The Khourmo Cu deposit is located in the northeastern part of the Ravar Copper Belt (RCB), near the southwestern edge of the Tabas Block, situated within East-Central Iran. Copper exploration activities in this region have focused on three mining blocks: A, B, and C. The Khourmo deposit is primarily hosted by the Garedu Red Bed Formation (Fm.), which spans from the Late Jurassic to the Early Cretaceous and is composed of alternating layers of sandstone, micro-conglomerate, and siltstone. The sandstone units are subdivided into oxidized, mineralized, reduced, and bleached zones. The copper mineralization is mainly confined to the reduced gray sandstone layers, especially within ancient fluvial paleochannels, and is represented by a range of sulfide and secondary minerals, including chalcopyrite, bornite, digenite, chalcocite, covellite, pyrite, as well as supergene minerals such as malachite, chrysocolla, and various iron oxides. Geochemical analysis indicates that the sandstone Formations hosting the Khourmo Cu deposit derived from igneous parent rocks of intermediate to felsic composition on an active continental margin. Evidence such as the presence of permeable host rocks, the formation of bleached, oxidized, and reduced mineralized zones, the Cu mineralization within paleochannels, the association of copper with plant fossils, and the occurrence of salt domes beneath the Garedu Red Bed Fm. suggest that the Khourmo deposit represents a stratabound, sediment-hosted Cu mineralization. This type of mineralization likely developed immediately after primary diagenesis of the host rock and before deep burial.
There are a variety of multicriteria decision-making approaches to pinpoint the areas with significant mineral potential. Since exploration data need to be weighted or transformed into the same range before integration, and because there are multiple approaches to weighting, the chosen weighting strategy has a strong influence on the resulting prospectivity model. Consequently, a major challenge in mineral prospectivity mapping is the sensitivity of the integration methods to input data and the methods applied to generate weighted exploration evidence layers, which results in inconsistency in the recognized targets. In this paper, we perform a noise analysis to assess the sensitivity of integration and modeling results to the variation of weighted layers of the same input exploration data. For this, we use a dataset of porphyry copper mineralization in the Chahargonbad district within the Urumieh-Dokhtar Volcanic Belt of Iran, and we employ the root mean square (RMS) function as an alternative to the existing geometric average (GA) integration approach for mineral exploration targeting. Furthermore, the isolation forest (IForest) algorithm, an unsupervised anomaly detection method, is employed for the identification of anomalous patterns for comparison purposes. All three methods were evaluated using the prediction–area plot and the normalized density index, demonstrating the superiority of the RMS method over other approaches in identifying Cu mineralization. The proposed integration framework exhibits reduced sensitivity to noise and weighting variability in exploration datasets. The outcomes demonstrate that the RMS method outperforms both the GA and IForest approaches in recognizing exploration targets.
The Gejiu district, the world’s most economically significant primary tin producer, served as our test area for developing an advanced mineral exploration targeting system integrating multi-source geospatial data with machine learning. In this paper, we constructed an exploration target model for tin-polymetallic deposits in Gejiu district using ASTER and Sentinel-2A images, stream geochemical datasets, and both random forest (RF) and convolutional neural network (CNN) modeling approaches. The workflow comprised: (1) generation of fused remote sensing datasets with optimized spectral-spatial resolution; (2) extraction of hydrothermal alteration features (iron oxide, Al-OH, Mg-OH) and structural elements; (3) spectrum-area fractal analysis of geochemical anomalies; and (4) integration of these predictive layers through ensemble machine learning. RF predictive modeling (AUC = 0.83) effectively delineated tin-polymetallic prospective zones through its robust handling of categorical geospatial data, with SHAP (SHapley Additive exPlanations) analysis identifying iron-stained alteration intensity and Sn-W-Bi multi-element geochemical anomalies as the most statistically significant predictors. CNN architecture (AUC = 0.96) demonstrated superior performance in exploring complex spatial mineralization patterns, particularly in recognizing non-linear relationships between complex ore-controlling factors and mineral distribution. This study confirms the tin-polymetallic potential of the Gejiu district and establishes a reproducible, data-driven exploration framework that identifies strategic targets for future mineral exploration.
