There are large to superlarge magnesite and talc deposits occurring in Mg-rich carbon-ate formations distributed in the early Proterozoic Dashiqiao Formation in eastern Liaoning Prov-ince, China. The discovery of the sedimentary gypsum, isotopic geochemistry of δ~(18)O_(SMOW),δ~(13)C_(PDB), δ~(34)S_(VCDT) and Sr/Ba ratio of carbonate, talc, quartz and gypsums with field investigationand sample analysis in laboratory demonstrate that the formation of magnesite and talc deposits isclosely related to marine evaporates, which then underwent reworking of regional metamorphismand hydrothermal metasomatism. Metasomatic fluids originating from the paleoseawater played acontrolling role in the formation of talc deposits. There are large to superlarge magnesite and talc deposits occurring in Mg-rich carbon-ate formations distributed in the early Proterozoic Dashiqiao Formation in eastern Liaoning Prov-ince, China. The discovery of the sedimentary gypsum, isotopic geochemistry of δ ~ (18) O_ (SMOW), δ ~ (13) C_ (PDB), δ ~ (34) S_ (VCDT) and Sr / Ba ratio of carbonate, talc, quartz and gypsums with field investigation and sample analysis in laboratory demonstrate that the formation of magnesite and talc deposits isclosely related to marine evaporates, which then underwent reworking of regional metamorphismand hydrothermal metasomatism. Metasomatic fluids originating from the paleoseawater played acontrolling role in the formation of talc deposits.