Reconstruction of Ancient Carboniferous Zhibo Volcanic Edifices in Western China Using Magnetotelluric Observations and Comparisons with Active Volcanoes

Volcanoes serve as the primary pathways for heat and material transfer from Earth’s interior to its surface, providing valuable insights into subsurface processes. Active and potentially active volcanoes have influenced human history and are closely related to current tectonic activity. Consequently, many active volcanoes have been studied using geophysical methods. However, the internal structure of ancient volcano complexes remains poorly understood. We investigated ancient volcano complexes by comparing magnetotelluric (MT) observations from Zhibo (ZB) ancient volcano with active mid-oceanic ridge volcanoes from Iceland and intracontinental volcanoes from north China. The MT responses of magma chambers in these active volcanoes showed similar low-resistivity values ranging from several to tens of Ω·m, indicating a comparable resistivity of the active magma. Assuming that the ancient active volcano chambers had a similar resistivity to that of current active volcanoes, we reconstructed the ancient Carboniferous volcano complex in ZB using the ratio of the lower portion of the MT responses from ZB ancient volcanic edifices and active volcanoes. The results implied the existence of fossil magma chambers at a depth of 5 to 7 km marking the site of a former volcanic center. This finding supports the magmatic origin of the ZB volcanic rock-hosted iron deposits.