Journal of Earth Science最新文献

Obtaining geological and landform dislocation features, as well as the measured stratigraphic activity age, provides direct evidence to evaluate fault activity, which is more difficult to do in areas with low tectonic activity, such as eastern and central China. A detailed investigation of the fault activity, trenching, drilling joint geological profile, geological survey, and chronological analysis were used to obtain the spatial geometry, fault kinematics, and activity chronology of the Jiulong fault. The conclusions are as follows: (1) The Jiulong fault was a fracture zone composed of four branch faults, with a width of around 30–40 m and good extendibility, while the maximum surface rupture length was 373 m. (2) The Jiulong fault has many strata dislocations, and the dislocation distance decreased from bottom to top, demonstrating synsedimentary structure characteristics, with a maximum stratigraphic dislocation distance of 18.2 m. (3) Preliminary analysis suggested the Jiulong fault as a secondary fracture of the Xiangfan-Guangji fault zone and provided evidence of the southeastward extension of the Xiangfan-Guangji fault. A preliminary hypothesis purported the Xiangfan-Guangji fault as the seismogenic fault of the Ms 5.0 magnitude earthquake in 1911. (4) According to OSL and ESR dating analyses, the upper breakpoint of the Jiulong fault cuts into the Late Pleistocene Xingang Formation (Qp³x) strata, and the latest active age of the Jiulong fault was 57.6 ka. The chronology analysis confirmed an active fault from the Late Pleistocene and identified a weak tectonic in Jiujiang Province, which represents the largest active fault outcrop uncovered in the area so far. This study provides evidence and research materials for the evaluation of fault activity and seismic stability in this region.

Landslides are widespread geomorphological phenomena with complex mechanisms that have caused extensive causalities and property damage worldwide. The scale and frequency of landslides are presently increasing owing to the warming effects of climate change, which further increases the associated safety risks. In this study, the relationship between historical landslides and environmental variables in the Hanjiang River Basin was determined and an optimized model was used to constrain the relative contribution of variables and best spatial response curve. The optimal MaxEnt model was used to predict the current distribution of landslides and influence of future rainfall changes on the landslide susceptibility. The results indicate that environmental variables in the study area statistically correlate with landslide events over the past 20 years. The MaxEnt model evaluation was applied to landslide hazards in the Hanjiang River Basin based on current climate change scenarios. The results indicate that 25.9% of the study area is classified as a high-risk area. The main environmental variables that affect the distribution of landslides include altitude, slope, normalized difference vegetation index, annual precipitation, distance from rivers, and distance from roads, with a cumulative contribution rate of approximately 90%. The annual rainfall in the Hanjiang River Basin will continue to increase under future climate warming scenarios. Increased rainfall will further increase the extent of high- and medium-risk areas in the basin, especially when following the RCP8.5 climate prediction, which is expected to increase the high-risk area by 10.7% by 2070. Furthermore, high landslide risk areas in the basin will migrate to high-altitude areas in the future, which poses new challenges for the prevention and control of landslide risks. This study demonstrates the usefulness of the MaxEnt model as a tool for landslide susceptibility prediction in the Hanjiang River Basin caused by global warming and yields robust prediction results. This approach therefore provides an important reference for river basin management and disaster reduction and prevention. The study on landslide risks also supports the hypothesis that global climate change will further enhance the frequency and intensity of landslide activity throughout the course of the 21st Century.

Topography can strongly affect ground motion, and studies of the quantification of hill surfaces’ topographic effect are relatively rare. In this paper, a new quantitative seismic topographic effect prediction method based upon the BP neural network algorithm and three-dimensional finite element method (FEM) was developed. The FEM simulation results were compared with seismic records and the results show that the PGA and response spectra have a tendency to increase with increasing elevation, but the correlation between PGA amplification factors and slope is not obvious for low hills. New BP neural network models were established for the prediction of amplification factors of PGA and response spectra. Two kinds of input variables’ combinations which are convenient to achieve are proposed in this paper for the prediction of amplification factors of PGA and response spectra, respectively. The absolute values of prediction errors can be mostly within 0.1 for PGA amplification factors, and they can be mostly within 0.2 for response spectra’s amplification factors. One input variables’ combination can achieve better prediction performance while the other one has better expandability of the predictive region. Particularly, the BP models only employ one hidden layer with about a hundred nodes, which makes it efficient for training.

