相山铀矿化蚀变矿物组合的成像光谱特征识别

Characteristics Recognition of Imaging Spectra for Uranium Mineralization Altered Mineral Assemblage in Xiangshan

蚀变矿物组合对热液型铀矿勘探具有重要的指示意义。相对于航空或航天成像光谱,地面成像光谱在小范围矿床尺度的蚀变精细识别方面更具优势。为研究江西相山铀矿化热液蚀变组合特征,利用HySpex地面成像光谱仪获取可见光-近红外-短波红外波段的钻孔岩心成像光谱数据,针对铀矿化的两种基本类型——水云母-萤石型和碱交代型,分别从蚀变单矿物和蚀变矿物组合两个角度分析和提取他们的诊断性光谱特征,建立了光谱识别标志。发现伊利石具有光谱多型特征,按特征波长位置分为Ⅰ型和Ⅱ型两类。水云母-萤石型铀矿化蚀变组合包含高岭石、高岭石+地开石、蒙脱石和Ⅰ型伊利石,碱交代型铀矿化蚀变组合包含绿泥石、碳酸盐、绿蒙混层、赤铁矿和Ⅱ型伊利石;基于光谱匹配模型和岩心填图结果对两类铀矿化段蚀变结构进行了分析,铀矿化中心由近及远分别具有蒙脱石→Ⅰ型伊利石→高岭石+地开石→高岭石和碳酸盐→赤铁矿+绿泥石→绿蒙混层→Ⅱ型伊利石的分布特征,均存在流体的叠置改造作用;通过岩心成像光谱编录及三维建模表明,两类伊利石具有空间上的上、下分带特点,这预示着两种铀矿化亦具有相似的空间分布特征。上述研究为相山地区进一步找矿勘探提供了一定参考。

The altered mineral assemblage is important for hydrothermal uranium deposit prospecting.Compared to aerial or aerospace imaging spectroscopy,the ground imaging spectra is with the advantageous of fine spatial resolution and high signal to noise ration.In order to study hydrothermal alteration assemblage characteristics of uranium mineralization in Xiangshan,Jiangxi Province,drill core imaging hyperspectral data with the wavelength from visible-near infrared to short-wave infrared(VNIR-SWIR)were obtained by using HySpex ground imaging spectrometer.In order to identify the two basic types of uranium mineralization of fluorite-hydromuscovite type and alkali metasomatism type,the diagnostic spectral features were respectively analyzed and extracted from two aspects of single mineral and mineral assemblage of the alteration related to the uranium mineralization,and the spectral identification marks were established.It was found that illite can be divided into two types according to the characteristics wavelength locations:type I and type II.Kaolinite and the assemblage of kaolinite and dickite,montmorillonite and typeⅠillite were recognized from the fluorite-hydromuscovite type uranium mineralization zone;chlorit,carbonate,hematite,I/C clay and typeⅡillite were recognized from the metasomatism uranium mineralization zone.Then,the alteration composition and structures of two types of uranium mineralization were analyzed based on the results of core alteration mapping by spectral matching model.Montmorillonite,typeⅠillite,assemblage of kaolinite and dickite,and kaolinite were followed by the distribution from the center of fluorite-hydromica type uranium mineralization to the periphery area.Carbonate,assemblage of chlorite and hematite,I/C clay,and typeⅡillite are followed by distribution from the center of alkali metasomatism type uranium mineralization to the periphery area.The distribution characteristics are the effects of superimposition and transformation of fluid.Finally,core imaging spectroscopy logging and three-dimensional modeling showed that the two types of illite have spatial zoning characteristics of upper typeⅠand lower typeⅡ,which indicate that the two types of uranium mineralization also have similar spatial distribution characteristics.The above research provides a reference to the further uranium exploration in Xiangshan area.