3D inversion of airborne gravity gradiometry data in mineral exploration: A case study in the Quadrilátero Ferrífero, Brazil

Abstract

We present a case study of applying 3D inversion of gravity gradiometry data to iron ore exploration in Minas Gerais, Brazil. The ore bodies have a distinctly high-density contrast and produce well-defined anomalies in airborne gravity gradiometry data. We have carried out a study to apply 3D inversion to a 20 km 2 subarea of data from a larger survey to demonstrate the utility of such data and associated inversion algorithm in characterizing the deposit. We examine multiple density contrast models obtained by first inverting T zz ; then T xz , T yz , and T zz jointly; and finally all five independent components to understand the information content in different data components. The commonly discussed T zz component is sufficient to produce geologically reasonable and interpretable results, while including additional components involving horizontal derivatives increases the resolution of the recovered density model and improves the ore delineation. We show that gravity gradiometry data can be used to delineate the iron ore formation within this study area.

Eigenvector of gravity gradient tensor for estimating fault dips considering fault type

“…Various analysis techniques using gravity gradient tensors have been suggested and discussed (e.g., Zhang et al 2000;Beiki 2010;Martinez et al 2013;Cevallos 2014;Li 2015). These are considered to be so-called inversion techniques.…”

Evaluating the utility of gravity gradient tensor components

“…Another useful gauge is how well the inverted model matches geological information, and whether certain known features are present in the inversion results. Adding more components to the data vector was also shown in a detailed study by Martinez et al (2013) to improve inversion results when compared to known geology.…”

“…Qualitative comparisons of results of inversions for the underdetermined problem (solving for densities in a 3D volume mesh) using different component combinations have been done by looking at solution character and comparing with known geology (Zhdanov et al, 2004;Martinez and Li, 2011;Martinez et al, 2013) An attempt at a quantitative comparison of tensor components and their combinations was made by Pilkington (2012) who used a measure of information content commonly used in optimal survey design to rate different components and some component combinations. Tzz was shown to provide the most information out of the single tensor components and that adding more components to the data vector improves the situation.…”

Determination of the Strike and the Dip of a Line Source Using Gravity Gradient Tensor

“…반면 중력 변화율 텐서의 측정은 여러 개의 가속도계를 복합적으로 이용하는 중력 변화율 측정 시스템이 개발되어 활발히 이용되 고 있다 (Dransfield, 2010;Lee, 2001). 중력 변화율 텐서는 기본적으로 서로 독립인 5개의 성분이 존재 하므로 중력이나 벡터 중력에 비해 정보의 양이 비 약적으로 증가하므로 이를 응용하려는 다양한 연구들 이 수행되고 있다 (Zhdanov et al, 2004;Beike, 2010;Beike and Pedersen, 2010;Rim and Li, 2012;Martinez et al, 2013;Braga et al, 2014).…”