry of the Neoproterozoic–Mesozoic intrusive rocks in the Xinlin area, northeastern China: new constraints on the tectonic evolution of the Erguna block

The occurrence of intrusive rocks within the Xinlin area, northeastern China, provides insights into the Neoproterozoic–Mesozoic geodynamic setting of the Erguna block. In this study, we present petrographic, geochemical, and geochronological data on intrusive rocks from the Xinlin area. Zircon U–Pb and muscovite 40Ar/39Ar geochronology reveal that magmatism occurred during the Neoproterozoic (ca. 864.98 Ma), Early Ordovician (ca. 470.0 Ma), Late Carboniferous (ca. 306.9 Ma), Early Permian (ca. 296.9 Ma), and Early Cretaceous (ca. 117.8 Ma) periods. The Neoproterozoic and Early Ordovician intermediate–mafic intrusive rocks have low Rb/Sr contents, high Mg#, and weakly negative Eu anomalies. These results suggest that the magma sources of these rocks varied: intermediate–acidic magmas were derived from the lower crust, and intermediate–mafic magmas originated from the mantle and were subsequently contaminated by crustal material. In contrast, the Late Carboniferous, Early Permian, Late Triassic–Early Jurassic, and Early Cretaceous intermediate–acidic intrusive rocks display high Rb/Sr contents, low Mg#, and strongly negative Eu anomalies, indicating derivation from the partial melting of the lower crust. Our findings, along with previous studies, suggest that Neoproterozoic intrusive rocks were formed during the breakup of the Rodinia supercontinent. The Paleozoic intrusive rocks are associated with the collision and amalgamation of the Erguna and Xing’an blocks, as well as the Songnen and Xing’an blocks. Early Mesozoic intrusive rocks were developed during the subduction of the Mongol-Okhotsk oceanic intracontinental system. Finally, the late Mesozoic intrusive rocks were formed in a non-orogenic extensional setting, potentially linked to the final closure of the Mongol-Okhotsk Ocean or the rollback of the Paleo-Pacific Plate.

The early Paleozoic intracontinental orogeny in South China: A far-field response to the closure of the Proto-Tethys Ocean in the Indochina Block

The nature and geodynamics of the early Paleozoic orogen in South China are modeled as either products of direct subduction-collision or intracontinental orogeny. The synchronous basaltic-andesitic rocks within the orogen are at the heart of this scientific debate, but they have been less systematically investigated. The petrogenesis and tectonic setting of these mafic rocks are highly controversial, given their arc-like geochemical characteristics. We systematically investigated the patterns of field relations, ages, chemistry, and Hf-Nd isotopes of the early Paleozoic basaltic-andesitic rocks in the Yunkai massif and those reported elsewhere in the orogen. Based on chemical and isotopic signatures, these basaltic-andesitic rocks (ca. 460−420 Ma) can be divided into calc-alkaline light rare earth element (LREE)-enriched basalts, LREE-enriched andesitic rocks, and tholeiitic LREE-depleted basalts. The calc-alkaline suites mostly display arc-type geochemical features, with enrichment in large-ion lithophile elements, LREEs, and Pb, but depletion in high field strength elements relative to heavy rare earth elements. Their high La/Nb and Ba/Nb ratios, and low Nb/Th ratios, along with negative εHf(t) and εNd(t) isotope values, indicate the distinctive fractionation of incompatible trace elements that may have been derived from the partial melting of ancient metasomatized lithospheric mantle sources. On the other hand, the tholeiitic basalts show normal mid-oceanic-ridge basalt-like rare earth element patterns and positive zircon Hf isotope compositions, which reflect the partial melting of a depleted asthenosphere. Given the “intraplate-type” sedimentary, tectonic deformation, and metamorphic signatures across South China, we conclude that these planar-distributed basaltic-andesitic rocks were associated with the activation of the lithospheric mantle and asthenosphere, which occurred in a postorogenic tectonic environment rather than a subduction-related arc regime. Therefore, all geological facts and data patterns favor the Wuyi-Yunkai orogen as a typical intracontinental orogen. Moreover, the Indochina and South China blocks display comparable early Paleozoic faunas and sedimentary records, while the early Paleozoic Tam Ky−Phuoc Son Suture has been identified in Central Indochina. The timing of orogenesis in South China (ca. 460−440 Ma) overlaps with the pre-450 Ma accretionary orogeny in the Central Indochina Block. Therefore, we propose a geodynamic model of linked South China and Indochina blocks in the northern margin of Gondwana, with the geodynamic stress of the Wuyi-Yunkai orogeny derived from a subduction-collision event in Central Indochina. The Wuyi-Yunkai orogen is thus an intracontinental orogen resulting from the far-field effects of plate tectonics.

