gems, jade, pyroxene jade, jadeite, omphacite, kosmochlor, geology, supercritical geofluid, genesis of jadeite jade, subduction zone, high field strength elements, fluid-melt inclusion

Supercritical geofluids are transitional fluids formed in silicate rock–H₂O systems under conditions of high temperature and pressure. Their chemical compositions lie between those of aqueous fluids and magmatic melts. Possessing strong capacities for dissolution, transport and reaction, they serve as important carriers and media for material circulation within the Earth. Traditional models for the origin of primary jadeite jade (jadeitite)—including regional metamorphic, magmatic and metasomatic theories—are supported by evidence from experimental petrology, petrography and petrogenesis. However, each encounters difficulties in explaining mineral crystallization sequences, mineral assemblages and their spatial distributions. The original fluid-precipitation and metasomatic-replacement theory proposes two modes for the formation of the constituent minerals of jadeite jade. Commonly observed fluid–melt inclusions within jadeite and omphacite grains and their aggregates indicate that primary jadeitites crystallized from fluid–melt miscible systems. Drawing upon advances in the study of supercritical geofluids in Earth sciences and recent research on jadeite jade, this paper presents a supercritical-geofluid model for jadeitite formation. In this model, supercritical geofluids generated by dehydration of the subducting slab transport dissolved materials under suitable pressure–temperature conditions. Changes in temperature, pressure and related parameters lead to the crystallization and infilling of early jadeitite within fractures and fissures of the mantle wedge, followed by superimposed metasomatism. This model is supported by multiple lines of evidence, including characteristic fluid–melt inclusions, pronounced dissolution relics, early infilling textures, middle- to late-stage metasomatic textures, enrichment in high-field-strength elements, abundant and complex mineral (or solid-phase) assemblages, and high- to ultra-high-pressure veins containing diagnostic minerals. Chromite, a magmatic mineral predating the formation of early jadeitite, was subsequently dissolved or replaced, providing the Cr³⁺ responsible for the green coloration of jadeite jade. Following its initial formation, jadeitite underwent multiple geological processes, including melt activity and fluid activity (both crystallization and metasomatism) associated with the separation of supercritical geofluids, as well as deformation, metamorphism and supergene alteration. To establish a comprehensive theoretical framework for jadeite jade formation, further investigation and reassessment are required, with particular attention to the timing and role of supercritical geofluid activity.