Identification and new discovery of Qiansxuilan fault belt in Gaudeanmus area, Namibia based on the multi-source remote sensing data
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摘要: 遥感影像因其可直观显示地质构造形迹的物理特征及地表形态，弥补野外点线观测的局限性，在成矿环境识别及资源评价领域受到众多地学工作者的青睐。以纳米比亚欢乐谷白岗岩型铀成矿区为研究区，基于ETM+、Radarsat-2多源遥感数据，通过开展彩色合成、纹理信息提取、光学和雷达信息融合等图像信息增强，从地层、岩体、构造、地形、水系、植被等方面构建了千岁兰断裂带遥感解译标志，如岩体、岩层被切割、错开或呈穹窿状，地貌为破碎的山体垭口形态或地形切割强烈破碎的深沟，发育硅化、高岭土化、钾化、方解石化、绿泥石化蚀变现象等。基于构建的遥感解译标志和断裂识别方法，识别出了区内部分出露、部分隐伏、规模最大且最重要的千岁兰控矿断裂，创新性提出了千岁兰断裂在区内并非为1组断裂，而是由北部、中部、南部3组断裂组成的断裂带。结合野外出露断裂判别特征和控矿作用分析，验证了千岁兰断裂带的真实存在，且正是该断裂带控制着区内含铀白岗岩和铀矿化的产出。Abstract: Because the images could display the physical characteristics and their surface morphology of geological structures intuitively and make up for the limitations of field investigation, remote sensing technology is favored by many geoscientists in the field of mineralization environment identification and resource evaluation. The paper took the leucogranite-type uranium metallogenic area in Gaudeanmus, Namibia as the research area, carried out the information enhancement of images such as color composition, texture information extraction, optical and radar image fusion, and constructed the marks for fault identification from stratum, leucogranite bodies, structure, geomorphology, water system, vegetation and so on, based on the multi-source remote sensing data of ETM+ and Radarsat-2.Leucogranite bodies and layers were cut or folded to form a vault.The landform appeared as a tectonic fracture, silicification, kaolinization, potassic alteration, calcitization, chloritization and were developed. Furthermore, the paper identified the partly outcropping and partly buried fault named Qiansuilan that was the largest and most important ore-controlled fault in the region, based on the fault identification marks and method. Furthermore, it was proposed innovatively that the Qiansuilan fault was not a group of faults in the area, but a fault zone consisting of three groups of faults named the northern, central and southern faults zone. Combined with the fault identification feature exposed in the field and ore-controlling analysis, the Qiansuilan fault existed truly and it controlled the occurrence of leucogranite rich in uranium and uranium mineralization in the area.
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Key words:
- multi-source remote sensing /
- Namibia /
- Gaudeanmus /
- Qiansuilan fault /
- new discovery
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图 1 欢乐谷地区铀矿地质简图(据文献[8]修改)
Figure 1. Uranium geological diagram of Gaudeanmus area, Namibia
图 2 ETM+和RadarSat-2遥感数据处理流程
Figure 2. Flow chart of remote sensing data processing of ETM+ and RadarSat-2
图 3 研究区千岁兰断裂带遥感地质解译图(以ETM+752遥感影像为底图)
Figure 3. Interpretation map of Qinsuilan fault zone based on the technology of remote sensing geology in the study area
图 4 基于ETM+752遥感影像(a)和RadarSat-2纹理提取影像(b)的千岁兰北部断裂带解译图
Figure 4. Interpretation map of the northern fault zone of Qiansuilan based on the ETM+752 image (a)and RadarSat-2 texture image (b)
图 5 基于ETM+752遥感影像(a)和基于RadarSat-2纹理信息与ETM+752融合(b)的千岁兰中部断裂带解译图
Figure 5. Interpretation map of the middle fault zone of Qiansuilan based on the ETM+752 image(a)and fusion image of RadarSat-2 texture and ETM+752 image(b)
图 6 基于ETM+2纹理影像(a)和RadarSat-2纹理影像(b)的千岁兰南部断裂带解译图
Figure 6. Interpretation map of the southern fault zone of Qiansuilan based on the ETM+2 texture image(a)and the RadarSat-2 texture image(b)
图 7 千岁兰北部断裂带野外验证
a.断裂构造破碎带；b.沿断裂侵入的方解石脉；c.D期富铀白岗岩近景图
Figure 7. Field validation of the northern fault zone of Qiansuilan: Fractured shatter zone (a), intrusion calcite veins along the fault (b), close up view of alaskite of stage D rich in uranium (c)
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