基于红外光谱技术的内蒙古达斯矿区蚀变地质填图及其勘查指示意义

红外光谱技术，辅以显微镜下鉴定和矿物地球化学分析，通过系统采集达斯矿区地表岩石与钻孔岩芯样品，开展精细蚀变矿物填图，利用绢云母矿物Al- OH基团在2200 nm附近的光谱变化特征，开展勘查区及其外围的找矿预测。结果显示：① 研究区主要矿物为钠长石、微斜长石、石英、绢云母、高岭石、蒙脱石和绿泥石，另含有少量明矾石、电气石、石膏和黑云母等；② 电气石、明矾石、高岭石和绢云母矿物及其组合与成矿关系密切，具有中硫化浅成低温热液型矿床蚀变矿物组合特征；③ 目前已发现的Pb矿（化）体，主要产于300 m以浅，矿体底板为一套蒙脱石+绿泥石为主的蚀变矿物组合。矿体赋存于绢云母（高岭石+少量明矾石+电气石）蚀变带内，蚀变分带特征（矿化体中心向外）表现为：绢云母化→绢云母+高岭石（+少量明矾石+电气石）→绢云母+蒙脱石→蒙脱石+绿泥石；④ 区内长波绢云母指示了深部热源的位置，短波绢云母反映出热液流体与浅部大气降水的混合作用，根据绢云母矿物Al- OH波长插值填图及矿物组合特征变化确定了成矿流体pH值偏中性、温度逐渐降低的变化趋势；⑤ 绢云母矿物在2200 nm附近的光谱吸收深度与Pb品位之间呈正相关关系，10%吸收深度阈值可区分具有相似Al- OH吸收特征的绢云母和高岭石矿物；⑥ 结合GIS空间叠加分析，认为勘查区外围仍具一定找矿潜力。

Alteration mapping and exploration indications based on SWIR and TIR spectroscopy in Dasi, Inner Mongolia

Dasi deposit is located in the middle of the Mesozoic Daxinganling- Yanshan volcanic belt, and it has great prospecting potential for porphyry and epithermal deposits. This area is recognized as an important metallogenic belt, characterized by extensive magmatic, volcanic, and subvolcanic activity. In our study of the Dasi deposit in Inner Mongolia, we utilized SWIR and TIR technology to measure rocks from the surface and cores. With the assistance of mineral geochemical analysis and microscope observation, we successfully completed the alteration mapping and prospecting potential prediction. The results show that: ① The main altered minerals at Dasi deposit include albite, microcline, quartz, sericite, kaolinite, montmorillonite, and chlorite, along with smaller amounts of alunite, tourmaline, gypsum, and biotite. ② The relationship between the identified alteration minerals through SWIR analysis and the Pb orebody shows a close association between mineralization and tourmaline, alunite, kaolinite, and sericite. Dasi deposit exhibits mineral assemblages typical of medium- sulfide epithermal deposits. ③ Pb mineralization dominates the deposits, mainly occurring at shallow depths of around 300 m underground. The exposed surface shows significant denudation, and the bottom plate of the Pb orebody is composed of argillization minerals, predominantly montmorillonite and chlorite. The alteration zoning, progressing from the mineralization center outward, follows the sequence of sericitization→sericite+kaolinite (+alunite+tourmaline)→sericite+montmorillonite→montmorillonite+chlorite. The orebody is located within a sericite (kaolinite) alteration zone. ④ Long- wavelength sericite indicates the presence of deep- seated thermal energy, while short- wavelength white mica reflects a combination of magmatic hydrothermal solutions and external atmospheric precipitation. Wavelength shifts at 2200 nm provide insights into the metallogenic environment, such as pH, temperature, and fluid flow. ⑤ The absorption depth of sericite at 2200 nm demonstrates a positive correlation with Pb grade, as expressed by the equation y(Pbgrade)=0. 1217 x(absorption depth)(R2=0. 9178). A threshold of 10% absorption depth can differentiate between sericite and kaolinite mineral types. ⑥ Combined with GIS spatial overlay analysis, we determined that the peripheral areas still hold promising prospecting potential.