Tungsten isotope evidence from ~3.8-Gyr metamorphosed sediments for early meteorite bombardment of the Earth
Abstract
The `Late Heavy Bombardment' was a phase in the impact history of the Moon that occurred 3.8-4.0Gyr ago, when the lunar basins with known dates were formed. But no record of this event has yet been reported from the few surviving rocks of this age on the Earth. Here we report tungsten isotope anomalies, based on the 182Hf-182W system (half-life of 9Myr), in metamorphosed sedimentary rocks from the 3.7-3.8-Gyr-old Isua greenstone belt of West Greenland and closely related rocks from northern Labrador, Canada. As it is difficult to conceive of a mechanism by which tungsten isotope heterogeneities could have been preserved in the Earth's dynamic crust-mantle environment from a time when short-lived 182Hf was still present, we conclude that the metamorphosed sediments contain a component derived from meteorites.
- Publication:
-
Nature
- Pub Date:
- July 2002
- DOI:
- 10.1038/nature00923
- Bibcode:
- 2002Natur.418..403S