| 青海松树南沟金矿区西矿床磁铁矿地球化学特征及成因意义 |
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| 关键词:magnetite geochemistry genetic type ore-forming fluid evolution Songshunangou gold district North Qilian metallogenic belt |
| 基金项目:本文由国家自然科学基金项目(编号: 42572103)、新一轮找矿突破战略行动科技支撑项目(编号: ZKKJ202427)、四川省自然科学基金项目(编号: 2024NSFSC1954)和中央引导地方科技发展资金项目(编号: XZ202401YD0006)联合资助。 |
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| Geochemical Characteristics and Genetic Implications of Magnetite from the Western Deposit in the Songshunangou Gold District, Qinghai Province |
| The western deposit in the Songshunangou district is a large-scale gold deposit within the North Qilian metallogenic belt. Mineralization occurred within the Late Ordovician quartz-diorite porphyry and adjacent basaltic andesite near the contact zone. However, genetic classification lacks systematic mineralogical support, and ore-forming fluid evolution remains poorly constrained, impeding deep and peripheral exploration. This study focused on magnetite veins within potassic alteration (Mt1) and potassic alteration overprinted by propylitic alteration (Mt2) in the western deposit. Mineralogical studies, combined with electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses, revealed distinct compositional differences. Mt1 exhibited higher concentrations of Ti (2 830×10–6–18 797×10–6), Al (1 309×10–6–19 165×10–6), Si (1 851×10–6–24 993×10–6), and Mn (130×10–6–2 982×10–6), with lower levels of Co (0.53×10–6–280.01×10–6), Ni (37.08×10–6–135.71×10–6), and Sn (3.52×10–6–39.90×10–6). In contrast, Mt2 exhibited significantly lower Ti (614×10–6–4 464×10–6), Al (539×10–6–7 268×10–6), Si (2 155×10–6–10 544×10–6), and Mn (137×10–6–467×10–6) content compared to that of Mt1, while containing slightly higher Co (90.97×10–6–196.58×10–6), Ni (20.95×10–6–163.04×10–6), and Sn (2.70×10–6–77.02×10–6). Formation temperatures indicate that Mt1 crystallized at relatively high temperatures (395 °C on average), whereas the lower temperature of Mt2 (337 °C on average) reflects overprinting by later moderate-to low-temperature hydrothermal fluids. This fluid evolution is characterized by a temperature decrease and an increase in oxygen fugacity. Elemental geochemical diagrams exhibited the diagnostic characteristics of a porphyry gold deposit. Both magnetite types (Mt1 and Mt2) are of hydrothermal origin. Furthermore, the high Ti, Al, and Mn contents of magnetite (Mt1) can be diagnostic altered and mineralized porphyry systems in exploration, providing a key vector for exploration targeting. |
| YE Zifeng,LANG Xinghai,ZHONG Shixin,WANG Xuhui,DONG Weicai,LUO Chao,LI Shancai,WANG Dengke,LI Ke,TANG Yongjiang.2026.Geochemical Characteristics and Genetic Implications of Magnetite from the Western Deposit in the Songshunangou Gold District, Qinghai Province[J].Acta Geoscientica Sinica,47(5):1150-1166. |
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