Microzone analysis of stalagmite chemical components in caves based on confocal controlled Raman and laser induced breakdown spectroscopy

Abstract

Cave stalagmites are recognized as excellent archives for studying contemporary and historical climate variations. They present a valuable opportunity for accurately identifying past climate signals through a combination of O and C isotopes(δ18O, δ13C), as well as trace elements. This study introduces confocal controlled Raman coupled to laser induced breakdown spectroscopy (LIBS) technology for analyzing of climate change using stalagmites for the first time. With a spatial resolution of 20 μm, this technology enables the detection of various elements and mineral. Correlation and principal component analysis of the ratio between elements, Raman, gray, fluorescence, δ13C, and δ18O revealed that the data are correlated and show significant grouping. These factors are related to the micro-environmental changes caused by the aragonite crystals in stalagmites. The increase/decrease in the Sr-Mg/Ca ratio and the decrease/increase in the (Ba-K-Fe)/Ca ratio were closely related to the water-rock interaction and prior calcite precipitation, the decrease/increase in soil biological activity, and the influx of detrital material caused by precipitation. This also corresponded to the decrease/increase in temperature. These findings indicate that the confocal controlled Raman-LIBS technique for detecting microscale chemical compositions in stalagmites holds significant promise and potential for studying past climate change.