The Luanchuan ore concentration area is rich in mineral resources and has a long history of mining. The environmental impact of long-term mining activities cannot be ignored. It is of great significance to study the ecological risk and the accumulation trends of heavy metals in the soil of mining areas for scientific prevention and control of heavy metal pollution. Taking the Taowanbeigou River basin in the ore concentration area as the research object, the ecological pollution risk and cumulative effect of heavy metals in the soil of the basin were studied by using the comprehensive pollution index method, potential ecological risk assessment method and geoaccumulation index method. On this basis, the cumulative exceeding years of specific heavy metals were predicted by using the cumulative early warning model. The comprehensive potential ecological risk of heavy metals in the soil near the Luanchuan mine concentration area is moderate, and the single element Cd is the main ecological risk factor, with a contribution rate of 53.6%.

In a polymetallic ore concentration area, large-scale mining activities can dramatically increase heavy metal concentrations in river sediments, and their temporal–spatial variation and source apportionment are significant for understanding heavy metal migration in rivers and formulating management strategies for environmental protection and the mining industry. Sediment samples were collected along the Yu River, which flows through the Luanchan polymetallic ore concentration area in China, during high-water period (HWP), low-water period (LWP) and flat-water period (FWP) to assess the pollution level and identify the sources of Mo, Cr, W, Cu, Zn, As, Cd, Pb and Hg in the sediments. The findings revealed that Mo, Cd, W, Zn, Pb and Cu were the main pollutants, and Hg was extremely high at some specific locations. Sediments in the upstream region of the Yu River were more severely polluted by heavy metals and had greater ecological risk due to stronger mine exploration. Furthermore, consistent distribution patterns of various heavy metals during different seasons were not found. Some sharp decreases in heavy metal concentrations between adjacent sediments were observed; moreover, at some sites, heavy metal concentrations during LWP and FWP were lower than those during HWP. The results indicated that heavy metals in the Yu River mainly migrated in dissolved form. Mo, Cu, Pb and As for HWP, Mo and As for LWP and Mo, Cr and W for FWP mainly originated from Mo/W mines. Pb/Zn mines contributed to the amounts of W, Zn and Cd during HWP, Cu, Zn, Cd and Pb during LWP and Cu, Zn, Cd and Pb during FWP. Hg was mainly attributed to Au mines, and Cr was the geogenic element. The results could contribute to the sustainability of the mining industry and the formulation of science-based remediation and protection strategies for the rivers near mining areas.

The Luanchuan Neoproterozoic gabbroic intrusions are located at the southern margin of the North China Craton (NCC), intruding into the marble and schist from the Nannihu and Meiyaogou Formations of the Neoproterozoic Luanchuan Group. The gabbroic rocks consist of plagioclase (30%–50%) and amphibole (40%–60%), with minor ilmenite (2%–5%), biotite (1%–3%), and titanite (~1%). Based on the occurrence and mineral chemistry, two types of biotites were identified. The first type of biotite (Bt I) is brown, with a fine- to micro-grained anhedral texture, occurring around the magmatic ilmenite and coexisting with titanite. Bt I is characterized by high TiO₂ and FeO contents, with TiO₂ > 2 wt% (2.03 wt%–3.15 wt%) and FeO ranging from 19.94 wt% to 22.08 wt%. The other type of biotite (Bt II) is light grayish-brown to dark reddish-brown, with a medium- to coarse-grained euhedral texture, coexisting with grayish-green amphibole. Bt II exhibits lower TiO₂ (1.40 wt%–1.90 wt%) and FeO contents (18.03 wt%–21.42 wt%). The K₂O (7.56 wt%–9.32 wt%) and SiO₂ (34.49 wt%–37.04 wt%) contents of Bt I are slightly lower than those of Bt II (8.28 wt%–9.73 wt% and 35.18 wt%–37.52 wt%, respectively). Despite the low Ti content in biotites, the mineral occurrence indicates that both types of biotite yield a magmatic origin, resulting from the reactions between early crystallized minerals and residual magma. Bt I originated from the reaction between ilmenite and residual magma, while Bt II resulted from the production of the reaction between clinopyroxne and residual magma. Ilmenite exhibits low MgO and Fe₂O₃ contents but high FeO and MnO contents, suggesting genetic similarities to the Skaergaard and Panzhihua intrusions. Both types of biotites record consistent temperatures (T = 766 to 818 °C), pressures (P = 5.30–8.80 kbar), and oxygen fugacities (log fO₂ = −12.35 to −14.06), aligning with those of the Fanshan complex and the Falcon Island intrusion. The mineralogy of ilmenite and biotite indicates that the Luanchuan gabbroic intrusions formed in a continental rift setting, which is considered to be associated with the breakup of the Rodinia supercontinent.

Yiyuan jade, a specific gem-quality jade variety in the East Qinling Orogen, occurs as lenticular and vein-shaped bodies hosted within the dolomite and biotite-quartz marble of the Neoproterozoic Meiyaogou Formation. Based on detailed petrological and mineralogical characterization, three subtypes are defined: tremolite jade (nephrite), serpentine jade (a green variety of serpentine group minerals that resembles true jade), and their transitional varieties. Among these, tremolite jade is predominantly white, moon-white, and light green, whereas serpentine jade (gem-quality serpentine) exhibits dark green, yellow-green, and yellow coloration. Comprehensive mineral composition analyses are presented, encompassing amphibole, serpentine, carbonate minerals, and titanite in metagabbro, aiming to constrain the physicochemical conditions and genetic model of these jades. We propose that tremolite jade and serpentine jade are probably formed simultaneously via metasomatic processes, primarily governed by variations in fluid volume and the activities of SiO₂ and CO₂. The serpentine jade is interpreted as serpentinized marble, within which local serpentine aggregation forms serpentine jade akin to Lantian jade in the western East Qinling region. The tremolite jade closely resembles Hetian tremolite jade within geochemical and mineralogical characteristics but differs significantly from serpentine-type tremolite jade associated with ultramafic rocks, thereby confirming its classification as dolomite-type jade. Application of the Ti-in-tremolite geothermometer yields a formation temperature exceeding 400 °C. Integrated with regional geochronological constraints, our findings link the formation of Yiyuan tremolite jade and serpentine jade to tectonic activity driven by the Late Devonian subduction of the Erlangping back-arc basin. This study not only enhances the current understanding of jade mineralization within collisional orogenic settings but also establishes a robust foundation for future exploration in the East Qinling Orogen.