Boron Isotope Geochemistry in Geological Processes

Boron isotopes provide a sensitive tracer of fluid–rock interactions, oceanic pH variations and magmatic processes across the Earth system. Variations in the ratio of 11B to 10B, conventionally expressed as δ11B, record changes in seawater chemistry adopted by marine carbonates, reveal the release of boron-rich fluids during serpentinisation of the mantle and track arc magmatic hydration. Advances in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), laser-ablation techniques and novel chemical separations now permit high-precision, high-resolution measurements on microgram-scale samples. These developments have broadened applications from palaeo-ocean pH reconstructions and atmospheric CO2 estimates to continental margin hydrogeochemistry and subduction zone fluxes. In magmatic systems, boron isotopic signatures elucidate slab contributions and fluid sources, while in biological carbonates they constrain calcification site pH and historic ocean acidification. Integration of methodological innovation with palaeoclimatic, hydrothermal and geodynamic studies underscores the global significance of boron isotope geochemistry as both an environmental proxy and a tracer of deep Earth processes.

Research from Nature Portfolio

Recent studies of tropical South Pacific coral archives have reconstructed surface-ocean pH back to the late 17th century, revealing long-term acidification trends modulated by interannual climate variability and the notable acceleration of pH decline after industrialisation. Experimental work on coccolithophore calcification has demonstrated maintenance of a constant calcifying-fluid pH across varying seawater pH conditions, elucidating cellular controls on boron fractionation and carbon sourcing. New measurements of fast-spread oceanic gabbros show that simple hydration in bending-fault settings does not impart significant boron to the upper mantle, refining models of fluid transport into subduction zones and the provenance of boron in arc magmas.

Boron Isotope Geochemistry in Geological Processes publication trend

The graph below shows the total number of articles in boron isotope geochemistry in geological processes across all publications each year (not limited to Nature Index journals).

Technical terms

δ11B: Relative difference in 11B/10B ratio of a sample expressed in per mil (‰) against an accepted standard.

MC-ICP-MS: Multi-collector inductively coupled plasma mass spectrometry, an instrument for high-precision isotope measurements.

Laser-ablation ICP-MS: Technique using focused laser pulses to sample solids directly for subsequent mass spectrometric analysis.

Serpentinisation: Hydration and transformation of ultramafic mantle rocks, often incorporating boron during fluid–rock interaction.

Partition coefficient (Kd): Ratio describing how an element distributes between mineral and fluid phases during crystallisation or precipitation.

pCO2: Partial pressure of carbon dioxide, indicating its concentration in gas or aqueous phase.

References

1. Surface ocean pH variations since 1689 CE and recent ocean acidification in the tropical South Pacific. Nature Communications (2018).
2. A coastal coccolithophore maintains pH homeostasis and switches carbon sources in response to ocean acidification. Nature Communications (2018).
3. No significant boron in the hydrated mantle of most subducting slabs. Nature Communications (2018).
4. Nanogram-scale boron isotope analysis through micro-distillation and Nu Plasma 3 MC-ICP-MS. Talanta (2023).
5. Historic ocean acidification of Loch Sween revealed by correlative geochemical imaging and high-resolution boron isotope analysis of Boreolithothamniom cf. soriferum. Earth and Planetary Science Letters (2024).
6. In-Depth Method Investigation for Determination of Boron in Silicate Samples Using an Improved Boron–Mannitol Complex Digestion Method by Inductively Coupled Plasma Mass Spectrometry. Molecules (2023).