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TitleAlteration mineralogy of the Zhengguang epithermal Au-Zn deposit, northeast China: interpretation of shortwave infrared analyses during mineral exploration and assessment
AuthorWang, L; Percival, J BORCID logo; Hedenquist, J W; Hattori, K; Qin, K
SourceEconomic Geology 2020 p. 1-18,
Alt SeriesNatural Resources Canada, Contribution Series 20200345
PublisherSociety of Economic Geologists
Mediapaper; on-line; digital
File formatpdf; html
Lat/Long WENS 120.0000 130.0000 50.0000 40.0000
Subjectseconomic geology; mineralogy; Science and Technology; Nature and Environment; mineral exploration; mineral deposits; gold; zinc; epithermal deposits; ore mineral genesis; mineralization; alteration; infrared spectral analyses; spectroscopic analyses; x-ray diffraction analyses; electron probe analyses; host rocks; thermal analyses; hydrothermal systems; Duobaoshan Ore District; Zhengguang Deposit
Illustrationslocation maps; geoscientific sketch maps; photographs; spectra; tables; plots; ternary diagrams; histograms; cross-sections
ProgramScience Laboratory Network
Released2020 12 28
AbstractAlteration mineralogy from shortwave infrared (SWIR) spectroscopy was compared with X-ray diffraction (XRD) analyses for samples from the Zhengguang intermediate sulfidation epithermal Au-Zn deposit, eastern Central Asian orogenic belt, northeast China. The SWIR and XRD analyses indicate that alteration minerals in the vein-adjacent halo mainly comprise quartz, illite, and locally pyrite (QIP) and chlorite, whereas samples from the pervasive propylitic alteration of host basaltic andesite lava contain epidote, chlorite, carbonate, montmorillonite, and locally illite. SWIR mineral identifications from automated mineral identification software may not always be accurate; thus, the results should be validated by the user. The wavelength position of the Al-OH (~2,200 nm; wAlOH) absorption feature can be used to approximate the composition of illite or white mica. However, caution is required when using the wAlOH value to assess paleotemperatures, as the composition of illite can be influenced by the composition of the host rocks or the hydrothermal fluid. In addition, values of the illite spectral maturity (ISM; ratio of the depth of the ~2,200 nm minima divided by the ~1,900 nm minima) can be affected by the presence of other hydrous minerals, quartz-sulfide veins, and absorption intensity (which can be a function of rock coloration). Despite these cautions, the spatial distribution and variation of the wAlOH and ISM values for illite suggest that the high paleotemperature hydrothermal upflow zones related to the Zhengguang Au-Zn deposit were located below ore zones I and IV, which are predicted to be proximal to the intrusive center of the system.
Summary(Plain Language Summary, not published)
This paper compares alteration mineralogy surrounding an epithermal gold-zinc deposit in northeastern China determined using two methods: X-ray diffraction and short-wave infrared spectroscopy. Also, the results are compared to detailed petrographic analyses of the same samples. Derived scalars such as illite crystallinity the AL-OH wavelength are then used to identify paleothermal vectors for ore deposition.

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