To investigate the status of heavy metal pollution and the associated ecological and health risks in farmland surrounding the Xicheng lead and zinc mining area, we collected soil samples (0–20 cm) and measured the level of As, Ni, Cu, Zn, Cd, Pb, Hg, and Cr. The characteristics of soil heavy metals, pollution levels, and ecological, and health risks were quantitatively assessed using Monte Carlo simulation in conjunction with the geo-accumulation index (Igeo), pollution index (Pi), ecological risk index (Er), and human health risk assessment model. The results indicated that the average concentrations of As, Ni, Cu, Zn, Cd, Pb, Hg, and Cr in the soil of the study area were 26.92, 39.46, 31.18, 340.23, 1.13, 184.61, 0.34, and 71.15 mg·kg⁻¹, respectively. These values were significantly higher than the soil background levels reported for Gansu Province. The average Igeo for Hg was 3.27, and the average Er was 679.13, indicating that Hg had the highest accumulation and posed the greatest ecological risk in the study area. The average single-factor pollution index for Cd was 2.52, marking it as the heavy metal with the highest pollution level. The cumulative probability of health risk derived from Monte Carlo simulation indicates that the non-carcinogenic hazard indices for adults and children were 2.79 × 10⁻¹ and 1.67, respectively, with 94.82% of children exceeding the non-carcinogenic risk threshold. The carcinogenic risk indices (TCR) for adults and children were 8.09 × 10⁻⁵ and 4.60 × 10⁻⁴, respectively, and 100% of the samples exceeded the TCR standard for children. As and Cd were identified as the primary contributors to both carcinogenic and non-carcinogenic risks. The findings enhance our understanding of heavy metal contamination in farmland soils and establish an empirical framework for developing targeted remediation approaches and sustainable land management practices.

The Weixi–Qiaohou Fault (WQF) is considered an important zone of the western boundary of the Sichuan–Yunnan block, and its seismicity has attracted much attention after a series of moderate–strong earthquakes, especially the Yangbi Ms6.4 earthquake that occurred on 21 May 2021. In the present research, we investigate major and trace elements, as well as hydrogen and oxygen isotopes, of 10 hot springs sites located along the WQF, which are recharged by infiltrated precipitation from 1.9 to 3.1 km. The hydrochemical types of most analyzed geothermal waters are HCO₃SO₄-Na, SO₄Cl-NaCa, and SO₄-Ca, proving that they are composed of immature water and thus are characterized by weak water–rock reactions. The heat storage temperature range was from 44.1 °C to 101.1 °C; the circulation depth was estimated to range between 1.4 and 4.3 km. The results of annual data analysis showed that Na⁺, Cl⁻, and SO₄²⁻ in hot springs decreased by 11.20% to 23.80% north of the Yangbi Ms5.1 earthquake, which occurred on 27 March 2017, but increased by 5.0% to 28.45% to the south; this might be correlated with the difference in seismicity within the fault zone. The results of continuous measurements of NJ (H1) and EYXX (H2) showed irregular variation anomalies 20 days before the Yangbi Ms6.4 earthquake. In addition, Cl⁻ concentration is more sensitive to near-field seismicity with respect to Na⁺ and SO₄²⁻. We finally obtained a conceptual model on the origin of groundwater and the hydrogeochemical cycling process in the WQF. The results suggest that anomalies in the water chemistry of hot spring water can be used as a valid indicator of earthquake precursors.

