The first continents were formed early in Earth’s history more than three billion years ago, but how they were created is still open to debate.
One of the studies suggested that the first supercontinents formed via subduction and plate tectonics, which is when the Earth’s plates move under one another, shaping the mountains and oceans.
According to new evidence offered by research from Curtin University, Earth’s first continents were not formed by subduction in a modern-like plate tectonics environment, as previously thought. Instead, it might be the result of an entirely distinct process.
For the study, scientists measured the iron and zinc isotopes in rock sourced from central Siberia and South Africa. They determined that the composition of these rocks may have formed in a non-subduction environment.
Lead author Dr. Luc-Serge Doucet, from the Earth Dynamics Research Group in Curtin’s School of Earth and Planetary Sciences, said, “Our research found that that the chemical makeup of the rock fragments was not consistent with what we would usually see when subduction occurs. If the continents were formed through subduction and plate tectonics, we would expect the ratio of iron and zinc isotopes to be either very high or very low. Still, our analyses instead found the ratio of isotopes was similar to that found in non-subduction rocks.”
“The team used a relatively new technique known as the non-traditional stable isotope method, which has been used to pinpoint the processes that formed continental and mantle rocks.”
“Our research provides a new but unknown theory as to how the Earth’s continents formed more than three billion years ago. Further research will be needed to determine what the unknown explanation is.”
The study was done in collaboration with Curtin’s Earth Dynamics Research Group, Université Libre de Bruxelles in Belgium, Institute for Geochemistry and Petrology in Switzerland, and Université de Montpellier in France.
- Luc S. Doucet et al. Archean lithospheric differentiation: Insights from Fe and Zn isotopes, Geology (2020). DOI: 10.1130/G47647.1