Original paper
Caves in iron formations in the Quadrilátero Ferrífero, Minas Gerais, southeastern Brazil: lithological, morphological and hydrological settings and speleogenesis
Calux, Allan; Cassimiro, Roberto; Salgado, André
Zeitschrift für Geomorphologie Volume 62 Issue 2 (2019), p. 125 - 144
published: Jun 11, 2019
published online: Mar 1, 2019
manuscript accepted: Feb 5, 2019
final revised version received: Jan 31, 2019
manuscript revision requested: Aug 1, 2018
manuscript received: Jun 5, 2017
ArtNo. ESP022006202002, Price: 29.00 €
Abstract
In Brazil, the first reference was made by Saint-Hilaire who described, in 1818, the Gruta do Eremita, located in the sanctuary of Serra da Piedade, Quadrilátero Ferrífero, Minas Gerais (Saint-Hilaire 1974). Decades later, in a cave in the Água Quente region, also in the Quadrilátero Ferrífero, the mineralogist Henwood (1871) described stalactites and crusts of iron hydroxide. However, it was not until the late 1950s, with the work of geologists from the United States Geological Survey (USGS) in Brazil, that more detailed studies of these cavities were carried out. The main work of this period was made by Simmons (1963), and resulted in the detailing of the mineralogy and the elaboration of a first morphogenetic and speleogenesis model of these iron caves. The understanding of the ferruginous landscape as karstic is controversial. Although there are similarities between the superficial and subterranean features of these environments and those typically karstic, the role of the dissolution process in the morphogenesis of these areas has not been well defined. However, the high amount of caves recorded in the iron formations of the Brazilian speleological provinces, which already total more than four thousand, arouse great scientific interest in the topic. This paper presents the general characterization of a sample of caves in the Quadrilátero Ferrífero Speleological Province, Minas Gerais State, southeastern Brazil. The method was based on the analysis of 11 caves. Lithostratigraphic, morphological, hydrological and depositional analyzes were performed in the field and laboratory. The main results point to the fact that the caves are preferentially located in the zones with the highest relative iron content, and that their initiation probably occurred in a phreatic or transitional (phreatic/vadose) environment, with development associated with vadose environment, where the occluded cavities were intercepted by backwearing process and thus exposed on the surface. The main control factors of speleogenesis in these caves are banding, fractures (tectonic and atectonic), axes and flanks of folds and the erosive geological contact between the duricrust and the banded iron formation.
Keywords
non-traditional karst • iron ore cave