An optimized thermal extraction system for preparation of water from fluid inclusions in speleothems

Abstract

The fluid inclusions present in speleothems (secondary mineral deposits formed in caves) are a relict sample of the parent seepage water from which the speleothem was deposited and determination of their composition can solve the palaeotemperature equation for the precipitation of speleothem carbonate. We have extracted fluid inclusions using a newly-designed thermal vacuum extraction method in stalagmites and stalactites from Nerja Cave, Southern Spain. Optimal conditions were found to involve heating samples crushed to 0.8-2mm for 3 hours at 300-400ºC. Waters extracted from modern aragonitic speleothem samples produced results on the Meteoric Water Line defined by modern infiltration and other waters associated with the cave and hence demonstrate an absence of fractionation effects. This successfully demonstrates the utility of the method.