Report

Evolution of the Continents and the Atmosphere Inferred from Th-U-Nb Systematics of the Depleted Mantle

See allHide authors and affiliations

Science  05 Mar 1999:
Vol. 283, Issue 5407, pp. 1519-1522
DOI: 10.1126/science.283.5407.1519

You are currently viewing the abstract.

View Full Text

Log in to view the full text

Log in through your institution

Log in through your institution

Abstract

Temporal evolution of depleted mantle thorium-uranium-niobium systematics constrain the amount of continental crust present through Earth's history (through the niobium/thorium ratio) and date formation of a globally oxidizing atmosphere and hydrosphere at approximately 2.0 billion years ago (through the niobium/uranium ratio). Increase in the niobium/thorium ratio shows involvement of hydrated lithosphere in differentiation of Earth since approximately 3.8 billion years ago. After approximately 2.0 billion years ago, the decreasing mantle thorium/uranium ratio portrays mainly preferential recycling of uranium in an oxidizing atmosphere and hydrosphere. Net growth rate of continental crust has varied over time, and continents are still growing today.

  • * To whom correspondence should be addressed. E-mail: k.collerson{at}mailbox.uq.edu.au

View Full Text