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    ZHANG Bi-min, WANG Xue-qiu, XU Shan-fa, YAO Wen-sheng, YE Rong. Models and case history studies of deep-penetrating geochemical exploration for concealed deposits in basins[J]. GEOLOGY IN CHINA, 2016, 43(5): 1697-1709. DOI: 10.12029/gc20160518
    Citation: ZHANG Bi-min, WANG Xue-qiu, XU Shan-fa, YAO Wen-sheng, YE Rong. Models and case history studies of deep-penetrating geochemical exploration for concealed deposits in basins[J]. GEOLOGY IN CHINA, 2016, 43(5): 1697-1709. DOI: 10.12029/gc20160518

    Models and case history studies of deep-penetrating geochemical exploration for concealed deposits in basins

    • In the past twenty years, more and more mineral deposits were discovered in basins. The traditional geochemical exploration methods are not effective in mineral exploration of concealed deposits in basins. Deep-penetrating geochemistry provides a new approach for exploration in basins. The case history studies from the concealed sandstone-type uranium deposit hosted in a sedimentary basin, the concealed Ag-polymetallic deposit in a volcanic basin, the concealed Cu-Ni deposit in a basin covered by metamorphic rocks and the concealed Au deposit covered by loess have led the authors to reach the following conclusions:(1) Uranium is converted to uranyl ionsUO22+ under the oxidizing condition and is easy to migrate under the influence of groundwater movement along sandstone pore structure and tectonic fissures; the uranyl ions are absorbed on clay minerals after migrattion to earth's surface, because clay layers have a net negative charge, which needs to be balanced by interlayer cations; leaching of mobile forms of elements in soils and separation of fine-grained soils can be used to determine the orebodies; (2) The Yueyang Ag-polymetallic deposit was nearly formed in the same period as the volcanic rock; Ore-bearing fluid migrated to earth's surface along tectonic fissures in the formation process of the deposit; mobile forms of metals in ore-bearing fluid were absorbed on clay minerals; leaching of mobile forms of elements in soils and separation of fine-grained soils can be used to determine the orebodies in volcanic basins; anomalies of elements are directly displayed over the blind orebodies; (3) the contact zone between intrusive mass and metamorphic rock generated a lot of tectonic fissures in the process of emplacement of the ultrabasic intrusion; and the fluid would take ore-forming elements Cu and Ni and migrate to earth's surface and form cyclic anomaly; (4) ore-forming elements Au and Ag in the form of complexes, nano-scale elemental or alloy particles taken by fluid migrated upward in the oreforming process of Au deposits in Luoning basin; compound or nanoparticles which dissociated from orebodies or rocks could penetrate loess pores and migrated upward to earth's surface and were absorbed on clay minerals; separation of fine-grained soils can be used to determine the orebodies. In this paper, the authors built deep-penetrating geochemical models for mineral deposits in basins based on application effects, anomaly shapes, characteristics of the covers, occurrences of the ore-forming elements, and migration patterns. The above results will provide theoretical and technical support for geochemical exploration in basins.
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