Application Of Short-wave Infrared Spectroscopy In Prospecting And Prediction

Qulong deposit is one of the typical porphyry copper-molybdenum deposits in Gangdese metallogenic belt.A lot of researches on geochronology and geochemistry have been carried by predecessors.Because of the complex metallogenic setting in Qulong deposit,the theories about metallogenic rock are still controversial.There are two main theories,one is that the mineralization is a single rock mass related to P porphyry,and Rongmucuola pluton is the wall rock;another one is that the Rongmucuola pluton is not the wall rock and closely related to the mineralization,which is the multi-complex formed by secondary magmatism.The research of metallogenic rock body,alteration zoning and hydrothermal mineralization center will directly affect the evaluation of ore prospecting potential in the deep and peripheral areas of the deposit,and will also determine the next exploration direction.Therefore,new technical methods are urgently needed to carry out in-depth research.Compared with the traditional methods,Short-wave infrared spectral reflectance(SWIR)can not only quickly identify the mineral species without destroying the sample,but also reflect the changes of mineral composition by extracting the spectral information of minerals.This study using SWIR technology analyzed the alteration mineral combination,distribution and mineral spectrum characteristic parameters,found the alteration mineral combination zone and the short-wave infrared mineral characteristics,combining with petrography and electron microprobe analysis(EPMA)results,inverted the conditions of mineralization,together with the superficial two-dimensional and spatial three-dimensional data,predicted the hydrothermal center,it provides the basis for further prospecting and exploration.The results of SWIR interpretation shown that the main minerals are white mica minerals(including phengite,muscovite and illite),chlorite,epidote,kaolinite,gypsum and montmorillonite,etc.In this study,the depth of the main mineral characteristic absorption peaks was extracted to reflect the alteration intensity,and the alteration mineral assemblage zoning was delineated in combination with the petrographic characteristics.Compared with the mineralization information,it is found that the alteration mineral assemblages of muscovite and gypsum and the alteration mineral assemblages of muscovite and chlorite are strongly related to the enrichment of copper mineralization.The EPMA results showed that the wavelength of the characteristic absorption peak(Al-OH)of the mica had positive correlation with Al^vi,and had negative correlation with Fe+Mg and Na/Na+K,but had no relation with Ti.Meanwhile,the IC of Muscovite had no relation with Al^vi,Fe+Mg and Ti,but weakly correlated with Na/Na+K,and those results are consistent with previous researches.According to the comprehensive study,here are the indicative significance of the characteristic parameters of SWIR in Qulong deposit:the distribution of short-wave Muscovite(2198-2201nm),high-IC Muscovite(>1.2)and short-wave chlorite(2246-2248nm)are close to the location where the degree of copper is high(Cu>0.4%),which indicates the location of hydrothermal center.Based on the above analysis,it is inferred that the deep position of ZK001-1,ZK1509-1 and ZK1601-1 are close to the hydrothermal center,and there may be more than one hydrothermal center.