Direct evidence for crust-mantle differentiation in the late Hadean

Alessandro Maltese,Dewashish Upadhyay,Klaus Mezger,Om Prakash Pandey,Guillaume Caro

doi:10.1038/s43247-022-00341-9

Abstract

Constraints on the evolution of the silicate Earth between 4.5 and 3.8 billion years ago are limited by the scarcity of pristine geological material from that period. The geodynamic evolution of the early Earth, prior to the preserved rock record, is thus mainly inferred from numerical modelling. To evaluate the geological significance of these simulations, geochronological constraints pertaining to the evolution of the Hadean crust are required. Here we show using Neodymium isotope variations generated by decay of now-extinct 146-Samarium that Paleoarchean rocks from the Singhbhum Craton, India derived from a Hadean depleted mantle reservoir that differentiated {4.19}_{-0.12}^{+0.06} billion years ago. The event postdates Neodymium model ages of mantle depletion inferred from other Archean rocks by 200 million years. This geochronological record is mirrored in the Hafnium isotope composition of the oldest zircon grains, suggesting that Hadean mantle differentiation proceeded via distinct pulses of large-scale magmatic activity and crustal rejuvenation.

Highlights

Constraints on the evolution of the silicate Earth between 4.5 and 3.8 billion years ago are limited by the scarcity of pristine geological material from that period
The extent to which plate tectonics was operating in the early Earth remains widely debated, as higher mantle temperatures are thought to impede long-lived subduction and favour instead a stagnant, sluggish, or episodic-lid regime[7,10,11,12,13]
In the stagnant-lid mode, the lithosphere constitutes a single plate that does not take part in convective overturn, so that crustal rejuvenation occurs by other mechanisms such as heat-pipe volcanism and plume tectonics[14,15]

Summary

Introduction

Constraints on the evolution of the silicate Earth between 4.5 and 3.8 billion years ago are limited by the scarcity of pristine geological material from that period. The 146Sm–142Nd and 147Sm–143Nd data, provide concordant results for all investigated units of the Singhbhum and Bastar cratons—the granitoids of the Bastar Craton bear no record of early differentiation, whereas part of the Singhbhum granitoids and associated supracrustal rocks of the IOG formed from isotopically

Results

Conclusion