Geological Society of America

Abstract Background Following the impoundment of the Three Gorges Reservoir, deposit-layer landslides in the reservoir basin have experienced cyclic deformation under the combined influence of seasonal precipitation and periodic water-level operations. The deformation amplitude accumulates annually, continuously bringing uncertainty to the safety of the reservoir basin. Purpose This study takes the Tanjiahe landslide (a typical feature in the Three Gorges Reservoir region) as the research object. By integrating its recent daily displacement measurements, daily rainfall data, and reservoir water-level observations, this research aims to establish a deep learning-based prediction model to forecast the landslide’s long-term deformation trends. Specifically, the aggregated displacement time series is segmented into a trend term and a cyclic term, so as to separately characterize the landslide’s long-term evolution and periodic dynamic behavior. Methods First, Grey Relational Analysis (GRA) and Pearson’s correlation analysis are used to identify the dominant influencing factors of the Tanjiahe landslide (including antecedent rainfall, reservoir water-level variation characteristics, and past displacement increments) as input features. Then, considering the timeseries nature of monitoring data and limited sample size constraints, a Long Short-Term Memory (LSTM) network is developed to predict the landslide’s cyclic displacement, while the trend component is modeled via Support Vector Machine (SVM) regression. Results The results indicate that the LSTM method significantly outperforms in depicting the complex nonlinear time-dependent features of landslide deformation; the SVM method stably captures the aggregate deformation trajectory and shows strong performance in low-frequency trend regression. Additionally, Rescaled Range (R/S) analysis of observed versus predicted sequences reveals significant long-term persistence in the Tanjiahe landslide’s deformation evolution at its current phase. Conclusion This study demonstrates that the combined LSTM-SVM model can effectively predict the Tanjiahe landslide’s long-term deformation. The identified long-term persistence of deformation provides a basis for long-term risk assessment and early warning of this landslide.

• Late Triassic (∼220 Ma) Au mineralization in the Dixu deposit linked to Indosinian post-collisional extension. • Magmatic-metamorphic-meteoric fluid mixing defines the ore-forming processes. • Sulfidation of mafic minerals drives Au precipitation, distinct from sedimentary-hosted systems. • The Late Triassic mineralization was not an isolated local phenomenon, but rather a regional-scale event. The Youjiang Basin in southwestern China constitutes a world-class gold province, predominantly characterized by Carlin-type gold deposits hosted in both sedimentary and intrusive rocks. The Dixu gold deposit represents a key example of Carlin-type mineralization occurring within Permian pyroclastic rocks, offering significant insights into the metallogenic processes of the basin. This study integrates U-Pb geochronology and oxygen isotope analysis of hydrothermal zircons to constrain the timing and source of ore-forming fluids at the Dixu deposit. The results indicate that the main gold mineralization event occurred at ca. 220 Ma. Hydrothermal zircons from mineralized samples yield δ 18 O values between +5.2 ‰ and +8.8 ‰, exhibiting a moderately wide range of calculated δ 18 O H2O values from +5.6 ‰ to +9.1 ‰, which suggests that the ore-forming fluids were derived from deep-circulating crustal waters with magmatic contributions. Based on diagnostic mineral assemblages and cross-cutting relationships of vein systems, the mineralization process can be divided into three stages: early-, main-, and late-ore stages. The main-stage mineralization occurred via sulfidation reactions between hydrothermal fluids and iron released through alteration of mafic minerals, leading to the formation of arsenian pyrite and arsenopyrite. This stage is characterized by a diagnostic alteration assemblage (silicification-chloritization-hydrothermal rutile), with a notable absence of decarbonation. These distinctive mineralogical signatures differ from those of carbonate- and siliciclastic-hosted deposits and bears similarities to basalt- and dolerite-hosted counterparts. Our findings demonstrate that the Late Triassic mineralization event in the Youjiang Basin was not an isolated local phenomenon, but rather a regional-scale event associated with post-collisional magmatic activity during the Indosinian orogeny. Moreover, this study reveals the critical role of multi-sourced fluids and lithology-controlled alteration processes in the formation of pyroclastic-hosted Carlin-type gold deposits.

