Earth's oldest known crystals offer clues on the origin of tectonics

“The dynamic tectonic nature of the modern Earth is one of the reasons why life exists today. Exploring the geodynamics and the lithological diversity of the early Earth could lead to revelations of how life first began on our planet,” said Wriju Chowdhury, an associate professor of Earth and environmental sciences at the university, in a press release. 

Examining the oldest-known crystals

For this, the team studied tiny time capsules found in the oldest-known crystals of the planet —recovered from the hills of Mid-West Western Australia. These Hadean zircon crystals were formed about 4.39 billion years ago.

They investigated the chemical composition of the parent magmas from which the crystals formed. This aided their understanding of early Earth's plate tectonic activity.

“Parent magmas are much more direct and reliable because they are closer to the source – the actual tectonic style. Our study describes the silicon and oxygen isotopic content of the zircons and the trace element content of the parental magmas, which has not been combined and presented before,” said Chowdhury.  

The results of a thorough chemical examination revealed "tectonic continuity from ancient to modern times." Simply put, Earth's tectonic movement most likely began more than 4.2 billion years ago. According to the authors, this is most likely when life first appeared on Earth. 

The team emphasizes that this study could help us learn more about the search for life on other planets.

The results have been published in the journal Nature Communications.

Study abstract:

Constraining the lithological diversity and tectonics of the earliest Earth is critical to understanding our planet’s evolution. Here we use detrital Jack Hills zircon (3.7 − 4.2 Ga) analyses coupled with new experimental partitioning data to model the silica content, Si+O isotopic composition, and trace element contents of their parent melts. Comparing our derived Jack Hills zircons’ parent melt Si+O isotopic compositions (−1.92 ≤ δ30SiNBS28 ≤ 0.53 ‰; 5.23 ≤ δ18OVSMOW ≤ 9.00 ‰) to younger crustal lithologies, we conclude that the chemistry of the parent melts was influenced by the assimilation of terrigenous sediments, serpentinites, cherts, and silicified basalts, followed by igneous differentiation, leading to the formation of intermediate to felsic melts in the early Earth. Trace element measurements also show that the formational regime had an arc-like chemistry, implying the presence of mobile-lid tectonics in the Hadean. Finally, we propose that these continental-crust forming processes operated uniformly from 4.2 to at least 3.7 Ga.