Tags: physical sciences, geology, acasta gneiss, isotopes
| Principal Investigator: | Reimink, Jesse R (6) |
| Licence Number: | 15856 |
| Organization: | Department of Terrestrial Magnetism, Carnegie Institution of Washington |
| Licensed Year(s): |
2016
|
| Issued: | Apr 04, 2016 |
| Project Team: | Dr. Richard Carlson, Dr. Steven Shirey, Dr. John Ketchum, Dr. D. Graham Pearson |
Objective(s): To investigate the role Hadean (> 4 billion year (Ga) old) crust played in the genesis of the Slave craton of the Northwest Territories, Canada.
Project Description: This project will use radioactive isotope systems, whole rock isotopic measurements, and 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. 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. For the samples to be collected during this project, the research team will first extract zircons for age determinations using either the Cameca 1280 ion-probe at the University of Alberta or by laser ablation. This capability will be complimented by the split-stream laser ablation facility at the University of Alberta. Laser ablation isotope analyses on feldspars also will be performed as a screening tool for ancient samples, particularly on zirconpoor samples. These survey data will be used for the selection of samples for more detailed study that will include whole rock isotope studies along with whole rock, high-precision analyses. For samples that contain zircons without complex zoning and age variability, the research team will perform solution studies of the zircons in order to provide a higher precision dataset for the initial isotopic compositions then can be obtained by laser ablation. For zircons with more complex age patterns, and where higher precision data are required, the research team will use the closed system laser ablation apparatus developed by collaborator Graham Pearson, to spatially sample zones within the zircon that will then be processed through standard chemical separation procedures for isotope analysis. Copies of publications resulting from this study will be provided to the Northwest Territories Geoscience Office (NTGO). The results of this study will also be presented at the Northwest Territories Geoscience Forum. The fieldwork for this study will be conducted from July 10, 2016 to August 26, 2016.
