VNIR-SWIR using OreXpress spectroradiometer as a spectral approximation method to differentiate epithermal mineralization alteration phases. A case study from Jacinto and Big Golden Hill, Cuba

Abstract

Spectral differences (range: 350-2500 nm) between the three alteration phases related to low and high sulfidation epithermal mineralization has been studied in the Jacinto deposit (Beatriz, Sur de Elena, and El Limon Nuevo veins) and the Big Golden Hill sector, respectively, located in the Cuban Cretaceous volcanic, Camagüey and Las Tunas provinces. This study has revealed the following differences between the phases: (a) Phase I: associated with the lithological type of quartz with massive and/or brecciated texture, where gold mineralization develops. At 600-800 nm, the signals identified responds with goethite and at 1400, 1900 y 2200 nm, as montmorillonite and nontronite. The reflectance value is 30 -50%, although in the El Limón Nuevo vein is 30-40%. (b) Phase II: Related to the argillic alteration zone composed by sericitic or silicified quartz and ferrous minerals such as limonite and hematite. It only occurs in Beatriz and Sur de Elena veins. At 600-800 nm, the signal is associated with ferrous minerals and at 1400, 1900, and 2200 nm, to clays minerals as montmorillonite, halloysite, and nontronite. The reflectance value is 30 – 50%. The difference between both Phases is in the amplitude and shape of the absorption feature at 1400 nm. (c) Phase III: it is located near the volcanic rock, composed by illite-smectite-quartz, without gold content and nearby to propylitic zone. At 600-800 nm, the feature indicates the presence of goethite and at 1400, 1900, and 2200 nm, to montmorillonite, illite, and nontronite. The reflectance value is 30 - 40%. The Big Golden Hill sector is characterized by peaks related to goethite and nontronite at 600-800 nm and pyrophyllite at 1400, 1950 and 2165 nm, typical of advanced argillic alteration. The reflectance value reaches 55%. This study represents one of the first applications of reflectance spcetroscopic techniques in Cuban mineral deposits.