Tectonic and metallogenic implications of a metasomatized mantle inferred from magnetotellurics and gravity data: An example of Tapajós Mineral Province, Amazon Craton

Abstract

The Tapajós Mineral Province (TMP) contains evidence of subduction processes during the Paleoproterozoic. Despite well-documented arc magmatism, the lack of solid geological evidence indicating a collision raises uncertainties about whether there was an arc-continent collision in the Paleoproterozoic or the process of subduction continued, and the closing of an ocean basin occurred only in Mesoproterozoic times. Additionally, world-class deposits have been linked with lithospheric electrical conductors using magnetotelluric (MT) data. On the lithospheric scale, an assessment of the potential for more significant deposits or correlated commodities is absent in the TMP. Therefore, we acquired MT data to provide constraints for the lithosphere of the TMP. The electrical resistivity model reveals a high resistivity zone (> 10,000 Ω.m) interpreted as the emplacement zone of granitoids in the upper crust. The mid-lower crust presents resistivity between 465 and 45 Ω.m, corresponding to depths of 10–35 km. A low resistivity zone below 35 km (45–10 Ω.m) represents a hydrated upper mantle due to the long-lived arc processes. Based on gravity-forward modeling, we estimate that the degree of serpentinization is <10% due to post-subduction magmatism. The lack of a lower crust conductor and paired high and low long wavelength Bouguer anomalies corroborates that a cryptic suture is unlikely. A low-angle conductor matches the limit of different magnetic domains and reveals the exhumation of the western portion of TMP's crust. The high correlation between the position of the deposits and electrical conductors corroborates that MT is a valuable tool for detecting fossil fluid pathways relevant to finding new mineral deposits.