摘要:

摘要:The Triassic was a crucial period in the tectonic evolution of the South China Block. Research on tectonic deformation during this period provides information on intracontinental orogenic mechanisms in South China. In this study, alongside thermochronological analyses, we examine the macroscopic and microscopic structural features of the Rongxian ductile shear zone, located south of the Darongshan granite in the southeastern part of Guangxi Province, on the southern margin of South China. Sinistral shear is indicated by the characteristics of rotated σ-type feldspar porphyroclasts, stretching lineations defined by elongated quartz grains and the orientations of quartz c-axes. LA-ICP-MS U-Pb dating of zircons from two samples of granitic mylonite and one of granite yielded ages of ca. 256 Ma. Furthermore, two samples of granitic mylonite yield muscovite 40Ar/39Ar plateau ages of 249–246 Ma. These results indicate that the Rongxian ductile shear zone resulted from Early Triassic deformation of the late Permian Darongshan granite. This deformation was likely related to the closure of the eastern Paleo-Tethys Ocean and the subsequent collision of the South China and Indochina blocks, during the early stage of the Indosinian orogeny.

摘要:The Sonid Zuoqi ductile detachment zone is located at the southeastern margin of the Central Asian orogenic belt (CAOB), striking EW and dipping to the S. The major rock type of the Sonid Zuoqi ductile detachment zone is mylonite derived from granite. The sequence of mylonite features is: (1) S and C foliations of mylonite, and (2) extensional crenulation cleavage (ecc) or C′ and the kinematic vorticity (Wk) value changed from 0.70 to 0.95 and from 0.37 to 0.69, respectively; the strain type of the mylonites within the Sonid Zuoqi ductile detachment zone is compressional to planar strain. The strong deformation mylonite and Halatu plutons yielded a zircon U-Pb age of 244 Ma and a zircon (U-Th)/He age of 214 Ma, respectively. Based on the strain and kinematic vorticity analysis, together with the zircon U-Pb and zircon (U-Th)/He ages and the regional tectonic background, the study area experienced three stage evolution: tangential simple-shear (244 Ma), simple-shear-dominated general shear represented by upper crustal extension (224 Ma) and pure–shear–dominated general shear represented by the Halatu pluton doming (214 Ma), which constrained the early Mesozoic NE–SW crustal extension at the southeastern margin of the CAOB. This NE–SW extension probably originated from the post-orogenic extensional collapse of the CAOB, subsequent exhumation being controlled by the far afield effects of the closure of the Mongol–Okhotsk belt.

摘要:Indicating the tectonic features of the Hanshan–Wuwei basin can reconstruct the framework of the basins formed in Mesozoic and further understand the Mesozoic tectonic evolution of the South China Block. Studies on surface structure, regional stress field and deep geophysical characteristics of the Mesozoic Hanshan–Wuwei basin in Lower Yangtze region were carried out. NE–NNE trending folds and faults developed in the northern margin of the basins. The reconstruction of tectonic stress fields indicates four stress stages dominating the basins’ evolution including NW–SE compression, N–S compression, NW–SE extension and NWW–SEE compression. 2D seismic profiles reveal coexistence of thrust, strike-slip and normal faults in the basin. Combined with regional geological studies, the geodynamic processes for the formation of the Hanshan–Wuwei basin can be divided into five stages: 1) During the Late Triassic, EW trending foreland basin was formed by N–S compression; 2) From Mid-Jurassic to Late Jurassic, continuous compression strengthened the foreland deformation and formed thrust nappes. In this stage, the integrated foreland basin was compartmentalized or fragmented, and transferred to the broken foreland basin; 3) NE-trending sinistral strike-slip movement at the beginning of the Early Cretaceous; 4) Regional extension resulted in normal faults and rift basins developing in the Late Cretaceous; 5) The NWW–SEE compression at the end of the Late Cretaceous caused NW sinistral strike-slip faults to form, which partly transformed the rift basin.

