Chlorine Isotope Geochemistry in Natural Systems
Summary
Chlorine isotopes have become an indispensable tool for tracing fluid–rock interactions, provenance of saline deposits and recycling processes in the Earth’s crust and mantle. The ratio of 37Cl to 35Cl, expressed as δ37Cl, records fractionation during evaporation, mineral precipitation, degassing and high-pressure metamorphic reactions. In sedimentary basins, variations in δ37Cl reveal shifts between marine, lacustrine and continental brines and can be used to reconstruct palaeoclimate and tectonic evolution. In volcanic settings, chlorine isotopes preserved in melt inclusions inform on subduction inputs, mantle heterogeneity and degassing histories. Advances in sample preparation and multi-collector inductively coupled-plasma mass spectrometry have driven precisions better than ±0.1‰, opening new possibilities for low-abundance environments such as deep-sea pore waters and diagenetic minerals. Across hydrothermal, evaporitic and magmatic systems, chlorine isotope geochemistry now provides insights into fluid sources, transport pathways and the global halogen cycle, with implications for groundwater tracing, mineral exploration and understanding Earth’s volatile budget.
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Chlorine Isotope Geochemistry in Natural Systems publication trend
The graph below shows the total number of articles in chlorine isotope geochemistry in natural systems across all publications each year (not limited to Nature Index journals).
Technical terms
δ37Cl: Per mille deviation of the 37Cl/35Cl ratio in a sample relative to an international standard, indicating isotopic fractionation.
Evaporite: A sedimentary mineral deposit formed by precipitation of salts from evaporating saline waters, often preserving Cl isotopic signatures.
Melt inclusion: A pocket of silicate melt trapped within a growing crystal, recording the chemistry and isotope ratios of the parent magma.
Isotopic fractionation: The process by which isotopes partition between substances or phases during physical or chemical processes, leading to measurable ratio differences.
Serpentinite: A hydrated ultramafic rock derived from oceanic lithosphere that releases fluids rich in chlorine when metamorphosed, influencing subduction zone signatures.
References
- Origin and Evolution of Eocene Rock Salts in Pakistan and Implications for Paleoclimate Studies: Insights From Chemistry and Cl Stable Isotopes. Frontiers in Earth Science (2021).
- Chlorine isotope behavior in subduction zone settings revealed by olivine-hosted melt inclusions from the Central America Volcanic Arc. Earth and Planetary Science Letters (2022).
- A New Sample Processing Protocol for Separation and Purification Enabling Precise Analysis of Various Non-Traditional Isotopes in Geological Samples with Low Concentrations. Separations (2023).
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