Episodic arc migration, crustal thickening, subduction erosion, and magmatism in the south-central Andes

Abstract

Research Article| January 01, 2005 Episodic arc migration, crustal thickening, subduction erosion, and magmatism in the south-central Andes Suzanne Mahlburg Kay; Suzanne Mahlburg Kay 1INSTOC, Snee Hall, Cornell University, Ithaca, New York 14853, USA Search for other works by this author on: GSW Google Scholar Estanislao Godoy; Estanislao Godoy 2SERNAGEOMIN, Casilla 10465, Santiago, Chile Search for other works by this author on: GSW Google Scholar Andrew Kurtz Andrew Kurtz 3Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Suzanne Mahlburg Kay 1INSTOC, Snee Hall, Cornell University, Ithaca, New York 14853, USA Estanislao Godoy 2SERNAGEOMIN, Casilla 10465, Santiago, Chile Andrew Kurtz 3Department of Earth Sciences, Boston University, Boston, Massachusetts 02215, USA Publisher: Geological Society of America Received: 27 Jun 2003 Revision Received: 04 Feb 2004 Accepted: 01 Mar 2004 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2005) 117 (1-2): 67–88. https://doi.org/10.1130/B25431.1 Article history Received: 27 Jun 2003 Revision Received: 04 Feb 2004 Accepted: 01 Mar 2004 First Online: 02 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 Suzanne Mahlburg Kay, Estanislao Godoy, Andrew Kurtz; Episodic arc migration, crustal thickening, subduction erosion, and magmatism in the south-central Andes. GSA Bulletin 2005;; 117 (1-2): 67–88. doi: https://doi.org/10.1130/B25431.1 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 The past ∼25 m.y. of geologic history in the northern ∼300 km (∼33°–36°S) of the Andean Southern Volcanic Zone has seen waxing and waning magmatic production rates and episodic eastward relocation of arc segments accompanied by abrupt chemical changes in the magmas. These changes can be linked to episodes of crustal thickening at times of backarc thrusting and to peaks of subduction erosion of forearc crust and mantle lithosphere at times of frontal-arc migration to the east. The magmatictectonic coupling is well seen in the history—enhanced by 28 new K-Ar ages, >160 major and trace element analyses, and Sr, Nd, and Pb isotope analyses—of a west to east transect through the El Teniente copper district near 34°S. The temporal trends in magmatic chemistry in this transect are like the well-documented south to north trends in Pleistocene to Holocene volcanic centers of the Southern Volcanic Zone, and both can be linked to the same events. The magmatic changes require differences in magma source regions as shown by isotopic data and in depths of crustal magma generation/fractionation as shown by pressure-sensitive trace element distributions. “Adakitic” magmas in the region are attributed to a combination of melting the base of thickened lower crust and crust entering the mantle through subduction erosion. Subduction erosion is argued to peak in episodes of frontal-arc migration at ca. 19–16 Ma and ca. 7–4 Ma. The combined effects of crustal shortening and forearc truncation in the past 20 m.y. near 34°S have led to the loss of ∼170 km of crustal width. The timing and arc length over which these events occurred show that subduction of the Juan Fernández Ridge on the Nazca plate cannot have been the major driving force. The history of the region shows the importance of non-steady-state processes in arc-magma production and the necessity of studying arc systems over millions, not tens of thousands, of years. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.