Base de données de recherche des TNO

étiquettes: physical sciences, geology, geochemistry, paleogeology, mineralogy, acasta gneiss, isotopes

Objectif(s): To further describe spatial relationships and rock structures present in areas that were sampled and found to be significantly old (>3.8 billion years). Additionally to explore and sample other units which are likely to be as old or older than previously documented samples and to use whole rock geochemical data to compare rocks within the Acasta Gneiss Complex (AGC).

Description du projet: The objectives of this research project are to: 1) further describe, sample, and document field relationships and structures present in areas that were sampled and found to be significantly old (>3.8 billion years) during the 2011 field session; 2) explore and sample other units which based on field relationships and mineralogy are likely to be as old or older than previously documented samples; 3) use whole rock geochemical data to compare rocks within the Acasta Gneiss Complex (AGC) that are not currently spatially related. The proposed study will make further use of state-of-the-art Cameca 1280 Ion Microprobe currently operating at the University of Alberta's Canadian Centre for Isotopic Microanalysis. This instrument is capable of isotopic analysis of minerals at very high spatial resolution (<20 micrometers), which is critical to the present study as only such high resolution analyses will enable the research team to read through later geological events that have obscured but not completely erased a record of the earliest history of the AGC. Collectively, the geochemical and isotopic data obtained in this study will provide insights on the formation of Earth's early continental crust. Using the previous season's field work and other published maps, the principal investigator plans to build on last year's work locating and describing the oldest units within the Acasta Gneiss Complex. During the previous year’s field work many of the currently published outcrops that contained the oldest rocks and identified others which were not reported by other researchers were identified and sampled. In the following years the descriptions of the structures and spatial relationships within these outcrops will be improved while also sampling other units near to the oldest ones. The surrounding area will also be explored for rock units that may be as old or related to the oldest units based on similarities in field relationship and mineralogy. 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 4, 2012 to August 25, 2012.