福建铁帽山钼矿床围岩蚀变的短波红外光谱学研究

Short-wave infrared spectroscopy study on wallrock alteration of the Tiemaoshan porphyry molybdenum deposit, Fujian Province, China

短波红外光谱分析技术是近年来兴起并逐渐走向成熟的一种热液矿床围岩蚀变研究方法。铁帽山斑岩型钼矿床的围岩蚀变作用强烈,主要蚀变类型包括钾化、硅化、伊利石化、蒙脱石化等,并具有明显的分带性特征。其中,伊利石-蒙脱石类蚀变与斑岩型钼矿化作用密切相关。经过对钻孔岩心开展系统的短波红外光谱测量,准确地鉴定了蚀变矿物类型,划分了蚀变带,并且根据短波红外光谱测量结果计算了样品的伊利石结晶度(SWIR-IC),定量地研究了伊利石化蚀变作用的强度。结果表明,在伊利石-蒙脱石化作用范围内,伊利石结晶度越高钼矿化作用越强,但在强硅化蚀变带内,伊利石含量会有所降低,而在钾化带内,伊利石结晶度与钼矿化作用无关。在斑岩型钼矿床的找矿勘查工作中,系统地开展短波红外光谱测量,一方面可以准确鉴别蚀变矿物的类型,另一方面可以根据伊利石结晶度的指标来判断含矿热液活动中心,指导勘查工程的布设。

In recent years, short-wave infrared(SWIR) spectroscopy analysis has been developed and is gradually becoming a mature research method for the study of wallrock alteration of hydrothermal deposits. The wallrock alteration of the Tiemaoshan porphyry molybdenum deposit is intense. The dominant forms of alteration include potassic alteration, silicification, illitization, smectitization, showing obvious zoning characteristics. The illite-smectite alteration is highly associated with molybdenum mineralization. Through systematic measuring of short-wave infrared spectra, the alteration minerals were accurately identified. In addition, illite crystallinity(SWIR-IC) was calculated according to the profile of the short-wave infrared spectra, which can represent the quantitative intensity of illitization. The results show that within the illite-smectite alteration zones, the higher the SWIR-IC value is, the stronger is the molybdenum mineralization that will occur. However, within the silicification zone, the content of illites decreases dramatically. Within the potassic alteration zone, the SWIR-IC is unrelated with mineralization. During the exploration program, systematic measurement of short-wave infrared spectra can help the identify alteration minerals and can also indicate the ore-forming hydrothermal center based on the SWIR-IC value.