DISCUSSION OF THE POCOS DE CALDAS (MG) VOLCANIC CALDERA EVOLUTION FROM A TOPOSEQUENCE PEDOGEOCHEMICAL ANALYSIS

Abstract

The pedogeochemical analysis refers to the chemical constituents of the weathering profile, which are originated by weathering of the rock minerals, the main natural source of these elements. The ordered development of a weathering profile can be interrupted countless times by climatic changes or as a consequence of a more abrupt intervention by geomorphic agents. The studied weathering cover is located within the volcanic caldera of Pocos de Caldas Alkaline Complex (MG), presents an extension of 150 m and is displaced by fractures/faults in ten weathering alteration levels/volumes (WAV's). The evolution under the geochemical constraints applied in the WAV's indicate at least three principal pedogenic/pedogeochemical sequences: (i) top of the profile, arid environment formation that subsequently lixiviated and/or precipitated as laterites during the high rainfall tropicalism; (ii) middle portion of the profi le, sub-humid/sub-dry tropicalism with tectonic reactivation conditions related to volcanism; (iii) bottom of the profi le, oxisols and plinthosols formation followed by the implosion or drop of the caldera and accumulation of residual mantles, which covered these profiles, leaving inside the lower portions of the structural high.