Henry Francisco Galbiatti

Palladseite and its oxidation: evidence from Au-Pd vein-type mineralization (jacutinga), Cauê iron-ore mine, Quadrilátero Ferrífero, Minas Gerais, Brazil

Abstract Palladseite (palladium selenide) and palladian gold occur as euhedral inclusions in specularite and as infill of microfractures and interstices in magnetite aggregates (host rock fragments) within speculariterich auriferous veins (jacutinga). Palladseite has minor amounts of Pt (0.6−3.5 wt.%), Cu (2.9−3.5 wt.%), Hg (0.9− 1.9 wt.%), and Ag (0.3− 0.5 wt.%). The palladian gold contains up to 6 wt.% Pd, and minor Cu and Ag. Isomertieite (Pd11Sb2As2) and sudovikovite (PtSe2) are also recorded. The veins cross-cut the main tectonic foliation of the wallrock (itabirite). The feature of fracture infill and the Se-Sb-As-Hg-Cu-Ag geochemical/mineralogical signature of the Au-Pd mineralization point to a post-ductile deformation and possibly low-temperature (epithermal) origin of the jacutinga mineralization style. Palladseite is replaced locally by a Pd-rich oxidation phase. Electron microprobe analysis of alteration halos around palladseite yields 76−80 wt.% Pd. Oxygen calculated by stoichiometry accords with a monoxide compound of the type PdO. However, the measured oxygen content is lower than expected for the PdO stoichiometry, suggesting loss of volatile species, and a more ‘hydrated’ compound, such as an oxyhydroxide.

Planejamento e controle de qualidade de dados de gradiometria gravimétrica 3D-FTG

This research job shows a detailed description of different steps of 3D-FTG (Full Tensor Gravity Gradiometry) planning and quality control (QC). The characteristics of 3D-FTG system, quality control during the flight and the result of the QC recorded through SNR (signal-to-noise ratio) analysis and the synthetical models of each gravity tensor component, will be presented. Iron oxide mineralization style is usually controlled by both crustal and local scale structures such as major shear, fault zones and lithological contacts. Air-FTG (Airborne Full Tensor Gravity Gradiometry) is nowadays the only existing airborne full tensor gradiometer technology can be used for both detailed and regional surveys. The system takes real time measurements of gravity gradient field in three orthogonal directions and at same time compensates for bias in the orientation and accelerations of the aircraft.

Correção de terreno para dados de aerogradiometria gravimétrica 3D-FTG no Quadrilátero Ferrífero, Minas Gerais, Brasil

The aim of this research is to show the application of terrain correction to 3D-FTG data at Bau-Gandarela, Quadrilaterio Ferrifero region at Minas Gerais State, Brazil. For this purpose we have used different digital terrain models with distinct resolutions (SRTM versus lidar).

EVALUATION OF GAMMA-GAMMA WELL LOGGING DATA APPLIED TO IRON ORE EXPLORATION – VALE GEOPHYSICAL WELL LOGGING TEST FACILITY

ABSTRACT. The present paper shows the results of density measurement tests determined by probing of gamma-gamma geophysical well logging, performed in two stages: one at VALE Geophysical Well Logging Test Facility (GWTF), and another in boreholes for iron ore exploration... Keywords: geophysical well logging, iron ore exploration, data evaluation. RESUMO. O presente trabalho mostra os resultados dos testes de afericao de valores de densidades determinados por sonda de perfilagem geofisica gama-gama, realizados em duas etapas, uma no Campo de Teste de Perfilagem Geofisica VALE e outra em furos de sondagem para exploracao de minerio de ferro. Palavras-chave: perfilagem geofisica, exploracao mineral de ferrosos, afericao de dados.

Modelagem numérica e validação de dados tensoriais de aerogradiometria gravimétrica 3D-FTG

Iron oxide mineralization style is usually controlled by both crustal and local scale structures such as major shear, fault zones and lithological contacts. Air-FTG (Airborne Full Tensor Gravity Gradiometry) is nowadays the only existing airborne full tensor gradiometer technology can be used for both detailed and regional surveys. The system takes real time measurements of gravity gradient field in three orthogonal directions and at same time compensates for bias in the orientation and accelerations of the aircraft. Each one of these measurements is related to either the density contrast or the geometry of discrete bodies. The aim of this work was to implement a numerical algorithm to compute the five gxx, gxy, gxz, gyy and gyz independent tensor components and use the knowledge acquired with them to help in real data interpretation and Air-FTG validation. To go over this subject, Air-FTG survey was flown over the Quadrilatero Ferrifero region, in Minas Gerais state, Brazil, to delineate and to map structures associated with iron oxide mineralizations. A complete procedure for data processing, together with joint interpretation of the geological models, ground gravity and air gravity gradiometry tensor components, indicates the high precision capability of the Air-FTG system in mapping and detecting iron oxide bodies with high accuracy. Results show that gradiometer depict a more observable advantage for identification of those near surface targets, revealing structures such as lineament, edges, corners and as a consequence, body shapes and their thickness. We have concluded that the best images of the subsurface rocks acquired by the Air-FTG platform can provide more realistic targets information than the conventional ground gravity field instruments.