Magnetic properties of a soil from Southeastern Brazil in the presence of magnetic biomineralization by social insects

Publication date: 1 June 2017
Source:Geoderma, Volume 295
Author(s): Jairo F. Savian, Marcia Ernesto, Odivaldo C. Alves, Thelma S. Berquó
It is known that the migratory ant Pachycondyla marginata, and its prey, the termite Neocapritermes opacus, synthesize magnetic minerals which may contribute to the magnetic characteristics of soil. A comparative study of the magnetic properties of the minerals found in those species, as well as their nests and surrounding soil aimed at investigating the contribution of the biogenic minerals to the magnetization of the soil. Partially oxidized magnetite (Tv ≈120K) was found in the Pachycondyla marginata as shown by the Verwey transition in the ZFC/FC and RTSIRM curves. Low-temperature remanence measurements of the Neocapritermes opacus indicated the presence of maghemite and/or titanomaghemite, while partially oxidized pseudo-single domain magnetites and/or titanomaghemite were recognized in the soil and insect nests. Based on the similarity in the magnetic characteristic of the samples it is concluded that there is significant influence of biogenic mineralization upon the pedogenic contribution.