Large calcium isotope fractionations by zeolite minerals from Iceland

• Published in: Communications Earth & Environment
• Main Authors: Nelson, Claire J., Jacobson, Andrew D., Kitch, Gabriella D., Weisenberger, Tobias B.
• Other Authors: National Science Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Science and Business Media LLC 2021
• Subjects: General Earth and Planetary Sciences; General Environmental Science; Iceland
• Online Access: http://dx.doi.org/10.1038/s43247-021-00274-9; https://www.nature.com/articles/s43247-021-00274-9.pdf; https://www.nature.com/articles/s43247-021-00274-9

Abstract Zeolites are secondary tectosilicates produced during the hydrothermal alteration of basalt. The minerals serve as major sinks of calcium, which readily exchanges with calcium from surrounding groundwater. However, no studies have specifically investigated the calcium isotope geochemistry (δ 44/40 Ca) of zeolites. Here, we report δ 44/40 Ca values for zeolites from East Iceland, where the minerals form during progressive burial of the lava pile. The zeolites show a δ 44/40 Ca range of 1.4‰, which strongly correlates with average mineral calcium-oxygen bond lengths. As this correlation appears most consistent with equilibrium isotope partitioning, our findings point toward developing a novel geothermometer for studying low-grade basalt metamorphism. The results also have significance for using calcium isotopes to trace basalt weathering, including its role in long-term climate regulation and application in carbon capture and storage, a leading strategy for mitigating anthropogenic climate change.