Exploration of epithermal Cu–Au–Ag deposits in the Saveh-Yazd copper metallogenic zone, within central Urmia-Dokhtar magmatic arc, Iran, is hindered by complex alteration patterns and structural overprinting. To address this, a novel integration of hyperspectral satellite data from EMIT (Earth Surface Mineral Dust Source Investigation) and PRISMA (PRecursore IperSpettrale della Missione Applicativa) with the Constrained Energy Minimization (CEM) algorithm was developed to map hydrothermal alteration and delineate high-potential mineralization zones. Using Adaptive Vertex Component Analysis (AVCA) for endmember extraction, major alteration assemblages, including argillic to advanced argillic, propylitic, oxidation/gossan, and carbonate–zeolitic, were mapped and found to correlate closely with regional faults such as Takht-e-Chaman, Khankeshi, and Kushk-e-Nosrat. Integration with field observations, petrography, and X-ray diffraction confirmed zones of silicification, sericitic, argillic, and propylitic alteration hosting Cu–Au–Ag sulfide mineralization. These results demonstrate that EMIT and PRISMA hyperspectral data combined with CEM processing provide an effective approach for early-stage, sustainable exploration in structurally complex terrains, highlighting the potential of next-generation hyperspectral missions for advancing critical mineral exploration across the Tethyan metallogenic belt.
Earthquake-triggered liquefaction can cause ground failure and damage to built-up structures. It is therefore necessary to determine the possible extent of the hazard during earthquakes. A common approach in predicting liquefaction occurrence is to relate the earthquake magnitude with its maximum liquefaction distance. However, while several empirical equations based on global datasets already exist, they contain sparse accounts from the Philippines. In this study, a total of 1,386 liquefaction observation sites from 130 earthquakes that occurred from 1619 to 2023 were reviewed and analyzed to determine empirical equations that may relate liquefaction occurrence with the distance to the epicenter and seismic source. Using the Linear Least Squares (LLS) method on liquefaction case histories, four bounding equations relating earthquake magnitude to the maximum liquefaction distance from the epicenter (Remax) and causative fault (Rfmax) were generated. The equation relating surface-wave magnitude (MS) to Remax is valid for 5.1 < MS < 7.8, while the equation relating MS to Rfmaxis valid for 5.1 < MS <7.6. The two equations relating moment magnitude (MW) to Remax and Rfmaxare valid for 4.70 < MW < 7.88. These equations are applicable for the Philippine setting and can be used to rapidly determine the possible extent of liquefaction for any given earthquake, especially in the absence of detailed geological or geotechnical data.
Immature organic-rich carbonate source rocks are widespread in sedimentary basins, serving as major oil shale resources and as analogs for thermally mature unconventional plays. Determining their baseline petrophysical and geomechanical properties prior to hydrocarbon generation is essential for predicting their behavior during advanced extraction. This study investigates a 20-meter vertical core from the Upper Cretaceous bituminous chalky marl interval of the Al Lajjun Graben, central Jordan, to evaluate vertical heterogeneity and identify the main controls on rock properties. An integrated workflow combined detailed core description, petrography, inorganic geochemistry, Rock-Eval pyrolysis, Multi-Sensor Core Logger (MSCL) data, spectral gamma-ray logging (SGR), and mechanical testing. Multivariate statistical methods, including principal component analysis (PCA) and hierarchical clustering on principal components (HCPC), were applied to establish a chemofacies classification. Five lithofacies, three chemofacies, and four chemostratigraphic zones were identified, indicating marked vertical variability. Bulk density ranges from 1.65 to 2.40 g/cc, porosity from 14 to 36%, and compressional wave velocity (Vp) from 2521 to 6383 m/s. Unconfined compressive strength (UCS) ranges from 19 to 132 MPa, Leeb hardness from 375 to 710 HLD, and total organic carbon (TOC) ranges from 2 to 17%. Dolomite and silica enrichment increase density and strength, whereas elevated clay content and porosity reduce mechanical competence. Porosity is negatively correlated with density, Vp, strength, and brittleness, but positively correlated with TOC. Collectively, mineralogy, diagenesis, porosity, and organic content govern vertical variability, improving reservoir characterization, exploration planning, and providing a global analog for immature unconventional carbonate source rocks.
Accurately and rapidly determining the relationship between induced magnetization (Mi) and remanent magnetization (Mr) of magnetic anomaly sources remains a critical challenge in magnetic exploration. It directly affects the reliability of geological interpretations inferred from magnetic survey data. Drawing on the temporal variations of the geomagnetic field, this study develops a set of theoretical formulas for the magnetic anomaly variation (A), its theoretical maximum (Amax), and the variation rate (ηa), under the assumption of uniform magnetization and co-directional remanent magnetization with the geomagnetic field. The results demonstrate that the magnetic anomaly variation (A) can serve as an indicator of the relationship between Mi and Mr. Under specific conditions, the magnetic anomaly variation (A) can assist in identifying whether the magnetic anomaly source originates from an iron ore body. Overall, this study offers valuable insights for magnetic anomaly studies, with particular relevance to iron ore exploration.
