Abstract

“The oxygen isotopic composition of the ocean varies over recent times (last 30-50 million years) as a function of ice volume but whether it varies over longer geological time (last 600 million years) remains uncertain and records suggest different things. Here I will discuss an attempt to reconstruct the oxygen isotopic composition of hydrothermal vent fluid recorded in quartz and epidote veins formed in ancient oceanic crust and preserved in ophiolites. High temperature vent fluids are evolved from seawater through water-rock interaction and if this can be accurately modelled then the composition of seawater can be known. I will discuss new approaches we are using involving reactive transport models to understand the controls on water-rock interaction and chemical evolution in hydrothermal systems.”