Boxwork and ferromanganese coatings in hypogenic caves: An example from Sima de la Higuera Cave (Murcia, SE Spain)
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URI: http://hdl.handle.net/10835/15605
DOI: 10.1016/j.geomorph.2012.07.022
DOI: 10.1016/j.geomorph.2012.07.022
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2012Resumen
This paper examines the greyish-blue deposits that were recently discovered in the lower levels of the Sima de la Higuera Cave (Murcia, SE Spain) which occur as patinas over the walls and ceilings, as well as coating boxwork formations. Their mineralogy was determined using XRD and micro-Raman spectroscopy, while EDX microanalysis was used to determine their elemental composition. The mineralogical analyses revealed the presence of Mn oxides (todorokite and pyrolusite) and Fe with a low degree of crystallinity, whereas EDX microprobe showed elevated concentrations of Mn (38.2 wt.%), Fe (15.2 wt.%) and Pb (8.1 wt.%). The ferromanganese
oxyhydroxides occur as botryoidal aggregates overlying blades of calcite that have a visibly sugary texture. The speleogenetic model proposed describes (1) an initial phase of precipitation of hydrothermal calcite veins (of hypogenic origin) within the fissures of the host rock under phreatic conditions and (2) a subsequent vadose phase involving prefere...
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Geología
Mineralogía