Beijing Institute of Geology for Mineral Resources

Abstract Epithermal deposits are characterized by complex low‐temperature hydrothermal alterations, but the links between mineralization and superimposed alteration are obscure and require further elucidation. This study employs short‐wave infrared (SWIR) spectral scalars for alteration mineral mapping and three‐dimensional modeling of the Ulan Uzhur Ag polymetallic deposit, a newly discovered epithermal deposit in the Qimantagh. Alteration zoning transitions from illite‐muscovite‐carbonate‐pyrite in the core (Zone I), through muscovite ± illite‐kaolinite‐chlorite‐carbonate (Zone II), to muscovite‐chlorite‐biotite (Zone III) at the periphery. The Zone I with mineralization features long‐wavelength white mica (wAlOH > 2207 nm) with a high Illite Crystallinity (IC) (mean > 2.0), suggesting a relatively high‐temperature environment conducive to mineralization. Petrographic analyses with fluid inclusion and IC curve characteristics suggests that fluid boiling may be a pivotal mechanism for mineral precipitation. Furthermore, surface mapping and deep three‐dimensional modeling of spectral characteristics reveal a correlation between long‐wavelength white mica, high IC and mineralization zones. These findings indicate that SWIR spectroscopy reveal the evolution of fluids and provide valuable guidance for future exploration efforts.

Microseismic/acoustic emission (AE) monitoring enables real-time, non-destructive observation of deformation and failure processes in rock during loading and unloading. Accordingly, this study designed two experimental schemes-sandstone loading and unloading-to comparatively investigate the spatiotemporal evolution characteristics of AE during sandstone failure under these distinct stress paths. Based on AE waveform time-frequency parameters and AE source location results obtained during testing, the failure evolution patterns of rock under both loading paths were analyzed. The results demonstrate that: (1) In both loading and load-unloading experiments, rock failure exhibited a distinct four-stage characteristic. Under pure loading conditions, failure concentrated near the point of catastrophic rupture, whereas unloading triggered premature rock fracturing, with a more pronounced AE response observed during the unloading phase. (2) For both loading paths, the dominant frequencies of AE waveforms were concentrated within the 0-200 kHz range. A distinct low-frequency (0-100 kHz), high-amplitude zone emerged prominently during Stage 4 in both cases. (3) AE source locations under load-unloading conditions revealed that during Stage 3-characterized by vertical loading combined with lateral unloading in the minimum principal stress direction-tensile failure cracks nucleated within the rock. Subsequently, during Stage 4 of the loading phase, these cracks propagated and coalesced, ultimately forming a macroscopic fracture surface on the sandstone specimen. (4) The AE source location results under pure loading failure conditions indicate that under uniaxial vertical loading, compression-shear failure fractures begin to develop within the rock mass during Stage 3. With continued loading in Stage 4, these shear fractures propagate through to the specimen surface, forming a through-going shear fracture plane.

