# Lead isotopes in over 1,000 rocks show ancient crust sources vanished 2.75–2.63 billion years ago

- Published: 2026-11-15 16:00 UTC
- Section: Planet › Earth sciences
- Tags: lead isotopes, early Earth crust, Neoarchaean, crustal recycling, plate tectonics onset, felsic magmatism, change point analysis, cratons, Curtin University
- URL: https://realtech.media/news/rt-5e65c197c652f4a9f51656e2_lead_isotopes_in/

**Lead isotope data from ancient rocks on four continents show an abrupt end of long-lived crustal sources. The authors link it to more efficient crustal recycling.**

![Lead isotopes in over 1,000 rocks show ancient crust sources vanished 2.75–2.63 billion years ago](https://realtech.media/media/2026/11/0cdcd38295830be8.jpg)
*ZME Science*

Researchers including Janne Liebmann of Curtin University analysed lead isotopes in more than 1,000 rocks from ancient landmasses in Australia, Africa, North America and Europe. They report that the isotopic signature of very old crust largely disappears from the accessible rock record after 2.75–2.63 billion years ago (Ga). The results were published in Proceedings of the Royal Society A Mathematical Physical and Engineering Sciences [1].

## Lead isotopes as a record of early crust

New continental crust does not always form directly from mantle magma. Often it is produced by melting older rock already present in the crust, and this leaves a lasting chemical trace in the new rocks. Lead isotopes record this trace and, unlike the commonly used Lu–Hf system, are particularly sensitive to fractionation within the crust, according to the authors [1].

In some minerals, including feldspar and certain sulfides, the signature can survive largely undisturbed for billions of years. The dataset covers nearly four billion years of Earth history and includes both newly analysed samples and data compiled from earlier studies.

## A sharp change in the record

The data indicate that long-lived, compositionally differentiated crustal reservoirs were established by 4.0–3.7 Ga. They contributed substantially to felsic magmatism until about 2.63 Ga, and their lead signature is preserved in several cratons worldwide [1].

After 2.75–2.63 Ga this fingerprint largely disappears. Statistical change point analysis identified the transition in the full data compilation and in subsets divided by geography and by mineral [1].

The authors interpret the disappearance as evidence of a Neoarchaean transition to more efficient crustal recycling and a reorganisation of magma generation towards plate margins. At present-day plate margins, fresh mantle melt rises while older crust is recycled at the same time. Before the transition, by the authors' reading, the same ancient crustal material was melted repeatedly with little input from other sources [1].

The loss of these long-lived sources coincides with independent geological and compositional evidence of a late Archaean secular change in continental evolution, the authors report. They state that the trigger of the shift is still unknown [1].

## Sources

1. [Proceedings of the Royal Society A Mathematical Physical and Engineering Sciences](https://doi.org/10.1098/rspa.2026.0587)
2. [ZME Science](https://www.zmescience.com/science/news-science/something-fundamental-changed-on-earth-2-5-billion-years-ago-scientists-think-theyve-found-what)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-5e65c197c652f4a9f51656e2_lead_isotopes_in/