Study of the relationship between mineralogical types and potential radon in rocks of the region of Serra do Gandarela – Quadrilátero Ferrífero-MG.

Natália Fonseca Taveira,Francisco Rios,Ariela Diniz,Mariza Franklin,Aimoré Neto,Zildete Rocha,Talita Santos,Maria Ângela Menezes,Frederico Guimarães

doi:10.15392/bjrs.v9i1a.1543

Abstract

The Quadrilátero Ferrífero (QF) is one of the most well-known metallogenetic provinces in the world and has its geological context well studied since the end of the 17th century. The Serra do Gandarela is positioned in the northeast of the QF and is supported by units of the Minas Supergroup. The Moeda Formation (MF) in the Serra do Gandarela hosts an uranium (U) occurrence which was recently characterized in terms of mineralogical context. Uraninite, coffinite and brannerite are the main U minerals present. It is expected that mineralogy and lithology contribute to radon emanation and exhalation, the radon (Rn) transport from the soil to the atmosphere. In this work, the Rn exhalation was correlated to the lithological types. Samples from the MF conglomerates and Nova Lima group schists were collected from the Serra do Gandarela. Rn exhalation measurements were performed on the samples with AlphaGUARD detector. These values were compared to the U content of samples obtained via INAA. The result of INAA was more expressive in the MF conglomerate sample from the NUCLEBRÁS drillcore, with a U concentration value of 24 µg.g-1. The sample that had the highest average exhalation rate was also the same. The lowest value presented for both U concentration and average exhalation rate was shale, which were, 2 µg.g-1 and 180 Bq.m-3, respectively. The results are relevant for exploration and mining activities, during which Rn can accumulate in galleries. Additionally, the knowledge of the characteristic emanometric can be an important tool for geological and environmental studies.

Highlights

The environment and the human being are constantly subject to a continuous flow of ionizing radiation from anthropogenic and natural sources
Some radiometric anomalies were identified in this area in the 70’s and 80’s, and were discovered to be related to the basal metaconglomerates of the Moeda Formation, which overlays the shales of the Nova Lima Group [12]
High and very high levels are associated with the occurrence of the Moeda Formation, in the contat between Moeda Fm. and Nova Lima Group

Summary

Introduction

The environment and the human being are constantly subject to a continuous flow of ionizing radiation from anthropogenic and natural sources. Primordial radionuclides have been present on Earth since its formation about 4.5 billion years ago. In this context, only radioactive isotopes whose half-life is long enough still exist naturally nowadays [1]. For radon to be present in a given site, the radionuclides that originate it must be present in the soil and in the rocks that surround that region. In this way, soils rich in uranium and thorium are the main factor of the presence of this gas

Methods

Results

Conclusion