Geoscience frontiers最新文献

The application of Artificial Intelligence in various fields has witnessed tremendous progress in the recent years. The field of geosciences and natural hazard modelling has also benefitted immensely from the introduction of novel algorithms, the availability of large quantities of data, and the increase in computational capacity. The enhancement in algorithms can be largely attributed to the elevated complexity of the network architecture and the heightened level of abstraction found in the network's later layers. As a result, AI models lack transparency and accountability, often being dubbed as “black box” models. Explainable AI (XAI) is emerging as a solution to make AI models more transparent, especially in domains where transparency is essential. Much discussion surrounds the use of XAI for diverse purposes, as researchers explore its applications across various domains. With the growing body of research papers on XAI case studies, it has become increasingly important to address existing gaps in the literature. The current literature lacks a comprehensive understanding of the capabilities, limitations, and practical implications of XAI. This study provides a comprehensive overview of what constitutes XAI, how it is being used and potential applications in hydrometeorological natural hazards. It aims to serve as a useful reference for researchers, practitioners, and stakeholders who are currently using or intending to adopt XAI, thereby contributing to the advancements for wider acceptance of XAI in the future.

The Itmurundy Zone of Central Kazakhstan is a key structure in the core of the Kazakh Orocline representing a typical Pacific-type orogenic belt hosting accretionary complex, ophiolite massifs and serpentinite mélange. The main controversies in the existing tectonic models of the Itmurundy Zone are about the timing of subduction and accretion, the direction and kinematics of subduction and the number of oceanic plates. A new model for the early Paleozoic tectonic story of the Itmurundy Zone is postulated in this paper, based on new detailed geological and U–Pb detrital zircon age data, combined with previously documented geological, U–Pb age, microfossil, geochemical and isotope data from igneous rocks, deep-sea sediments and greywacke sandstones. The present study employs the Ocean Plate Stratigraphy (OPS) model to explain the tectonic processes involved in the evolution of the Itmurundy Zone and to present a holistic story of Ordovician oceanic plate(s), which accretion formed an accretionary complex. The detailed mapping allows distinguishing three types of OPS assemblages: (1) Chert-dominated, (2) OIB-hosting, and (3) MORB-hosting. The U–Pb ages of detrital zircons from sandstones of OIB and Chert types show unimodal distributions with similar main peaks of magmatism at 460–455 Ma in the provenance, and their maximum depositional ages (MDA) span 455–433 Ma. Two samples from OPS Type 3 show the peaks of magmatism both at ca. 460 Ma and the MDA of 452 Ma and 459 Ma, respectively. The MDA of sandstones and microfossils data from chert show the younging of strata to the south and SE in Types 1 and 2 and to NEE for Type 3 (in present coordinates) suggesting double-sided subduction to the NNW and SEE and, accordingly, the co-existence of pieces of two oceanic plates in Ordovician time. The U–Pb zircon data from both igneous and clastic rocks indicate a period of subduction erosion in early Ordovician time. As a whole, the accreted OPS units of the Itmurundy Zone record the timing of subduction and accretion from the early Ordovician to the early Silurian, i.e., 60 Ma at shortest.