Remote Mapping of Bedrock for Future Cosmogenic Nuclide Exposure Dating Studies in Unvisited Areas of Antarctica

Cosmogenic nuclide exposure dating is an important technique for reconstructing glacial histories. Many of the most commonly applied cosmogenic nuclides are extracted from the mineral quartz, meaning sampling of felsic (silica-rich) rock is often preferred to sampling of mafic (silica-poor) rock for exposure dating studies. Fieldwork in remote regions such as Antarctica is subject to time constraints and considerable logistical challenges, making efficient sample recovery critical to successful research efforts. Remote sensing offers an effective way to map the geology of large areas prior to fieldwork and expedite the sampling process. In this study, we assess the viability of multispectral remote sensing to distinguish felsic from mafic rock outcrops at visible-near infrared (VNIR) and shortwave infrared (SWIR) wavelengths using both the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and very high-resolution Worldview-3 (WV-3) imagery. We applied a combination of spectral mapping and ground truth from spectral measurements of 17 rock samples from Mount Murphy in the Amundsen Sea sector of West Antarctica. Using this approach, we identified four dominant rock types which we used as a basis for felsic–mafic differentiation: felsic granites and gneisses, and mafic basalts and fragmental hydrovolcanic rocks. Supervised classification results indicate WV-3 performs well at differentiating felsic and mafic rock types and that ASTER, while coarser, could also achieve satisfactory results and be used in concert with more targeted WV-3 image acquisitions. Finally, we present a revised felsic–mafic geological map for Mt Murphy. Overall, our results highlight the potential of spectral mapping for preliminary reconnaissance when planning future cosmogenic nuclide sampling campaigns in remote, unvisited areas of the polar regions.

Geochemical signatures and contamination levels of rare earth elements in soil profiles controlled by parent rock and soil properties.

Rare earth elements (REEs) are emerging contaminants rendering potential risks in soils to environmental quality and human health. The causation between their geochemical signatures and contamination levels with parent rocks and soil properties are critical for REEs risk assessments, which are urgently needed globally. Thus, this study aimed to elucidate cause-and-effect among hydrofluoric-acid-digested total and ethylenediaminetetraacetic acid extracted bioavailable soil REEs and their contamination degree evaluated by pollution indices in 268 soil layer (horizon) samples from 50 soil profiles derived from felsic, intermediate, mafic, ultramafic, and sedimentary rocks in Taiwan. The total REEs was 133 ± 61.9mg/kg and all individual REEs were classified as minimal contamination by the enrichment factor. The highest total soil REEs was from granite, followed by sandstone and shale, mafic rocks, andesite, and ultramafic rocks. All soils were ranked as significantly pollution risk by the pollution loading index. Furthermore, REEs were accumulated in all subsoils due to the co-translocation with soil colloids during the intensive leaching, corresponding with their higher geoaccumulation index value than those in surface soils. The contamination degree and bioavailable REEs significantly increased with the increasing total REEs. However, the stronger sequestration of clay and free Fe oxides for heavy REEs (HREEs) over light REEs (LREEs) mitigated their bioavailability, especially in the highly weathered soils like Ultisols and Oxisols. This study highlighted the dominance of soil properties in REEs fractionation, where the preferential fixation of soil colloids for HREEs throughout soil profiles reduced their uptake risk for biome even under the rising contamination potential.

