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MARINE GEOCHEMISTRY

The oceans are the most important carbon reservoir on Earth’s surface and help regulate atmospheric CO2 concentrations through geologic time. Short and long-term changes in oceanic geochemical cycles, therefore, have had large compounding effects on the evolution and present state of Earth’s atmosphere and biosphere. Given the importance of this geochemical reservoir, a great deal of effort has been devoted to understanding marine geochemical cycles, yet several important questions remain, such as: (i) how have changes in continental weathering and hydrothermal circulation affected the composition of the oceans over geologic time? And (ii) how has the availability of key nutrients in seawater affected the evolution of life and composition of the atmosphere?

Other than my work concerning the feedback between seawater and hydrothermal fluid compositions through the Phanerozoic (Antonelli et al., 2017, PNAS), I have recently submitted a manuscript reassessing the radiogenic 40Ca budget of seawater, confirming that continental Ca (enriched in 40Ca from 40K decay), and not hydrothermal circulation, is the main source of Ca in the modern oceans (Antonelli et al., 2021, under review). I am also involved in several projects (in collaboration with D. Stolper and D. DePaolo, UC-Berkeley) aimed at understanding low-temperature alteration of ocean floor basalts.

Atlantic ocean (as seen from the Azores).
Photo credit: M. Antonelli

Relevant Publications:

Antonelli, M.A., DePaolo, D.J., Christensen, J.N., Wotzlaw, J-F., Pester, N.J., Bachmann, O. (2021) “Radiogenic 40Ca in seawater: implications for modern and ancient Ca cycles” ACS Earth and Space Chemistry 5(9), 2481–2492.

Antonelli, M.A., Pester, N.J., Brown, S.T., DePaolo, D.J. “Effect of Paleo-Seawater Composition on Hydrothermal Reactions in Mid-Ocean Ridges” (2017) Proceedings of the National Academy of Sciences, USA 114(47).

 

Stolper, D.A., Antonelli, M.A., Ramos, D.S., Bender, M.L., Schrag, D.P., DePaolo, D.J., Higgins, J.A. “Isotopic Constraints on the Formation of Carbonates During Low-Temperature Hydrothermal Oceanic Crust Alteration” AGU Fall meeting, San Francisco, December 2016.

 

Brown, S.T., Antonelli, M.A., Staudigel, H. Owens, T.L., DePaolo, D.J. “The Ca Isotope Composition of Altered MORB” V.M. Goldschmidt Conference, Sacramento, June 2014.

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