Alteration characteristics of wall rocks in the Liba orogenic gold deposit,West Qinling:Based on information extraction from GF-5B spaceborne hyperspectral data
Orogenic gold deposits have a wide range of alteration,especially for those hydrothermal-alteration-type.Due to variations in the distance from the ore body,different hydrothermal alteration mineral assemblages exist in the wall rocks.This study conducted data collection and alteration information extraction based on the GF-5 B spaceborne hyperspectral remote sensing image,and identified alteration mineral assemblages of the Liba giant orogenic gold deposit in the West Qinling region.The results from the GF-5B hyperspectral remote sensing data and proximal spectral measurements(Analytical Spectral Devices)indicates that the predominant alteration types in the study area include pyrite mineralization,sericitization,phengitization,chloritization and carbonatization.Validation through field investigations and proximal wavelength measurements suggest the hyperspectral remote sensing can recognize the alteration information extration.The wavelength shift of the short-wave infrared between muscovite and chlorite is usually related to the temperature and pressure conditions in the mineralization process.For example,the absorption wavelength position of the Al-OH combination of muscovite minerals near 2200nm is controlled by the ore fluid.In this paper,based on the wavelength absorption features near 2200nm,minerals were classified into sericite and phengite.These two minerals exhibit distinct alteration patterns.Phengite typically appears in the wall rock close to the ore body and is closely associated with mineralization.Chlorite is indicative of distal alteration,pointing to an acidic environment of the mineralizing fluids.Both minerals can serve as ideal spectral indicators for tracing gold mineralization.This study verifies that High-Resolution 02 satellite's AHSI hyperspectral data has a good application effect and potential in predicting the ore-forming prospects of orogenic gold deposits.