摘要:The study of sedimentary mélanges holds pivotal importance in understanding orogenic processes and unveiling geodynamic mechanisms. In this study, we present findings on zircon U-Pb isotopes and whole-rock elemental data concerning the recently uncovered Zongzhuo Formation sedimentary mélanges within the Dingri area. Field observations reveal the predominant composition of the Zongzhuo Formation, characterized by a matrix of sandstone-mudstone mixed with sand-conglomerates within native blocks exhibiting soft sediment deformation. Moreover, exotic blocks originating from littoral–neritic seas display evidence of landslide deformation. Our study identifies the depositional environment of the Zongzhuo Formation in Dingri as a slope turbidite fan, with its provenance traced back to the passive continental margin. Notably, this contrasts with the Zongzhuo Formation found in the Jiangzi–Langkazi area. Based on existing data, we conclude that the Zongzhuo Formation in the Dingri area was influenced by the Dingri–Gamba fault and emerged within a fault basin of the passive continental margin due to Neo-Tethys oceanic subduction during the Late Cretaceous period. Its provenance can be attributed to the littoral–neritic sea of the northern Tethys Himalaya region. This study holds significant implications for understanding the tectonic evolution of Tethys Himalaya and for reevaluating the activity of the Dingri–Gamba fault, as it controls the active deposition of the Zongzhuo Formation.

摘要:Identifying deformational mechanisms and associated structures at various scales, ranging from regional-scale structures to microscopic fabric, is crucial for the assessment of tectonic development. Thirty-three samples were taken from the Qazzaz metamorphic core complex to estimate the finite strain for felsic and mafic minerals. These samples included gneisses rocks, monzogranite, and metavolcano–sedimentary rocks for both the Thalbah and Bayda groups. Using the Rf/j and Fry methods, the axial ratios (XZ) range about 2.20 to 7.10 and 1.90 to 9.10, respectively. For various rock units, the strain measurements show moderate to highly deformation. Most of the observed samples show shallow WNW dipping along a N to WNW trend of finite strain (X). The short axes (Z) based to be subvertical foliation related with a subhorizontal foliation. The results demonstrate that contacts generated at semi-brittle to ductile deformation and that the strain of magnitude has the same value for different lithologic units. It concluded that nappe generation in orogens results from pure shear deformation.

摘要:The newly discovered Oligocene granitoids (33.1–28.7 Ma) at Pagele are magmatic rocks related to beryllium mineralization during the India–Asia late-collisional stage. This discovery provides an ideal example to study the late-collisional orogeny and beryllium prospecting in the Lhasa terrane. The Oligocene granitoids include porphyritic granodiorite, Stage I, II and III granites, and granitic pegmatite. Geochemical analysis shows that the porphyritic granodiorite is characterized by high SiO2, K2O, total ΣREE contents, and (La/Yb)N ratios; while the latter two by higher SiO2, lower ΣREE and (La/Yb)N ratios. Notably, the granitic pegmatite has extremely high Y/Ho, low K/Rb and Zr/Hf, and distinct REE tetrad effect?(1.14–1.21). This study suggests that the porphyritic granodiorite may be derived from partial melting of beryllium-rich materials composed of Lhasa ancient crust (70%–80%) and enriched Lhasa lithospheric mantle (20%–30%) under the tearing subduction of Indian slab. The three-stage granites and granitic pegmatite, which contain higher beryllium contents or beryls, were likely generated by highly fractionation of the porphyritic granodioritic magma or other homologous magma. Considering the possible genetic and spatial link between Indian slab tear and rifts, we suggest that highly-fractionated granites in rifting systems represent important Be prospecting targets in the Lhasa terrane.

摘要:The Guanpo pegmatite field in the North Qinling orogenic belt (NQB), China, hosts the most abundant LCT pegmatites. However, their emplacement conditions and structural control remain unexplored. In this contribution, we investigated it combining pegmatite orientation measurement with oxygen isotope geothermometry and fluid inclusion study. The orientations of type A1 pegmatites (Pf < σ2) are predominantly influenced by P- and T-fractures due to simple shearing in Shiziping dextral thrust shear zone during D2 deformation, whereas type A2 pegmatites (contemporaneous with D4) are governed by hydraulic fractures aligned with S0 and S0+1 stemming from fluid pressure (Pf < σ2). Additionally, type B pegmatites (Pf ≤ σ2) exhibit orientations shaped by en echelon extensional fractures in local ductile shear zones (contemporaneous with D3). The albite-quartz oxygen isotope geothermometry and microthermometric analysis of fluid inclusions in elbaites from the latest pegmatites (including types B and A2) suggest that the crystallization P-T for late magmatic and hydrothermal stages are 527.5–559.2℃, 320℃, 3.1–3.6 kbar and 2.0 kbar, respectively. Our observations along with previous studies suggest that the genesis of the LCT pegmatites was a long-term, multi-stage event during early Paleozoic orogeny (including the collision stage) of the NQB, and was facilitated by various local fractures.

