Generation of Eoarchean tonalite-trondhjemite-granodiorite series from thickened mafic arc crust

Abstract

Research Article| April 01, 2012 Generation of Eoarchean tonalite-trondhjemite-granodiorite series from thickened mafic arc crust Thorsten J. Nagel; Thorsten J. Nagel 1Steinmann-Institute, Universität Bonn, 53115 Bonn, Germany Search for other works by this author on: GSW Google Scholar J. Elis Hoffmann; J. Elis Hoffmann 1Steinmann-Institute, Universität Bonn, 53115 Bonn, Germany2Institut für Geologie und Mineralogie, Universität zu Köln, 50674 Köln, Germany Search for other works by this author on: GSW Google Scholar Carsten Münker Carsten Münker 2Institut für Geologie und Mineralogie, Universität zu Köln, 50674 Köln, Germany Search for other works by this author on: GSW Google Scholar Author and Article Information Thorsten J. Nagel 1Steinmann-Institute, Universität Bonn, 53115 Bonn, Germany J. Elis Hoffmann 1Steinmann-Institute, Universität Bonn, 53115 Bonn, Germany2Institut für Geologie und Mineralogie, Universität zu Köln, 50674 Köln, Germany Carsten Münker 2Institut für Geologie und Mineralogie, Universität zu Köln, 50674 Köln, Germany Publisher: Geological Society of America Received: 08 Aug 2011 Revision Received: 23 Nov 2011 Accepted: 29 Nov 2011 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2012 Geological Society of America Geology (2012) 40 (4): 375–378. https://doi.org/10.1130/G32729.1 Article history Received: 08 Aug 2011 Revision Received: 23 Nov 2011 Accepted: 29 Nov 2011 First Online: 09 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 Thorsten J. Nagel, J. Elis Hoffmann, Carsten Münker; Generation of Eoarchean tonalite-trondhjemite-granodiorite series from thickened mafic arc crust. Geology 2012;; 40 (4): 375–378. doi: https://doi.org/10.1130/G32729.1 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 The earliest compounds forming Earth's first continental crust were magmatic rocks with tonalitic-trondhjemitic-granodioritic composition (TTGs). TTGs are widely seen as originating from melting of hydrated oceanic crust in subduction zones. Alternative models argue that they may have formed by melting within thickened mafic oceanic protocrust. To simulate formation of Eoarchean TTGs in different tectonic regimes, we combine for the first time the thermodynamic calculation of residual assemblages with subsequent modeling of trace element contents in TTGs. We compare water-absent partial melting of two hydrated starting compositions, a modern mid-oceanic-ridge basalt (MORB) and a typical Eoarchean arc tholeiite from the Isua Supracrustal Belt that represents the country rock of Earth's oldest TTGs in southern West Greenland. At 10 kbar, partial melting of MORB-like residues results in modeled TTG compositions that are very different from natural ones. Melting at higher pressures (14 and 18 kbar) leads to a better match, but several key trace element parameters in TTGs are still amiss. A perfect fit for trace element compositions is achieved by melting of Eoarchean arc tholeiites at 10 and 14 kbar. These protoliths contain less Al and Na and more Fe and Mg as compared to present-day MORB and form amphibole-rich and plagioclase-free residues even at low pressures. Formation of Earth's oldest continental crust is therefore best explained by melting within tectonically thickened mafic island-arc crust. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.