Search Results (410)

This study investigates the metasedimentary sequences of terrigenous–carbonate Sakar-type Triassic (TCSTT) and Sakar-type Triassic (STT) in the Sakar Unit, southeastern Bulgaria. Both share lithological similarities (alternation of carbonate–silicate schists, mica schists, marbles, and impure marbles) and are affected by post-Triassic metamorphism, but with differences in metamorphic grade and partly in the variation of potential sources of the sedimentary material. STT shows a higher metamorphic grade (lower amphibolite facies) when compared to TCSTT (lower greenschist facies). Petrographic observations and geochemical analyses indicate protoliths composed of arkosic sandstones, shales, and limestones derived from a quartz-dominated source with minor contributions from intermediate magmatic sources. The U-Pb geochronology of the detrital zircons reveals a dominant Carboniferous age complemented by an Early Ordovician age, which is consistent with the presence of Carboniferous–Permian igneous rocks in the basement. The presence of Early Paleozoic and Cambrian–Neoproterozoic zircons in the detrital zircon populations suggests that older rocks of the basement of the Sakar Unit and the Srednogorie Zone are also sources of the sedimentary material. Based on the immobile trace element content and discrimination diagrams, the siliciclastic component originates from rocks formed in a continental-arc setting. REE patterns indicate a negative Eu anomaly inherited from granitic-source rocks. Full article

The integration of petrological and geochemical analyses serves as an effective methodology for reconstructing depositional environments and constraining sediment provenance within distinct tectonic frameworks. This study investigates the provenance characteristics of the Silurian Kepingtag Formation in the northwestern Tarim Basin through an integrated approach combining field outcrop observations and laboratory analyses. Fieldwork covers the Sishichang, Dawangou, and Tongguzibulong sections, while laboratory analyses include clastic component identification, whole-rock major and trace element geochemical analysis, and rare earth element (REE) profiling. These efforts enable a systematic evaluation of sediment sources and their tectonic linkages. The research provides a theoretical basis for understanding the tectono-sedimentary framework of the northwestern Tarim Basin during the Early Silurian and offers significant guidance for reconstructing the lithofacies paleogeographic pattern of the basin during this period. Petrographic analyses reveal a lithological assemblage dominated by lithic quartz sandstones and lithic sandstones, with subordinate feldspathic lithic sandstones. Quartz exhibits secondary overgrowths. In a relatively stable tectonic environment, sediments undergo a gentle burial rate, which favors the formation of this phenomenon. Lithic fragments are dominated by magmatic lithics, indicating that the source contains magmatic rocks. Detrital component analysis reveals that the provenance of Kepingtag Formation sandstones in the study area is predominantly characterized by stable craton and recycled orogenic belt tectonic settings. Integrated geochemical datasets from major element compositions and trace element signatures constrain the provenance characteristics of the Kepingtag Formation sandstones. Major element ratios demonstrate predominant contributions from felsic igneous source rocks, while trace element ratios are diagnostic of sediment derivation from passive continental margin settings, consistent with prolonged tectonic quiescence along the northern Tarim cratonic margin during Silurian deposition The CIA index indicates that the Silurian Kepingtag Formation in the study area exhibits weak to moderate weathering. Integrating the above analyses, the Tabei Uplift—ancient craton setting—is interpreted as the likely provenance source for the sandstones of the Kepingtag Formation in the northwestern Tarim Basin. Full article

A necessary evaluation of freshwater ecosystem pollution levels and radiation risks remains crucial for maintaining environmental health, especially within economically developing areas. This study presents a comprehensive evaluation of the mineralogical, geochemical, and radiological characteristics of sediments in Nasser Lake, Egypt, to determine potential ecological and health risks. Forty sediment samples were collected from multiple locations, including both surface and bottom sediments, for analysis of textural attributes, mineral composition, potentially toxic elements, and natural radionuclides (²³⁸U, ²³²Th, and ⁴⁰K). Results revealed sand-dominated sediments with low organic matter content. The heavy mineral assemblages derived from Nile River inputs, wind-deposited materials, and eroded igneous and metamorphic rocks. Geochemical analysis showed that arsenic, cadmium, chromium, and lead concentrations exceeded upper continental crust background values, with enrichment factors and geo-accumulation indices indicating significant anthropogenic contributions. The pollution indices revealed heavy contamination levels and extreme ecological risks, which were primarily driven by arsenic and cadmium concentrations. Radiological assessments detected activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K below the world average, with hazard indices indicating minimal radiological risk except where localized hotspots were present. The study emphasizes the need for targeted monitoring and sustainable management practices to mitigate pollution and preserve the crucial freshwater environment of Nasser Lake. Full article

