纳米地球化学：穿透覆盖层的地球化学勘查

摘要

Deep-penetrating geochemistry have revealed that anomalies do exist at surface overlying mineral deposits covered by transported overburden.We do not yet fully understand the dispersion processes though many researchers recently have given different migration models.Nanoparticles of metals were observed in gases,soils and ore rocks at the copper-nickel and gold deposits using a transmission electron microscope（TEM） equipped with an energy dispersive spectroscope.Particle diameters range from 10 to 200 nm.Most of them are generally tens of nanometers in diameters with ordered crystal structure observed by the TEM.The particles tend to assemblage shaped like a grape cluster.The particles are composed of native copper,compound metals of Cu-Fe,Cu-Fe-Mn,Cu-Ag,Cu-Cr,Cu-Ni,and compound metals with Si,Al,Ca,O,P from the copper-nickel deposit and Au,Cu-Au,Cu-Fe,Cu-Ti from the gold deposit.The facts show that nanoscale particles both in gases and soils are from the same source and the nanoscale particles with ordered crystal structures further indicate that they originated from the concealed Cu-Ni deposit.The migration model can be interpreted as that nanoscale particles of metals from the ore body are adsorbed onto surface of gas bubbles and migrated with an ascending flow of gases upward to the surface,arriving at the surface,part of particles are persisting in the soil gases and the other part of particles are trapped by soil geochemical barriers.The findings of nanoscale particles of mineralization metals provide direct observation evidence for migration mechanism of deep-penetrating geochemistry and a new method for separation of nanoscale particles from soils to search for concealed deposits.%盖层下方隐伏矿成矿及伴生元素如何穿透覆盖层到达地表,是深穿透地球化学迁移机理研究的热点。笔者以隐伏铜镍矿和金矿为例,同时采集地气、土壤、矿石样品,使用透射电子显微镜（TEM）,对样品中微粒物质的粒径、形貌、成分、结构进行了观测,发现微粒具有下列特点：（1）广泛观测到的微粒成分是铜及铜合金,金只在金矿上方土壤孔隙气体中能被观测到;（2）单个金属微粒粒径主体为几十nm,也有个别小到几个nm,大到上百个nm,微粒大多呈团聚体;（3）微粒晶形完整,内部原子呈有序晶体排列;（4）迁移柱实验表明纳米微粒具有快速迁移能力。在地气、土壤和矿石中同时观测到纳米级金属微粒,粒径大小、微粒形态、元素组合都非常相同或相近,表明两者具有来源一致性并具有序晶体结构,表明形成于内生作用。这是首次同时观测到矿石、土壤、气体介质中具有继承性关系的纳米金属微粒。矿石中纳米级金属微粒通过与微气泡表面相结合,以地气流为载体,或纳米微粒本身具有类气体性质,可以克服重力影响,穿透厚覆盖层迁移至地表,到达地表后一部分纳米颗粒仍然滞留在气体里,另一部分被土壤地球化学障（粘土、胶体、氧化物等）所捕获。这为深穿透地球化学从描述性或推测性模型走向实证性科学迈出了重要一步,为利用土壤作为采样介质、精确分离含矿信息用于寻找外来盖层下的隐伏矿提供了纳米地球化学技术。