Some geodynamic and compositional constraints on "postorogenic" magmatism

Abstract

Research Article| October 01, 1992 Some geodynamic and compositional constraints on "postorogenic" magmatism Simon Turner; Simon Turner 1Department of Geology and Geophysics, University of Adelaide, GPO Box 498, Adelaide 5001, Australia Search for other works by this author on: GSW Google Scholar Mike Sandiford; Mike Sandiford 1Department of Geology and Geophysics, University of Adelaide, GPO Box 498, Adelaide 5001, Australia Search for other works by this author on: GSW Google Scholar John Foden John Foden 1Department of Geology and Geophysics, University of Adelaide, GPO Box 498, Adelaide 5001, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Simon Turner 1Department of Geology and Geophysics, University of Adelaide, GPO Box 498, Adelaide 5001, Australia Mike Sandiford 1Department of Geology and Geophysics, University of Adelaide, GPO Box 498, Adelaide 5001, Australia John Foden 1Department of Geology and Geophysics, University of Adelaide, GPO Box 498, Adelaide 5001, Australia Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1992) 20 (10): 931–934. https://doi.org/10.1130/0091-7613(1992)020<0931:SGACCO>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Simon Turner, Mike Sandiford, John Foden; Some geodynamic and compositional constraints on "postorogenic" magmatism. Geology 1992;; 20 (10): 931–934. doi: https://doi.org/10.1130/0091-7613(1992)020<0931:SGACCO>2.3.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 SocietyGeology Search Advanced Search Abstract Postorogenic magmatic suites are common to many orogens, in many cases apparently just postdating the cessation of deformation. They differ from preceding orogenic suites in that they have higher temperatures, more primitive isotopic signatures, and bimodal natures, and thus are compositionally similar to suites found in extensional regimes. We propose that thinning of the lithospheric mantle, which may be an automatic response to orogenic lithospheric thickening, is responsible for these magmatic suites. Mantle lithospheric thinning moves the asthenospheric-lithospheric thermal boundary higher in the lithospheric column, thereby raising the overall thermal budget of the orogen and the likelihood of basaltic magmatism. This removal of much of the dense, lithospheric mantle root of the orogen also invokes uplift capable of producing horizontal orogenic buoyancy forces that will oppose and potentially terminate deformation. Extreme fractionation of the magmas is promoted by high temperatures and a noncompressional or tensional lithospheric stress regime to produce accompanying felsic (A-type) magmas. This model explains why the cessation of deformation is coincident with high-temperature bimodal magmatism and inferred uplift, as well as the long-noted similarity and confusion between "postorogenic" and extensional magmatic suites. This arises because both reflect thinning of the lithospheric mantle, not because both reflect extensional tectonics. We suggest that these magmatic episodes may be important in transferring lithospheric mantle material and its compositional signatures into the crust. 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.