遥感图象在找寻铀矿中的应用

THE APPLICATION OF REMOTE SENSING IMAGINES IN URANIUM PROSPECTING

作者先后在滇西腾冲、湘东北、江西、华北等地参加过多次多种遥感试验工作,特别在对我国华南(包括华东和西南地区)花岗岩、火山岩、碎屑岩及变质岩等四大类型铀矿之成矿地质背景、成矿构造、景观地貌与铀矿化在遥感图象上的显示特征、标志及找矿方向等诸方面,积累了一些新资料,现撰写成此文,与读者共同讨论。

This paper is mainly intended to point out that the remote sensing imagines can demonstrate the important role the most obvious heat source bodies and heat source structural activities play in uranium mineralization. Taking three major ring structure systems of heat sources in South China (Fig. 1) as examples, it also indicates that the heat source ring structures are main structures for uranium mineralization. In particular, the structural knot, where the heat source ring structure caused by medium and small sized granite intrusion and volcanic activities intersect the arc and linear structure, controls the major uranium deposits in South China (Fig. 3).The "denudation coefficient" is put forward and calculated in this paper to express the modes of formation of uranium deposits along the uranium-producing heat source ring structure. In general, mineralization is distributed from the inside to the outside of the ring with the increasing denudation coefficient. In addition, the new concept of "image geological body" is established. With it, the metallogenic prognosis can be performed. Each sort of uranium mineralization usually occurs in its peculiar image geological body (called hereafter "image body" for short): the volcanic type uranium mineralization frequently occurs in dark-toned image body with complicated rhomboidal-netted stripes; the granite type mineralization in light-toned one with simple spotted stripes; and the mineralization of Mesozoic and Cenozoic basin type in medium-toned one with more complicated vermicular stripes.The thermal alteration image zone might be looked upon as one of the image indicators in prospecting for uranium ore deposits, with uramum mineralizations often found along the margin of the light-toned spotted thermal alteration image zone. Two major craters, one being new and the other old, have been recognized in the 610 mining district, which serve as new evidence for superimposed concentration of uranium-thorium type mineralization and single uranium type mineralization within this district.The characteristic geomorphic landscape division seems to be a geomorphic guide to regional or ore-district metallogenic prognosis, with uranium ores unexceptionally confined to fault-depression hills or relict hills lying below the denuded-graded line 400m of elevation. The general ore-forming elevation range of±400m suggests that uranium mineralization is genetically related to the median line (0m level) and that the intermediate structural region is a reaction area where "mixing-combination-neutralization" mineralization of deep-and shallowseated uranium-rich substances occurs. The determination of the position of this "three-combination surface", therefore, seems to possess key importance in search for uranium deposits.Furthermore, some clues to uranium ore deposits might be found by studying such characteristics as the reflection of uranium mineralization on thermal infrared images and variation in diurnal difference of temperatures between the heat carrier of uranium and surrounding rocks in the early morning when the crust dissipates heat to the minimum.