PP51D-06
Outside the pH box: Boron isotopes in synthetic calcite precipitated under varying solution chemistry

Friday, 18 December 2015: 09:15
2012 (Moscone West)
Jesse R Farmer1, Joji Uchikawa2, Donald E Penman3, Baerbel Hoenisch4 and Richard E Zeebe2, (1)LDEO Columbia University, Palisades, NY, United States, (2)University of Hawaii at Manoa, Honolulu, HI, United States, (3)Yale University, New Haven, CT, United States, (4)Columbia University of New York, Palisades, NY, United States
Abstract:
Boron isotopic measurements (δ11B) in marine carbonates are a powerful tool for reconstructing past ocean carbon chemistry and the carbon cycle. Boron systematics in marine carbonates are rooted in the equilibrium dissociation of dissolved boron in seawater, but existing evidence from biogenic carbonates (corals, planktic and benthic foraminifers) suggests somewhat variable controls on boron concentration and δ11B. Synthetic precipitation experiments provide an opportunity to study boron systematics without biological interference, and recent studies (e.g., Uchikawa et al., 2015, GCA v150, 171-191) suggest that boron incorporation (measured as B/Ca ratios) into synthetic carbonates varies both with the elemental composition of experimental seawater and precipitation rate. Here we extend the geochemical characterization of synthetic calcite by investigating the influences of changing solution chemistry (pH, [Ca2+], [DIC] and [B]) and precipitation rate on their boron isotopic composition. Our results will be evaluated in the context of carbonate precipitation rates, modes of boron incorporation, and changing seawater chemistry through geologic time.