Reconstruction of Ancient Carboniferous Zhibo Volcanic Edifices in Western China Based on the Comparison of Magnetotelluric Observation from Active Volcanoes

Volcanoes serves as the main pathways for the heat and material from internal to surface of the Earth. It is the window into the Earth because they provide and record many clues to what is going on in the subsurface. Active and potentially active volcanoes greatly affected the course of human history and are closely related to the present tectonics of the Earth. As a result, a great number of active volcanoes have experienced comprehensive geophysical studies. However, understanding to the internal structure of the ancient volcano complexes remains very poor. We propose a new approach to study the structure of the ancient volcano complexes based on the comparison of the magnetotelluric (MT) observation from Zhibo (ZB) ancient volcano and the active mid-oceanic ridges volcanoes from Iceland and intracontinental volcanoes from north China. MT responses of magma chambers from active volcanoes from Iceland and north China shows very close low resistivity values ranges from several to tens Ω.m, which indicates that the active magma have very close resistivity. Based on these observations, we assumed that the ancient active volcano chambers have similar resistivity as current active volcanoes. We then reconstruct the ancient Carboniferous volcanoes complex in ZB using the ratio of the lower portion of the MT responses from ZB ancient volcanic edifices and active volcanoes. The results imply the existence of the fossil magma chambers at around 5 km in depth. It serves as the critical indication for a volcanic center and confirms the magmatic origin of the ZB volcanic rock-hosted iron deposits.