Advances on Exploration Indicators of Mineral VNIR-SWIR Spectroscopy and Chemistry: A Review

Abstract

Establishing exploration vectors to infer the properties of ore-forming fluids, locate blind ore bodies with the aid of visible to near-infrared (VNIR) and short-wave infrared (SWIR) spectroscopy, and infer the chemistry of minerals, is a new research interest for economic geology. Common alterations and clay minerals, including sericite, chlorite, epidote, alunite, kaolinite, tourmaline, etc., are ideal objects for the study of exploration indicators due to their sensitivity to variations in the nature of hydrothermal fluid. The diagnostic spectral feature and chemistry vary spatially and systematically with physicochemical change. VNIR spectroscopy can characterize the REE-bearing clay minerals directly. Obtaining spectral or chemical parameters with the aid of VNIR-SWIR spectroscopy, electron probe micro-analyzer (EPMA) or laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) can help to establish exploration vectors. This paper systematically summarizes recent advances in mineral exploration indicators (MEIs) of VNIR-SWIR spectroscopy and chemistry, and compares them in different regions or deposits. We found that some MEI spatial variation trends are random, even the same type of deposit can show an opposite trend. The controlling factors that limit the application of the established MEIs are vague. Conducting further research on petrology and mineralogy with the aids of observation under microscopy, X-ray diffraction (XRD), TESCAN Integrated Mineral Analyzer (TIMA), and EPMA are suggested to discover alteration mineral assemblage, alteration stages, and behaviors of “the pathfinder elements” related to mineralization. Based on the above research, the physicochemical properties of ore-forming fluids and their control over MEIs can be inferred. Refining the theoretical basis is critical to understanding and popularization of spectral and chemical MEIs.

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

“…), diverse software such as: ENVI, ERDAS, Spec_minTM, and others, are also useful for mineral discrimination based on their absorption features in different wavelength positions (Grove et al, 1992, Clark et al, 1993. Many authors have used these tools for various purposes Thomp-son et al, (1999), Ducart et al, (2006), Simpson, (2015, Arbiol and Lyne (2021), Wang et al, 2021, Zhou et al, 2022, Zhou et al, 2023 Jacinto deposit is a vein system (Figure 2) where Beatriz, Sur de Elena and El Limón Nuevo veins are the most prospective (Piñero et al, 2021). GH mineral deposit comprises three sectors (Figure 3), where Three Hill (TH) and Little Golden Hill (LGH) sectors are exploited.…”