The rock cycle, a cornerstone of geosciences, describes rock formation and transformation on Earth. However, this Earth-centric view overlooks the broader history of rock evolution across the cosmos, with two fundamental limitations: (i) Earth-centric paradigms that ignore extraterrestrial lithogenesis, excluding cosmically significant rocks and processes, and (ii) disciplinary fragmentation between geological and astrophysical sciences, from the micro- to the macroscale. This review proposes an extension of the rock cycle concept to a cosmic scale, exploring the origin of rocks and their evolution from interstellar space, through the aggregation of solid materials in protoplanetary disks, and their subsequent evolution on planetary bodies. Through systematic analysis of igneous, metamorphic, and sedimentary processes occurring beyond Earth, we identify four major domains in which distinct dynamics govern the rock cycle, each reworking rocks with domain-specific characteristics: (1) stellar and nebular dynamics, (2) protoplanetary disk dynamics, (3) asteroidal dynamics, and (4) planetary dynamics. Here we propose the cosmic rock cycle as a new epistemic tool that could transform interdisciplinary research and geoscience education. This perspective reveals Earth’s rock cycle as a rare and invaluable subset of rock genesis in the cosmos. Full article

The 1.1 Ga Mesoproterozoic Midcontinent rift hosts the Eagle, Eagle East, and Tamarack Ni-Cu-PGE deposits and Embayment Prospect. These deposits are hosted by ultramafic igneous rocks and have some of the highest Ni-Cu grades on Earth. We use new bulk-rock data and published datasets (bulk-rock, mineral chemistry, and isotopic analyses) to examine major, minor, and trace element trends of both Midcontinent rift-related alkaline and tholeiitic intrusions. In addition, we compare the geochemical data to local kimberlite-hosted lower-crustal xenoliths and local igneous (Archean) and sedimentary (Paleoproterozoic) country rocks. We found the peridotite magma compositions dominantly consist of primitive mantle compositions with varying abundances of subduction-related components, alkaline-transitional melts, and local country rock contaminates (e.g., Baraga and Animikie Basin sediments). The subduction-related components are interpreted to be derived from previous Archean and Paleoproterozoic subduction events and likely hosted within the sub-continental lithospheric mantle. Importantly, these subduction-related components are also interpreted to have acted as oxidizing agents within the melt, stabilizing sulfate (+2 FMQ (fayalite–magnetite–quartz) to FMQ) while inhibiting sulfide crystallization as the magma ascended through ~50 km of the Superior craton. This study largely corroborates the previous findings with respect to the contribution of local country rock contamination to the Eagle–Tamarack peridotite host rocks, which is estimated to be minimal (<5%). However, the incorporation of <5% reductive pelitic siltstone contamination results in strong shifts in the oxygen fugacity of the peridotite melt, from +2 FMQ to slightly below FMQ, as determined from spinel Fe³⁺/∑Fe ratios. This shift in oxygen fugacity resulted in the transition from total sulfate (+2 FMQ) to sulfate + sulfide (<+2 FMQ to FMQ) to total sulfide (<FMQ). This shift in oxygen fugacity is a key contributor to the formation of Ni-Cu-PGE-rich massive sulfides within the Eagle peridotite. This study presents an expanded geochemical interpretation for the exploration of Midcontinent rift-related Ni-Cu-PGE deposits to include peridotites with subduction-like signatures and contaminated via <5% reductive sedimentary country rocks. Full article

