UCL Earth Sciences


Xi (Helen) Chen

“Systematic study of the Precambrian strontium isotope.”

PhD project title:

Research on the strontium isotope of Precambrian seawater.

Image of Helen Chen
Project description:

The temporal trend of seawater strontium (Sr) isotope ratio (87Sr/86Sr) retained in marine sedimentary rocks reflects changes in the relative contributions of the continental versus mantle chemical reservoirs to ocean composition, thus playing a significant role in interpreting global weathering rate and hypothesizing tectonic, chemical and biological changes during Earth history. However, the Precambrian strontium isotope database, for which the geological record is sparse, has considerably lower temporal resolution, which to some extent has made interpretations of continental weathering rate and crustal evolution highly controversial during early Earth history. Therefore, a new compilation and systematic study of the Precambrian strontium isotope is required.

My research aims to: 1) compile and select recently published Precambrian strontium isotope data to complement previous compilations and complete the Precambrian 87Sr/86Sr curve; 2) interpret the updated strontium isotope curve in depth in terms of  tectonic evolution and global weathering rate, using a combination of other geochemical proxies such as lithium, hafnium isotopes etc.; 3) measure the Sr isotope compositions of newly obtained Mesoproterozoic rocks (thus filling a data gap) from my research field area (North China Craton), and select the least altered values to be used for detailed interpretation. Overall, an updated Precambrian strontium isotope curve and corresponding interpretation would be established based on my work, which would contribute to deciphering early Earth evolution. The study is partially funded by Dean’s Prize.