• Sphalerite geochemistry can be used to reveal the ore-forming conditions and metallogenic processes. • The principal component analysis demonstrates the sphalerite color correlates with Fe, Cd, Mn, Co contents, with different colors indicating specific elemental enrichments. • The decrease Fe and Cd contents, sulfur fugacity and temperature were key factors for mineralization centre. The Jiama copper polymetallic deposit is a typical representative of the post-collision porphyry copper deposits in the eastern segment of the Gangdese metallogenic belt in China. Currently, the occurrence mechanism of the trace elements in sphalerite and the genesis of the distal lead–zinc mineralization are not clear in the Jiama deposit. Sphalerites, the primary ore minerals in the Jiama distal lead–zinc mineralization, have rich colors and are hosted in skarn (Sp1), hornfels (Sp2), and manto (Sp3) orebodies. In this study, we utilized laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and in-situ sulfur isotope analysis to investigate the genesis of sphalerite and reveal the distal lead–zinc mineralization processes. Sp1 had high Fe and Cd contents, Sp2 had low Mn and Ga contents, and Sp3 had high Cu and Co contents. The trace elements in sphalerite (e.g., Fe, Mn, Cd, Co, Ga, In, and Cu) primarily existed in the form of isomorphic substitution. The substitution mechanisms mainly included (Fe, Mn, Cd) 2+ ↔ Zn 2+ , (Cu + , Ag + ) + Ga 3+ ↔ 2Zn 2+ , and Cu + + In 3+ ↔ 2Zn 2+ . The sphalerite showed a diverse array of colors; based on these colors, the sphalerites were classified into three categories: brown with high contents of Fe, Cd, Mn, and Ga (Type 1); yellow with Ge and Cu enrichment (Type 2); and dark blue with high Ag concentrations (Type 3). The sulfur in the sphalerite in the Jiama deposit was derived from magma; this sphalerite generally formed under medium-to-high temperatures and moderate sulfur fugacity conditions. As the ore-forming fluids moved away from the hydrothermal center, the temperature and sulfur fugacity of the sphalerite formation gradually decreased, accompanied by a reduction in the Fe and Cd content of sphalerite. Thus, sphalerite can be utilized as one of the prospecting indicators for identifying the fluid source of porphyry mineralization systems.

A total of 895 surface soil samples （0-20 cm） and five road-dust samples were collected in a typical vanadium-titanium magnetite mining area of Hongqi-Damiao catchment in the Chengde City and analyzed for 12 heavy metals （Cu, Ni, Cd, Cr, Pb, Zn, Hg, V, Ti, Mn, As, and Co） and their chemical speciation. The accumulation and ecological risk characteristics of soil heavy metals （HMs） were clarified by geological accumulative index, potential ecological risk index （RI）, risk assessment coding （RAC）, and modified Nemerow integrated ecological risk index （mNIER）. Multiple statistical methods including principal component analysis, correlation analysis, cluster analysis, redundancy analysis, and GIS spatial analysis were used to investigate the spatial variation response of soil HMs to the environmental impact factors （distance to the road network, land use, and soil parent material types）. The sources of HMs were quantitatively analyzed using a positive matrix factorization （PMF） model. The results showed that the over-standard rates of Cu, Cr, Cd, Ni, Pb, and Zn were 5.70%, 2.79%, 1.01%, 0.67%, 0.11%, and 0.11%, respectively, in comparison to China's soil environmental quality standard risk screening values （GB15618-2018）. The average accumulation index of soil HMs followed the order of Cu>Ti>Cr>V>Co>Ni>Cd>Zn>Mn>As>Hg>Pb, while the average accumulation index of Cu was 1.23 and categorized as moderate accumulation. The accumulation of Cu, Zn, Cr, Mn, V, Ti, Co, and Ni gradually decreased within a distance of 200 m, while the content of Cd in soil was relatively stable within the distance from 25 m to 800 m to the road network, and the accumulation index of Pb, Hg, and As in soil was highest at the 200 m buffer zone. The average RAC value of 12 HMs followed the order of Cd>Mn>Ni>Zn>Hg>Co>Pb>Cu>As>Cr>V>Ti. The average RAC value of the Cd element was 46.45%, showing high biological activity, while the bioavailability RAC value of other elements was generally categorized as low-risk or risk-free level. The potential ecological risk of HMs in soil was relatively low with the RI value range between 51.48 to 1 152.39 （average of 131.2） and the mNIER value range between 10.32 to 745.57, with an average value of 32.85, in which 97.43% of the samples were classified as light to moderate risk. Based on the PMF model, 44.82%, 33.45%, 32.27%, and 24.35% of Pb, Hg, Cd, and Zn in surface soil were contributed by intensive transportation activities, respectively. The main sources of 12 HMs in the study area were the combined sources of natural sources （soil parent materials）, weathering sources of V-Ti-Fe-P deposits, dust deposition from industrial and mining activities and coal combustion, agricultural sources, and traffic sources, with their contribution rates of 27.46%, 21.12%, 19.29%, 17.05%, and 15.08%, respectively.