Magmatic lobes as "snapshots" of magma chamber growth and evolution in large, composite batholiths: An example from the Tuolumne intrusion, Sierra Nevada, California

Research Article| November 01, 2010 Magmatic lobes as "snapshots" of magma chamber growth and evolution in large, composite batholiths: An example from the Tuolumne intrusion, Sierra Nevada, California Valbone Memeti; Valbone Memeti † 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA †E-mail: memeti@usc.edu Search for other works by this author on: GSW Google Scholar Scott Paterson; Scott Paterson 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Search for other works by this author on: GSW Google Scholar Jennifer Matzel; Jennifer Matzel 2Lawrence Livermore National Laboratory, Livermore, California 94550, USA Search for other works by this author on: GSW Google Scholar Roland Mundil; Roland Mundil 3Berkeley Geochronology Center, Berkeley, California 94709, USA Search for other works by this author on: GSW Google Scholar David Okaya David Okaya 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Valbone Memeti † 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Scott Paterson 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA Jennifer Matzel 2Lawrence Livermore National Laboratory, Livermore, California 94550, USA Roland Mundil 3Berkeley Geochronology Center, Berkeley, California 94709, USA David Okaya 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA †E-mail: memeti@usc.edu Publisher: Geological Society of America Received: 09 Jan 2009 Revision Received: 01 Dec 2009 Accepted: 02 Dec 2009 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2010 Geological Society of America GSA Bulletin (2010) 122 (11-12): 1912–1931. https://doi.org/10.1130/B30004.1 Article history Received: 09 Jan 2009 Revision Received: 01 Dec 2009 Accepted: 02 Dec 2009 First Online: 08 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 Valbone Memeti, Scott Paterson, Jennifer Matzel, Roland Mundil, David Okaya; Magmatic lobes as "snapshots" of magma chamber growth and evolution in large, composite batholiths: An example from the Tuolumne intrusion, Sierra Nevada, California. GSA Bulletin 2010;; 122 (11-12): 1912–1931. doi: https://doi.org/10.1130/B30004.1 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 Precise chemical abrasion–thermal ionization mass spectrometry (CA-TIMS) U-Pb zircon ages in combination with detailed field mapping, 40Ar/39Ar thermochronology, and finite difference thermal modeling in the magmatic lobes of the Tuolumne batholith characterize these 10–60 km2 bodies as shorter-lived, simpler magmatic systems that represent increments of batholith growth. Lobes provide shorter-term records of internal and external processes that are potentially obliterated in the main body of long-lived, composite batholiths. Zircon ages complemented by thermal modeling indicate that lobe-sized magma chambers were present between ∼0.2 and 1 m.y., representing only a small fraction of the total duration of melt presence in the main body. During these shorter intervals, a concentric pattern of normal compositional zoning formed during inward crystallization and widespread zircon recycling in the lobes. Lobes largely evolved as individual magma bodies that did not interact significantly with the main, more complex magma chamber(s). Antecrystic zircons and the range of autocrysts, used to track the extent of interconnected melt, record only a limited range of ages and have contrasting zircon populations to those found in the same units in the main batholith. We consider lobes to either be single batches formed during continuous magma flow or multiple, quickly coalescing pulses that in either case formed separate magma chambers that failed to amalgamate with other compositionally distinct pulses such as those occurring in the central batholith. Zircon age comparisons between all four lobes and the main body imply that growth of the Tuolumne intrusion was not stationary, but that the locus of magmatism shifted both inward and northwestward. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.