Assembly of a dike-fed magma chamber: The Jackass Lakes pluton, central Sierra Nevada, California

Abstract

Research Article| August 01, 1996 Assembly of a dike-fed magma chamber: The Jackass Lakes pluton, central Sierra Nevada, California Brendan A. McNulty; Brendan A. McNulty 1Earth Sciences Department, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Weixing Tong; Weixing Tong 1Earth Sciences Department, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar Othmar T. Tobisch Othmar T. Tobisch 1Earth Sciences Department, University of California, Santa Cruz, California 95064 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1996) 108 (8): 926–940. https://doi.org/10.1130/0016-7606(1996)108<0926:AOADFM>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Brendan A. McNulty, Weixing Tong, Othmar T. Tobisch; Assembly of a dike-fed magma chamber: The Jackass Lakes pluton, central Sierra Nevada, California. GSA Bulletin 1996;; 108 (8): 926–940. doi: https://doi.org/10.1130/0016-7606(1996)108<0926:AOADFM>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 SocietyGSA Bulletin Search Advanced Search Abstract The mechanisms of ascent, assembly, and emplacement of granitic magma in the crust are critical to understanding the dynamics of continental margin growth, yet these mechanisms remain controversial and poorly understood. Detailed study of structural and petrologic fabrics in the middle Cretaceous Jackass Lakes pluton-wall-rock system, central Sierra Nevada, California, coupled with U-Pb geochronology, indicates that the pluton formed via sheet-like assembly of a dike-fed magma chamber. Final emplacement of the pluton was facilitated by multiple brittle and ductile mechanisms that were active at different times and places within the system; this supports hybrid viscoelastic emplacement models as realistic alternatives to end-member models (i.e., dike versus diapir). Fracture propagation, which initiated ≈40% of the space required for emplacement, may have been facilitated by a small component of arc-parallel dextral shear that produced north-northwest-striking tension gashes. A combination of ductile wall-rock shortening during lateral expansion of sheets, and return flow of elongate, strongly deformed wall-rock septa, produced an additional ≈25% of the space required. Other mechanisms, including coeval formation of the overlying Minarets caldera and stoping in the subvolcanic part of the magma chamber, must account for the remaining ≈35% space, implying that vertical transfer of material is an important emplacement mechanism at shallow crustal levels. 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.