A systematic study of highly fractionated S-type granites enhances our understanding of tectonic evolution and rare metal mineralization. The Longling granites are surrounded by several rare metal deposits. Zircon U-Pb ages, whole-rock geochemistry, ore-forming elements, and Sr-Nd-Pb isotopic data were obtained from Longling granites to constrain their metallogenic and tectonic significance. The zircon U-Pb dating indicates that the Longling biotite granite and two-mica granite were formed at 88 Ma and 77 Ma, respectively. They exhibit strong peraluminous features (A/CNK = 1.23-1.82), with high SiO2, Al2O3, volatile elements (F, B), and Rb/Sr (17.5-100.8), and low MgO (0.03-0.21 wt%), total iron (Fe2O3t = 0.62-1.31 wt%), and Nb/Ta (2.1-5.0). These geochemical features, along with enriched Nd isotopes (epsilon Nd(t) =- 13.6 to-13.1) and Pb isotopic compositions ((206Pb/204Pb)i = 18.19-18.91, (207Pb/204Pb)i = 15.69-15.75, (208Pb/204Pb)i = 39.06-39.20), suggest that they are highly fractionated S-type granites derived from muscovite-dehydration melting of ancient crustal pelite. We infer that the breakdown of rare-metal-enriched minerals (muscovite) and volatile-caused prolonged fractional crystallization caused the extraordinary enrichment of Sn, W, Nb, and Ta in the Longling Sn-W-Nb-Ta poly-metallic deposit. Simulation calculations suggest that the two-mica granite underwent the most extensive fractional crystallization and is the most enriched in rare metals, making it a prime target for future exploration. Based on geological and geochemical evidence, we propose that the Longling granites formed in a syn-collision compressional tectonic setting as a result of the collision between the Tengchong and Baoshan blocks following the closure of the Meso-Tethyan Nujiang Ocean.
Saltpeter deposits preserved in karst caves are large and widely distributed in southwest China. These deposits historically served as the principal source of saltpeter for traditional gunpowder production in pre-industrial China. Despite their long mining history, the sources and enrichment mechanisms of these cave nitrate deposits are poorly constrained. This study presents a comprehensive isotopic analysis of cave nitrate deposits, combining geological field observations in Southwest China. The active formation of nitrate deposits in the Dashiwei Tiankeng (DT) system (Guangxi) was discovered. The continuous emission and accumulation of nitrate–bearing aerosols occurs through gas emission pores distributed across ground and cave walls in the DT system. Consistent δ15N and δ18O values of nitrate in between Dashiwei Cave and Jinfo Cave reveal a common nitrate formation pathway across temporal and spatial scales. The absence of oxygen isotope mass–independent fractionation definitively excludes atmospheric nitrate sources, confirming that soil ammonium is the important precursor through microbial nitrification. Exceptionally low sulfate δ34S values in Jinfo Cave occur due to large–scale sulfide oxidation in coal–bearing strata. We propose that these cave nitrate systems originate primarily from water vapor above subterranean rivers rather than from conventional bat guano or drip water sources, with transport and enrichment mediated by a novel evaporative-refrigeration mechanism of the karst cave system. When gas flows through narrow cave passages into large chambers, rapid pressure release induces water vapor cooling condensation, and humidity drop results in the supersaturation of soluble salts, leading to the precipitation of salt aerosols.
This study investigates the distribution and enrichment patterns of the rare earth elements (REEs) in phosphorites from the Hirapur Formation of the Paleoproterozoic Bijawar Group in the Mardeora area, Madhya Pradesh, India. The geochemical analysis of phosphorite samples reveals that the total REE concentrations ranging from 34.71 to 215.65 ppm (mean: 99.13 ppm), with middle rare earth element (MREE) exhibiting significant enrichment over light rare earth element (LREE) and heavy rare earth element (HREE) having (MREE/LREE)(N) and (MREE/HREE)(N) ratios averaging 6.39 and 3.11, respectively. The PAAS-normalized REE patterns are characterized by MREE enrichment and minor negative or no Ce/Ce* anomalies (Ce/Ce*: 0.80-1.01). Positive Eu/Eu* anomalies (1.06-1.52) and Y/Y* variations (0.47-1.67) are linked to suboxic pore-water conditions during late-stage diagenetic processes and the significant influence of detrital input (Y/Ho similar to 28.78). Geochemical proxies, including La/Nd, Y/Y*, La/Yb, and La/Sm ratios, indicate limited weathering influence and diagenetic alteration, with REE enrichment primarily driven by substitution and recrystallization during late diagenesis. The studied phosphorites, despite having a low to moderate Sigma REE concentration, can be categorized as promising, with a tendency towards being a highly promising critical REE resource.
