GLOBAL EPISODIC GROWTH OF CONTINENTAL CRUST RECORDED BY DETRITAL ZIRCONS

A meta-analysis compilation of detrital zircons has been constructed over the past two years by the Virginia Tech Geosciences Sedimentary Geology Group. The data set includes approximately 61,000 individually dated detrital zircon grains cited in peer-reviewed literature. Initial work with the database included statistical analysis of sample size issues and characterization of the error in estimating stratigraphic age of host sediments from detrital zircon age dates (Voice et al. 2006; 2007). This abstract presents new data based on analysis of histograms of the entire dataset from individual continents and from different tectonic settings.

A “Global Age Spectra” constructed from the data set exhibits prominent peaks at 3.5-3.4 Ga, 2.7-2.5 Ga, 2.0-1.7 Ga, 1.2-1.0 Ga, 0.7-0.5 Ga and 0.2-0.1 Ga. The global age spectra exhibits peaks similar to those recorded by magmatic zircons (Condie, 1989), although the younger peaks are not as intense in the magmatic zircon record. The presence of distinct peaks suggests that continental crustal generation was episodic.

Construction of histograms for each of the seven continents shows that the major peaks observed in the global age spectra, with the exception of the 0.2-0.1 Ga and 3.5-3.4 Ga peaks, are present on all continents. The datasets from individual continents were also sorted by tectonic setting. Histograms for four sets of tectonic settings (rifts, passive margins, foreland basins, and arc settings) from the entire database, illustrate the same set of peaks observed in the global age spectra in all four settings. Detrital zircons from modern sediments (fluvial, eolian and paralic deposits) exhibit the younger four peaks. The older peaks were not observed.

Global and Continental age spectra provide a means of understanding sediment recycling patterns. This detrital zircon dataset suggests that regardless of tectonic setting or geographic location, sedimentary systems preserve a record of continental crustal growth.