Paleomagnetic data from volcanic rocks in the southern Central Andes of Argentina and their implications for tectonics and geomagnetic field behavior

Abstract A paleomagnetic study of basaltic lava flows exposed in the northern Neuquén Cordillera, southernmost Central Andes, along the Antiñir-Copahue fault zone (ACFZ), involved 25 sites of the Cola de Zorro Formation (Pliocene–Early Pleistocene) along two different sections. The sites show exclusive normal polarity, corresponding to the Late Pliocene Gauss chron (3.6–2.6 Ma). The angular standard deviation of virtual geomagnetic poles (VGPs; ASD = 14.8°) is consistent with the expected values from recent geomagnetic models, in opposition to anomalously low dispersion found in previous studies in Pleistocene VGPs of reverse polarity from neighboring areas to our study zone. Mean paleomagnetic directions for Bella Vista (Dec = 0.0°, Inc = −50.0°, α₉₅ = 7.6°, K = 36.7, N = 11) and Río Huaraco sections (Dec = 354.9°, Inc = −57.0°, α₉₅ = 7.5°, K = 55.7, N = 8) do not show tectonic rotation around vertical axes. Combining and regrouping our and previous data by area confirmed the absence of tectonic rotations in the Huaraco-Trohunco block and a statistically significant clockwise rotation of 14.4° ± 10.3° of three adjacent tectonic blocks located south of our study locality in Pleistocene times. These results suggest that strike-slip deformation along some sections of the ACFZ was significant in the Pleistocene structural evolution of this region.

On-land evidence for subduction of the proto−South China Sea beneath northern Borneo and tectonic reconstruction of Southeast Asia during the early Permian–Oligocene

The development of the Mesozoic proto−South China Sea was closely related to the tectonic evolution of the Tethys and Paleo-Pacific domains and may have been a key driving mechanism for the opening of the South China Sea. Despite its importance, direct geologic evidence for the proto−South China Sea remains limited, and its development is debated between two primary models: intra-oceanic subduction and oceanic-continental subduction. Here, we present petrographic, geochronologic, and geochemical data from tuffs and Eocene−Pliocene sedimentary records in Sabah, northern Borneo. The results reveal that these tuffs, formed ca. 28 Ma, possess geochemical characteristics indicative of oceanic arc origins. Combined with changes in sediment provenance since the Oligocene and various subduction timelines around Borneo, we suggest that these tuffs resulted from the subduction of the proto−South China Sea. This oceanic arc, along with Eocene mid-ocean-ridge−like mafic rocks in Sabah, indicates that a younger oceanic basin had formed within the proto−South China Sea. This aligns with observations in Palawan, Philippines, illustrating the transition from an oceanic spreading center to a subduction zone and indicating the proto−South China Sea extended from eastern Sabah to Palawan. In addition, inherited zircons (ca. 280 Ma) in the tuffs exhibit geochemical signatures typical of continental arcs. Combined with the Permian−Cretaceous arc-related igneous rocks in Southeast Asia, this suggests that southern Sabah was part of the Paleo-Tethys Ocean before integrating into the Paleo-Pacific domain since the Triassic. By shedding light on these processes, our research provides critical insights into the existence, extent, and evolution of the proto−South China Sea and reconstructs the multiphase transitions between different tectonic domains in Southeast Asia.

Transition of CO2 from Emissions to Sequestration During Chemical Weathering of Ultramafic and Mafic Mine Tailings

Weather-enhanced sulphide oxidation accelerates CO2 release into the atmosphere. However, over extended geological timescales, ultramafic and mafic magmatic minerals may transition from being sources of CO2 emissions to reservoirs for carbon sequestration. Ultramafic and mafic mine tailings present a unique opportunity to monitor carbon balance processes, as mine waste undergoes instantaneous and rapid chemical weathering, which shortens the duration between CO2 release and absorption. In this study, we analysed 30 vanadium-titanium magnetite mine tailings ponds with varying closure times in the Panxi region of China, where ~60 years of mineral excavation and dressing have produced significant outcrops of mega-mine waste. Our analysis of anions, cations, saturation simulations, and 87Sr/86Sr; δ13C and δ34S isotopic fingerprints from mine tailings filtrates reveals that the dissolution load of mine tailings may depend significantly on early-stage sulphide oxidation. Despite the abundance of ultramafic and mafic minerals in tailings, dolomite dominates chemical weathering, accounting for ~79.2% of the cationic load. Additionally, due to sulphuric-carbonate weathering, the filtrates undergo deacidification along with sulphide depletion. The data in this study suggest that pristine V-Ti-Fe tailings ponds undergo CO2 emissions in the first two years but subsequently begin to absorb atmospheric CO2 along with the filtrates. Our results provide valuable insights into monitoring weathering transitions and carbon balance in ultramafic and mafic rocks.

