Central Slave Basement Complex Evolution
✦ The surface rocks in this picture, unfortunately with some lichen cover, are part of the Central Slave Basement Complex (CSBC) and were sampled during fieldwork for the CSBC project. Except where covered by lakes, these 3.2 to 3.7 billion year old rocks can be easily sampled with a rock hammer. (Photo: Steve Shirey)
Central Slave Basement Complex Project
Slave Craton Map
Jesse Reimink (Project Leader), Carnegie Institution for Science
Richard Carlson, Carnegie Institution for Science
Graham Pearson, University of Alberta
Steven Shirey, Carnegie Institution for Science
Only a small fraction of the crust existing on Earth today dates to the first billion years of Earth's existence. What Earth's original crust looked like, and what processes led the planet to form continental crust and underlying mantle that could resist 4 billion years of later tectonic reworking are largely unknown. Answers to these questions can provide key information on the dynamic processes operating in Earth's interior shortly after Earth formation.
This project will collect and analyze gneisses from a much wider spatial and temporal coverage from the central Slave basement in order to define the extent of reworking of Hadean material and its importance in the formation of this fragment of ancient crust.
We will make use of the 146Sm-142Nd and 182Hf-182W radioactive isotope systems, whole rock 147Sm-143Nd, Lu-Hf, and U-Pb isotopic measurements, and U-Pb and Hf isotope data for zircons to investigate the role Hadean (> 4 billion year (Ga) old) crust played in the genesis of the Slave craton of the Northwest Territories, Canada. Data of this nature for rocks from the best-studied locality in the Slave craton, the Acasta Gneiss Complex, show that these circa 3.8-4.02 Ga rocks contain much older components, approaching ages suggesting derivation from what may be the first crust formed on Earth. While the Acasta Gneiss Complex has seen extensive study, it represents but a small fraction of the basement rocks of the Slave craton.
Demonstration of the existence and extent of these ancient components in old crustal rocks across a broad region of the Slave craton will lead to new advances:
- illumination of the nature of Earth's earliest crust prior to the time when significant crustal fragments began to be preserved
- establishment of the role such ancient crust played in forming the oldest preserved crustal sections
- potential detection of whether Earth experienced an enhanced bombardment of extraterrestrial material circa 3.9 Ga
- information on the connection between crust formation and the development of a thick section of underlying mantle
- the potential for a fundamental change in the mechanism of continent formation occurred circa 3 Ga.