Geochemical characteristics of manganese-bearing sequences of Gaoyuzhuang formation in the north Hebei depression

Manganese-bearing sequences is widely distributed at the lower part of Gaoyuzhuang formation of the Mesoproterozoic Changcheng system in the north Hebei depression. The layer thickness is about 60～80m,most of which are composed of manganese-bearing dolostone. The 82 pieces of rock samples taken from Gaoyuzhuang formation are made chemical analysis. The results indicate that there is a positive correlation among the elements of K,Ti,V,Rb,Sc and Th of manganese-bearing sequences. Sr/Ba value suggests that the manganese-bearing sequences are deposited from marine environment of low-salinity. Mn/Fe is extremely high,resulted from strong fractionation between manganese and iron during transportation and metallization. The correlation of Sr,V,Zn and Mn displays that the manganese and provenance is from the same place. Analysis of sedimentary features,geological evolvement and geochemical characteristics indicates that the manganese is mainly origin from the submarine volcanism during the period of Chuanlinggou-Dahongyu formations. One part of manganese is transported to sea water by the submarine volcanism,and another part is diagenesis to volcanic rocks with the volcanic eruption. Manganese-bearing district from the weathering and transportation is then in occlusive and anoxic platform subtidal zone setting where the Manganese-bearing sequences are deposited.