摘要:The Tarim Craton is an ancient Precambrian continental block, and detailed knowledge of its thermo-tectonic history is crucial for understanding the early history of continental evolution. Abundant layered mafic rocks, which have commonly been regarded as basalts, occur within the Ediacaran Sugetbrak Formation (Fm.) in the Aksu region of the northwestern Tarim Craton. Clear intrusive features have now been discovered, including mafic rocks truncating Ediacaran sedimentary layers, exhibiting an intrusion-baked margin where they interact with both the overlying and bottom wall rocks, and displaying a fine-grained transition zone from their interior to their margins. The new findings demonstrate that these mafic rocks within the Aksu Ediacaran strata were not erupted basalts but instead are intrusive diabase dykes. Therefore, these mafic rocks cannot be used to constrain the timing of the Sugetbrak Fm. in the Aksu area, nor as marker layers for regional stratigraphic correlation. Furthermore, the Ediacaran thermo-tectonic evolution in this region, deduced from the assumption that the mafic rocks are lavas, needs to be revised.

摘要:The Tieshanlong ore field is an important part of the Nanling Range, which is famous worldwide for its W-Sn mineralization. Notably, the mineralization age of the Tieshanlong ore field is not well constrained, and our field investigation reveals that granitic emplacement occurred at different stages. However, previous studies have not distinguished these multiple stages of magmatism. The Tieshanlong granite complex is closely related to the Huangsha quartz vein-type W-Sn deposit and Tongling skarn-type Cu-W-Sn deposit in this field. Through field investigations and isotopic age analyses, this work studies the relationship between multistage magmatic activity and mineralization in the Tieshanlong ore field. LA-ICP-MS zircon U-Pb isotope analyses revealed that the first- and second-staged granites formed at 154.2 ± 0.6 Ma (MSDW = 1.4) and 151.2 ± 0.4 Ma (MSDW = 1.5), with zircon εHf(t) values ranging from ?13.1 to ?10.5 and from ?14.7 to ?11.1, respectively. These data suggest that the Tieshanlong granite complex was derived from the partial melting of ancient crustal material. LA-ICP-MS U-Pb dating of wolframite and cassiterite reveals that W-Sn mineralization occurred at 160–150 Ma, which agrees well with the U-Pb dating results of the second-staged granite within analytical errors. The magmatic activity in this ore field can be divided into three stages: 175–154 Ma, 154–150 Ma and 150–145 Ma. The quartz vein- and skarn-type W-Sn mineralization is closely related to second-staged fine-grained two-mica granite, and formed earlier than skarn-type Cu- mineralization. This study establishes a metallogenic model for the Tieshanlong ore field, and this model has important practical significance for identifying concealed W-Sn(-Cu) deposits around other granitic complexes in the Nanling Range.

摘要:In order to study the hydrocarbon generation (HCGE) characteristics of coal-bearing basins, the coal-measure source rocks of the Middle Jurassic–Lower Jurassic (MLJ) of the piedmont thrust belt in the southern margin of the Junggar Basin in Northwest China are taken as research objects. More than 60 MLJ samples were collected from outcrops and wells. Total organic carbon (TOC), rock pyrolysis (Rock–Eval), organic petrological, vitrinite reflectance (%Ro), and hydrous pyrolysis were performed to analyze the relevant samples. The pyrolysis gases and liquid products were measured, and then the chemical composition, as well as carbon isotopes of the gases, were analyzed. The results indicate that the MLJ source rocks have the capacity for large-scale gas generation. In addition, for coal-measure source rocks, the heavier the carbon isotope of kerogen (δ13Ckerogen), the lower the liquid hydrocarbon and hydrocarbon gas yield, and the easier it is to produce non-hydrocarbon gas. It is worth noting that when the δ13Ckerogen in organic matter (OM) is relatively heavier, the fractionation of its products may become weaker in the evolutionary process. The vital contribution of the MLJ source rock to natural gas resources in the study area was further confirmed by comparing it with the Jurassic source gas.

摘要:The Lower Cretaceous Manville Group of Upper McMurray Formation is one of the main bitumen reservoirs in Athabasca. In this study, the relationship between reservoirs heterogeneity and bitumen geochemical characteristics were analyzed through core and microscopic observation, lab analysis, petrophysics and logging data. Based on the sedimentology framework, the formation environment of high-quality oil sand reservoirs and their significance for development were discussed. The results indicate that four types lithofacies were recognized in the Upper McMurray Formation based on their depositional characteristics. Each lithofacies reservoirs has unique physical properties, and is subject to varying degrees of degradation, resulting in diversity of bitumen content and geochemical composition. The tidal bar (TB) or tidal channel (TC) facies reservoir have excellent physical properties, which are evaluated as gas or water intervals due to strong degradation. The reservoir of sand bar (SB) facies was evaluated as oil intervals, due to its poor physical properties and weak degradation. The reservoir of mixed flat (MF) facies is composed of sand intercalated with laminated shale, which is evaluated as poor oil intervals due to its poor connectivity. The shale content in oil sand reservoir is very important for the reservoir physical properties and bitumen degradation degree. In the context of regional biodegradation, oil sand reservoirs with good physical properties will suffer from strong degradation, while oil sand reservoirs with relatively poor physical properties are more conducive to the bitumen preservation.