Formation mechanism of boehmite and diaspore in karstic bauxites: trace element geochemistry in source materials using large sample geochemical dataset and random forest model

Abstract Boehmite and diaspore are the two economic ore minerals of karstic bauxites. Although their genesis has been studied from different perspectives, their formation mechanism is controversial. Random forest (RF) model of machine learning was employed to extract the combining characteristics of trace elements in boehmite-type bauxite (BTB) and diaspore-type bauxite (DTB). The BTB predominantly exhibits higher median concentrations of Co, Ni, V, and Cr, while the DTB exhibits a more significant enrichment in elements of U, Hf, Th, and Zr. Combining the characteristics of La/Yb and Ga/Al ratios, it is found that disparities between BTB and DTB are mirroring to those between basic rocks and intermediate-felsic rocks. Furthermore, the Zr-Cr-Ga diagram and Ni/Zr versus Cr/Zr plot were utilized to examine the correlation between karstic bauxite (BTB or DTB), lateritic bauxite, and their respective weathered parent rocks. It is found that BTB exhibits consistent characteristics with lateritic bauxite weathered from basic rock and its parent rocks. Similarly, DTB displays consistent characteristics with lateritic bauxite weathered from intermediate-felsic rock and its parent rocks. Through studying the relationship between Ni content and Fe3+/Fe2+ ratios, it has been discovered that the presence of trace elements like Ni in source materials can affect or regulate ore-forming process, ultimately driving the transformation of gibbsite into either boehmite or diaspore. Consequently, the formation of BTB and DTB is significantly influenced, or even governed, by the composition of their source materials. Our study initially highlights a novel insight into the significant impact of source material’s geochemical composition on the formation of boehmite and diaspore, which is associated with weathered igneous rocks categories.

Apatite Geochemical Perspectives on the Maturation of Continental Arc Crust via Mush‐Facilitated Processes During Magmatic Flare‐Up

AbstractIn volcanic arcs, magma evolves from basaltic to intermediate and felsic composition, resulting in arc crust maturation. It remains unclear whether processes involving mush during magmatic flare‐ups would enhance this evolution. This study revealed a temporal‐compositional evolution of plutonic rocks from mafic (∼94 Ma) to intermediate (∼92–88 Ma) to felsic (∼88 Ma) during a magmatic flare‐up event in the Gangdese arc, Tibet, with increasing radiogenic Sr–Nd isotope enrichment. Apatites in mafic and felsic rocks have εNd(t) values similar to their hosts, while intermediate rocks show higher values. The elemental composition of apatites in mafic and intermediate rocks is similar but differs from those in felsic rocks. Textural and compositional features indicate varying degrees of influence of mafic rock compositions by accumulation. Triangular and linear covariation relationships between apatite‐compatible (e.g., La) and ‐incompatible (e.g., Rb) elements with SiO2, respectively, for all plutonic rocks as a whole, confirm the incorporation of apatite‐rich mushes into the mixing process. These findings suggest that mafic magma crystallized into apatite‐rich mush, which was later remobilized and mixed with felsic magma to form intermediate magma. Felsic rocks represent end‐member magmas resulting from crustal anatexis and/or mafic magma differentiation. Thus, the Gangdese arc's maturation during the magmatic flare‐up progressed sequentially through mafic magma crystallization and mush formation, mush remobilization and mixing with felsic magma, and the eventual accumulation and segregation of felsic magma. This sequence of events during flare‐ups illustrates a common crustal maturation process in volcanic arcs, as also seen in the Andean Cordillera.

Effects of high temperature annealing and low temperature metamictization on Archean zircon: constraints from U–Pb isotopes, trace elements and Raman dating