Rare earth elements (REYs) are crucial components of billions of products worldwide. Transitioning from foreign to domestic REY sources requires utilizing both primary (i.e., carbonatites, alkaline igneous rocks, pegmatites, skarn deposits) and secondary (unconventional) sources (i.e., ion-adsorption clays, placer deposits, weathered rock, black and/or oil shales). Coal and coal-bearing strata, promising secondary REY resources, are the focus of this study. Understanding REY mineral associations in unconventional resources is essential to quantifying resource volume and identifying viable mineral separation and processing techniques. Highly REY-enriched (>750 ppm) coal or mudstone samples from the Uinta Region, Utah, USA, were selected for scanning electron microscopy (SEM) analysis. Energy dispersive X-ray spectroscopy (EDS)-determined REY enrichment occurs in: (1) a silt-size fraction (5–30 μm) of monazite and xenotime REY-enriched grains, (2) a clay-size fraction (2–5 μm) of monazite REY-enriched grains dispersed in the clay-rich matrix, and (3) organically confined REY domains < 2 μm. Findings suggest possible REY enrichment from multiple sources, including: (1) detrital silt-size grains, (2) volcanic ash fall, largely in clay-size grains, and (3) organic REY uptake in the peat swamp depositional environment. Full article

Rare earth elements (REEs) and trace elements, due to their relative stability during sedimentary processes, are effective geochemical proxies for sediment provenance. In the Dongdaohaizi Depression of the eastern Junggar Basin, the provenance of the Middle Jurassic Sangonghe Formation remains contentious. In this study, representative sandstone samples were systematically collected from all three members of the Sangonghe Formation in both the Dongdaohaizi Depression and its western margin. Through comprehensive petrographic and geochemical analyses, we obtained the following results. The Sangonghe Formation is primarily composed of feldspathic lithic sandstones, lithic sandstones, and minor lithic–feldspathic sandstones. The heavy mineral assemblage includes zircon, garnet, chromite, and rutile, suggesting source rocks of intermediate to acidic igneous, metamorphic, and mafic lithologies. The total REE contents range from 101.84 to 192.68 μg/g, with an average of 161.80 μg/g. The ∑LREE/∑HREE ratios vary from 6.59 to 13.25 (average 10.96), and the average δEu values are close to 1. The δCe value ranges from 1.09 to 1.13 (average 1.11). Trace element discrimination diagrams, including La-Th-Sc, Th-Co-Zr/10, Th-Sc-Zr/10, and La/Y-Sc/Cr ternary plots, indicate that most samples fall within the continental island arc domain, with a few plotting in the passive continental margin field. Comparison with potential surrounding source regions reveals dual provenances: an eastern source from the Kalamaili Mountains and a western source from the Zhayier Mountains. During the Early Jurassic, these two orogenic belts acted as distinct sediment sources. The Zhayier Mountains provided stronger input, with fluvial and tidal processes transporting sediments into the basin, establishing the primary subsidence center in the west of the depression. By the Middle Jurassic, continued thrusting of surrounding fold belts caused a migration of the lake center and the main depocenter to the western edge of the Dongdaohaizi Depression, while the former depocenter gradually diminished. Furthermore, sustained erosion and denudation of the Mosowan Uplift during the Early–Middle Jurassic reduced its function as a structural barrier, thereby promoting increased mixing between eastern and western sediment sources. The study not only refines existing paleogeographic models of the Junggar Basin, but also demonstrates the utility of REE–trace geochemistry in deciphering complex provenance systems in tectonically active basins. Full article

Alteration is a common metamorphic process in igneous formations and recorded geological information in different times and spaces. Owing to its unique location, the igneous rocks of the buried hills in the northern South China Sea exhibit complex lithology and alteration patterns resulting from multi-phase tectonic, magmatic, and climatic influences. Here, we report buried hills igneous rock samples with both hydrothermal alteration and weathering leaching. Based on multi-scale geophysical–chemical data—including scanning electron microscopy, core slice identification, petrophysical–chemical experiments, zircon dating, wireline logs, element cutting logs, seismic profiles, and others—we analyzed the multi-scale alteration characteristics of buried hills igneous rocks and proposed a four-stage alteration model related to Earth activities. Results demonstrate that tectonic movements develop continuous cracks enabling hydrothermal alteration, while burial-hill uplift facilitates weathering leaching. We further find that multi-phase tectonic movements and associated magmatic activities not only influence global hydrothermal cycles but also govern elemental migration patterns, driving distinct alteration mechanisms in these igneous rocks—including plagioclase metasomatism, hornblende replacement, and carbonate dissolution. Additionally, we identify the Cretaceous arid–cold climate as the primary controller for generating chlorite-dominated hydrothermal alteration products. These multi-scale alteration characteristics confirm Late Jurassic Pacific Plate subduction and Cretaceous South China Plate orogeny and may indicate an earlier initial expansion of the South China Sea. Full article