The Alborz Mountains of northern Iran stand out as an exceptional site for studying the Ediacaran-Paleozoic evolution of the northern Gondwana margin. The Alborz forms the inverted continental shelf of the Central Iranian microcontinent that was part of the northern Gondwana margin until the Permian period. Here, we present a paleostress analysis of the Paleozoic tectonic evolution in the eastern Alborz, supported by published studies of stratigraphy, petrology and regional tectonics. This analysis confirms and supplements the findings of a previous study in the central Alborz. The two studies complement each other. Late Neogene internal deformation has had less of an effect on the central Alborz, whereas the stratigraphy is more comprehensive in the eastern Alborz. The overall aim of the paleostress analysis in the central and eastern Alborz is to elucidate the Paleozoic structural-tectonic framework and the transition of geodynamic regimes, from the Cambrian active margin of Gondwana to the Permian Paleotethys post-rift passive margin of the Central Iranian Microcontinent. The paleostress tensor analysis of fault-slip data confirms that the Alborz Margin was dominated by a main N-S-directed (present-day reference frame) extension during the Paleozoic. This extension was nearly perpendicular to the main basin-bounding normal faults and the margin. The Paleozoic stress field remained unchanged during successive geodynamic regimes, from proto-Tethys subduction to Neotethys rifting. Research on past plate rotations and internal deformation in the Alborz and Central Iranian microcontinent may benefit from the findings.
The Eocene magmatism in NE Iran represents a significant component of the broader Cenozoic magmatic activity associated with the subduction of the Neotethys Ocean beneath the Iranian plateau. This study focuses on the petrogenesis, geochronology, and mineralization of magmatic rocks from the Nokeh area, which hosts Fe-skarn mineralization, in comparison with the Torud intrusions, associated with Cu-Au mineralization. Both sites are located in the northeastern sector of the Iranian back-arc belt, behind the Urumieh-Dokhtar magmatic front. Our comprehensive dataset includes bulk rock geochemistry, zircon U-Pb ages, zircon trace element compositions, and Lu-Hf isotopes. Geochemical and isotopic signatures indicate that Torud rocks are predominantly intermediate to felsic, derived from a metasomatized mantle source with limited crustal interaction, whereas Nokeh rocks display broader compositional diversity (e.g., zircon Hf isotope) and higher degrees of crustal assimilation. Zircon U-Pb dating constrains magmatic activity in Nokeh between 53 and 52 Ma, coeval with Eocene arc-backarc magmatism across Iran. Zircon trace element compositions and Hf isotope data further reveal distinct melt evolution pathways at each site. These differences in magmatic evolution correlate with contrasting mineralization styles: iron-rich skarn formation in Nokeh versus Cu-Au porphyry-style mineralization in Torud. The results provide new insights into the spatial and temporal variation of Eocene back-arc magmatism and its control on the metallogenic fertility in NE Iran.
This study presents a novel gravity anomaly separation technique and demonstrates its application in delineating the crustal density structure and Moho depth configuration of the East Vietnam Sea (South China Sea). The proposed method employs correlation analysis between Bouguer gravity anomalies approximated by higherorder two-variable polynomial functions and their upward-continued counterparts at varying altitudes to isolate the regional gravity field. The resulting regional component, associated with long-wavelength gravity signals, was used to model the depth to the Moho boundary, while the residual component, reflecting shortwavelength anomalies, was inverted to estimate lateral variations in crustal density. The results reveal that crustal density varies from approximately 2.54 g/cm(3) in sedimentary basins to about 2.90 g/cm(3) along the midoceanic ridge, indicating significant lithological contrasts. The Moho depth ranges from similar to 8 km beneath the midoceanic ridge to similar to 32 km beneath the southwestern margin, particularly near the Red River basin. These observations correlated well with previous interpretations derived from ocean bottom seismometer data, validating the effectiveness of the approach. This study develops an integrated regional-residual separation and inversion framework that refines constraints on crustal architecture while offering critical geodynamic insights for delineating tectonic domains with potential resource significance. It offers a new perspective for gravity-based crustal modeling and provides a first-order geophysical framework for understanding the lithospheric structure of the East Vietnam Sea. The method also demonstrates potential for global and broader applications in tectonic studies and regional geodynamic investigations.
