Universität zu Köln

Riffo Contreras, Camila Javiera ORCID: 0000-0002-9640-7280 (2026). The Geological Cycle of Atacama Desert Nitrate Deposits, Northern Chile. PhD thesis, Universität zu Köln.

PDF (Dissertation Camila Javiera Riffo Contreras) Dissertation_Riffo_Camila.pdf Download (7MB)

Abstract

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.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Riffo Contreras, Camila Javiera criffoco@uni-koeln.de https://orcid.org/0000-0002-9640-7280 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-797355
Date:	2026
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute of Geology and Mineralog
Subjects:	Earth sciences
Uncontrolled Keywords:	Keywords Language Nitrate deposits UNSPECIFIED Atacama Desert UNSPECIFIED Triple oxygen isotopes UNSPECIFIED
Date of oral exam:	19 January 2026
Referee:	Name Academic Title Riffo Contreras, Camila Javiera UNSPECIFIED
Funders:	SFB 1211, GSGS fellowships, DAAD Scholarship
Projects:	CRC1211 - Earth - Evolution at the dry limit
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/79735