Geological Journal最新文献

The Wayand-Nilambur granulite terrain in Kerala (India) is well-known for vein-type gold mineralization within the quartz veins. Based on the previous geological, petro-physical and geophysical characteristics of Wayand-Nilambur gold deposit, the integrated geophysical survey was carried out to delineate the favourable prospecting zones. In the present study, detailed ground geophysical surveys, that is, magnetic, electrical resistivity/chargeability surveys were carried out in an area of 2 km² in Kattikallu and Kalkulam blocks to delineate the ore deposits in terms of depths and extensions through the structural shear zone, locate the anomalous sources and the geometry of the Au-rich sulphide zone and its depth continuity in the subsurface. These surveys brought out prominent resistivity and chargeability zones over known magnetite-quartz veins that are associated with low-grade sulphide bands at the central part of the Kattikallu block. The prominent potential zone is characterized by strong bipolar magnetic anomalies over the quartz veins. Based on the 2D inversion of resistivity data, the resistivity low zone of order 80–600 Ω m and chargeability of 21–25 mV/V are observed at a depth range of 5–20 m. In Kalkulam block, the magnetic survey has also brought out high intensity anomaly zones over quartz veins, the same quartz veins are mapped by high chargeability of 10–35 mV/V and low resistivity of 185–400 Ω m. The dipole-dipole configuration produces two parameters, that is, resistivity and chargeability, these methods distinguish the anomalies along the two selected profiles in the study area. An attempt was made for combining the resistivity and chargeability values to identify the anomalous zone boundaries. The results of inversion indicated that the conductive bodies are located at the subsurface, with depths ranging from 5 to 25 m. Based on this integrated geophysical study, we suggested two borehole sites for further geo-scientific studies in view of mineralization.

Pore-throat structure is a key factor that influences the storage and fluid flow capacity of tight sandstone reservoirs. Taking the tight sandstone reservoir of Xu2 Fm in Zhongba area as an example, the reservoir quality, pore-throat type and pore size distribution of tight sandstone in the study area were described by casting thin section, scanning electron microscope and high-pressure mercury injection test. In order to quantitatively characterize the complexity and heterogeneity of pore-throat structure, fractal analysis was performed using mercury saturation and pore size data. This study mainly reveals the relationship between the geometric shape characteristics and fractal dimension of the binary pore structure of ultra-low permeability tight sandstone and clarifies the influence of different scale pore throats on reservoir physical properties. The results indicate that the physical properties of the reservoir in the study area are poor, the pores are mainly intergranular pores and dissolution pores, the throat is flake and necked and the pore size distribution range is large. The fractal curve obtained by the mercury saturation method shows a significant turning point, and the pore-throat system is divided into two types: small-scale and large-scale. The fractal dimension of large-scale pore throat is greater than the three-dimensional Euclidean space dimension, which does not conform to the fractal theory. The fractal dimension of small-scale pore throat is closely related to the pore-throat structure and has obvious fractal characteristics. The geometric shape of binary pore-throat structure in tight sandstone is the main factor affecting the difference of fractal dimension. The development of small pores in sandstone is positively correlated with the total porosity, but its contribution to permeability is relatively low. The physical properties of tight sandstone are mainly controlled by the development degree of large-scale pore throat.

Submarine geohazards significantly threaten human economic activities and essential infrastructure. Based on multi-beam data and high-resolution 2D seismic data, two types of submarine geohazards are identified: direct and indirect geohazards on the northwestern continental slope and the Xisha Uplift of the South China Sea (SCS). Direct geohazards include submarine landslides and active faults, while indirect geohazards include buried channels, submarine canyons, pockmarks, volcanoes and magma diapirs. This study comprehensively analyzes geomorphological features, including their characteristics, genesis and distribution. Statistical analysis reveals that the gradient of the Xisha Uplift slope is steeper than the shelf break, making it a more unstable region. However, assessing disaster potential indicates that submarine geohazards at the shelf break pose a greater threat than those at the Xisha Uplift. Many factors, including tectonic activity, sediment supply and relative sea-level changes, influence submarine geohazards' formation. These hazards do not occur in isolation but often interact with one another. The research results provide a scientific basis for predicting deep-sea geohazards near the northern continental margin and Xisha Island in the SCS.

