Geosciences

This study investigates the presence of Technology-Critical Elements in the Trepça mine (Stan Tërg, Mitrovicë), representing the first assessment of their distribution within this mining district. Samples were collected in all ore bodies (three samples per ore body) in horizons VIII-XI. Mineralogical, geochemical and microstructural characterization was performed using X-ray diffraction (XRD), Inductively Coupled Plasma Mass-Spectrometry (ICP-MS), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). The analyses confirmed the presence of several Technology-Critical Elements, especially Bi, Co, Ge, W, Ga, In, Te and Sb, whose distribution, correlation with mineral phases and structure were also identified. XRD enabled the identification of mineral phases while SEM-EDX provided structural and morphological characteristics of these mineral phases. The ICP-MS results indicate significant variability in the distribution of these elements. Bi reached extremely high concentrations (up to 2570.68 ppm in ore body 136), well above the method detection limit (MDL = 0.01 ppm), whereas Co exhibited elevated yet moderate concentrations that increased with depth, indicating a depth-dependent rise in concentration. V, W, Sb and Sn also exhibited elevated concentrations. Peak enrichment levels were observed for Bi (up to 2750 ppm) in Horizon IX, Sb (up to 504 ppm) in Horizon XI, W (up to 308 ppm) in Horizon VIII, and In (up to 34,730 ppm) within selected ore bodies, indicating pronounced vertical geochemical zonation. The results demonstrate that selected ore bodies represent significant potential sources of Technology-Critical Elements, supporting future resources and strategic raw material assessment within the Trepça mining district.

Recent exploration has demonstrated significant prospecting potential at the Huayagou Au deposit in Longnan mineral Field, Gansu Province, West Qinling Orogen, Central China. However, the nature and evolution of the auriferous fluids responsible for gold enrichment remain poorly constrained, hindering effective exploration targeting of high-grade ores. In this study, apatite and tourmaline closely associated with gold mineralization are investigated as mineralogical recorders of fluid composition and evolution. Integrated petrographic observations, TIMA phase mapping, cathodoluminescence imaging, electron probe microanalysis, and in situ trace element analyses were used to distinguish magmatic, metamorphic, and syn-ore hydrothermal generations of apatite and tourmaline, together with in situ Nd isotopic analyses of apatite and B isotopic analyses of tourmaline. Syn-ore hydrothermal apatite is characterized by homogeneous blue cathodoluminescence, fluorapatite compositions, strong LREE depletion, and εNd(t) values overlapping those of Triassic magmatic apatite, whereas Early-Devonian magmatic and metamorphic apatites display more distinct signatures. Tourmaline records a systematic evolution from early dravite to late schorl, accompanied by trace element enrichment and a shift toward heavier δ¹¹B values. These mineralogical and isotopic features, together with published sulfur isotope constraints, indicate that gold mineralization at Huayagou was dominantly controlled by structurally focused metamorphic fluids, with localized Triassic magmatic–hydrothermal overprinting enhancing gold enrichment in high-grade ores. The Huayagou Au deposit is, therefore, best interpreted as an atypical orogenic gold system, highlighting enhanced exploration potential in structurally favorable zones at depth, particularly in the western part of the district where Triassic magmatism is inferred.

Conventional wisdom posits that smog suppresses outdoor activity while shifting peoples’ activities indoors. Using anonymized Mobile Phone Data Provider Records fused with Point-of-Interest (POI) data sourced from the Gaode (Amap) open database for Beijing (2–22 February 2015), we test this substitution hypothesis at an hourly resolution across 12 POI-defined activity categories. We estimate the adjusted population density (APD) from mobile phone data via usage-bias calibration, interpolate city-wide AQI (Air Quality Index) and PM2.5 fields, and identify associations with a two-way fixed-effects design (Voronoi polygon (VP), day × hour model. We also handle time-invariant POI activities, while factoring in weather and day types. We find a dual suppression of both outdoor and indoor physical activities: worsening air quality is associated with lower participation in most outdoor and indoor activities. Effects are heterogeneous across categories and hours; shopping shows all-day negative marginal effects, whereas a few categories (e.g., sightseeing) display positive correlations in select afternoon hours consistent with congestion-avoidance rather than health-driven indoor substitution. Quantitatively, a 100-point AQI increase is associated with an order of 1–5 persons/km2 decline at peak hours for most activities. A Comprehensive Impact Index (CII) summarizes the spatial heterogeneity across the city. POI venue operators should anticipate city-wide activity reduction both indoors and outdoors under heavy pollution, rather than plan solely for outdoor-to-indoor activity shifts.