Different types of hard and soft speleothems
(stalactites, stalagmites, columns, crusts, flowstones,
micro-gours and botryoidal coralloids) have been
observed throughout lava tubes in the Galapagos
archipelago, Ecuador. Three lava tubes were studied in
this work: Gallardo and Royal Palm volcanic caves
(Santa Cruz Island) and Sucre Cave (Isabela Island).
The studied speleothems were mainly formed by opal,
calcite and clay minerals, including plagioclase and
pyroxenes from the basaltic host rock. Rarely, iron
oxides, gypsum were found in some speleothems,
which were interpreted as alteration products of the
primary volcanic materials. Field emission scanning
electron microscopy revealed abundant filamentous
17th International Vulcanspeleology Symposium 2
bacteria, and reticulated filaments similar to those
recently observed in others lava tubes around the world.
These filaments are associated with EPS and mineral
deposits rich in Si, Ca or Fe. The identified minerals
and the evidence of biosignatures suggest a biological
contribution to speleothem development within
Gallardo, Royal Palm and Sucre lava tubes.