Several volcanoes in Japan have summit craters filled with water, including Zao, Kusatsu-Shirane, Kirishima, and Aso volcanoes. Aso Volcano, located in central Kyushu, is an active caldera volcano with a crater lake whose water volume varies from nearly zero to full capacity depending on volcanic activity. Following the latest eruption of Aso Volcano in October 2021, we conducted UAV-based hot water sampling at the Nakadake First Crater (NFC) in 2022, 2023, and 2024. These efforts enabled the development of sampling method using a weight, rope, and sterilized sampling bottle with a long fluorinated ethylene propylene (FEP) sleeve, allowing hot water collection at temperatures higher than previously possible. We found that crater lake chemistry changed drastically within one year, with sulfate concentrations decreasing rapidly from 211,900 ppm in 2022 to 19,940 ppm in 2023 (approximately one-tenth), while temperature changes were smaller (about 5 °C). Compared with intermittent records from 1993 to 2009, these sulfate values were up to twice as high as previously reported maxima. Such deviations suggest increased inputs of magma-derived fluids, possibly associated with the 2021 eruption. Based on compiled data, we propose that extremely high chlorine concentrations in lake water can serve as significant indicators for predicting forthcoming eruptions, regardless of temperature changes. Our findings indicate that short-interval monitoring of the NFC is necessary to understand the transition between open and closed hydrothermal systems, especially after eruptions. Combined with UAV-based methods capable of sampling during eruptions, this approach will enhance understanding of crater lake hydrothermal dynamics and eruption forecasting.
The southern Jinsha Orogenic Belt records the subduction-accretion-collision processes during the closure of the Paleo-Jinsha Ocean. Detailed structural analysis conducted along this belt and U-Pb zircon dating of tectonic-related plutons put robust constraints on a three-stage deformation history of the southern Jinsha orogenesis. The D-1 deformation is developed within the high-grade metamorphic complex. Based on parallelism between multiscale structures, two plutons (SK21-1 & -2) are inferred as syntectonic and constrain the D-1 deformation to Middle Permian (269 similar to 267 Ma). The D-2 deformation is characterized by pervasive fabrics outcropped through the whole belt. An internal undeformed pluton (SK18), which was affected by the D-2 deformation at its margin, combined with post-D-2 plutons, constrain the D-2 deformation to 258 similar to 240 Ma. The D-3 deformation is interpreted as a local effect of pluton diapirism due to its density-driven vertical structures and limited range of distribution, rather than a regional deformation. Combined with previous published Early Permian to Late Triassic geological records, we propose that the D-1 deformation records an accretionary orogenesis during the subduction of the southern Jinsha oceanic lithosphere, the D-2 deformation represents the Early-Middle Triassic continental collision between the eastern Qiangtang terrane and Zhongza massif, and the D-3 deformation was generated by the post-collisional pluton diapirism. Moreover, based on the uniformly west-dipping S-2 foliations and west-plunging L-2 lineations with local west-side up, we suggest a westward subduction of the southern Jinsha oceanic plate.
Coastal terraces, whether erosional, depositional, or bio-constructed, have been widely used to quantify Late Cenozoic vertical deformation and relative sea-level changes. Here, we review and investigate the Holocene coastal terraces of Sumba Island, Indonesia. We describe fifteen coastal sites, evenly distributed between the South and North coasts. The terraces are Holocene age, based on 14C and U/Th ages. We show that the preservation of coastal terraces in Sumba is favoured on the leeward coast (North). Holocene and older Pleistocene coastal terraces are almost absent on the windward coast (South), although modern coral reefs almost ubiquitously thrive. The morphology and the nature of the bedrock varies between the two sides of the island: while sequences of earlier Pleistocene coral reef limestones dominate in the North, Miocene/Pliocene tuffs and pelagic carbonates outcrop on the southern coast. The elevations of the Holocene inner edges range from 2.4 +/- 0.7 to 6.9 +/- 0.7 m above the present mean sea level. Despite disparate uplift rates, the three preserved windward terraces (out of the seven sites investigated) generally have a higher inner edge than leeward terraces. We conclude that neither glacio-eustatic oscillations, vertical deformation rates nor hydrodynamics by themselves can explain the variability in inner edge elevations on Sumba, but only a complex combination of these processes. Finally, our study serves as a solid basis for future investigation of the Holocene landforms of the island of Sumba and other similar tropical coastal zones.
