Atomic-scale age resolution of planetary events

L F White,D Bullen,T J Prosa,I Martin,J R Darling,D A Reinhard,D E Moser,D Lawrence,D J Larson,D Olson

doi:10.1038/ncomms15597

Abstract

Resolving the timing of crustal processes and meteorite impact events is central to understanding the formation, evolution and habitability of planetary bodies. However, identifying multi-stage events from complex planetary materials is highly challenging at the length scales of current isotopic techniques. Here we show that accurate U-Pb isotopic analysis of nanoscale domains of baddeleyite can be achieved by atom probe tomography. Within individual crystals of highly shocked baddeleyite from the Sudbury impact structure, three discrete nanostructural domains have been isolated yielding average 206Pb/238U ages of 2,436±94 Ma (protolith crystallization) from homogenous-Fe domains, 1,852±45 Ma (impact) from clustered-Fe domains and 1,412±56 Ma (tectonic metamorphism) from planar and subgrain boundary structures. Baddeleyite is a common phase in terrestrial, Martian, Lunar and asteroidal materials, meaning this atomic-scale approach holds great potential in establishing a more accurate chronology of the formation and evolution of planetary crusts.

Highlights

Resolving the timing of crustal processes and meteorite impact events is central to understanding the formation, evolution and habitability of planetary bodies
Pb isotopes 206Pb, 207Pb and 208Pb in the 2 þ charge state was ranged and quantified at 103, 103.5 and 104 Da respectively, counts of 207Pb and 208Pb are below detection limits. This comprehensive analysis of U and Pb isotope systematics is facilitated by the absence of Si within the baddeleyite lattice, limiting a large portion of the isobaric interferences that prevent accurate U measurements in zircon[19]
Our findings show that the development of localized nanometre-scale structures controls the mobilization potential of Pb in baddeleyite and results in subdomains that preserve either protolith crystallization or impact-reset 206Pb/238U ages

Summary

Introduction

Resolving the timing of crustal processes and meteorite impact events is central to understanding the formation, evolution and habitability of planetary bodies. Isotopic heterogeneities within meteorite samples caused by shock metamorphism[1,2,3] complicate efforts to characterize and date these precious materials This has resulted in conundrums regarding the timing of major planetary events, including the timing of lunar magma ocean crystallization[4], Martian volcanism[1,2] and impact bombardment of the inner Solar System[5,6]. We use atom probe tomography (APT) to accurately resolve chronological end-members (that is, protolith crystallization and impact metamorphism) within highly shocked baddeleyite of the Matachewan dyke swarm[16] (Ontario, Canada) This approach has the unique potential to produce coupled isotopic and structural data sets from nanoscale domains[17], facilitating direct U-Pb dating of nanometre-scale features

Methods

Results

Conclusion