Joint interpretation of magnetic and gravity data at the Golgohar mine in Iran

Geophysical modelling can take advantage of combining more geophysical data with the aim of decreasing the non-uniqueness of the resulting interpretation. The combination of gravity and magnetic data can yield useful information about the source properties by using the Poisson's analysis, which may help to infer the source properties, density and magnetic susceptibility, of the causative sources. Such estimates can be set as constraints for further interpretation. We consider first the synthetic data of a homogeneous block, for which correlation analysis allows the estimation of the Poisson ratio. The estimated source parameters are then used to invert gravity and magnetic data successfully. We applied this approach to the gravity and magnetic datasets in the Golgohar iron ore complex area, located in the Sanandaj-Sirjan zone (Iran). We performed a correlation analysis between the reduced to the pole magnetic data and the vertical gravity gradients of the 1st and 2nd order, respectively. We estimated strong magnetization contrasts between the mineral rocks and the surrounding host rocks. Further quantitative information about the source depth and geometry are obtained by 2D inverse modelling of both gravity and magnetic data, based on the damped weighted minimum-length solution. Even in this case, a-priori information from the correlation analysis leads to constrain the inverse process of both gravity and magnetic data. Inverse modelling confirms a high correlation between both susceptibility and density models, both horizontally and vertically, and show the presence of isolated sources with high density and magnetization contrasts, in good accordance with the average physical parameters of iron‑gold deposit formations.