Mapping hydrothermal alteration of the Au-Cu deposits in the Zhenghe magmatic-hydrothermal mineralization system, SE China, using Short Wavelength Infrared (SWIR) reflectance spectroscopy

Magmatic–hydrothermal mineralization developed in Zhenghe area, where a potential of blind porphyry Cu polymetallic deposits is expected. To explore alteration characteristics and their relationship with mineralization, alteration mineral mapping with the help of SWIR reflectance spectroscopy was carried out in the Dongji Au deposit, the Maluntou Au deposit, the Shizigang Cu polymetallic deposit, and the Dongkeng volcanic basin. The results suggest that illite ± chlorite assemblage predominates in the Dongji deposit, whereas phengitic illite ± chlorite ± epidote occurred in the Maluntou deposit. Chlorite ± epidote ± actinolite developed pervasively in the Shizigang deposit. The alteration feature and ore geology indicate the Dongji and Maluntou deposits formed in a low-intermediate sulfidation epithermal environment with moderate-low temperatures. Maluntou is more likely approached to a heat source. Four alteration zones including potassic–silicic zone, propylitic zone, phyllic zone, and surficial argillic zone are divided, and a heat center is roughly inferred in the Shizigang district, suggesting a proximal porphyry-hydrothermal alteration style. A model demonstrating mineralization and alteration is established, along with mineral spectral vectors to mineralization. Illite with Pos2200 (wavelength of sericite Al-OH absorption peak position) of about 2203 nm is correlative with Au mineralization in the Dongji deposit and phengitic illite with Pos2200 ranging from 2215 nm to 2219 nm is the product of metallogenesis in the Maluntou deposit. Illite with Pos2200 of approximately 2205 nm–2206 nm in the Nanyuan Formation and illite with Pos2200 of about 2207 nm in the Huangkeng Formation are formed in the non-mineralization stage or weathering. Muscovite with the Pos2200 of roughly 2206 nm has the potential to be an orebody vector in the Shizigang district. Pos2250 (wavelength of chlorite Fe-OH absorption peak position) variation in the Shizigang district indicates the location of drill hole ZK1-1 is approximal to the hydrothermal center. Shizigang Cu, Maluntou Au, Dongji Au, and other deposits in Zhenghe are probably part of an integrated metallogenic system with epithermal-porphyry features. High-intensity magmatic-hydrothermal activity indicates the potential for deep prospecting in the region. [Display omitted] •SWIR reflectance spectroscopy was used to systematically mapping the alteration.•Zhenghe developed IS-type mineralization and porphyry style alter