Research Grant FInal Report: "The influence of evaporites on the terrestrial alteration of CO carbonaceous chondrites from the Atacama Desert: Evidence from oxygen isotope analysis"

The project investigates how terrestrial weathering affects CO carbonaceous chondrites recovered from different dense collection areas in the Atacama Desert. CO chondrites are among the most primitive meteorites, preserving early Solar System materials such as organic matter and presolar grains, but their original chemical and isotopic signatures can be modified after falling to Earth. The study focuses on terrestrial evaporitic minerals and other alteration phases formed in the Atacama Desert that influence a shift in the bulk oxygen isotopic composition of CO chondrites. By comparing leached and unleached fragments from meteorites collected across different dense collection areas, this project aims to distinguish primary meteoritic signatures from terrestrial alteration effects. A key objective is to understand how local environmental factors, such as coastal fog, soil chemistry, water availability, and desert geology, control the formation of evaporites within meteorites and how they potentially affect the bulk oxygen composition. Because Atacama CO chondrites show scattered oxygen isotope compositions compared with Antarctic samples, this work will help determine whether these differences reflect terrestrial alteration, metamorphic grade, or local climatic conditions. Overall, the project uses high-precision oxygen isotope analyses, petrographic and mineralogical descriptions, and bulk chemical data to identify alteration sources and improve the recognition of the most pristine CO chondrites in meteorite collections.

The funds were used to pay for the oxygen isotopes measurements performed at the Laboratory for Stable Isotope analyses hosted at CEREGE. PANISS is equipped with a fluorination line for silicates and an associated Delta V Plus IR-mass spectrometer. This system is used routinely to measure meteoritic samples. PANISS is staffed with two permanent research engineers (C. Sonzogni and D. AuYang) who ensure maintenance, calibration, and users’ training.