Characterization of boron incorporation and speciation in calcite and aragonite from co-precipitation experiments under controlled pH, temperature and precipitation rate

Vasileios Mavromatis (1) , Valérie Montouillout (2) , Johanna Noireaux (3) , Jérôme Gaillardet (3) , Jacques Schott (1)

1 GET - Géosciences Environnement Toulouse
2 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation
3 IPGP - Institut de Physique du Globe de Paris

About 20 years ago, the boron isotopic composition of marine carbonates was proposed as a proxy of ancient seawater pH. Since that time, a large body of studies has used boron isotopes in carbonates to reconstruct seawater paleo-pH and atmospheric paleo-CO₂ concentration. To date, however, no systematic investigation of the physicochemical parameters that control boron incorporation in calcite and aragonite (pH, temperature, precipitation rate, etc.) has been performed. To fill this gap, we have experimentally investigated the inorganic co-precipitation of boron with calcite and aragonite at 5 and 25 °C in the presence and absence of seed crystals and over the pH_NBS range 7.4 < pH < 9.5 in 0.1 or 0.2 M NaCl solutions. The boron partition coefficient, D_B, between CaCO₃ and the fluid is defined as:

Domains: Sciences of the Universe [physics]

Vasileios Mavromatis, Valérie Montouillout, Johanna Noireaux, Jérôme Gaillardet, Jacques Schott. Characterization of boron incorporation and speciation in calcite and aragonite from co-precipitation experiments under controlled pH, temperature and precipitation rate. Geochimica et Cosmochimica Acta, 2015, 150, pp.299-313. ⟨10.1016/j.gca.2014.10.024⟩. ⟨insu-03580029⟩