3D magnetic interpretation of the Regis kimberlite pipe, Minas Gerais, Brazil

Abstract

In the present work, high-resolution ground magnetic data are used to unveil the structure of the Regis kimberlite pipe, which is located in a well-known diamondiferous province in the central portion of Brazil. The main tectonic feature of the area is a NW-SE major crustal fracture zone, extending for more than 3000 km within Brazil, along which Regis and several other kimberlite pipes have intruded. The area is located at low magnetic latitude (inclination approximately 27 o south) and the ground magnetic anomaly associated with the Regis pipe appears as an isolated asymmetric dipole-like source caused by magnetization primarily in the direction of the Earth's magnetic field. We inverted this high-resolution magnetic data set in order to recover the 3D effective susceptibility model of the studied pipe. We obtained an asymmetric conical-shaped strongly magnetized body (35 × 10 -3 SI units) extending from 50-720 m depth. Prior to the inversion, the data were upward continued to 30 m above the surface to attenuate high-frequency noise and mitigate inversion artefacts. Our results were used to better define the subsequent drilling positions to thoroughly evaluate the economic potential of the Regis pipe. One available borehole drilled approximately in the centre of the structure corroborates our interpretation. 2007). The magnetic study described herein was initiated prior to

Audiomagnetotelluric 3D imaging of the Regis kimberlite pipe, Minas Gerais, Brazil

“…The Regis kimberlite is located in the central portion of the APIP, and it intruded along the so-called 125-AZ lineament, a major NW-SE crustal zone extending over 3000 km within the Brazilian territory (Menezes and La Terra, 2011). The pipe intruded into plane layers of inter-bedded red quartzites and green schists of the São Francisco Supergroup (Castro and Dardenne, 2000).…”

Inversão gravimétrica 3D e interpretação integrada dos métodos CSAMT, gravimétrico e magnetométrico no estudo do Kimberlito Régis, MG, Brasil

“…Estes valores são associados ao kimberlito alterado no centro (em azul) e nos tons de verde e amarelo, a rocha encaixante, indicando que a densidade do kimberlito alterado é menor que o filito, rocha encaixante. Este contraste pode ser observado visto que a densidade do kimberlito alterado (menores profundidades), é em média 2.4 g/cm 3 enquanto que do filito, é 2.6 g/cm 3 (Menezes et al, 2011;Hoover et al, 1993). Da mesma forma, a figura 8, representa o perfil norte-sul, apresentando um corpo com contraste de densidade negativo no interior, envolto por um corpo de densidade maior, apresentando contraste positivo.…”

“…Esses valores foram obtidos a partir de bibliografias que discutem estes valores para kimberlitos (MENEZES et al, 2011;HOOVER et al, 1993). Nesta modelagem, uma inversão 1D é aplicada, de modo que estes valores puderam ser modificados e ajustados para a área.…”

Inference of minerals at Redondão kimberlite crater, Parnaíba Basin, Brazil, based on interpretation of airborne gamma-ray spectrometry and ASTER data

“…Previous works have demonstrated that indicator minerals of kimberlitic intrusions, such as olivine, chromium-diopside, enstatite, serpentine and phlogopite, may have their respective spectral signatures detected by multispectral images (Tessema et al 2012;Nndanduleni and Tessema 2021;Guha et al 2015). Although magnetic and electromagnetic data are commonly used to map kimberlites (Macnae 1995;Pettit 2009;Menezes and La Terra 2011;Kaminski and Oldenburg 2012;Tessema et al 2012;Nndanduleni and Tessema 2021;Matende and Mickus 2021), analysis of airborne gamma-ray spectrometry (AGRS) data can also contribute to reveal the presence of kimberlite-related minerals or to indicate areas where processes related to the formation and alteration of the FIGURE 1. Regional geological map of the study area.…”