The Haoyaoerhudong gold deposit, located in the northwestern part of the North China craton (NCC), has produced over 120 metric tonnes (t) of gold since 2007. It has a total reserve of > 240 t at average gold grade of 0.62 g/t, making it one of the largest open pit gold mines in China. The steeply dipping, large-tonnage, low-grade, vein- or veinlet-type gold orebodies are hosted in strongly-deformed Mesoproterozoic carbonaceous schist of the Bayan Obo Group. The laminated/boudinaged veins/veinlets in the sinistral ductile–brittle shear zones are dominated by quartz, biotite, gold-bearing löllingite, pyrrhotite, (arseno)pyrite, with minor native gold, titanite and xenotime. In this paper, we present new in situ U–Pb geochronological data on magmatic zircon from the pre-ore dikes, on metamorphic and hydrothermal xenotime, and on hydrothermal titanite from the hydrothermally altered carbonaceous schist and auriferous quartz–sulfides veins/veinlets, as well as He-Ar isotopic analysis on gold-bearing (arseno)pyrite in the syn-ore stage. The metamorphic xenotime U–Pb age of 426 ± 6.0 Ma (2σ) records a regional metamorphic event, possibly related to the accretion of the Bainaimiao arc onto the NCC. Two pre-ore andesitic dikes yielded similar emplacement ages at ∼ 278 Ma constrained by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U–Pb zircon data. Hydrothermal xenotime grains from the altered carbonaceous schist and auriferous quartz–sulfides veins yielded U–Pb ages of 256.0 ± 4.1 Ma (2σ) and 254.4 ± 2.1 Ma (2σ), respectively, overlapping with that of the hydrothermal titanite at 255.4 ± 0.8 Ma (2σ) from the laminated quartz–sulfides veinlets. This indicates that the gold mineralization occurred at ca. 255 Ma. The ∼ 255 Ma gold mineralization age is much younger than the previously reported Early–Middle Permian regional magmatic activity (ca. 291 Ma to 268 Ma), and may be associated with the regional sinistral strike-slip event in the late orogenic cycle related to the collision between the Siberian craton and the NCC. The ³He/⁴He (R/Ra) and ⁴⁰Ar/³⁶Ar values of the gold-bearing (arseno)pyrite are 0.04 to 0.09 (average = 0.07) and 375.8 to 2023 (average = 1045), which reveal the ore-forming fluids dominantly originated from the crustal rocks, with limited involvement from the mantle. Collectively, our new geochronological data, noble gas isotopic analyses, and geological evidence support a typical orogenic gold deposit model at Haoyaoerhudong.

Oceanic plateau accretion and subsequent flat-slab subduction in modern convergent settings have profoundly influenced the nature of subduction and mantle dynamics. However, evaluating similar impacts in ancient convergent settings, where oceanic plateaus have been subducted but geological records are limited, remains challenging. In this study, we present geochronological and geochemical data for a suite of ore-associated plutonic rocks from the Gaobaoyue area of northern Tibet. These rocks have zircon U–Pb ages of 152–146 Ma, with high Sr contents and Sr/Y and La/Yb ratios, low MgO, Yb, and Y contents, and depleted Sr–Nd–Hf isotopic compositions, consistent with an adakitic affinity that was generated by the partial melting of subducting oceanic crust. We compare the Late Jurassic adakitic magmatism with the spatiotemporal evolution of magmatism in northern Tibet to infer oceanic plateau subduction and subsequent flat-slab subduction in the Bangong–Nujiang Tethyan Ocean. This tectonic model explains (i) slab-derived adakitic magmatism, (ii) the observed lull in magmatic activity, (iii) intraplate compression and uplift, and (iv) subduction jump and initiation. We also propose that the subduction of heterogeneous oceanic crust (i.e., buoyant oceanic plateau subduction) provided favorable conditions for tectonic exhumation, vertical slab tearing, and the formation of Cu–Au deposits. Our findings not only have implications for establishing the fundamental process of oceanic plateau accretion in ancient subduction zones but also provide an alternative explanation for Late Jurassic complex tectonomagmatic activity in northern Tibet.

Detrital geochronology fundamentally involves the quantification of major age ranges and their weights winthin an age distribution. This study presents a streamlined approach, modeling the age distribution of detrital zircons using a normal mixture model, and employs the Expectation-Maximization (EM) algorithm for precise estimations. A method is introduced to automatically select appropriate initial mean values for EM algorithm, enhancing its efficacy in detrital geochronology. This process entails multiple trials with varying numbers of age components leading to diverse k-component models. The model with the lowest Bayesian Information Criterion (BIC) is identified as the most suitable. For accurate component number and weight determination, a substantial sample size (n > 200) is advisable.

Our findings based on both synthetic and empirical datasets confirm that the normal mixture model, refined by the EM algorithm, reliably identifies key age parameters with minimal error. As a kind of probability density estimator, the normal mixture model offers a novel visualization tool for detrital data and an alternative foundation for KDE in calculating existing similarity metrics. Another focus of this study is the critical examination of quantitative metrics for comparing detrital zircon age patterns. Through a case study, this study demonstrates that metrics based on empirical cumulative probability distribution (such as K-S and Kuiper statistics) may lead to erroneous conclusions. The employment of the Kullback–Leibler (KL) divergence, a metric grounded in probability density estimation, is proposed. Reference critical values, simulated via the Monte Carlo method, provide more objective benchmarks for these quantitative metrics.