摘要:Cambrian shales in China and elsewhere contain abundant oil and gas resources. However, due to its deep burial and limited outcrop, there has been relatively little research conducted on it. The Cambrian shale of the Tadong low uplift in the Tarim Basin of western China, specifically the Xidashan–Xishanbulake Formation (Fm.) and overlying Moheershan Fm. provide a case study through the use of organic petrology, mineralogy, organic and elemental geochemistry.

摘要:How gabbro affects the generation and expulsion of hydrocarbons in muddy surrounding rocks is clarified by analyzing thin section, major and trace elements, total organic carbon (TOC), pyrolysis, extracts and vitrinite reflectance data from source rocks in the Chunxi area the Dongying Sag, Bohai Bay Basin, eastern China. The results show that a magma intrusion brings copious heat to the source rocks, which promotes abnormal maturation of organic matter (OM) and rapid hydrocarbon generation. The CH4 and H2 produced by gabbro alteration play a role in hydrocarbon generation of source rocks. The hydrothermal process during magma intrusion provides many different minerals to the source rock, resulting in carbonate-rich surrounding mudstone. The carbonate and clay minerals produced by volcanic mineral alteration jointly catalyze the hydrocarbon generation of the source rock. The high-temperature baking of the intrusion results in hydrothermal pressurization and hydrocarbon generation pressurization, causing many fractures in the surrounding rock. The generated oil and gas are discharged through the fractures under diffusion and pressure. Mantle-derived CO2 is also conducive to the expulsion of hydrocarbons because of its strong enrichment capacity for hydrocarbons.

摘要:The Upper Cretaceous Qingshankou Formation black shales, deposited in the late Turonian (LTB shales), are the main source rocks of the Songliao Basin. The origins of organic matter enrichment of the shales is a contentious subject fuelling many ongoing debates. This study investigates the genesis of the organic matter-rich shale by using molecular geochemistry. The LTB shales can be divided into three sections. The Section I shales were deposited in saline, stratified and anoxic water conditions, which are related to seawater incursion events. At least three episodic and periodic seawater incursion events were recognized during Section I shale deposition. The Section II shales deposited in brackish to fresh and deep lake-level conditions with high primary productivity, which are related to lake-level transgression. The Section III shales were deposited under fresh and slightly oxidized water conditions, which are related to lake-level regression. Two organic matter enrichment models for the LTB shales are identified, that is, the seawater incursion model and the maximum lake-level transgression sedimentation model, which act on different shale sections, both playing significant roles in the enrichment of organic matter.

摘要:The Jenkyns Event, more widely known as the Toarcian Oceanic Anoxic Event (T-OAE), is marked by globally distributed negative carbon-isotope excursions, widespread oxygen depletion, and large-scale organic carbon burial, which indicate major climate/environmental perturbations in Earth’s surface systems during the Early Jurassic. Although extensive research has been conducted in European continental settings, particularly in the western peri-Tethys regions, the impacts of this event beyond Europe remains largely unexplored. Here, a multiapproach study including investigations into the spore-pollen assemblages, pyrite framboids, clay minerals, total organic carbon (TOC) levels, and organic carbon isotope (δ13Corg) levels in a lacustrine borehole section (MED1) from the Yin'gen–Ejinaqi Basin, North China, provides evidence of the occurrence of the Jenkyns Event and its extensive sedimentary responses in the eastern Tethys terrestrial systems. Two distinct spore-pollen assemblages have been identified in MED1 (drilling depth: 982.4 m to 1267.5 m), with the Cycadopites–Protopinus–Osmundacidites assemblage in the lower part (1267.5 m to 1132.9 m) indicating a middle Early Jurassic age and the Classopollis assemblage in the upper part (1132.9 m to 985.7 m) suggesting a Toarcian age. Framboidal pyrite data suggest more anoxic conditions during the deposition of black mudstone and shale intercalations in the lower part of the Classopollis assemblage (1132.9 m to 1066.9 m), which combined with organic carbon enrichment and negative δ13Corg excursions, are considered the paleoenvironmental response to the Jenkyns Event in the study area. Furthermore, the evolution of vegetation groups changed from plant groups characterized by bisaccate and cycad pollen, as well as fern spores, to vegetation groups represented by Cheirolepidiaceae pollen across the Jenkyns Event, as evidenced by spore-pollen data, together with the clay mineral assemblage change characterized by a notable increase in illite at the expense of kaolinite, suggests that while a subtropical-temperate climate persisted, a change toward warmer and drier conditions most likely occurred in the early Toarcian in the study area. In contrast to the humidification evidenced in many coastal settings, this aridification trend in the Yin'gen–Ejinaqi Basin aligns with the conditions in many inland areas. It is hypothesized that the underlying cause of these divergent changes may be linked to certain patterns of spatially variable water availability on land, potentially driven by extremified hydrological conditions.

