Granite Denudation Degree and Its Implications for Fluorite Prospecting in Hu’an Area, Northwest Zhejiang Province:Evidence from Apatite Fission Track Thermochronology

In recent years, a series of fluorite deposits have been discovered in the Hu’an volcanic basin, northwest Zhejiang Province, which shows a good metallogenic potential of fluorite deposits in this area.With the development of exploration and increasing difficulty of surface prospecting, more and more attention has been paid to the study of deep potential of fluorite deposits in Hu’an area.In this paper, the authors selected the granite rock in typical fluorite mining areas in Hu’an area to investigate the denudation degree in different places and predict the deep prospecting potential through apatite fission track technology and temperature-time thermal history simulation inversion study.The results show that the fission track age of the samples is concentrated in the range of (29±2) ~ (53±3) Ma, and the age becomes gradually younger from west to east.The temperature-time inversion simulation shows that the Hu’an area has been in a state of constant uplift and denudation since the Late Cretaceous, and Cenozoic uplift and extension existed in some areas, with an average denudation rate of 0.062 mm/a and the denudation amount more than 4km.Using the temperature time model, the authors calculated the denudation degree of typical fluorite mining areas in different places.The results show that the average denudation amount in the west, middle and east of this area is 2.89 km, 3.69 km and 4.08 km, respectively.Combined with the characteristics of surface topography and geomorphology and the age interval between fluorite mineralization age and granite age in the mining area, the authors hold that the granite outcropped in the study area may not be the ore-forming geological body of fluorite deposit, and the ore-forming geological body of fluorite deposit may still be deep.In addition, the denudation amount in the west of this area is lower than that in the east.Therefore, it is considered that the fluorite deposit in the west of the area may have better metallogenic potential.This conclusion can provide a basis for further exploration of fluorite in Hu’an area.