Karst in granitic rocks, South Cameroon: cave genesis and silica and taranakite speleothems

Abstract

A cave in granitic rocks was studied in Mezesse, South Cameroon. Coralloid speleothems, draperies and dissolution traces on the cave walls attest to its truly karstic nature. The speleothems consist of microlayers of opal and taranakite (K,NH4)Al3(PO4)3(OH).9H2O. They indicate a significant mobilization of silica, Al and K from granite during the formation of the cave. Identification of silicified bacteria in the speleothems layers suggests a possible role of these micro‐organisms in silica deposition. The presence of taranakite and of silicified organic remains within the speleothems lead to a better understanding of the genesis of the cave.

Sandstone caves on Venezuelan tepuis: Return to pseudokarst?

“…Solubility of silicate rocks is generally very low and caves which formed in silicate rocks were often attributed to pseudokarst because most workers believed that mechanisms other than dissolution play the main role in their formation. However, recently several works emerged which apply the term karst for silicate caves that occur either in granites (Willems et al, 2002;Vidal Romaní and Vaqueiro Rodrigues, 2007) or, more frequently, in sandstones (see the reviews in Wray, 1997Wray, , 1999. According to these authors dissolution, although slow, is the main process that forms the caves.…”

Kaolinite, illite and quartz dissolution in the karstification of Paleozoic sandstones of the Furnas Formation, Paraná Basin, Southern Brazil

“…7H and 11F) suggest an organic influence on their geomorphic evolution. However, a mere trapping between mineral layers is not yet to be discarded, as discussed by Willems et al (2002).…”

Exceptional silica speleothems in a volcanic cave: A unique example of silicification and sub‐aquatic opaline stromatolite formation (Terceira, Azores)

“…The predominantly microbial origin of some silica speleothems has been recognized by several authors (e.g. Forti, ; Léveillé et al ., ; Willems et al ., ; Aubrecht et al ., , ), with some noting the existence of filamentous bacteria, e.g. Willems et al .…”