The Xicheng ore field in West Qinling contains numerous Pb‒Zn deposits of varying sizes and is one of the largest areas of Pb‒Zn mineral resources in China. The Xiejiagou Pb‒Zn deposit is in the central part of the southern belt of the Xicheng ore field. No research has been completed on the trace elements and origin of this deposit. To supplement the geochemical information for each deposit in the Xicheng ore field and provide a scientific basis for the exploration of critical metals in the region, the sulfide in the Xiejiagou deposit is selected as the subject of investigation in this study, and its trace element composition is examined using laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP‒MS), accompanied by fluid inclusion thermometry and sulfur isotope analysis, to elucidate the geochemical characteristics of the deposit and propose its genesis. The results showed that the compositions of the trace elements in different sulfides differ greatly, with sphalerite mainly enriched in Cd and relatively enriched in Ge, Mn and In; galena mainly enriched in Ag and relatively enriched in Se, Ge and Tl; chalcopyrite relatively enriched in Sn and Ge; and pyrite relatively enriched in Ni, Co, Ge and Tl. The critical metals are mainly in sphalerite. Zn and Cd mapping diagrams of sphalerite suggest a possible Zn²⁺ ↔ Cd²⁺ substitution mechanism; Fe and Mn are positively correlated, while Fe and Zn are negatively correlated, suggesting a possible Fe²⁺ + Mn²⁺ ↔ 2Zn²⁺-coupled substitution mechanism; and the positive correlation between Cu and Ge is strong, while the difference in the content is large, suggesting a substitution mechanism involving (n + 1)Zn²⁺ ↔ Ge²⁺ + nCu²⁺. The sulfur isotopes show obvious heavy sulfur characteristics; the sulfur source is likely Middle Devonian seawater sulfate or marine sulfate from the strata, and the production of reduced sulfur is closely related to thermochemical sulfate reduction (TSR). The trace element compositions of sulfides in the Xiejiagou Pb‒Zn deposit exhibit characteristics that are essentially consistent with those of Mississippi valley-type (MVT) deposits, which clearly distinguish them from sedimentary exhalative (SEDEX) deposits. Additionally, the homogenization temperatures of the fluid inclusions in this deposit are lower than those of the SEDEX deposits; they range between 120 and 160°C, with a mean value of 172°C. Overall, the results indicate that the deposit is classified as an MVT Pb‒Zn deposit, and in this article, a mineralization model diagram has been drawn for the Xiejiagou Pb–Zn deposit.

北山成矿带是我国西北地区重要的战略性金属矿产资源地之一,区内的岩浆岩年代学工作已得到广泛开展,但对成矿带内成岩与成矿关系等缺乏系统研究。红尖兵山作为北山成矿带最具代表性的钨多金属矿床受到了较多关注,但其成矿时代、矿床成因等一直存在较大争议,已成为理解区域成矿构造事件的重要制约因素。本文对红尖兵山矿床详细的野外地质调查工作显示,该矿床成矿岩体为双驼峰式二长花岗岩,矿化类型可以划分为云英岩型矿石和黄玉-石英脉型矿石。对红尖兵山成矿岩体中的锆石、云英岩型矿石中的黑钨矿和黄玉-石英脉型矿石中的日光榴石进行了LA-ICP-MS U-Pb年代学,研究结果显示其形成时代分别为221.7±1.3 Ma、221.6±2.1 Ma、220.5±7.9 Ma,指示红尖兵山的成岩成矿时代在误差范围内一致,是晚三叠世岩浆-热液活动的产物。黑钨矿、日光榴石和白云母的LA-ICP-MS 成分分析结果显示,黑钨矿中富集Sc、Mo等元素,而日光榴石和白云母则分别富集Be、Zn、Sc和Li、Sc关键金属等元素。通过主成分分析(PCA)和元素相关性分析,揭示了黑钨矿、日光榴石和白云母中关键金属元素的赋存状态。综合分析显示,红尖兵山矿床形成于陆内造山后伸展构造背景下,在强烈的岩石圈伸展减薄和幔源岩浆底侵诱发下,地壳发生部分熔融产生的酸性岩浆经分异演化形成的岩浆热液与围岩相互作用后形成富含挥发组分、偏还原、低pH和低Eh的成矿流体,它们沿构造薄弱部位充填交代形成石英脉-云英岩型钨多金属矿床。本研究成果对于理解北山造山带三叠纪陆内伸展构造背景下构造-岩浆-成矿事件具有重要意义,并为该区域同类矿床的勘查和关键金属找矿提供了指导。