Lack of information regarding lithium (Li) crystal chemistry in numerous minerals, especially those containing trace amounts of Li (ranging from a few to tens of ppm), limits our understanding of Li isotopic fractionation in pegmatites. In this study, we examined the Li isotopic composition and Li content in various Li-poor (e.g., quartz or feldspar) together with Li-rich (sopdumene or lepidolite) mineral phases within granitic pegmatites. We compiled a comprehensive dataset, encompassing a broad spectrum of Li contents (ranging from a few to tens of thousands of ppm) and Li isotopic values (−8‰ to 41‰). The minerals exhibit distinct Li isotopic signatures. Specifically, elbaite and beryl show the highest values, while biotite displays a negative average. Compared to individual minerals, whole rocks demonstrate lower Li isotopic values, with pegmatites exhibiting the highest and non-granitic pegmatite wall rocks showing the lowest. Our study also uncovers a clear “V”. shape relationship between Li isotopic values and logarithm of Li contents, with different mineral groups occupying specific regions within this shape. Furthermore, a significant correlation was observed between average Li isotopic values and Li-O (OH, F) bond lengths in various minerals. These discoveries underscore the crucial role of crystal chemistry in shaping the Li isotopic behavior in pegmatites from a statistical perspective.

Based on a compilation of AFT, AHe ages and apatite MTLs from previous studies, the following conclusions can be made regarding the spatial and temporal distribution of exhumation in Altai-Sayan region.

1. (1)

   The oldest AFT ages, found in the Gobi Altai, suggest that this region has been tectonically stable since the Late Jurassic.

2. (2)

   Early Cretaceous rapid cooling is focused in northern Chinese Altai and western Gorny Altai, associated with the Mongol-Okhotsk orogeny. Late Cretaceous rapid cooling identified in most other areas of Altai-Saya region is best explained as being associated with fault reactivation due to the subsequent collapse of the Mongol-Okhotsk Orogen.

3. (3)

   Cenozoic reactivation is difficult to be record with low-temperature systems due to very limited exhumation over this time frame. As a result, the timing and mechanism of any Cenozoic reactivation in the Altai-Saya region remains unclear.

4. (4)

   At the orogenic scale, the AFT ages in the northern part of the Altai-Saya region are younger than those in the southern part, indicating that the basement of northern part, weakened by its earlier extensional tectonism, was more easily reactivated.

Synthesized iron oxyhydroxide was applied for the adsorptive removal of As(V) and As(III) from the aquas media. Additionally, this investigation highlighted the synergistic effect of calcium carbonate in conjunction with iron oxyhydroxide, resulting in enhanced removal efficiency. The experiment was conducted under various conditions: concentration, dosage, pH, agitation, and temperature. Material characterizations such as Brunauer Emmett Teller, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy were implied to understand adsorption mechanisms. The Langmuir model revealed optimal concentrations for As(V) = 500 µg/L at pH-5 and As(III) = 200 µg/L at pH-7, resulting in 95% and 93% adsorption efficiencies, respectively. Maximum adsorption capacities “q_m” were found to be 1 266.943 µg/g for As(V) and 1 080.241 µg/g for As(III). Freundlich model demonstrated favorable adsorption by indicating “n > 1” such as As(V) = 2.542 and As(III) = 2.707; similarly, the speciation factor “R_L < 1” for both species as As(V) = 0.1 and As(III) = 0.5, respectively. The kinetic study presented a pseudo-second-order model as best fitted, indicating throughout chemisorption processes for removing As(V) and As(III). Furthermore, incorporating calcium carbonate presented a significant leap in the removal efficiency, indicating As(V) from 95% to 98% and As(III) from 93% to 96%, respectively. Our findings offer profound motivation for developing effective and sustainable solutions to tackle arsenic contamination, underscoring the exceptional promise of iron oxyhydroxide in conjunction with calcium carbonate to achieve maximum removal efficiency.

To investigate the stability and interaction mechanism of the slope-pile-footing system under surcharge effects, the finite difference method (FDM) was adopted to analyze the response laws of the stability of the reinforced slope, evolution of the critical slip surface, stress characteristic of retaining structures, deformation and failure modes of the slope foundation and building footing under surcharge parameters, including the surcharge intensity, the surcharge position, and the surcharge width. The results show that surcharge parameters significantly affect the stability and the deformation characteristics of the slope-pile-footing system. Specifically speaking, with the increasing surcharge intensity and the decreasing surcharge position and width, the deformation and failure mode of the system will gradually evolve in a direction that is harmful to its stability. The interaction mechanism of the slope-pile-footing system is further clarified as the load transfer of the building footing, the generation of the additional stress in the slope foundation, and the adjustment of pile bending moment due to the stress redistribution. Correspondingly, the safety of anti-slide piles will determine the stability of the slope foundation and building footing. These findings are expected to provide guidance for the comprehensive development and utilization of filled slopes after reinforcement.

