Enrichment of REE and HFSE during the magmatic-hydrothermal evolution of the Baerzhe alkaline granite, NE China: Implications for rare metal mineralization

Multi-stage metasomatic Zr mineralization in the world-class Baerzhe rare earth element Nb-Zr-Be deposit, China

“…These observations contradict the subsolvus interpretation of this unit and suggest that it is the Na-metasomatized, agpaitic, transsolvus granite described by Wu et al (2021). It is not known, however, whether the hydrothermal zircon reported earlier by Yang et al (2013Yang et al ( , 2014 was actually from the agpaitic transsolvus granite that was incorrectly described as subsolvus by Yang et al (2020), and is equivalent to one of the four types of metasomatic zircon identified by Wu et al (2021), or is from an unspecified subsolvus granite. In addition, classification of these two types of zircon by Yang et al (2013Yang et al ( , 2014 was based on their zoning characteristics in cathodoluminescence images and their REE patterns.…”

“…The subsolvus character of the latter, however, was not supported by any petrological description, and this granite phase was not observed by Wu et al (2021). However, in Yang et al (2020), four photos are provided (their Fig. 3) of what they interpreted as a subsolvus granite, which contains euhedral perthite and microcline crystals, zircon-quartz pseudomorphs, and replacement of amphibole by aegirine.…”

“…2.8 Mt of ZrO 2 at an average grade of 2.73 wt % and 48,470 t of BeO at an average grade of 0.05 wt % are potential by-products from the extraction of REE and Nb (Qiu et al, 2019;Wu et al 2021). The Baerzhe deposit contains a large variety of rare-metal silicates, oxides, and carbonates, however, most REE and almost all Be are hosted in hingganite ((REE,Ca) 2 (□,Fe 2+ )Be 2 [SiO 4 ] 2 (OH) 2 ), a member of the gadolinite supergroup; zircon is the only ore mineral for Zr (Yang et al, 2020;Wu et al, 2021).…”

“…However, the assignment of zircon origin was achieved through interpretation of the textural and chemical features of mineral separates, without documentation of the associated mineral assemblages and occurrences of zircon in the rocks. Although Yang et al (2014Yang et al ( , 2020 concluded that hydrothermal Zr and REE-Nb-Be mineralization both formed during a transitional, magmatichydrothermal period, they did not describe the relationship between Zr and REE-Nb-Be mineralization, nor the mineralogical characteristics of the host rocks. Furthermore, as mentioned in the Introduction, concluding that zircon types are magmatic or hydrothermal based on their REE patterns is unreliable at best and could lead to erroneous interpretations of zircon origin (Pettke et al, 2005;Bell et al, 2019).…”

“…The zircon-quartz pseudomorphs shown in Figure 3D of Yang et al (2020) were equated by those authors to the hydrothermal zircon of Yang et al (2013Yang et al ( , 2014Yang et al ( , 2020, in which only zircon mineral separates were analyzed. If that is the case, their hydrothermal zircon would be the same as the pseudomorph zircon described in Wu et al (2021) and this study, although without petrographic context for the mineral separates, there is still some uncertainty.…”