Controls on trace element incorporation into travertine carbonates

Summer 2017

Holly Barnhart : Environmental Earth Science

Mentor: Laura Lammers

A multitude of different trace metals can readily incorporate into the crystal lattice of calcite, depending on factors like solution chemistry, temperature, and growth rate. Measurements of these elemental abundances in calcite can be an effective means of understanding rates and environments of crystal growth and have been widely utilized over the past decades to decode paleo-environmental growth conditions and, to some extent, in environmental remediation of polluted systems. Much of the present understanding of microscale controls on trace element incorporation into carbonates is based on laboratory experiments and studies of marine or cave carbonates. However, these studies are limited in their ability to precisely describe conditions at the time of carbonate deposition, which limits our understanding of growth mechanism acting at the time of precipitation. Travertines, or continentally-deposited limestones, provide the opportunity to study trace element incorporation in a modern system where source fluids and other system characteristics are readily accessible. I will study the hot spring travertines in Bridgeport, CA, focusing on how aqueous complexation and interactions on mineral surfaces control incorporation of trace elements iron (Fe), manganese (Mn), lithium (Li), and toxic metals copper (Cu) and lead (Pb) into the crystal lattice.

I learned a lot this summer, especially in the context of the practice of science. Prior to this summer, I had knowledge of a lot of experimental techniques. This fellowship gave me the opportunity to focus in on specific research questions, figure out a way to test them using the techniques I already knew, and then interpret and make sense of the resulting data. This experience definitely boosted my confidence in my ability to conduct independent research. Additionally, this summer really solidified my goals to go to graduate school for environmental geochemistry.