Plate Tectonic Model for the Evolution of the Central Andes

Research Article| December 01, 1971 Plate Tectonic Model for the Evolution of the Central Andes DAVID E JAMES DAVID E JAMES Carnegie Institution of Washington, Department of Terrestrial Magnetism, Washington, D. C. 20015 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1971) 82 (12): 3325–3346. https://doi.org/10.1130/0016-7606(1971)82[3325:PTMFTE]2.0.CO;2 Article history received: 26 Apr 1971 rev-recd: 08 Jul 1971 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation DAVID E JAMES; Plate Tectonic Model for the Evolution of the Central Andes. GSA Bulletin 1971;; 82 (12): 3325–3346. doi: https://doi.org/10.1130/0016-7606(1971)82[3325:PTMFTE]2.0.CO;2 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 Data on the geophysics and geology of the central Andes are interpreted in terms of plate theory and a model for Andean evolution is presented. Analysis of upper mantle structure and seismicity shows that the underthrusting Pacific plate is now about 50 km thick and the overriding South American plate 200 to 300 km thick. Underthrusting of the Pacific plate probably began in Triassic time and has continued without substantial change to the present. Prior to underthrusting, the west coast of South America was quiescent, and great thicknesses of Paleozoic continental shelf deposits were laid down in an area east of the present volcanic arc. In Late Triassic or Early Jurassic time, an incipient arc began to form at or west of the present coast of South America. Igneous activity has since migrated eastward, culminating in the Pliocene-Pleistocene volcanic episode. The crust beneath the volcanic cordillera is more than 70 km thick and probably consists largely of rocks compositionally equivalent to those of the volcano-plutonic suites observed at the surface.Increase in crustal volume of the volcanic arc between Cretaceous time and the present implies either that the mantle above the under-thrust plate has undergone 18 to 36 percent partial melting or that 1 to 2 km of rock has been melted from the underthrusting plate. The intrusion of melt into the crust beneath the volcanic cordillera and the resultant crustal dilatation produced continentward compression of the Paleozoic sedimentary rocks which form an easterly belt of thrust and fold mountains. Here crustal shortening has produced crustal thicknesses of 50 to 55 km. Few deposits of the type normally termed eugeosynclinal, and no ophiolites, are observed between trench and volcanic arc; only in the intermontane foredeep behind the arc has a clastic wedge of geosynclinal proportions formed. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.