Interpretation of the gravity anomaly field in the Noranda – Val d'Or region, Abitibi Greenstone Belt, Canadian Shield

Abstract

Gravity data from the Noranda – Val d'Or region have been reprocessed: the Bouguer anomaly map, the first vertical derivative map, and an apparent density map have been used for geological interpretation of the gravity field in this region. It is found that variations in the Bouguer anomaly can be mainly explained by density structures located within the uppermost 5 km of the crust. The vertical derivative map helps to better locate some geological contacts, and the apparent density map allows the easy distinction between thin and thick batholiths. Generalized inversion was used to calculate density cross sections from the Bouguer anomaly values, and measured surface formation densities were used as constraints. Analysis of a detailed profile in the Rouyn–Noranda area shows that steep north-dipping reflectors observed in a seismic reflection survey are associated with a north-dipping density structure.