Abstract:Longbaoshan rare earth deposit in Lanling county is an important rare earth deposit in western Shandong. Its distribution is significantly controlled by hydrothermal fluids. As a good fluid channel and ore bearing space, crypto-explosive breccia is a favorable target for rare earth exploration. Through field exploration, petrographic observation, scanning electron microscopy, and energy spectrum analysis, the structure of crypto-explosive breccia tube and its corresponding hydrothermal alteration, and rare earth distribution pattern of crypto-explosive breccia in Longbaoshan area have been studied. It is showed that crypto-explosive breccia ore bodies in Longbaoshan can be divided into crypto-explosive breccia, crypto-explosive hydrothermal—Magma rounded breccia, crypto-explosive shattered breccia and crypto-explosive fractured rock from inside to outside. The main types of rocks affected by mineralized fluids include cryptoexplosive breccia, crypto-explosive shattered breccia, crypto-explosive hydrothermal rounded breccia, which correspond to pyrite sericitization, silicification carbonation, and potassium feldspar sericitization. Potassium hydrothermal fluids are rich in rare earth complex anions, which facilitate their migration. Moreover, pyrite sericite and potassium feldspar can cause a decrease in pH value and temperature, which is conducive to the precipitation of REE. Cryptoexplosive breccias and cryptoexplosive hydrothermal magma rounded breccias that undergo such alteration are favorable for rare earth enrichment.
