Georgechaoite and bobtraillite, rare zirconosilicates, were discovered as secondary alteration products of eudialyte within the Saima alkaline complex in Liaoning Province, China. An integrated study encompassing petrography, mineralogy, geochemistry, and isotopic geochronology was conducted to revealtheir occurrence, crystal structure, and chemical composition. This investigation aimed to constrain the ages of magmatic enrichment and hydrothermal alteration of Zr- REE- bearing minerals, ultimately exploring the relationship between post- magmatic fluid events and the mobilization- precipitation of ore- forming elements. Georgechaoite, an early alteration mineral, commonly occurs as anhedral crystals associated with secondary gaidonnayite, natrolite, britholite- (Ce), and other alteration minerals. It crystallizes in the orthorhombic system with unit cell parameters: a=1. 18325(5) nm, b=1. 29141(3) nm, c=0. 67292 (1) nm, V=1. 02825(4) nm3, and an empirical formula of (Na0. 97K0. 78Ca0. 06Pb0. 01Sr0. 01)Σ1. 83(Zr0. 98Ti0. 01Hf0. 01)Σ1. 00Si3. 02O9·2H2O. Bobtraillite,a later alteration mineral, posterior to georgechaoite, exhibits anhedral crystals or aggregates in close association with secondary natrolite, zircon, strontianite, calcite, britholite- (Ce), and other alteration minerals in the pseudomorph after eudialyte, with few remnants of eudialyte, gaidonnayite, or georgechaoite. It crystallizes in the trigonal system with unit cell parameters: a=1. 96634(3) nm, c=0. 99581(3) nm, V=3. 33445(1) nm3, and an empirical formula of (Na7. 10Ca0. 99K0. 01□3. 90)Σ12. 00(Sr10. 42Ca1. 56Ba0. 01Pb0. 01)Σ12. 00(Zr12. 85Ti0. 49Hf0. 13Al0. 08Nb0. 06□0. 39)Σ14. 00Si42. 01B5. 99O132(OH)12·12H2 O. Geochronological data indicate that the primary eudialyte alteration occurred around 218±5 Ma. Georgechaoite formation is attributed to alkali- rich metasomatic fluids derived from the Saima alkaline magmas. In contrast, the age of bobtraillite formation is 107±5 Ma, probably related to external carbonate fluids mobilized by the subduction of the ancient Pacific plate. Hydrothermal alteration led to the release of a significant portion of REEs from the precursor eudialyte into the fluid system, with only the minority being preserved in secondary minerals (e.g. , georgechaoite and bobtraillite). The discovery and characterization of georgechaoite and bobtraillite provide valuable insights into the nature and ages of post- magmatic fluid eventsin the Saima alkaline complex. These findings have significant implications for understanding the remobilization- precipitation mechanisms of critical metals (e.g. , Zr and REEs) in hydrothermal environments.