3. "Study of the Morin Transition in Pseudocubic α-Fe2O3 Particles”

C. PREZZI; R. SOMOZA; ROBERTO CARLOS MERCADER

Hyperfine Interactions

Año: 2006 p. 1 - 1

0304-3843

We study the mineralogical changes suffered by specimens of natural miocene red and green continental sandstones (from Pozuelos Formation  and Tiomayo Formation) cropping out in the Argentine Puna that increase their bulk magnetic susceptibility and change color when thermally treated. We hypothesize that on heating  siderite, which is present in small quantities as cement in  the studied sandstones, would oxidize and decompose into maghemite and/or magnetite. Subsequent heating to higher temperatures sometimes would bring about the conversion of maghemite and/or magnetite to hematite. Mössbauer  spectroscopy proved to be a very valuable tool for the determination of the presence of siderite in small amounts in the studied samples. The present results show that further work is needed in order to fully understand the mineralogical changes suffered by continental  sandstones  during  heating. The characterization of such changes  occurred during laboratory routines is relevant, since they  can help  to better understand natural processes.