The role of the ocean crust in recording and regulating ocean chemistry

Feb 11 2025 12:30 - 1:30PM

Colloquium

Speaker: Sasha Turchyn
·
U. Cambridge
Hosted by: Hal Bradbury
Description/Abstract

Seawater circulating through the oceanic crust has been suggested to provide a negative feedback on the surface carbon cycle, helping regulate Earth's temperature via the seafloor weathering hypothesis. Through this hypothesis increased surface carbon leads to increased temperatures which leads to increased mineralisation of carbon in the oceanic crust, helping stabilise the amount of carbon in Earth's surface environment. In this talk I will discuss how carbonate veins in the oceanic crust record past circulation of seawater through the crust, and how they may in some circumstances preserve past seawater chemistry, particularly the calcium isotopic composition of past oceans. I will argue that rather than hydrothermal circulation driving changes in ocean chemistry that the opposite is equally true - changes in seawater chemistry critically impact water-rock interaction in the oceanic crust and the formation of secondary and alteration mineralogy.