Geological model and application of “Trinity” prospecting prediction for altered granite-type lithium deposits in Yifeng-Fengxin Area, Jiangxi Province

At present, the lithium resource reserves in Yifeng-Fengxin Area are the largest hard rock altered granite-type lithium deposit found in China, located in Yichun City in the west of Jiangxi Province. Based on the summary and analysis of the regional geological background, geological characteristics, ore-forming structure, ore-forming rock mass and its alteration and mineralization characteristics of the lithium deposit in this area, a “Trinity” geological model of prospecting and prediction of tectonic + magmatic + hydrothermal metasomatic alteration in Yifeng-Fengxin Area is established. The model indicates that the Yanshan collisional orogeny in the study area caused mantle magma to encase and crust to partially melt and circulate to form magmatic hydrothermal liquid containing rare metal elements, which provided material source for mineralization. Under the conditions of near east-west, NEE and NW trending fault activity, the late Yanshanian provides migration channels for deep ore-bearing magmas or hydrothermal fluids. The magmas containing a large amount of sodium and rare metal mineral fluids gradually differentiate and evolve from morning to night, from inside to outside, towards the direction of rich sodium, rich volatile components, rich Li, Rb and other rare elements, and low temperature and pressure. It migrates to the top and edge of Baishitong rock mass with high differentiation evolution in the latest stage of Early Cretaceous, and superimposes albitization and lipolite alteration during post-magmatic hydrothermal metasomatism, and finally forms the altered granite-type lithium deposit in this area. The establishment of the model provides an important reference for prospecting prediction, delineation of target areas and major prospecting breakthroughs in the study area, and has achieved remarkable exploration application results. It predicts the favorable ore-forming areas in the depth of some existing mining rights and the blank areas at the edges of known deposits, such as Sanjiaoling and Ziyun, and puts forward systematic geological exploration suggestions.