The Mongol-Okhotsk Ocean, which has been closing gradually from the west to the east beginning since the Late Paleozoic, was an important part of the Central Asian Orogenic Belt. It influenced the tectonic framework of Northeast Asia in the Mesozoic, especially the Late Mesozoic arc-basin system that is widely distributed in the Great Xing’an Range. However, the manner in which the Mongol-Okhotsk Ocean affected the sedimentary basin development remains poorly understood. To address this issue, we conducted U-Pb dating of detrital zircon deposited sedimentary basins of the central Great Xing’an Range. By examining the possible provenances of the detrital zircon and the structural controls of the basins, we found that a key sedimentary unit was deposited around Late Jurassic-Early Cretaceous. Its provenance was a felsic source in a back-arc setting of an active continental margin. The findings also suggest the existence of a unified geodynamic setting that affected the coeval development of basins in the northern Great Xing’an Range and the Yanshan fold-thrust belt along the northern margin of North China Craton. This research helps to better understand the complex tectonic processes which shaped the Northeast Asia during the Late Mesozoic.

The deformation mechanisms of the Tianshan orogenic belt (TOB) are one of the most important unresolved issues in the collision of the Indian and Eurasian plates. To better understand the lithospheric deformation of the eastern Tianshan orogenic belt, we combined the S-wave tomography and gravity data to develop a three-dimensional (3D) density model of the crust and upper mantle beneath the eastern Tianshan area. Results show that the crust of the eastern Tianshan is mainly characterized by positive density anomalies, revealing widespread subduction-related magmatism during the Paleozoic. We however have also observed extensive low-density anomalies beneath the eastern Tianshan at depths deeper than ∼100 km, which is likely linked to a relatively hot mantle. The most fundamental differences of the lithosphere within the eastern Tianshan occur in the uppermost mantle. The uppermost mantle layers in the Bogda Shan and Harlik Shan are relatively dense. This is likely associated with an eclogite body in the uppermost mantle. The most significant negative anomaly of the uppermost mantle is however found in the Jueluotage tectonic belt and the central Tianshan Block and is possibly associated with depleted mantle material. We suggest that these differences related to compositional changes may control the strength of the lithospheric mantle and have affected the uplift of the northern and southern segments of the eastern Tianshan after the Permian.

The Gaoaobei tungsten-molybdenum deposit is a newly discovered large-scale quartz-vein-type deposit in the Nanling metallogenic belt in South China. The ore bodies are hosted in the Indosinian granites and the Cambrian Xiangnan Group slates and are controlled by NWW-oriented faults, which are obviously different from the “five-story building” model in southern Jiangxi Province. The magmatic rocks in the study area are dominated by medium- to coarse-grained biotite monzogranite, with a few NW-oriented fine-grained granite dykes. The medium- to coarse-grained biotite monzogranite and fine-grained granite dykes have zircon U-Pb ages of 229.4 ± 1. 9 Ma (MSWD = 1.5) and 164.9 ± 3.3 Ma (MSWD = 0.75), respectively, corresponding to the Indosinian and Yanshanian magmatism. The monzogranites have higher contents of FeO, CaO, K₂O, P₂O₅, and TiO₂, while the granite dykes have slightly higher contents of SiO₂, Al₂O₃, MnO, and Na₂O. Their A/CNK values are 1.11–1.75 and 1.19–2.25, and the contents of CIPW normative corundum are 1.71%–6.66% and 2.41%–9.50%, suggesting both the monzogranites and granite dykes are S-type granite. The total amount of rare earth elements in the monzogranites (from 84.7 ppm to 129 ppm) is slightly lower than that in the granite dykes (from 128 ppm to 133 ppm). The Eu/Eu* values range from 0.12 to 0.30 in monzogranites and from 0.001 1 to 0.001 3 in granite dykes, indicating the fine-grained granites underwent more intense fractional crystallization. The monzogranite and granite dykes have high ⁸⁷Sr/⁸⁶Sr_i values of 0.716 9–0.719 3 and 0.728 25–0.728 80, low ε_Nd(t) values ranging from −10.2 to −9.6 and from −11.5 to −11.4, and T_DM2 ages of 1 835–1 785 and 1 957–1 946 Ma, respectively. These isotope data indicate their origin from the remelting of the Paleoproterozoic crustal materials. Combined with regional geology, it is concluded that the medium- to coarse-grained biotite monzogranite was formed in a post-collisional extensional environment. In addition, ⁴⁰Ar-³⁹Ar dating of the greisen type tungsten-molybdenum ore gave consistent plateau age of 164.0 ± 1.2 Ma, isochronal age of 162.0 ± 2.4 Ma and anti-isochronal age of 161.4 ± 1.8 Ma. Combined with the published molybdenite Re-Os age, the Gaoaobei tungsten-molybdenum deposit was formed at ∼164 Ma, which is inferred to be genetically related to the contemporaneous finegrained granite dykes (165 Ma). The deposit was likely formed during the large-scale magmatism and mineralization event in the early Yanshanian of the Nanling Range in an intra-continental extensional environment caused by the subduction of the paleo-Pacific plate. The late and small granite dykes within the large granite plutons thus require further attention during mineral prospecting in the regions.