Chris Ballentine

Geochemistry: The application of chemistry to natural systems allows us to address some of the most exciting scientific questions in the Earth Sciences today. These encompass understanding the origin of our solar system and the process that formed the inner planets, how life formed and has been sustained, and the mechanisms that have changed Earth since its formation to give us the planet we now live on. Geochemistry also provides the science to address some of societies most pressing issues. These include resource discovery, safe waste disposal, and understanding local and global environmental change.

Noble Gases: My own research, somewhat ironically as a geochemist, uses the properties of the most chemically inert species we know, the noble gases (helium, neon, argon, krypton and xenon). I use their unique properties to understand the role that fluids and gases play in geological systems. For example, the noble gas low concentrations and large number of stable isotopes means that fluids from different sources often have characteristic isotopic signatures. This allows us to identify where the fluids have come from. Precisely because they are chemically inert, we know that the changes in the source signatures are only caused by the physical processes controlling the fluids in the system. This combination of properties allows us to reconstruct the fluid sources and detail the physical framework controlling liquid and gas migration and interaction that underpin many geological systems – on local to planetary scales.

Applications: I have taken the properties of the noble gases and applied them to make significant advances in our understanding of the origin of the Earth’s atmosphere and the chemical evolution and structure of the Earth’s mantle. I use the same noble gas tools and principles to understand how natural gas fields form, where different gases come from and the role that groundwater plays in hydrocarbon reservoir formation. A subset of this work has been developing quantitative techniques to show how carbon dioxide behaves in the subsurface, essential for safe burial of anthropogenic CO₂. This approach extends to understanding the crustal carbon cycle and how critical carbon-rich fluids play a role in supporting life in the subsurface on geological timescales.

Laboratory: The noble gas abundance and isotopic composition of natural samples are determined by static sector gas-source mass spectrometers. Recent advances in multi-collector technology provide us with an unprecedented improvement in the precision and accuracy of sample isotope ratio determination, and in particular for the heavier noble gases. My research team has led the application of this new capability. The Oxford laboratory currently hosts a suite of Thermo instruments and includes a Helix-MC, Helix-SFT, and Argus VI – each providing state of the art multi-collection capability for different sample types.