Discharge and deposition metallogenic model of “Datangpo-type” manganese deposits in China: Geophysical evidence from deep electrical structure of manganese-bearing grabens

The “Datangpo-type” manganese (Mn) deposits in China, which are rhodochrosite deposits formed at the base of the Datangpo Formation of the Neoproterozoic Nanhua Period under the control of the Nanhua rift, represent the most important type of Mn deposits found in China. Along diapir channels and synsedimentary faults, Mn-bearing fluids from the deep lithosphere have undergone large-scale discharge and deposition metallogenesis of Mn deposits at the center of multiple level-IV grabens in the Nanhua rift. This study used geophysical exploration methods that included magnetotellurics and audio magnetotellurics to investigate and summarize the characteristics of the deep electrical structure in the Songtao–Guzhang graben (level Ⅲ) and several level-IV grabens in the Wuling secondary rift (level II) of the Nanhua rift (level I). Based on two- and three-dimensional inversion techniques, five sets of fluid diapir channels were found deep in the graben basins that controlled the formation and distribution of the Mn deposits, corresponding to known Mn deposits within the study region—Liangfengao, Lijiawan, Shitang, Datangpo, and Juxian in Songtao County. The findings of this study represent geophysical evidence for discharge and deposition metallogenesis of the Datangpo-type Mn deposits in China, as confirmed by deep seismic reflection profiling.