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Midcrustal emplacement of the Sausfjellet pluton, central Norway: Ductile flow, stoping, and in situ assimilation

2005; Geological Society of America; Volume: 117; Issue: 3 Linguagem: Inglês

10.1130/b25464.1

1943-2674

Gregory Dumond, Aaron S. Yoshinobu, Calvin G. Barnes,

High-pressure geophysics and materials

Research Article| March 01, 2005 Midcrustal emplacement of the Sausfjellet pluton, central Norway: Ductile flow, stoping, and in situ assimilation Gregory Dumond; Gregory Dumond 1Department of Geosciences, Texas Tech University, Lubbock, Texas 79409-1053, USA Search for other works by this author on: GSW Google Scholar Aaron S. Yoshinobu; Aaron S. Yoshinobu 1Department of Geosciences, Texas Tech University, Lubbock, Texas 79409-1053, USA Search for other works by this author on: GSW Google Scholar Calvin G. Barnes Calvin G. Barnes 1Department of Geosciences, Texas Tech University, Lubbock, Texas 79409-1053, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Gregory Dumond 1Department of Geosciences, Texas Tech University, Lubbock, Texas 79409-1053, USA Aaron S. Yoshinobu 1Department of Geosciences, Texas Tech University, Lubbock, Texas 79409-1053, USA Calvin G. Barnes 1Department of Geosciences, Texas Tech University, Lubbock, Texas 79409-1053, USA Publisher: Geological Society of America Received: 04 Aug 2003 Revision Received: 23 Aug 2004 Accepted: 03 Sep 2004 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2005) 117 (3-4): 383–395. https://doi.org/10.1130/B25464.1 Article history Received: 04 Aug 2003 Revision Received: 23 Aug 2004 Accepted: 03 Sep 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 Gregory Dumond, Aaron S. Yoshinobu, Calvin G. Barnes; Midcrustal emplacement of the Sausfjellet pluton, central Norway: Ductile flow, stoping, and in situ assimilation. GSA Bulletin 2005;; 117 (3-4): 383–395. doi: https://doi.org/10.1130/B25464.1 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 Midcrustal (25–30 km) emplacement of the dioritic Sausfjellet pluton into rocks of the Helgeland Nappe Complex, central Norway, occurred in two stages. Stage 1 consists of two-pyroxene hornblende gabbro and diorite. Stage 2 is asymmetrically zoned, with a modally layered central zone of diorite and anorthosite and a western/annular zone of quartz-bearing monzodioritic rocks. Igneous layering was locally attenuated, folded, and boudinaged in the hypersolidus state. The magmatic foliation trajectory pattern in the pluton defines a shallowly southwest-plunging synform that crosscuts compositional zones. Mineral lineations plunge shallowly to moderately to the southwest. The pluton intruded a major lithologic boundary within the nappe; migmatitic pelitic gneisses are the main host rocks to the western part of the pluton, whereas the eastern and central parts are hosted predominantly by metacarbonate rocks. Calcsilicate, marble, quartzo-feldspathic, and dioritic xenoliths (up to 200 m in length) are present throughout the pluton; they are most common in Stage 1 and the central zone of Stage 2. Metapelitic xenoliths are conspicuously absent. Ductile flow during emplacement produced an ∼1-km-wide structural aureole in which host-rock structures were deflected into subparallelism with the steeply inward-dipping margin of the pluton. Tight antiforms developed along the northeastern, southeastern, and southwestern margins. Amphibolite-grade shear zones in the host rocks preserve pluton-side-up kinematic indicators. In addition to the abundance of dioritic, calcsilicate, and quartzo-feldspathic gneiss xenoliths and geochemical evidence for assimilation in the western/annular zone, regional discordance of the pluton–host-rock contacts indicates that stoping was also an important emplacement process at midcrustal depths. Following magma emplacement, foundering of the central portion of the chamber combined with possible ca. 445 Ma regional contraction produced the map-scale synform defined by magmatic foliations and igneous layers. This study demonstrates that stoping and assimilation may occur simultaneously with host-rock ductile flow during magma chamber evolution at midcrustal levels and offers an explanation of why xenolith preservation may be compositionally dependent. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.