(PT) Ocorrência de espeleotemas fosfáticos e feições morfológicas raras em cavernas ferríferas da Serra de Carajás, no Pará.

Author(s): SCHERER, Rafael dos Santos
Summary: In a little more than 10 years, Carajás region has become the largest speleological province of iron formation caves in the country. About 2,300 caves are currently known. However, a portion of these caves developed distinct morphological features and differentiated speleothems, considered rare, including stalagmites, columns and stalactites of phosphate, as well as choriorids with reduced occurrence. The objective of this work is to deepen the knowledge about the distinct morphological features and rare speleothems studying its mineralogy and morphology. For this, cartographic, geospeleological and mineralogical studies were carried out in seven caves in order to better understand the origin and evolution of these chemical deposits and morphological features.To investigate the mineralogy of the chemical deposits, methods of X-ray diffraction and X-ray fluorescence were used. The morphological analysis was performed from topographic surveys at 5D level and geospeleological studies. These evaluations allowed to identify caves with only composite chambers consisting of more than one compartment. Planimetrically the seven caves fit the spongiform pattern. The longitudinal sections showed caves with inclined floors, concordant with the slope. All of them present perennial or temporary drainage where rainwater accumulates and participate in the subsurface flow of the slopes. Drip and drainage are the main responsible for the generation of diverse features on floors and walls. The guano in the caves is possibly responsible for generating the expressive acidity of the water circulating in these caves. The processes that form these speleothems and rare features are mainly biogenetic and these are formed almost exclusively of phosphate. The main phosphatic minerals identified were: francoanellite, fosfosiderite, calcium phosphate, leucophosphite, newberyite, spheniscidite, variscite and strengite. In the phosphate group, two rare minerals, Francoanellita and the Newberyita, both with little occurrence in the world and registered for the first time in Brazil.
Year: 2016
Pages: 112 f.
Year of publication: 2016
Supervision: Pedro Walfir Martins Souza-Filho, Dr.
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Course: Master's Degree in Sustainable Use of Natural Resources in Tropical Regions