Mineral Chemistry of the Lower Cretaceous Jinling Iron Skarn Deposit, Western Shandong Province, North China Craton: Implications for the Iron Skarn Mineralization Process

Abstract

The source of iron material and the mineralization process of iron skarn deposits within the eastern North China Craton are ambiguous. In this study, we present new mineral chemical data of the Jinling skarn deposit, located in western Shandong Province, east China. Based on the petrography study and mineral chemical data, we suggest that the Jinling iron skarn deposit is hydrothermal and the metallogenic iron is enriched by leaching of Fe-rich fluids derived from primitive magmatic melt from the solidified diorites. The Jinling iron skarn deposit formed as a result of several mineralization processes: (1) Fe-rich hydrothermal fluids exsolved from a hydrous parental magma that was characterized by high iron content, oxygen fugacity (fO2), and salinity; (2) the Fe content of the fluids was augmented during the alkali metasomatism stage via the leaching of Fe from the solidified dioritic rocks; (3) diopside and garnet in skarns formed under relatively alkaline and oxidizing conditions during the later prograde skarn stage; (4) during the retrograde skarn stage, amphibole, chlorite, epidote, phlogopite, serpentine, biotite, and chlorite formed under more oxidizing conditions, and subsequent mixing of the Fe-rich fluids with meteoric water triggered the precipitation of the massive magnetite; and (5) the final sulfide–carbonate stage was involved in the formation of carbonate and sulfide minerals as a result of a change in conditions from oxidizing to reducing.