This comprehensive study investigates the organic matter characteristics within the Late Cretaceous Rakopi and Taniwha formations, based on data from four exploration wells situated in New Zealand's Taranaki Basin. It employs a multifaceted approach, integrating bulk geochemical analyses, biomarker measurements and carbon isotopes to unveil the geological history of these formations. Analytical results include total organic carbon content, ranging from 7.27 to 75.78 wt%, and generation potentials spanning from 28.24 to 309.16 mg hydrocarbon/g rock. These observations underscore the source rock potential of these Late Cretaceous strata. These rocks show a mixed organic matter of hydrogen-rich Type II and Type II/III kerogens, as evidenced by hydrogen index values (HI) between 237 to 428 mg hydrocarbon/g rock. These formations demonstrate promise potential for both oil and gas generation. Biomarker analysis uncovers distinct signatures, featuring a pristane/phytane (Pr/Ph) ratio ranging from 3.27 to 10.91, a Tm/Ts ratio surpassing 7 and elevated concentrations of C₂₉ regular steranes relative to C₂₇ and C₂₈ regular steranes. These biomarker characteristics suggest a composite organic matter composition, influenced by terrigenous organic matter, likely deposited in oxygenated fluvial deltaic environments. Bulk carbon isotopic data corroborate these findings, highlighting the abundance of terrigenous organic matter. Collectively, these insights reveal that the coal and carbonaceous shale intervals in the examined wells are in the early stages of oil generation. Therefore, the Rakopi and Taniwha formations have not yet yielded commercially viable oil and/or gas quantities. In this case, these formations hold substantial promise for future exploration activities in relatively deep wells, with limited oil expulsion from coals.

The Weiningbeishan fold-thrust belt (WFTB), located in the transitional zone of the Tibetan Plateau, Alxa Block and Ordos Basin, is an ancient intracontinental orogenic belt. In this article, structural analysis is conducted to more finely reveal differential deformation between the Devonian and Carboniferous strata in the WFTB. We found that the E–W-trending open folds are mainly developed in the Upper Devonian Zhongning Formation (D₃z), while the E–W-trending close and tight folds are mainly developed in the Carboniferous strata. The N–S minimum shortening strain of the bottom boundary of Member 2 of the Upper Devonian Zhongning Formation (D₃z²) is 21.1%, whereas the N–S minimum shortening strain of the bottom boundary of Member 2 of the Upper Carboniferous Danliangshan Formation (C₂d²) is 64.1%. We propose that the E–W-trending open folds in the Upper Devonian Zhongning Formation (D₃z) and E–W-trending close and tight folds in the Carboniferous strata were formed under the N–S compression during the Middle–Late Triassic. The Zhangyigou and Laoyagou faults are the main tear faults to accommodate differential displacement on the surface between the Upper Devonian Zhongning Formation (D₃z) in the east and Carboniferous strata in the middle, which change into a décollement fault in the deep part of the Dafosigou fold area in the middle to accommodate differential deformation between the deep Upper Devonian Zhongning Formation (D₃z) and Carboniferous strata. This study enables us to better understand the Mesozoic intracontinental deformation in response to far-field plate-boundary convergence in NW China.

This contribution reports two graptolite assemblages from the Puna Turbidite Complex, outcropping in Sierra de Lina and Cauchari locality, western Puna, Jujuy and Salta provinces, Argentina. In Sierra de Lina, the graptolite assemblage comprises Didymograptus sp., Glossograptus fimbriatus, Cryptograptus schaeferi, Archiclimacograptus sp., Pseudamplexograptus distichus, Pseudamplexograptus latus, ?Urbanekograptus retioloides and Hustedograptus sp. The graptolite fauna collected from Cauchari locality includes Didymograptus spp., Archiclimacograptus caelatus, Archiclimacograptus sp. cf. A. micidus, scarce and incomplete specimens doubtfully referred to the genera Archiclimacograptus and Acrograptus and scarce siculae of Cryptograptus sp. The associations allow us to identify the Pseudamplexograptus distichus Zone in Sierra de Lina and possibly the Pterograptus elegans Zone at Cauchari locality. Graptolite assemblages recorded in both zones allow assigning a middle-late Darriwilian (Middle Ordovician) age for the bearer levels.

