Impact melt sheet zircons and their implications for the Hadean crust

Research Article| October 01, 2009 Impact melt sheet zircons and their implications for the Hadean crust J. Darling; J. Darling * 1Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK *E-mail: j.darling@bristol.ac.uk. Search for other works by this author on: GSW Google Scholar C. Storey; C. Storey 2School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth PO1 3QL, UK Search for other works by this author on: GSW Google Scholar C. Hawkesworth C. Hawkesworth 1Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK Search for other works by this author on: GSW Google Scholar Geology (2009) 37 (10): 927–930. https://doi.org/10.1130/G30251A.1 Article history received: 20 Mar 2009 rev-recd: 21 May 2009 accepted: 26 May 2009 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation J. Darling, C. Storey, C. Hawkesworth; Impact melt sheet zircons and their implications for the Hadean crust. Geology 2009;; 37 (10): 927–930. doi: https://doi.org/10.1130/G30251A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Impacts may have been important mechanisms of crustal redistribution and differentiation, particularly during intense postaccretionary bombardment between 4.5 Ga and 3.9 Ga ago. Evidence of crustal processes during this period is largely provided by detrital zircons from the Yilgarn craton, Australia. Trace element compositions, crystallization temperatures, and inclusion populations of these ancient zircons have been taken as evidence for predominantly granitic source magmas, implying widespread felsic continental crust on the early Earth. However, there is little knowledge of zircons formed in impact melt sheets, a potential source for the Hadean zircons. Here we present Ti thermometry, trace elements, and inclusion populations of zircons from the 1.85 Ga Sudbury impact melt sheet (Ontario, Canada). Our results demonstrate that large variations in zircon crystallization temperature and composition will be an inevitable consequence of the evolution of such magmatic systems. We also show that zircons in mafic rocks crystallize in residual liquids of granitic composition, producing inclusion assemblages that are remarkably similar to those reported for the ancient Yilgarn grains. Thus, we conclude that the trace element compositions and inclusion populations of the Hadean zircons are consistent with crystallization from more mafic melts than previously recognized, although high crystallization temperature distributions of Sudbury zircons indicate that impact melt sheets were not a dominant source for the grains older than 3.9 Ga. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.