Abstract
Anshan-Benxi area in Liaoning province is an important banded iron formations (BIFs) ore-mining district in China. Chlorite is widely distributed in this area, which is related to BIFs and high-grade iron ore, respectively. A fast and convenient method to identify the type and spatial distribution of different chlorites is crucial to the evaluation of high-grade iron ore in this area. Qidashan iron mine is a typical BIFs deposit, and its BIFs-related high-grade iron ore reserves are the second largest in the area. In this paper, the laboratory-based HySpex-320m hyperspectral imaging was used to study the wall rock in Qidashan iron mine. A hyperspectral imaging processing model was established for mineral identification, mineralogy mapping, and chlorite spectral features extraction. The results show that the wavelength positions of OH, Fe-OH, and Mg-OH absorptions of chlorite in the altered wall rock of high-grade iron ore are between 1400 and 1410, 2260 and 2265, and 2360 and 2370 nm, respectively, which are longer than those around BIFs. The relationship between cations in the octahedral layer of chlorite and the wavelengths of OH, Fe-OH, and Mg-OH indicates that Mg and Mg/(Mg + Fe) are inversely related to these wavelengths, whereas Fe is positively related. The wavelengths appear to be weakly influenced by AlVI. Since the bandpass of hyperspectral imaging systems is usually less than 10 nm, these chlorite wavelength differences can be used as a favorable tool for the high-grade iron ore exploration and the iron resources evaluation in the Anshan-Benxi area.
Highlights
Nowadays, hyperspectral remote sensing is a hot topic in the remote sensing field
All samples were measured by the FieldSpec-3 pro spectrometer, and theand spectra spectra were carefully investigated for identification mineral identification
Discussion be inferred that the different absorption wavelengths of chlorite in the wall rock of banded iron formations (BIFs) and high-grade iron ore are due to their different chemical compositions
Summary
Hyperspectral remote sensing is a hot topic in the remote sensing field. In the 1980s, based on the study of mineral reflectance spectroscopy models by Clark and Hapke [1,2,3], the unique advantages of hyperspectral remote sensing in geological applications were gradually recognized by many scholars. Traditional hyperspectral imaging is mostly used in aircraft or satellite platforms and suitable for large-scale geology mapping. [10,11,12] Compared to those of airborne and satellite-borne, the laboratory-based hyperspectral imaging can On the other hand, emerging terrestrial imaging spectroscopy methods, such as laboratory-based and field-based methods, have been used for various geoscience applications, including mineral exploration [4,5,6,7], sedimentology analysis [8,9], mineral identification, and alteration zonation mapping, etc. [10,11,12].
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