Hydrodynamic fractionation of zircon age populations

Abstract

Research Article| January 01, 2011 Hydrodynamic fractionation of zircon age populations Rebecca L. Lawrence; Rebecca L. Lawrence 1Geosciences Department, Williams College, Williamstown, Massachusetts 01267, USA Search for other works by this author on: GSW Google Scholar Rónadh Cox; Rónadh Cox † 1Geosciences Department, Williams College, Williamstown, Massachusetts 01267, USA †E-mail: [e-mail] Search for other works by this author on: GSW Google Scholar Russell W. Mapes; Russell W. Mapes § 2Department of Geological Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA §Current address: ExxonMobil Corporation, Houston, Texas 77210, USA Search for other works by this author on: GSW Google Scholar Drew S. Coleman Drew S. Coleman 2Department of Geological Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Rebecca L. Lawrence 1Geosciences Department, Williams College, Williamstown, Massachusetts 01267, USA Rónadh Cox † 1Geosciences Department, Williams College, Williamstown, Massachusetts 01267, USA Russell W. Mapes § 2Department of Geological Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA Drew S. Coleman 2Department of Geological Sciences, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA †E-mail: [e-mail] §Current address: ExxonMobil Corporation, Houston, Texas 77210, USA Publisher: Geological Society of America Received: 11 Aug 2009 Revision Received: 18 Dec 2009 Accepted: 19 Jan 2010 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (1-2): 295–305. https://doi.org/10.1130/B30151.1 Article history Received: 11 Aug 2009 Revision Received: 18 Dec 2009 Accepted: 19 Jan 2010 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Rebecca L. Lawrence, Rónadh Cox, Russell W. Mapes, Drew S. Coleman; Hydrodynamic fractionation of zircon age populations. GSA Bulletin 2011;; 123 (1-2): 295–305. doi: https://doi.org/10.1130/B30151.1 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 SocietyGSA Bulletin Search Advanced Search Abstract Zircons in transport in the modern Amazon River range from coarse silt to medium sand. Older grains are smaller on average: Mesozoic and Cenozoic grains have average equivalent spherical diameter (ESD) 122 ± 42 μm (lower fine sand), whereas grains >2000 Ma have average ESD 67 ± 14 μm (upper coarse silt). As a full Wentworth size class separates the two values, zircons in these age populations are hydraulically distinct.Host sand size is correlated with average size of co-transported zircons, implying hydrodynamic fractionation. Zircon size is positively correlated with percent medium sand, and inversely correlated with percent very fine sand (p <0.0001 in both cases). In samples with >50% medium sand, average zircon size is 100 μm, compared with 80 μm in samples with >50% very fine sand. We infer from these data that zircon deposition is not size-blind, and that zircons track with hydraulically comparable sand grains. As different aged grains tend to have different characteristic sizes, this indicates the possibility of hydrodynamic fractionation of age populations.Five samples representing different hydrodynamic microenvironments of a single dune present significantly different detrital zircon age spectra, apparently the result of hydraulic processes. Peak mismatch (age peaks failing to overlap at 2σ level) is the most common disparity; but age populations present in some samples are missing from other samples. The lack of correspondence among the samples appears to exceed that attributable to random sampling. We conclude that hydrodynamic fractionation of zircons and zircon-age populations does occur. Zircon size should therefore be taken into consideration in detrital zircon provenance analysis. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.