The Cenozoic uplift of the North Qinling Range has profoundly influenced climatic and ecological patterns across northern and southern China. However, key aspects of this orogenic event, including its principal phase(s) of exhumation, total magnitude, and detailed evolutionary processes remain poorly constrained. We present a series of apatite and zircon (U-Th)/He ages from a drill core and surface relief of Zhongnan Mt., in the middle part of North Qinling Range. Comparative analysis of apatite (U-Th)/He age discrepancies between drill core and surface samples provides a perspective to figure out variation of isotherms and then helps figure out that fault activity and topographic wave length were dominant controls on isotherm geometry in the study area. The composite vertical pseudo-transect constructed from apatite and zircon (U-Th)/He ages indicates a very fast cooling period since at least similar to 82.7 Ma and lasted to 77 Ma, followed by a relatively slow cooling stage until 49 Ma, and then a slow cooling period to 33 Ma. These three exhumation stages are widely documented in the adjacent region, with the subduction of the Pacific Plate considered the primary driving mechanism.
Soil contamination by heavy metals poses significant risks to ecosystems and human health, necessitating assessments beyond total concentrations to evaluate bioavailability and mobility. This study investigates heavy metal distribution in soils derived from ultramafic-rich ophiolitic complexes in the Sabzevar Range, northeastern Iran, focusing on Nickel (Ni), Chromium (Cr), and Cobalt (Co). Surface soils from Davarzan (sections A and B) and Namen areas were analyzed using total digestion, The diethylenetriaminepentaacetic acid (DTPA) single-step extraction, and The European Community Bureau of Reference (BCR) sequential extraction protocol to assess total concentrations, bioavailability, mobility and geochemical partitioning of heavy metals. Results indicate elevated total Ni and Cr concentrations exceeding Iranian maximum permissible concentrations (MPCs), with Ni and Cr classified as "heavily polluted" via geoaccumulation indices (I-geo >= 3). DTPA extraction revealed higher bioavailability in agricultural soils, emphasizing anthropogenic influences. BCR sequential extraction demonstrated that > 70 % of Co, >80 % of Cr, and > 75 % of Ni were sequestered in residual fractions, suggesting limited inherent mobility. However, absolute bioavailable and mobile fractions exceeded MPC thresholds in several samples, highlighting latent ecological risks. Spatial variability in metal behavior correlated with lithological provenance: ultramafic-derived soils (Davarzan Section A) exhibited maximal metal enrichment and mobility, while alluvial soils (Namen) showed dilution effects. Agricultural practices increased organic carbon and phosphate content, enhancing metal retention and mobilization. This study underscores the critical role of speciation analysis in environmental risk assessments in ultramafic terrains. Integrating bioavailability metrics with total concentrations provides a robust framework for prioritizing remediation strategies in contaminated ecosystems.
In this paper, we present results of sedimentary facies analysis and U-Pb dating of detrital zircons from the Lower Cretaceous uranium-bearing sandstones in northern Sichuan Basin, to investigate the influence of provenance and sedimentation process on the temporal and spatial distribution of uranium-bearing sandstones. The results show that there are four major zircon U-Pb age populations that cluster at 2800-2200 Ma (group 1), 2200-1600 Ma (group 2), 1600-538 Ma (group 3), and 538-145 Ma (group 4), respectively. The age data, combined with regional tectonic events, indicate that zircons of group 1, group 2 and group 3 in the western part of the Sichuan basin were mainly derived from the Bikou and Songpan-Ganzi terranes, and the varieties of group 4 were mainly originated from the Longmenshan thrust belt. Whereas zircons of group 1, group 2 and group 3 in the eastern part of the Sichuan basin were primarily sourced from the South Qinling Belt and the Bikou terrane, and those of group 4 were likely affiliated with the Hannan Micangshan massif and Dabashan thrust belt. The Paleozoic lowgrade metamorphic rocks and Mesozoic sedimentary rocks and minor intermediate-acidic magmatic and volcanic rocks represented by group 4 zircons are considered as the primary source for uranium mineralization in the Lower Cretaceous sandstones. The Neoarchean to Proterozoic metamorphic rocks and plutonic and volcanic rocks, as revealed from the group 1, group 2 and group 3 zircons also contributed partially to the uranium sources.
