Retrieving geological units with unsupervised clustering of gamma-ray spectrometry data

Weihermann, Jessica Derkacz; Ferreira, Matheus Pinheiro; Castro, Luís Gustavo de; Ferreira, Francisco José Fonseca; Silva, Adalene Moreira

doi:10.1016/j.jappgeo.2020.104225

Cited by 12 publications

(1 citation statement)

References 17 publications

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“…The hydrothermal alteration zones are well defined by the geological maps (Alvarenga et al., 2007; Moreira et al., 2008; Weihermann et al., 2020). We remark that the anomalies follow an NE–SW pattern and are restricted basically to the Mara Rosa Sequence (chlorite‐schist), orthogneiss‐biotite gneiss (gneiss, tonalite and granite) and to gabbro–diorite (diorite, quartz–diorite and gabbro) (see Figure 1).…”

Section: Field Example and Discussionmentioning

confidence: 94%

Two‐dimensional inversion of airborne radiometric data for source concentrations: Application to Cu–Au targeting at Mara Rosa Magmatic Arc, Brazil

Weihermann

Oliveira

et al. 2023

Geophysical Prospecting

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Airborne radiometrics (radiometric surveying) has been used in many applications, such as geological mapping, environmental studies, mineral exploration and lithology mapping. The standard processing of gamma-ray spectrometry data provides good results when the acquisition conditions such as the flight and sensor orientation are constant. In practice, abrupt changes in flight height when flying in mountainous terrain are common, and standard processing neglecting this factor can lead to erroneous interpretation. The primary cause is the fact that the successive corrections applied to radiometric data in standard processing do not consider the effective sampled area of a survey (i.e. the field of view), which can have significant and variable overlaps between adjacent samples due to changing observation height. For this reason, standard height and sensitivity corrections may lead to incorrect estimates of the concentrations of the radioelements on the ground. To ameliorate this problem, we have developed a twodimensional inversion-based processing method that incorporates the aircraft height, replaces the sensitivity correction and accounts for a positivity condition using a logarithmic barrier. Some minerals associated with potassium, uranium and thorium allow the mapping of hydrothermal alteration, especially potassium which is an important constituent of hydrothermal fluids. We demonstrate the new methods by comparing the standard processing results with the inversion-based processing of airborne gammaray spectrometry data in the gold deposit-rich area of Mara Rosa Magmatic Arc, Brazil. The inversion-based processing results enhance the anomalies and suppress the interpolation artefacts as well as increase the signal-to-noise ratio. The application of airborne radiometric transformed maps also improved the footprint knowledge around Cu-Au mineralization and highlighted potential areas for further studies.

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Section: Field Example and Discussionmentioning

confidence: 94%