Geosoft Talk

Qualitative and quantitative MVI applied to the Pirapora Anomaly

August 5, 2015
3:45pm - 4:10pm
SulAmerica Convention Centre
Rio de Janeiro, Brazil


Mark your calendar for the paper presentation, Qualitative and quantitative Magnetization Vector Inversion applied to the Pirapora Anomaly by Telma Aisengart - Technical Resources Manager of Geosoft Latinoamerica Ltda. The presentation will take place during the CISBGf 2015. To see the full list of Geosoft events at the show, visit our CISBGf event page.


The Pirapora magnetic anomaly is located at the North of the Quadrilatero Ferrifero Area in Minas Gerais, Brazil and has been object of several studies (Borges, 2013; Borges and Drews,, 2009), but its source was not already defined. The general sense from observing the anomaly is that it is a very deep source with strong remanence.

In this paper we have performed Magnetization Vector Inversion both on the total and residual magnetic fields confirming the strong remanence. We have also estimated the depth to the top and the apparent Inclination and Declination of the main source.

Several coincidences, as the geological context, depth of the main source and very strong remanence, have lead us to propose further investigation to verify the possibility of a geological model for Pirapora similar to the one that represents the anomaly in the Cobar Area, central western New South Wales, Australia.

The Cobar area is very well covered in scientific literature (Emerso, 1980; Clark and Tonkin, 1994), and there are three main types of sulphide mineralisation: a copper + gold-rich deposits southeast of the town; a copper + lead + zinc-rich deposit 10 km north of the town (CSA mine); and the silver + lead + zinc-rich Elura deposit 40 km north of Cobar. The Cobar regional magnetic anomaly is essentially produced by Pyrrothite with strong remanence and anisotropy.

We have also applied the Magnetization Vector Inversion for the Cobar area, using publicly available regional data as well as calculated an estimate for the inclination and declination of the area. Follow up studies need to be applied to corroborate the proposed geological model.

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