White mica SWIR spectral and geochemical signatures: Key exploration vectors for the giant Dahutang tungsten ore field, Jiangxi Province, South China

• High Pos2200 (>2209 nm) and low SWIR-IC (<0.9) values in white mica effectively indicate tungsten mineralization in Dahutang ore field. • Ore-bearing intrusions have white mica rich in Si, Mg, Fe, F, Li, Sn and Cs but poor in Al and Na, which distinguishes them from barren ones. • Elevated F, Li, and Cs in magmatic white mica reflect highly evolved magmas. • High V, Sc, and W in hydrothermal white mica suggest tungsten mineralization occurred under reducing conditions. • In W deposits, falling temperature and rising pH shift Tschermak's substitution toward Si, Mg, and Fe, making phengite a key exploration vector. Infrared hyperspectral technology, characterized by its high efficiency and non-destructive nature, is capable of accurately identifying minerals and can be effectively applied to prospecting. As a widely developed alteration mineral in magmatic-hydrothermal deposits, white mica has been successfully applied to the exploration of porphyry, epithermal, volcanogenic massive sulfide (VMS) deposits based on its short-wave infrared (SWIR) spectrum. However, the exploration vectors of white mica vary among different types of deposits. The hyperspectral exploration vector of white mica in tungsten ore remains to be improved, and the study on the significance of trace element indication of white mica is still immature. In this study, the giant Dahutang tungsten ore field in Jiangxi Province is selected as the research object. The research focuses on five types of intrusions associated with mineralization in Dahutang: biotite granodiorite, porphyritic biotite granite, porphyritic fine-grained biotite granite, fine-grained muscovite granite, and granite porphyry. The significance of spectral and geochemical characteristics of white mica for tungsten ore exploration is discussed through comprehensive study on the characteristic parameters, major and trace elements of white mica SWIR spectrum in different intrusions. The results show that the high Pos2200 (Pos2200 > 2209 nm) and low SWIR-IC (SWIR-IC < 0.9) values of white mica in Dahutang can be used as important vectors of mineralization, which mainly occurred in the inner and outer contact zone of biotite granodiorite of Jinningian period (Tonian, ∼1000–800 Ma) and Yanshanian period (Jurassic to Cretaceous, 200–90 Ma). The white mica in ore-bearing intrusions are characterized by high Si, Mg, Fe, F, Li, Sn, Cs and low Al, Na, whereas those in ore-barren intrusions show the opposite features. In addition, the Pos2200 value of SWIR spectrum of white mica in intrusions is positively correlated with Si, Mg, Fe, F, Li, Sn and Cs, and negatively correlated with Al and Na. The value of SWIR-IC is primarily controlled by temperature and exhibits a weak correlation with the major and trace elements in white mica. The high contents of F, Li and Cs in magmatic white mica also indicate that the magmatic evolution of ore-bearing intrusions has higher degree than ore-barren intrusions. The hydrothermal white mica in biotite granodiorite and porphyritic biotite granite all show higher content of V, Sc and W, indicating that metallogenic environment is relatively reduction conditions. Contrasting with other types of deposits, the decline in temperature and rise in fluid pH value prompt the substitution of Tschermak’s component towards Si, Mg, and Fe enrichment, rendering phengite a crucial mineralization indicator in tungsten deposits. Compared with geochemical analysis, SWIR technology has economic, rapid, convenient advantages. The SWIR spectral and geochemical characteristics of white mica can be used as efficient methods for tungsten ore exploration.