The Early-Middle Jurassic is one of the crucial coal-forming geologic periods in the world and an important target for hydrocarbon exploration in the Turpan-Hami Basin, China. The paleoenvironment and vegetation reconstruction of the Early-Middle Jurassic have been investigated using elemental geochemistry and palynological analysis to reveal paleoclimate evolution. A total of 48 genera of pteridophyte spore and 35 genera of gymnosperm pollen were identified, and 5 palynological assemblages were longitudinally divided, which showed significant differences in geochemical behaviours. The paleoenvironment was a transition from suboxidation to anoxia and then to an oxidation environment under freshwater conditions. The paleowater in the northern Taibei Sag was deeper than that in the southern part during the Middle Jurassic, which coincided with the sedimentary background of the sublacustrine fan in the north and the shallow braided river delta in the south. The paleovegetation evolved from mixed lowland–upland forest in the Hettangian-Toarcian, to lowland fern forest in the Aalenian-Bajocian, to upland conifers forest in the early Bathonian, to upland Cheirolepidiaceae forest in the late Bathonian-Callovian. The Toarcian and Bathonian-Callovian arid climate and the Hettangian-Pliensbachian and Aalenian-Bajocian warm-humid climate were responses to the continued global warming events and the intensification of the East Asian monsoon circulation, respectively. The influence of the Bathonian-Callovian aridification event on the sedimentary response in the southern Taibei Sag will be delayed due to the gradual southward migration of the depositional centre.

The Lower Cretaceous Dabeigou Formation (135–130 Ma) in the Luanping Basin, associated with its contemporary strata in northeastern China, contains the earliest documented fossils of the Jehol Biota. This includes the Luanpingella—Eoparacypris—Ocrocypris ostracod assemblage, referred to in this study as the Dabeigou-type ostracod fauna (DOF). Ostracods, which are small (0.5–2 mm) aquatic crustaceans, are abundant and easily preserved as fossils. Outlining a clear palaeobiogeographic range of the DOF can help expand the distribution range of the early Jehol Biota, providing valuable information on its origin. Results show that the DOF is mainly distributed in a series of rift basins along the Yanliao area of China to the eastern Transbaikal region of Russia, with a roughly narrow north-south distribution. Rift basin development in the eastern part of the North China Craton, combined with humid climatic conditions, provided a suitable environment (e.g., fluvial-lacustrine systems) for the emergence of the Jehol Biota.

Carbon emissions, ecological pollution and a steadily rising global temperature have been widely acknowledged as the most severe risks to human survival in the last few decades. Alarming increases in global temperature and sudden climatic shifts are nature's way of warning us to curb the use of fossil fuels and adopt more sustainable practices. Therefore, the present study investigates the impact of financial stability, environmental regulations and uncertain economic policies on carbon emissions and investment in renewable energy. The study used a nonparametric DEA-DDF technique to fulfil this objective using a balanced panel dataset comprising 28 Chinese provinces from 2011 to 2021. Overall results demonstrated that financial stability reduces carbon emissions and accelerates investment in renewable energy projects. The findings imply that a financially stable economy like China encourages businesses to invest in cutting-edge, environmentally friendly technology to boost productivity while reducing carbon emissions. Likewise, results show that stringent ecological regulations decrease carbon emissions and promote investment in renewable energy. Hence, stakeholders are keen to comply with environmental regulations in China to reduce carbon emissions by investing in renewable energy resources to avoid penalties. Finally, results suggest that uncertain economic policies increase carbon emissions and restrict access to credit from financial institutions for investment in renewable energy purposes in China. Findings imply that uncertainty in economic policies could lead to less environmentally friendly production practices that may increase carbon emissions and reduce the demand for renewable energy products.

Large igneous provinces (LIPs) are often the surface expressions of mantle plume process. Intensive magma could occur in the continental crust when a mantle plume penetrates the Moho. How magmas migrate in the crust, forming LIPs, remains debated. In this study, we employ 2D thermo-mechanical numerical modelling to study the dynamics of magma intrusion and migration within the continental crust affected by a mantle plume. Our results suggest that (1) lateral magma migration dominates crustal deformation, promoting the possible formation of metamorphic core complexes; (2) two distinct crustal deformation modes are recognized regarding the presence or absence of crustal break-up, affected by whether a significant vertical magma migration occurs; (3) the crustal thickness, Moho temperature and the length of the preset weak crust–mantle decoupling zone are the three key parameters controlling crustal magma migration. This study highlights the importance of lateral magma migration in the lower crust and provides physical mechanisms for the interpretation of magma migration under LIPs.