Determining the production rate of cosmogenic 3He using basalt lavas from the volcanic islands of the Azores and Canaries

Background
Accurately determining when and how frequently volcanoes have erupted is imperative for determining the hazard they pose to population centres. There are few techniques for precisely determining the age of young (< 50 ka) basaltic volcanism. The accumulation of cosmogenic 3He and 36Cl in minerals in the upper few cm of basaltic lava flows can be used to date the most recent basalt eruptions, and is particularly useful in arid regions where organic material is not present. We have used cosmogenic 3He in basaltic lavas to determine the collapse history of tsunami-producing ocean island volcanoes [1] and the slip history of edifice-controlling faults on Etna [2].

Unlike radiometric dating techniques that rely on invariant decay rate, the production rate of cosmogenic isotopes is sensitive to altitude, latitude and mineral composition. The application of the technique depends crucially on accurate and precise determinations of the production rate. Recently erupted basaltic lava flows are ideal for determining cosmogenic 3He production rate calibrations as the flow top features (e.g. pahoehoe ropes and hornitos) rule out surface erosion, and they can be potentially dated independently using 14C and palaeomagnetic techniques. So far cosmogenic isotope production rates have mainly been measured in high latitudes in surfaces produced since the Last Glacial Maximum. Improving the precision of the technique requires that long-term production rates are determined from equatorial regions. Initial studies of basalts from Cape Verdes produced new data that implies long-term 3He production rates may be lower than previously thought [3].

The project
The main aim of this project is to determine the absolute production rate of cosmogenic 3He and 36Cl in basaltic lavas from the Atlantic Ocean volcanic islands of Pico and São Jorge (Azores) and La Palma and El Hierro (Canaries). This will involve two fieldwork campaigns, specifically aimed at sampling basalt lava flows. Laboratory work will use high precision He isotope determinations using a new ThermoFisher Helix-SFT noble gas mass spectrometer at SUERC. If appropriate sample material is available, training will be given in the chemical techniques necessary for cosmogenic 36Cl determinations using the SUERC accelerator mass spectrometer. Absolute age determinations of the lavas will use the 14C laboratories. The data will be incorporated into the existing production rate algorithms.

SUERC is home to a range of world-class analytical facilities and research groups that are at the forefront of the Earth and environmental sciences. The student will work in close collaboration with colleagues in the Azores.

Requirements
Applicants should have a good undergraduate degree in physical sciences (e.g. physics, engineering, geology). A commitment to laboratory and fieldwork is expected. The student is expected to be competent in mathematics.

Application process
This project is suited to students with their own research funding. Interested applicant should contact Prof. Finlay Stuart ([Email Address Removed]) to discuss the project.

The studentship will be based at the Scottish Universities Environmental Research Centre in East Kilbride (http://www.gla.ac.uk/research/az/suerc/).

Closing date for applications: 1 July 2018

Start date: 1 October 2018