All methodologies discussed are encapsulated in a series of MATLAB scripts, available as open-source code and a standalone application, facilitating wider adoption and application in the field.

Densely populated region of Ganga Plain is facing aquifer vulnerability through waterborne pollutants and groundwater stress due to indiscriminate abstraction, causing environmental and socio-economic instabilities. To address long-term groundwater resilience, it is crucial to understand aquifer heterogeneity and connectivity, groundwater recharge sources, effects of groundwater abstraction etc. In this context, present study aims to understand factors responsible for vertical and spatial variability of groundwater chemistry and to identify groundwater recharge sources in an intensively exploited agrarian region of the Ganga Plain.

Interpretation of chemometric, statistical, and isotopic analysis categorises the alluvial aquifer into zone 1 (G1; ground surface to 100 m) and zone 2 (G2; >100 m-210 m). The group G1 samples are characterized by a wide variation in hydrochemical species, noted with pockets of F^– and NO₃^– rich groundwater, and fresh to more evolved water types, while group G2 groundwater is characterized by a sharp increase in freshwater types and limited variation in their isotopic and hydrochemical species. The G1 groundwater chemistry is governed by soil mineralogy, local anthropogenic inputs (SO₄^2-, Cl ^-, and NO₃^–), and manifested by multiple recharge sources (local precipitation, river, canal water, pond). The G2 group is dominated by geogenic processes and mainly recharged by the local precipitation. Geospatial signatures confirm more evolved water type for group G1 in northwestern region, while freshwater type covers the rest of the study area. Fluoride rich groundwater is attributed to sodic water under alkaline conditions and enriched δ¹⁸O values emphasizing role of evaporation in F^- mobilization from micas and amphiboles abundant in the soil. The findings provide insight into potential groundwater vulnerability towards inorganic contaminants, and groundwater recharge sources. The outcome of this study will help to develop aquifer resilience towards indiscriminate groundwater extraction for agricultural practices and aim towards sustainable management strategies in a similar hydrogeological setting.

Inter-provincial carbon compensation is an important means for a country to realize regional environmental protection and achieve coordinated regional development and realize the carbon neutral goal. It is easier to realize inter-provincial carbon compensation compared with the national level. Based on the multi-regional input-output model and the input–output data of 30 provinces in China, this study measured the carbon transfer in, carbon transfer out and net carbon transfer of each province, and based on the undesirable slacks-based measurement model under the common frontier, the provinces were given the shadow price of carbon emission in line with the situation of the local economic development, resource endowment, and industrial structure, and based on which, the amount of carbon compensation of each province was measured. The results show that: China's provinces and regions have a larger share of trade-implied carbon emissions; the net carbon transfer in areas mainly concentrated in the traditional energy provinces, which provide industrial products for other regions and undertake the transfer of carbon emissions, and become the main carbon compensation recipient areas; the net carbon transfer out is mainly concentrated in the economically developed and densely populated areas such as Beijing–Tianjin region and the eastern and southern coasts, which satisfy the end-consumption by purchasing a large number of industrial products and generate a large amount of carbon emissions. Transfer out; becoming the main carbon offset payment area. Based on the results of this study, it is proposed to improve the national provincial carbon offset mechanism and implement a differentiated and synergistic carbon emission reduction cooperation approach. The research program of this study can provide a reference for the development of inter-regional carbon offset programs.

