Multi-proxy geophysical modeling of subsurface Neoproterozoic limestones: Applications for mining industry in the Tandilia System, Argentina

Abstract

In this contribution, multi-proxy geophysical methods have been used to analyze the subsurface Neoproterozoic limestone mantle configuration. We also evaluate the relationship between the sedimentary cover and the crystalline basement in order to propose an integrated geophysical model for the graben structures of the Olavarría-Sierras Bayas area, Tandilia System, Argentina. We obtained gravimetric and magnetometric field measurements and vertical electrical sounding profiles (VES) over the prospected area to achieve this objective. The gravimetric and magnetometric high anomalies were associated with the surface basement's proximity recognized in the north and south-central regions. In contrast, the low anomalies correspond to a thickening of the sedimentary cover in the rest of the area. The explored graben configuration is defined by the NW-SE and NE-SW system faults of the Tandilia System. In the study area, the calculated sedimentary cover thickness is ca. 230 m in the south-central high anomaly region and reaches a maximum thickness of ca. 360 m in the southwest sector. The limestone mantle was detected inside the Neoproterozoic sedimentary succession sequence with the vertical electrical sounding (VES) at depths between ca. 40–60 m in the north sector and at ca. 130–145 m in the southern, with a degree of error close to 10% with respect to the drilling data. The link between the geophysical and the stratigraphic-structural models proves that the multi-proxy geophysical methods applied in this work constitute an improvement in order to understand the crystalline basement - sedimentary succession configurations. Moreover, this multi-proxy geophysical methodology allows estimating the depth and thickness of limestone mantle occurrence into graben-like structures with a high degree of confidence.