遥感和光谱地质进展及其对矿产勘查的实践应用

Remote Sensing and Spectral Geology and Their Applications to Mineral Exploration

根据2009年Economic Geology出版的专辑Remote Sensing and Spectral Geology,近年来发表的相关文献以及研究和应用的实践,对遥感与光谱地质进行了综述。内容从测谱学、TM/ETM和ASTER宽波段遥感应用,到地面和航空高光谱遥感应用与热红外遥感。传统的信息填图主要是解译,现代遥感不仅能提取地质和蚀变信息,还能进行其他手段无法进行的有效填图,结合地球物理、地球化学、野外和实验室光谱等,还能加深对矿床成因的理解。现代光谱地质结合XRF和GPS能够对矿物和蚀变带原地定量填图。TM/ETM从铁氧化物和含羥基矿物来提取矿化蚀变信息,大区域快速圈定成矿靶区。ASTER在粘土区SWIR的5个波段,提供了区分粘土矿物类型和一些硫酸盐、碳酸盐的能力,可以区分粘土、高级粘土、绢英岩和青盘岩,以及方解石和白云石。短波区的3个铁波段可以区分黄钾铁矾与赤铁矿和褐铁矿。障碍是需要校正到反射率来区分这些矿物组合,没有辅助数据很难做到这点,这极大地限制了该仪器作为常规勘探工具的能力。Crosta提供了多元统计方法对蚀变带填图,不需要大气校正。ASTER有5个热波段,像元大、信/噪比低。有能力对硅质岩和碳酸盐填图,但噪音多,并不总是有效。航空高光谱具有矿物填图的实用信/噪比。但航天高光谱Hyperion的信/噪比不能满足勘探和填图的要求。热红外是正在发展、尚未应用的勘探工具,其前景是可对硅质、硅酸盐类和碳酸盐填图。高分辨率遥感图像也为矿区快速评价、矿产勘查以及矿山建设提供了有效的技术支持。最后,结合国内外研究进展,讨论了勘查中的数据选择,给出了建设性的结论。

Based on the papers published in journals including the Review in Economic Geology, Volume 16, 2009. Remote Sensing and Spectral Geology, combined with our new achievements in mineral exploration with Crosta method, a review of remote sensing and spectral geology and their applications to mineral exploration are presented in this paper. Here the spectroscopy, broad-band remote sensing with TM/ETM and ASTER, hyperspec- tral remote sensing including surface spectral geological application and airborne hyperspectral geological application, additional with thermal infrared geological application are discussed. The traditional information mapping is mainly interpretation. Modern remote sensing can not only extract the geological and alteration information, but also conduct effective mapping, which is unable to do so with other methods. Through combining with geophysies, geochemistry and field and laboratory spectra, modern remote sensing techniques can be used to improve the under- standing of the metallogenisis. Spectral geology combined with XRF and GPS can quantitatively map minerals and alteration in the fields. TM/ETM can be used to extract mineralized alteration information from the iron-oxide minerals and hydroxyl minerals to outline the targets on large scale. ASTER has five bands in SWIR, which can distinguish argillic from advanced argiUic, phyllic, and propylitic assemblages as well as calcite from dolomites. Shorter wavelength bands were designed to distinguish iron oxides. Jarosite can be distinguished from hematite and limonite. A major technical hurdle is that it must be corrected to reflectance to distinguish these assemblages. Crosta （2009） presents a method by which ASTER can be used for alteration mapping without the need of atmospheric correction, by applying multivariate statistics. ASTER has five thermal bands, but the pixels is 90m, too large, and the signal to noise is poor. Silica and carbonates can be mapped with the thermal bands, but it is noisy and does not always work well. Airborne hyperspectral sensors have effective signal-to-noise ratio for mineral mapping. The space-borne Hyperion has poor signal-to-noise ratio, and can not be effectively used for mineral exploration and mapping. The thermal data is an underappreciated and underutilized exploration tool. It has the potential for map- ping silica, silicates, and carbonates. High spatial resolution image is useful to rapid assessment for new grass-root exploration^area, advanced mineral exploration and mine design and construction. At last, the platform and data selection is discussed, and constructive conclusions are presented.