The Ediacaran–Cambrian transition witnessed some of the most important biological, tectonic, climatic and geochemical changes in Earth’s history. Of utmost importance for early animal evolution is the likely shift in redox conditions of bottom waters, which might have taken place in distinct pulses during the late Ediacaran and early Paleozoic. To track redox changes during this transition, we present new trace element, total organic carbon and both inorganic and organic carbon isotopes, and the first iron speciation data on the Tamengo and Guaicurus formations of the Corumbá Group in western Brazil, which record important paleobiological changes between 555 Ma to < 541 Ma. The stratigraphically older Tamengo Formation is composed mainly of limestone with interbedded marls and mudrocks, and bears fragments of upper Ediacaran biomineralized fossils such as Cloudina lucianoi and Corumbella werneri. The younger Guaicurus Formation represents a regional transgression of the shallow carbonate platform and is composed of a homogeneous fine-grained siliciclastic succession, bearing meiofaunal bilateral burrows. The new iron speciation data reveal predominantly anoxic and ferruginous (non-sulfidic) bottom water conditions during deposition of the Tamengo Formation, with Fe_HR/Fe_T around 0.8 and Fe_Py/Fe_HR below 0.7. The transition from the Tamengo to the Guaicurus Formation is marked by a stratigraphically rapid drop in Fe_HR/Fe_T to below 0.2, recording a shift to likely oxic bottom waters, which persist upsection. Redox-sensitive element (RSE) concentrations are muted in both formations, but consistent with non-sulfidic bottom water conditions throughout. We interpret the collected data to reflect a transition between two distinct paleoenvironmental settings. The Tamengo Formation represents an environment with anoxic bottom waters, with fragments of biomineralized organisms that lived on shallower, probably mildly oxygenated surficial waters, and that were then transported down-slope. Similar to coeval successions (e.g., the Nama Group in Namibia), our data support the hypothesis that late Ediacaran biomineralized organisms lived in a thin oxygenated surface layer above a relatively shallow chemocline. The Guaicurus Formation, on the other hand, records the expansion of oxic conditions to deeper waters during a sea level rise. Although the relationship between global biogeochemical changes and the activities of early bioturbators remains complex, these results demonstrate an unequivocal synchronous relationship between oxygenation of the Corumbá basin and the local appearance of meiofaunal bioturbators.

The examination of fluctuations in the correlations between ${\delta }^{13}$C and ${\delta }^{18}$O is of significant importance for the reconstruction of the Earth’s climate history. A key challenge in paleoclimatology is finding a suitable method to represent the correlated fluctuation system between ${\delta }^{13}$C and ${\delta }^{18}$O. The method must be able to handle data sets with missing or inaccurate values, while still retaining the full range of dynamic information about the system. The non-linear and complex correlations between ${\delta }^{13}$C and ${\delta }^{18}$O poses a challenge in developing reliable and interpretable approaches. The transition network, which involves embedding the ${\delta }^{13}$C and ${\delta }^{18}$O sequence into the network using phase space reconstruction, is a coarse-grained based approach. This approach is well-suited to nonlinear, complex dynamic systems, and is particularly adept at emerging knowledge from low-quality datasets. We have effectively represented the fluctuations in the correlation between ${\delta }^{13}$C and ${\delta }^{18}$O since $66$ million years ago (Ma) using a system of complex network. This system, which has topological dynamical structures, is able to uncover the stable modes and key patterns in Cenozoic climate dynamics. Our findings could help to improve climate models and predictions of future climate change.

An intramolecular isotopic study was conducted on natural gases collected from coal-derived gas reservoirs in sedimentary basins of China to determine their position-specific isotope distributions. The propane from the Turpan-Hami Basin exhibited negative Δ_C-T (δ¹³C_central-δ¹³C_terminal) values ranging from −3.9‰ to −0.3‰, with an average of −2.1‰. Propane from the Ordos Basin, Sichuan Basin, and Tarim Basin showed positive Δ_C-T values, with averages of 1.3‰, 5.4‰ and 7.6‰, respectively. Position-specific carbon isotope compositions reveal the precursors and the propane generation pathways in the petroliferous basins. Propane formed from the thermal cracking of Type III kerogen has larger δ¹³C_central and δ¹³C_terminal values than propane from Type I/II kerogen. The precursor for natural gases collected in this study is identified to be Type III kerogen. Comparing our data to calculated results for thermal cracking of Type III kerogen, we found that propane from the low-maturity gas reservoir in the Turpan Basin was generated via the i-propyl radical pathway, whereas propane from the Sulige tight gas reservoir in the Ordos Basin was formed via the n-propyl radical pathway. δ¹³C_terminal values covered a narrow range across basins, in contrast to δ¹³C_central. The terminal carbon position in propane is less impacted by microbial oxidation and more relevant to maturity levels and precursors. Thus, δ¹³C_terminal has a good potential to infer the origin and maturity level of natural gas. In examining post-generation processes, we proposed an improved identification strategy for microbial oxidation of natural gases, based on the position-specific carbon isotope distributions of propane. Samples from the Liaohe Depression of the Bohai Bay Basin and the Sichuan Basin were detected of post-generation microbial oxidation. Overall, position-specific carbon isotope composition of propane provides new insights into the generation mechanism and post-generation processes of natural gas in the geological period at the atomic level.