Abstract Zircon is a common accessory mineral that can survive extreme temperature conditions in the crust, although U-Th series radioactive decay is responsible for its self-destruction over long time scales. Upon exhumation at lower temperatures, metamict zircon grains are then more susceptible to isotopic and trace element disturbance. In this work, we investigated the isotopic and trace element behavior of zircon through LA-ICP-MS, coupled with Raman spectroscopy, from two Archean mylonitic samples within the São José do Campestre Massif, northeastern Brazil. U–Pb in zircon dating indicates Paleoarchean (3.3 Ga) sedimentation followed by Mesoarchean (3.0–2.9 Ga) high temperature metamorphism in the mylonitic paragneiss sample, while the mylonitic amphibolite was emplaced during the late Neoarchean (2521 ± 22 Ma) and reached high-temperature conditions during shear zone development and deformation during the Paleoproterozoic (2.0 Ga). Inherited zircon grains in the amphibolite are consistent in morphology and ages with zircon grains from the host paragneiss. However, high temperature annealing and structure recovery upon entrainment of inherited zircon grains in the hot mafic magma led to homogenization of trace elements and preservation of internal textures. On the other hand, zircon grains from the host paragneiss accumulated radiation damage for a longer time, leading to self-destruction of the crystalline structure. Upon later low temperature fluid influx, non-formula elements were incorporated in metamict grains, as evidenced by the positive correlation between trace elements and radiation damage. Raman zircon dating indicates Cambrian to Late Paleozoic exhumation for these rocks, which agrees with U–Pb in zircon lower intercept ages. Although often avoided in geochronological studies, metamict zircon can provide important constraints on low temperature events. Collectively, these observations show a complex trans-crustal history of zircon recycling and exhumation from the Paleoarchean to the Paleozoic and the rock-dependent behavior of zircon upon fluid flow and deformation. The results have implications for the interpretation of trace 36 elements in naturally annealed zircon grains, especially those inherited in mafic rocks.

Revisiting the 10th‐Century Eldgjá Eruption: Modeling the Climatic and Environmental Impacts

AbstractThe 10th‐century Eldgjá eruption in Iceland is the largest basaltic flood lava eruption of the Common Era. However, the extent of its impacts is unclear due to limited historical records. Combining volcanology and ice‐core analyses from both recent and earlier studies, we present a gas emissions scenario for the Eldgjá eruption spanning 937 to 940 CE, co‐injecting volcanic sulfur and halogens. The combined tropospheric and stratospheric sulfur emissions are 3–8 times higher than those adopted for Eldgjá in existing paleoclimate simulations. Earth system modeling of this scenario under pre‐industrial conditions reveals a compound event with maximum northern extratropics surface cooling of C in summer‐autumn of 939 and 940 CE, prolonged Arctic sea ice growth, and large‐scale precipitation changes, concurrent with stratospheric ozone depletion and elevated pollution. These results imply that the combined climatic and environmental effects of the Eldgjá eruption may have significantly impacted human populations at the time.

Late Paleozoic potassic intrusions of the eastern part of the “Nikolaev Line” and associated W–Mo–Cu–Au mineralization: first isotopic U–Pb zircon data (LA-ICP-MS method) for rocks from the Adyrtor intrusions (Middle Tien Shan, Eastern Kyrgyzstan)

The paper presents first data on isotopic U–Pb study (LA-ICP-MS method) of zircon from intrusive rocks of the Adyrtor intrusions – a group of small intrusives situated in the easternmost part of the deep-seated fault system of the “Nikolaev Line”. Here, these intrusions cut through one of the oldest (1.8-2.6 Ga) complexes of the basement rocks of Tien Shan (metamorphic rocks of the “Kuilyu suite”). These intrusive rocks belong to the high-potassic calc-alkaline to shoshonitic series, with some geochemical signatures also of anorogenic (A-type) magmatism. These intrusions are accompanied by skarn and porphyry W–Mo–Cu–Au mineralization. Together with the other Au, W and Cu deposits and occurrences, they are parts of the extended metallogenic belt of Tien Shan. The concordant isotopic U–Pb age data for zircon autocrysts indicate the crystallization of quartz syenite (330.7±4.3 Ma) and quartz monzonite (329.5±5.8 Ma) in the latest Early Carboniferous. The distinct W–Mo “specialization” of ore mineralization related to the intrusions studied is in agreement with post-collisional tectonic setting during their emplacement, despite of their older or similar age compared to the ore-bearing plutons in more western segments of the Middle Tien Shan, which corresponded to subduction-related setting. This supports the possibility of the ‘scissor-like” (from east to west) closure of the Turkestan paleoocean that resulted in the earlier cessation of subduction in the eastern Tien Shan compared to the western Tien Shan. The rocks also contain zircon xenocrysts with older (in the order of 1.7–2.6 Ga) age that is in agreement with the age of the host metamorphic rocks of the Tarim craton basement. This highlights the possibility of magma chamber development in the continental crust, together with the magma chambers in the metasomatically-enriched subcontinental upper mantle, the latter being common for high-potassic magmatism.

