Uranium isotopic study of aragonite-calcite stalagmites: Implications for uranium-series dating

摘要

This paper focuses on the relationship between re-crystallization and erroneous U-series dating based on 82 precise ICP-MS 230Th data collected during analysis of two big stalagmites. Aragonite is susceptible to conversion to calcite with major loss of chemical elements during recrystallization, a process induced by drip water infiltration. Conversion of aragonite to calcite leads to errors in dating, resulting in false apparent ages.Because 230Th dating assumes that all changes in isotope ratios are the result of radioactive decay and ingrowth within a closed system (no chemical/diagenetic shifts in isotope ratios), the effects of recrystallization must be considered.