Identification of the expression of earthquake-induced surface flooding by groundwater using detailed regolith mapping at the buried Atlántida Deposit, northern Chile

This paper describes saline pockets (10 cm-3 m in diameter) of fine-grained material distributed on alluvial surfaces. These saline pockets are localized along structural trends at the Atlantida buried porphyry-skarn Cu-Au-(Mo) deposit in the Atacama Region of Chile. The distribution and highly saline nature of the material suggest formation by the pooling and evaporation of groundwater forced through fractures to the surface during seismic activity. These saline pockets are a surface expression of the hydrological effects of seismic activity along faults. Saline pockets with similar distribution and characteristics were also identified at three additional alluvium-covered areas, all located in the Antofagasta Region of Chile. Identification and mapping of these saline pockets relies on the ability to identify the continuation of structures through overlying gravels. Regolith mapping using high-resolution drone imagery and digital elevation modelling identified geomorphic markers of faulting which aided mapping the distribution of saline pockets. Saline pockets provide a unique opportunity to sample the direct expression of transported groundwater reaching the surface from depth and provide a prime target medium for mineral exploration through transported gravels.