川滇黔成矿区碳酸盐岩影像图形特征变异研究

William Morris Davis (1899) presented a theory in which "all the varied forms of the lands are dependent upon-or, as the mathematician would say, are functions of three variable quantities, which may be called structure, process, and time" Therefore, in one region where the same lithology exposed at surface, under the same environment conditions and in the same weathering processes, if the drainage pattern, microrelief, vegetation and soil changed, it is most because of some geologic features of the rock changed, such as structure position, stratum attitude, outcrop area, bed thickness and so on. For example, the famous Guilin peak-forest karst is formed only at the plunging crown of a N-S anticline, and cliffs of displacement are well developed in close-jointed limestone..Remote sensing images represent in microcosm of the landscape, broad lithological information is deduced from a number of parameters observed in remote sensing images, viz. general geologic setting, weathering and landform, drainage, structural features, soil, vegetation, and spectral characteristics..Carbonatite, wide exposed in Dian-Chuan-Qian metallogenic region, is the host strtum of Pb-Zn-Ag deposits, but only some special structure position could be the ore-holding space, e.g. the crest of anticline. Variation of image characters of carbontite including spectral characteristics and figures characteristics (e.g. microrelie, drainage pattern, structural features), was observed at different structure position. Due to topography, cover of vegetation and soil, together with the same composition of alteration and wall rock, the spectral characteristics did not performed well. However, the figure characteristics were little affected by environment, from which not only lithological information but also structure information could be extracted. Examination of drainage density, drainage pattern and vegetation patterns may also provide clues to lithology even when beds are not directly exposed..Therefore, in most cases, a remote sensing data interpreter has to rely on indirect clues, such as general geologic setting, alteration zones, associated rocks, structure, lineaments, oxidation products, morphology, drainage, and vegetation anomaly, since only rarely is it possible to directly pinpoint the occurrence and mineralogy of a deposit based solely on remote sensing data. .Establishment of the interpretation key should be the first step of how to use those clues. Base on the "3S" technology, about 5 large-middle scale deposits will be select in this project to study the variation regularities of the figure characteristics of carbonatite at different structure position with visual interpretation. ETM+, ASTER, RADAR and high-resolution remote sensing data will be used. A interpretation key atlas about ore bearing carbonatite and carbonatite around the mine in Dian-Chuan-Qian metallogenic region will be established also.

滇川黔成矿区铅锌银矿床的赋矿地层为碳酸盐岩，容矿空间为背斜转折端、岩层挠曲等特殊的构造部位。不同构造部位的碳酸盐岩形成的微地貌、水系等存在差异，在遥感影像上显示为光谱特征和图形特征变异现象。由于地形、植被等因素影响，加之该类矿床围岩蚀变与围岩成分接近等原因，在该区进行光谱特征试验效果不佳。碳酸盐岩的图形特征受环境影响较小，且能从中提取构造、岩层产状等地质信息，但目前还不能进行自动解译。时效性要求不高的地质工作中可采用目视解译方法提取，但目前缺乏详细的解译标志。本项目将选择已知大中型铅锌银矿床5例左右，利用ETM、ASTER、雷达和高分辨率数据，在"3S"技术平台支持下，用目视解译的方法提取各种含矿构造的含矿地段、近矿地段和远离矿体地段的碳酸盐岩的图形特征（微地貌、水系、纹理等），结合野外地质检查，探讨含矿与非矿碳酸盐岩的图形特征变异规律，建立滇川黔成矿区不同构造部位碳酸盐岩解译标志图谱。

由于植被和土壤的覆盖、蚀变信息微弱以及矿体的隐伏-半隐伏特点，仅靠光谱特征在滇川黔铅锌成矿区进行遥感找矿难度较大。遵循地质规律，探寻矿床的空间定位特征及含矿部位在遥感影像上（特别是高空间分辨率遥感图像）的图形特征，是覆盖区遥感找矿的解决途径之一。本项目在“3S”技术平台上，利用多种分辨率的遥感影像，从不同尺度研究了会东大梁子矿床等5个矿床的宏观的遥感地质背景、矿区遥感线、环构造，含矿层及上覆、下伏地层在近矿区与远矿区的微地貌、水系、植被和色调等的特征，建立解译标志；研究认为大梁子矿床、茂租矿床和毛坪矿床具有相似的成矿地质背景，即位于不同时代沉积拗陷中心（拗陷盆地）的边缘，同时基底隐伏的东西向构造痕迹明显；矿区内环形构造发育；含矿的碳酸盐岩岩溶地貌不发育，水系稀疏；起隔挡作用的上覆页岩层形成带状负地形，下伏地层线性构造发育，三个因素须同时存在；将宁南银厂沟矿床与大梁子矿床进行对比，探讨其勘查效果不佳的原因；将茂租矿床与白马厂勘查区进行对比，分析勘查区的地层岩性组合的影像特征及环形构造等方面的异同；对比毛坪矿床猫猫山背斜东西翼地层，讨论产状陡倾的碳酸盐岩与产状平缓的碳酸盐岩的影像特征差异及对矿化的影响；将麒麟厂矿床与车家坪勘查区分别进行比对，分析其地层岩性组合的影像特征差异，推测可能存在的隐伏穹窿构造，为勘查工作提出建议。