The Sverdrup Basin, Arctic Canada, is ideally situated to contain an archive of tectono-magmatic and climatic events that occurred within the wider Arctic region, including the exhumation of the adjacent (northeastern) part of the Canadian-Greenlandic Shield. To test this, a multi-analytical provenance study of Middle Jurassic to Cretaceous sandstones from the eastern Sverdrup Basin was undertaken. Most of the samples analysed were recycled from sedimentary rocks of the Franklinian Basin, with possible additional contributions from the Mesoproterozoic Bylot basins and metasedimentary shield rocks. The amount of high-grade metamorphic detritus in samples from central Ellesmere Island increased from Middle Jurassic times. This is interpreted to reflect exhumation of the area to the southeast/east of the Sverdrup Basin. Exhumation may have its origins in Middle Jurassic extension and uplift along the northwest Sverdrup Basin margin. Rift-flank uplift along the Canadian–West Greenland conjugate margin and lithospheric doming linked with the proximity of the Iceland hotspot and/or the emplacement of the Cretaceous High Arctic Large Igneous Province may have contributed to exhumation subsequently. The southeast-to-northwest thickening of Jurassic to Early Cretaceous strata across the Sverdrup Basin may be a distal effect of exhumation rather than rifting in the Sverdrup or Amerasia basins. Full article

To address overfitting due to limited sample size, and the challenges posed by “Spectral Homogeneity with Material Heterogeneity (SHMH)” and “Material Consistency with Spectral Divergence (MCSD)”—which arise from subtle spectral differences and limited classification accuracy—this study proposes a deep integration model that combines the Adaptive Boosting (AdaBoost) algorithm with a convolutional recurrent neural network (CRNN). The model adopts a dual-branch architecture integrating a 2D-CNN and gated recurrent unit to effectively fuse spatial and spectral features of rock samples, while the integration of the AdaBoost algorithm optimizes performance by enhancing system stability and generalization capability. The experiment used a hyperspectral dataset containing 81 rock samples (46 igneous rocks and 35 metamorphic rocks) and evaluated model performance through five-fold cross-validation. The results showed that the proposed 2D-CRNN-AdaBoost model achieved 92.55% overall accuracy, which was significantly better than that of other comparative models, demonstrating the effectiveness of multimodal feature fusion and ensemble learning strategy. Full article

The eastern Tianshan region in the Central Asian Orogenic Belt (CAOB) is characterized by multiple complex tectonic activity of uncertain historical contribution to the construction of the CAOB. This study utilizes a multi-proxy geochemical approach to characterize I-type monzogranite pluton rocks and their associated hornblende-rich dioritic enclaves to decipher the tectonic and magmatic evolution of the Xigebi area, eastern Tianshan. Zircon geochronology indicates a Triassic and Permian crystallization age of ca. 224.2 ± 1.7 Ma and ca. 268.3 ± 3.0 Ma for the host monzogranites and the dioritic enclaves, respectively. Major, trace and rare earth element distribution, together with Hf isotope systematics displaying noticeable positive εHf(t) anomalies for both rock types, point to partial melting of meta-mafic rocks in an intraplate extensional setting. The diorite was formed by the melting of lower crustal meta-igneous rocks mixed with mantle melts, and the monzogranite, predominantly from deep crustal meta-basalts contaminated by shallow metasedimentary rocks, with some degree of mixing with deeply sourced mantle magma. While both the host monzogranites and their dioritic enclaves are the products of upwelling magma, the younger Triassic monzogranites captured and preserved fragments of the dioritic Permian lower continental crust during crystallization. These multiple stages of magmatic underplating and crustal reworking associated with vertical stratification of the juvenile paleo-continental crust suggest the monzogranites and diorites indicate a change from a post-collisional setting to a regional intraplate regime on the southern margin of the CAOB. Full article