The self-excited oscillation pulsed waterjet (SOPW) offers simplicity and effective pressure source separation, making it widely utilized. This study investigates the oscillation characteristics and flow field effects of SOPW generated by a Helmholtz nozzle. A transfer function model for the nozzle is established, and the natural frequency is found to correlate with structural parameters such as the oscillation chamber’s cross-sectional area, length, and downstream nozzle diameter. Numerical simulations reveal optimal structural parameters that closely match experimental results, with errors under 15%. Notably, submerged pulsed jets exhibit faster velocity decay compared to non-submerged jets. Additionally, the study examines the effect of area discontinuity at the nozzle inlet on axial velocity, showing that the area enlargement or contraction enhances velocity at lower pressures but inhibits it at higher pressures. This work advances the understanding of nozzle design and the flow field behavior of SOPW.

Abstract The Pamir Plateau is situated at the northwestern edge of the India–Eurasia Plate collision zone, making it a key region for studying continental collision and plateau uplift. The deep structure and dynamic processes of this region have long been of great scientific interest. This paper synthesizes recent advancements in the application of geophysical techniques to investigate the deep structure of the Pamir Plateau. The study focuses on the heterogeneity of the crust and lithosphere, the morphology of the Moho and the double Moho structure, the depth variations of the lithosphere‐asthenosphere boundary (LAB), and the complex features of the mantle transition zone (MTZ). The results indicate that the deep tectonic structure of the Pamir region is closely associated with subduction of the Indian Plate, the southward compression of the Asian lithosphere, and lateral tectonic interactions from the Tarim Basin, which jointly drive the region's uplift and deformation. The paper further examines the deep interactions between the Pamir Plateau and adjacent regions. Additionally, the study discuss key controversies in current research, such as the spatial relationship between the Moho and deep seismic zones, the mechanisms of lithosphere delamination, and its effects on shallow structural deformation, etc.

It is generally believed that the ancient oceans during the “boring billion” (1.85–0.8 Ga) lacked the capacity to form large-scale iron formations (IFs), though localized small-scale IFs deposition persisted. The Altyn region of China hosts abundant IFs, with the Dimunalike IFs being the largest and most representative, characterized by typical banded iron–silica layers. Detailed fieldwork identified a tuff layer conformably contacting the IFs at the roof rocks of IFs and a ferruginous mudstone layer at the floor rocks of IFs in drill core ZK4312. Geochemical and zircon U-Pb-Hf isotopic analyses were performed. The tuff has a typical tuff structure, mostly made of quartz, and contains a significant amount of natural sulfur. It also has high SiO2 content (77.90%–80.49%) and sulfur content (0.78%–3.06%). The ferruginous mudstone has a volcanic clastic structure and is mainly composed of quartz and chlorite, with abundant coeval pyrite. It shows lower SiO2 content (53.83%–60.32%) and higher TFe2O3 content (10.29%–16.24%). Both layers share similar rare earth element (REE) distribution patterns and trace element compositions, with light REE enrichment and negative Eu, Nb, and Ti anomalies, consistent with arc volcanic geochemistry. Zircon U-Pb ages indicate crystallization of the tuff at 1102 ± 13 Ma and maximum deposition of the mudstone at 1110 ± 41 Ma. These data suggest formation during different stages of the same volcanic–sedimentary process. The ɛHf(t) values (3.60–12.35 for tuff, 2.92–8.19 for mudstone) resemble those of Algoma-type IF host rocks, implying derivation from re-melted new crust. The Dimunalike IFs likely formed in a submarine volcanic–sedimentary environment. In conclusion, although the Mesoproterozoic ocean was generally in a low-oxygen state, which was not conducive to large-scale IF deposition, localized submarine volcanic–hydrothermal activity could still lead to IF formation.