Geochemical variations in igneous rocks of the Central Andean orocline (13 S to 18 S): Tracing crustal thickening and magma generation through time and space

Research Article| January 01, 2010 Geochemical variations in igneous rocks of the Central Andean orocline (13°S to 18°S): Tracing crustal thickening and magma generation through time and space Mirian Mamani; Mirian Mamani † 1Abteilung Geochemie, Geowissenschaftlichen Zentrum der Universität Göttingen, Goldschmidtstrasse 1, D-37077 Göttingen, Germany †E-mail: mmirian@gwdg.de Search for other works by this author on: GSW Google Scholar Gerhard Wörner; Gerhard Wörner 1Abteilung Geochemie, Geowissenschaftlichen Zentrum der Universität Göttingen, Goldschmidtstrasse 1, D-37077 Göttingen, Germany Search for other works by this author on: GSW Google Scholar Thierry Sempere Thierry Sempere 2Institut de Recherche pour le Développement and Université de Toulouse Paul Sabatier (SVT-OMP), Laboratoire Mécanismes de Transfert en Géologie, 14 avenue Edouard Belin, F-31400 Toulouse, France Search for other works by this author on: GSW Google Scholar Author and Article Information Mirian Mamani † 1Abteilung Geochemie, Geowissenschaftlichen Zentrum der Universität Göttingen, Goldschmidtstrasse 1, D-37077 Göttingen, Germany Gerhard Wörner 1Abteilung Geochemie, Geowissenschaftlichen Zentrum der Universität Göttingen, Goldschmidtstrasse 1, D-37077 Göttingen, Germany Thierry Sempere 2Institut de Recherche pour le Développement and Université de Toulouse Paul Sabatier (SVT-OMP), Laboratoire Mécanismes de Transfert en Géologie, 14 avenue Edouard Belin, F-31400 Toulouse, France †E-mail: mmirian@gwdg.de Publisher: Geological Society of America Received: 10 Sep 2008 Revision Received: 31 Mar 2009 Accepted: 03 Apr 2009 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2010 Geological Society of America GSA Bulletin (2010) 122 (1-2): 162–182. https://doi.org/10.1130/B26538.1 Article history Received: 10 Sep 2008 Revision Received: 31 Mar 2009 Accepted: 03 Apr 2009 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Mirian Mamani, Gerhard Wörner, Thierry Sempere; Geochemical variations in igneous rocks of the Central Andean orocline (13°S to 18°S): Tracing crustal thickening and magma generation through time and space. GSA Bulletin 2010;; 122 (1-2): 162–182. doi: https://doi.org/10.1130/B26538.1 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 Compositional variations of Central Andean subduction-related igneous rocks reflect the plate-tectonic evolution of this active continental margin through time and space. In order to address the effect on magmatism of changing subduction geometry and crustal evolution of the upper continental plate during the Andean orogeny, we compiled more than 1500 major- and trace-element data points, and 650 Sr-, 610 Nd-, and 570 Pb-isotopic analyses of Mesozoic-Cenozoic (190–0 Ma) magmatic rocks in southern Peru and northern Chile (Central Andean orocline), mostly from new data and the literature. This data set documents compositional variations of magmas since Jurassic time, with a focus on the Neogene period, when major crustal thickening developed and its influence on magma composition was most pronounced. We relate the observed variations in Sr/Y, La/Yb, La/Sm, Sm/Yb, and Dy/Yb ratios, as well as in Sr-, Nd-, and Pb-isotopic ratios, to the crustal structure and evolution of the Central Andean orocline. In particular, the evolution of Dy/Yb and Sm/Yb ratios, which track the presence of the higher-pressure minerals amphibole and garnet, respectively, in the lower crust, documents that crustal thickness has grown through time. Spatial variations in trace elements and isotopic ratios further suggest that crustal domains of distinct composition and age have influenced magma composition through some assimilation. The crustal input in Quaternary magmas is quantified to have been between 7% and 18% by simple two-components mixing. When comparing our geochemical data set to the geological record of uplift and crustal thickening, we observe a correlation between the composition of magmatic rocks and the progression of Andean orogeny. In particular, our results support the interpretation that major crustal thickening and uplift were initiated in the mid-Oligocene (30 Ma) and that crustal thickness has kept increasing until present day. Our data do not support delamination as a general cause for major late Miocene uplift in the Central Andes and instead favor continued crustal thickening. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.