The Geological Cycle of Atacama Desert Nitrate Deposits, Northern Chile

In this thesis, I investigate the origin and post-depositional evolution of nitrate deposits in the Atacama Desert, which host the largest natural nitrate accumulations on Earth. I integrate field observations with chemical and stable isotope analyses (δ¹⁸O, Δ¹⁷O, δ¹⁵N, δ³⁴S) across all deposit types. The consistently high Δ¹⁷O and δ¹⁸O values confirm an atmospheric origin linked to ozone-driven photochemical reactions. Lower isotope values in vein-hosted deposits indicate partial oxygen exchange with fossil hydrothermal waters during interaction with hot, saline, acid fluids. Geological, mineralogical, and sulfur isotope evidence further supports hydrothermal dissolution and reprecipitation of pre-existing atmospheric nitrate. Based on these results, I propose a two-stage geological cycle involving atmospheric deposition followed by tectonically driven hydrothermal recycling. Nitrogen isotope data show no significant microbial overprinting. This work demonstrates that Atacama nitrate deposits record a coupled atmospheric–geological system shaped by hyperaridity, tectonics, and magmatism.