干旱荒漠景观区金属微粒迁移机制浅析

Analysis on the migration mechanism of metal particles in arid desert area

干旱荒漠景观区面积辽阔,找矿潜力巨大,受限于常规地球化学勘查方法,被认为是勘查地球化学的难点重点区。本研究简要总结干旱荒漠景观区潜在的金属微粒向上迁移的机制,依据其作用范围分为:潜水面以下的机制,包括地下水作用、压力泵机制、地气流和电化学迁移机制;潜水面以上的机制,包括毛细管作用、植物吸收、气态物质迁移和生物扰动。研究中介绍各迁移机制的作用原理、有效性及其局限性,认为每种机制在特定的环境条件下均能以不同形式运移相关的金属微粒,但由于复杂的地形地貌、漫长的地质演化,任何机制不可能独立单一地存在,彼此间相互协同作用。另外,潜水面以上与包气带有关的机制主要发生在沉积地段的运移覆盖层中,在开展深穿透地球化学(地气类方法、选择性提取方法、植物地球化学方法和地球电化学方法)找矿之前,有必要了解研究区古气候、沉积物性质和地貌演化史,便于合理选择采样层位和采样介质,尽可能发现由金属运移机制引起的综合异常。

The arid deserts are vast areas and has great potential for prospecting.It is considered to be a difficult area for geochemical exploration due to the limitaions of conventional exploration methods.This paper briefly summarizes the migration mechanism of metal particles in the arid desert area and classifies the capable mechanisms of moving metal particles upwards into the phreatic zone(groundwater action,dilatancy pumping,geogas flow,and electrochemical migration)and the vadose zone(capillary,plant uptake,gaseous migration,bioturbation),and introduces the principles,effectiveness,and limitations of each migration mechanism.The metal particles relevant to each mechanism can be transported in different forms in specific environmental conditions.However due to the complex topography and long geological evolution,these mechanisms cannot exist independently and synergistically need each other.In addition,above the phreatic surface,the mechanism associated with the vadose zone mainly occurred in the transport cover of depositional section.Before conducting deep penetrating geochemistry methods(geogas method,selective extraction method,plant geochemical method,geoelectrochemical method),it is necessary to understand the paleoclimate,sediment properties and geomorphological evolution of the study area,strategically select the sampling horizon and sampling medium,and find synthesis anomaly caused by metal migration mechanism as much as possible.