The Varnous Mt. area in the northern Pelagonian Nappe is characterized by the intrusion of an Early Permian pluton, with its tectonic setting and igneous petrology well constrained in earlier studies. The metamorphic basement rocks warrant further detailed investigation due to their complex history. These rocks are polymetamorphosed, preserving a sequence of overprinting metamorphic and deformational events. The metapelitic rocks have undergone an initial, pre-Carboniferous regional metamorphism of unknown grade before or during Hercynian Orogeny, followed by a thermal metamorphic event associated with the intrusion of the Varnous pluton at 297 Ma. The assemblage attributed to this event is And + Crd + Bt + Ms (west), while the first assemblage identified at the eastern part is Sil + Bt + Gt. Additionally, three regional tectonometamorphic events occurred during the Alpine Orogeny. For the Alpine events, the assemblages are as follows: first, the development of St + Gt + Chl + Kfs + Pl + Qtz at 150–130 Ma; second, retrograde metamorphism of these assemblages with Cld + Gt + Ser + Mrg + Chl ± Sil (Fi) at 110–90 Ma; and finally, mylonitization of all previous assemblages at 90–70 Ma with simultaneous annealing and formation of Cld + Chl + Ms. Full article

The Parnassos-Ghiona region constitutes the most significant bauxite-bearing province in Greece, with a well-documented history of research highlighting its geotectonic complexity and its importance for bauxite exploitation. Among the three principal bauxite horizons, the lower stratum (b1) remains the least thoroughly investigated, in contrast to the upper (b3) and intermediate (b2) strata. This disparity is primarily attributed to the limited surface exposure of the b1 horizon within the broader Parnassos-Ghiona Unit. The present study examines the characteristics of the b1 strata through an integrated mineralogical and geochemical approach. For the first time, the confirmed presence of rare earth element (REE) minerals within the b1 horizon is documented. Geochemical proxies, including REE distribution patterns and elemental ratios, indicate a genetic relationship with igneous parent rocks of intermediate to basic affinity. Full article

This study applies the Weighted Overlay Analysis (WOA) method integrated with GIS to assess landslide susceptibility along Al Figrah Road in Al-Madinah Al-Munawarah, western Saudi Arabia. Seven key conditioning factors, elevation, slope, aspect, drainage density, lithology, soil type, and precipitation were integrated using high-resolution remote sensing data and expert-assigned weights. The output susceptibility map categorized the region into three zones: low (93.5 million m²), moderate (271.2 million m²), and high risk (33.1 million m²). Approximately 29% of the road corridor lies within the low-risk zone, 48% in the moderate zone, and 23% in the high-risk zone. Ten critical sites with potential landslide activity were detected along the road, correlating well with the high-risk zones on the map. Structural weaknesses in the area, such as faults, joints, foliation planes, and shear zones in both igneous and metamorphic rock units, were key contributors to slope instability. The findings offer practical guidance for infrastructure planning and geohazard mitigation in arid, mountainous environments and demonstrate the applicability of WOA in data-scarce regions. Full article

The present study provides a detailed compilation and analysis of the bulk density and magnetic susceptibility of the rocks from the northwest Himalayas, Pakistan. The area is tectonically extremely complex and comprises sedimentary, metamorphic, and igneous rocks. These rocks range in age from Early Proterozoic to Recent. During the fieldwork, 476 rock samples were collected for density measurements and 410 for magnetic susceptibility measurements from the major rock units exposed in the study area. The measured physical parameters reveal a significant difference in the density and susceptibility of the rocks present in the investigated area. The sedimentary rock units belonging to the Indian Plate show the lowest mean values for bulk density, followed by metasedimentary rocks, Early Proterozoic rocks, igneous and metaigneous rock units of the Indian Plate, Indus Suture Melange Zone, and Kohistan Island Arc rocks, respectively. The magnetic susceptibility of sedimentary rock units of the Indian Plate has the lowest mean values, followed by metasedimentary rocks of the Indian Plate, igneous and metaigneous rock units of the Indian Plate, Early Proterozoic rocks of the Indian Plate, Kohistan Island Arc rocks, and Indus Suture Melange Zone. In brief, the sedimentary rocks of the Indian Plate have the lowest bulk density and magnetic susceptibility values, whereas the Kohistan Island Arc rocks have the highest values. Overall, the bulk density and magnetic susceptibility of rock units in the study area follow those predicted for different types of rocks. These measurements can be used to develop possible potential field models of the northwest Himalayas to better understand the tectonics of the ongoing continental-to-continental collision, as well as for many other geological analyses. Full article