GRAVITY INVERSION ON GRANITE-GREENSTONE BELT AREAS: CRIXÁS, GUARINOS AND PILAR DE GOlÁS, BRAZIL

Abstract

A gravity survey was carried out in the central and northern state of Goías portions, covering an area of 9000 km 2 of granitegreenstone belt rock associations. Using a fixed density of 2.67 g/cm 3 and removing a second-degree trend surface for modeling and inversion, we determined the residual anomalies. Each anomaly was associated to well-known geological surface information, and airborne magnetic data, and density determinations. Final solution was obtained in by interactive inversion. The initial models were generated in 2-D, for latter 2.5-D inversion, interpretation and geological sections sketching based on geologic knowledge. The anomalies were also inverted in 3-D in an automatic process. Estimated depths are coherent with those obtained in the 2.5-D inversion, indicating the targets can reach 2 km deep.

Modelagem e inversão de métodos potenciais do terreno granito-greenstone Rio das Velhas no Noroeste do Quadrilátero Ferrífero

“…Apesar de não ser regra, em todos os exemplos de modelagem gravimétrica em greenstone belt do mundo e do Brasil (Blum et al, 2000;Souza et al, 1992;Baltazar e Raposo, 1993, e as demais referências da introdução), a anomalia Bouguer sobre o greenstone belt e caracterizada por um alto, no GP nãoé diferente, eleé caracterizado por um contraste positivo de anomalia Bouguer maior que +10 mGal nas regiões centrais. Este contraste era esperado devido ao GP ser composto por rochas metaígneas, metassedimentares e metavulcanossedimentares que são, em geral, mais densas que as rochas onde o GP está inserido (granitos/gnaisses).…”

“…A profundidade máximaé um pouco menor que 10 km. Blum et al (2000) fizeram o uso da magnetometria e gravimetria para estudar três greenstone belts na região de Crixás, no Estado de Goiás: Crixás, Guarinos e Pilar de Goiás. Foi feita uma inversão gravimétrica 3D naárea, que utilizou como vínculos medidas de furos de sondagem, geologia de superfície e medidas de laboratório de propriedades físicas.…”

Gravity evidence for a mafic intrusion beneath a mineralized zone in the Bondy gneiss complex, Grenville Province, Quebec — Exploration implications

“…9), representing the gravity response from rocks to ca. 5000 m (Blum et al, 2000;Joly et al, 2009;Rahman and Ullah, 2009). Gravity models were calculated supposing that a mafic to intermediate pluton similar to Chevreuil or Rolleau intrusive rocks Fig.…”

2.5D Crustal Models Derived from Analytical Polynomial Separation Technique and Spectral Analysis of Gravity Data with Their Probable Gold Mineralization Migrations (Batouri, SE-Cameroon)

“…Basically, the variations of gravitational field values due to lateral and vertical changes of density, although very small, can be detected and used in order to understand the geology of a given area. As an example, [1] [2] applied gravity inversion and spectral analysis respectively, to characterise granite-greenstone belt areas in Brazil, and to model a sedimentary basin in Cameroon. [3] successfully used gravity study to investigate solid minerals potentialities over the Congo Craton Belt in Cameroon and South West Central African Republic.…”