摘要:Rock-ice avalanches have frequently occurred in the Eastern Himalayan Syntaxis region due to climate change and active tectonic movements. These events commonly trigger catastrophic geohazard chains, including debris flows, river blockages, and floods. This study focuses on the Zelongnong Basin, analyzing the geomorphic and dynamic characteristics of high-altitude disasters. The basin exhibits typical vertical zonation, with disaster sources initiating at elevations exceeding 4000 m and runout distances reaching up to 10 km. The disaster chain movement involves complex dynamic effects, including impact disintegration, soil-rock mixture arching, dynamic erosion, and debris deposition, enhancing understanding of the flow behavior and dynamic characteristics of rock-ice avalanches. The presence of ice significantly increases mobility due to lubrication and frictional melting. In the disaster event of September 10, 2020, the maximum flow velocity and thickness reached 40 m/s and 43 m, respectively. Furthermore, continuous deformation of the Zelongnong glacier moraine was observed, with maximum cumulative deformations of 44.68 m in the distance direction and 25.96 m in the azimuth direction from March 25, 2022, to August 25, 2022. In the future, the risk of rock-ice avalanches in the Eastern Himalayan Syntaxis region will remain extremely high, necessitating a focus on early warning and risk mitigation strategies for such basin disasters.

摘要:The understanding of the spatial distribution of soil organic carbon (SOC) and its influencing factors is crucial for comprehending the global carbon cycle. However, the impact of soil geochemical and climatic conditions on SOC remains limited, particularly in dryland farming areas. In this study, we aimed to enhance the understanding of the factors influencing the distribution of SOC in the drylands of the Songliao Plain, Northeast China. A dataset comprising 35,188 measured soil samples was used to map the SOC distribution in the region. Multiple linear regression (MLR) and random forest models (RFM) were employed to assess the importance of driving indicators for SOC. We also carried out partial correlation and path analyses to further investigate the relationship between climate and geochemistry. The SOC content in dryland soils of the Songliao Plain ranged from 0.05% to 11.63%, with a mean value of 1.47% ± 0.90%. There was a notable increasing trend in SOC content from the southwest to the northeast regions. The results of MLR and RFM revealed that temperature was the most critical factor, demonstrating a significant negative correlation with SOC content. Additionally, iron oxide was the most important soil geochemical indicator affecting SOC variability. Our research further suggested that climate may exert an indirect influence on SOC concentrations through its effect on geochemical properties of soil. These insights highlight the importance of considering both the direct and indirect impact of climate in predicting the SOC under future climate change.

摘要:As important geological data, a geological report contains rich expert and geological knowledge, but the challenge facing current research into geological knowledge extraction and mining is how to render accurate understanding of geological reports guided by domain knowledge. While generic named entity recognition models/tools can be utilized for the processing of geoscience reports/documents, their effectiveness is hampered by a dearth of domain-specific knowledge, which in turn leads to a pronounced decline in recognition accuracy. This study summarizes six types of typical geological entities, with reference to the ontological system of geological domains and builds a high quality corpus for the task of geological named entity recognition (GNER). In addition, GeoWoBERT-advBGP (Geological Word-base BERT-adversarial training Bi-directional Long Short-Term Memory Global Pointer) is proposed to address the issues of ambiguity, diversity and nested entities for the geological entities. The model first uses the fine-tuned word granularity-based pre-training model GeoWoBERT (Geological Word-base BERT) and combines the text features that are extracted using the BiLSTM (Bi-directional Long Short-Term Memory), followed by an adversarial training algorithm to improve the robustness of the model and enhance its resistance to interference, the decoding finally being performed using a global association pointer algorithm. The experimental results show that the proposed model for the constructed dataset achieves high performance and is capable of mining the rich geological information.