覆盖区勘查地球化学理论研究进展与案例

覆盖区勘查地球化学近年在迁移机理研究上最显著的进展是在矿体上方覆盖层土壤中直接观测到Cu、Au等纳米金属微粒和植物细胞中的成矿元素，从纳米尺度和分子水平直接观测到的微观迁移证据使得覆盖区勘查地球化学迁移机理研究从描述性模型向实证性模型实现了质的飞跃.通过对北方干旱沙漠覆盖区金矿、中部湿润农田覆盖区铜镍矿、南方植被红土覆盖区的铜金银矿研究表明，Cu、Au元素主要以纳米微粒形式穿透火山岩、变质岩和土壤覆盖层，用深穿透地球化学的微粒分离和铁锰氧化物提取技术可以有效指示隐伏矿体.干旱盆地砂岩型铀矿的研究表明，铀在氧化条件下以铀酰络阳离子(UO₂2+) 形式迁移到地表，并被土壤中粘土所吸附，吸附相中的铀占全部的铀比例最高(17%~40%)，使用物理分离粘土或化学提取粘土吸附相铀可以有效地指示深部铀矿体. 

New Evidences for Transport Mechanism and Case Histories of Geochemical Exploration through Covers

Recent years, a great progress on exploration geochemistry has been made in findings of evidences of nanoparticles of metals and metals in vegetable cells. The findings have provided nanoscale and molecular-level understanding of metal transportation from the concealed ore bodies through the overburden covers. The case history studies from concealed Au, Cu-Ni, Cu-Au-Ag deposits show that these nanoparticles of metals could penetrate through sedimentary, metamorphic and soil covers to the surface. Nanoparticle sampling and selective leaching of oxide coatings are effective to indicate concealed deposits. Case study on sandstone-type uranium deposits show that uranium is converted to uranyl ions (UO₂2+) under oxidizing conditions and is sorbed on clay minerals to accumulate in anomalous concentrations, which comprise from 17.9% to 40% of the total U content. Separation of fine-grained clay-rich soils or selective leaching of absorbed U onto clays are effective for deep-penetrating geochemical surveys for sandstone-type uranium deposits.