IMAGE FRACTAL FEATURE OF HYDROTHERMAL URANIUM ORE-FIELDS IN SOUTH CHINA

Remote sensing image was used to study the fractures of rocks in typical hydrothermal uranium ore-fields in South China. Visually, rocks of uranium ore-field are with multi-direction fracture in remote sensing image of various scale, while rocks of the nearby areas which was believed to have similar metallogenic condition but few deposit was found after exploration only show multi-direction fractures in remote sensing image of certain scale . Rocks of ore-fields such as Xiangshan in Jiangxi province have significant NE, NNE, NW strike fractures in the remote sensing images of scale from 1:1,000, 000 to 1:50000, while rocks of nearby area with occurrences such as Yuhuashan only show clear NE, NNE strike fractures in 1:1,000, 000 to 1:250,000 images. Mathematically, remote sensing image of Rocks of the ore-fields are with large box dimension and more symmetrical shape of multi-fractal spectrum , while rocks of the nearby area with occurrences are of less fractal dimension and asymmetrical multi-fractal spectrum. The rocks remote image of Xiangshan have the box dimension of 2.61 and the Hoder exponent of -0.35 to 0.4, while thats of Yuhuashan are 2.56 and -0.2 to 0.6. Furthermore, remote sensing image of rocks of the same type in uranium ore-field and nearby area with less economical minereralization may have the same fractal dimension but with different multi-fractal spectrum. Box dimensions of the images of the west and east parts of Guidong pluton in Guangdong province are both 2.65, but the multi-fractal spectrum of the east part with over 10 uranium deposits is of typical bell shape with the Holder exponent of -0.4 to 0.3, while that of the west part with only several uranium occurrences is of incomplete bell shape with the Holder exponent of -0.5 to 0.18. In geology , the texture of remote sensing image mainly reflect fractures and joints of rocks, the box dimension of rocks image can be explained as the complexity of fractures and joints on the whole, and the multi-fractal spectrum as the degrees of irregular distribution (singularity) of fracture and joints at different scales. Because fractures have been found a key role in the formation of uranium deposit in South China, therefore, the fractal feature of rocks image may used as an criteria in screening the potential area.