North Kara and Vize–Ushakov Composite Tectono-Sedimentary Elements, Kara Sea

The North Kara Shelf and adjoining Severnaya Zemlya Archipelago represent a region of a complex tectonic interplay between two large Arctic fold-and-thrust belts: the Early Mesozoic Pay-Khoy–Novaya Zemlya–South Taimyr belt in the SW and the Late Paleozoic Taimyr–Severnaya Zemlya belt in the SSE and east; and an inferred early Carboniferous deformation zone in the north. Contractional deformations of different ages formed a series of basement highs and inverted sediment-cored swells that separate deeply subsided sedimentary basins. In the framework of this volume's terminology, this region consists of two composite tectono-sedimentary elements (CTSEs): the Vize–Ushakov CTSE and the North Kara CTSE. The principal difference between these elements is in the age of the underlying basement rocks, which, in turn, determines the stratigraphic span of the overlying sedimentary successions. In this chapter we characterize the geology of this remote Arctic region based on the available seismic data supported by published results and our own studies.

Delineating Structural Features Related to Hydrothermal Alterations for Possible Mineralization in Share Area, Kwara State Nigeria Using Aeromagnetic Data

Mineral deposits of significant economic value are abundant in the subsurface of Nigeria, presenting a promising alternative to the nations over dependence on petroleum revenues. This study interprets aeromagnetic data from Share, Kwara State, Nigeria, to delineate subsurface structural features associated with hydrothermal zones, which are key indicators for potential mineralization. The methodologies applied upward continuation, analytic signal, tilt derivative, and first vertical derivative (FVD). These offer insights into subsurface geology that can be broadly applied in geophysical exploration and mineral resource management. The results reveal structural trends predominantly in the NE–SW direction, with some NW–SE alignments, indicative of hydrothermal alterations linked to mineral deposits. The analytical signal map identified amplitude values ranging from 0.004 nT/m to 0.073 nT/m, with low and intermediate magnetic intensities linked to sediment-filled basement rocks and possible limestone and sandstone formations. High-gradient anomalies, 1.280 nT/m to 1.374 nT/m, were attributed to geological contacts, fractures, dykes, and hydrothermal vents. Depth estimates from the source parameter imaging map revealed hydrothermal and structural zones at depths ranging from 287.9 m to 1360.7 m, with deeper sources >1202.1 m indicating tectonic activity and mineralization potential. The FVD and Tilt Derivative maps further highlighted faulted zones, shear structures, and intrusive bodies with intensities between 0.031 nT/m and 0.041 nT/m, suggesting active tectonics. High magnetic anomalies in the central, northeastern, and southeastern regions were identified as prime targets for exploration, indicating magnetite-rich bodies, igneous intrusions, and hydrothermal zones. Integrated exploration strategies combining geophysical, geochemical, and structural data are recommended to refine anomaly delineation, prioritize field validation, and enhance mineralization discovery. These findings establish the Share area as a promising site for regional mineral exploration, supporting Nigeria’s diversification efforts toward sustainable resource development.

Investigating the Structural Framework Beneath Riyadh Region for Potential Geothermal Exploration Utilizing Geological and Geophysical Data

With growing electricity demand and an increasing focus on renewable energy, geothermal energy exploration is gaining prominence in Saudi Arabia. This study investigates the geothermal potential of the Riyadh region by integrating various geophysical data with geological information, providing a detailed image of the structural framework and thermal distribution. We generated a 2D density and susceptibility model using gravity and aeromagnetic data, constrained by well-logs information for sedimentary rocks. Distinct salt layers with low densities (2.15 g/cm3) were introduced in the model overlying the basement rocks, as well as unexposed faults, which may play a crucial role in the thermal regime in the study area. We produced a comprehensive thermal model extracted from the density and susceptibility model, along with temperature measurements from the Minjur Aquifer. The presence of the salt layer not only affects the geothermal gradient, but also suggests the potential for enhanced surface heat flow in specific areas. The results highlight the presence of a promising geothermal reservoir, the Minjur Formation, which exhibits significant potential for geothermal energy extraction due to its porosity, permeability, and sufficient thermal gradient ranging from 80 °C to 120 °C at depths of 2 to 3 km. These findings offer significant implications for Saudi Arabia’s transition to cleaner energy sources and support the future development of geothermal infrastructure in urban areas like Riyadh.