• Metamorphism causes Mg loss as dolomite, enriching magnesite orebodies. • Silica-rich hydrothermal fluids metasomatize magnesite to talc, inducing Mg isotope kinetic fractionation. • Complete magnesite-to-brucite transformation avoids significant Mg isotope kinetic fractionation. • Mg-rich carbonate formations (parent δ 13 C: between −2.7‰ and + 1.6‰). The talc ore bodies are clearly controlled by regional folds and fault structures formed during the Lvliangian movement(1.9 Ga ∼1.8 Ga). Interlayer faults are the most favorable sites for the formation of talc ore bodies, which result from reactions between metamorphic-related siliceous hydrothermal fluids and dolomitic magnesite, whose magnesium isotopic composition ( δ 26 Mg: between −0.48‰ and + 1.06‰) no longer reflects marine geochemical characteristics. Brucite ore bodies occur as lenticular forms within carbonate strata in skarn-type external contact zones of granitic rocks that formed during the Phanerozoic era. These ore bodies are formed through the heating of atmospheric precipitation by magmatic bodies that subsequently reacts with carbonate rocks, and they still retain a marine-like REE distribution pattern and magnesium isotope characteristics (range from −1.33‰ to −1.13‰). Therefore, the nonmetallic magnesite, talc, and brucite deposits belong to a typical metallogenic series of Paleoproterozoic magnesium carbonate formations, which formed via metamorphic recrystallization, siliceous hydrothermal metasomatism, and late magmatic–hydrothermal mineralization, respectively.
Zheng et al. (Sun,) studied this question.