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Reactive bulk assimilation: A model for crust-mantle mixing in silicic magmas

2005; Geological Society of America; Volume: 33; Issue: 8 Linguagem: Inglês

10.1130/g21470.1

1943-2682

James S. Beard, Paul C. Ragland, M. L. Crawford,

High-pressure geophysics and materials

Research Article| August 01, 2005 Reactive bulk assimilation: A model for crust-mantle mixing in silicic magmas James S. Beard; James S. Beard 1Virginia Museum of Natural History, 1001 Douglas Avenue, Martinsville, Virginia 24112, USA Search for other works by this author on: GSW Google Scholar Paul C. Ragland; Paul C. Ragland 1Virginia Museum of Natural History, 1001 Douglas Avenue, Martinsville, Virginia 24112, USA Search for other works by this author on: GSW Google Scholar Maria Luisa Crawford Maria Luisa Crawford 2Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, USA Search for other works by this author on: GSW Google Scholar Author and Article Information James S. Beard 1Virginia Museum of Natural History, 1001 Douglas Avenue, Martinsville, Virginia 24112, USA Paul C. Ragland 1Virginia Museum of Natural History, 1001 Douglas Avenue, Martinsville, Virginia 24112, USA Maria Luisa Crawford 2Department of Geology, Bryn Mawr College, Bryn Mawr, Pennsylvania 19010, USA Publisher: Geological Society of America Received: 16 Dec 2004 Revision Received: 25 Apr 2005 Accepted: 26 Apr 2005 First Online: 03 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 The Geological Society of America, Inc. Geology (2005) 33 (8): 681–684. https://doi.org/10.1130/G21470AR.1 Article history Received: 16 Dec 2004 Revision Received: 25 Apr 2005 Accepted: 26 Apr 2005 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation James S. Beard, Paul C. Ragland, Maria Luisa Crawford; Reactive bulk assimilation: A model for crust-mantle mixing in silicic magmas. Geology 2005;; 33 (8): 681–684. doi: https://doi.org/10.1130/G21470AR.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 SocietyGeology Search Advanced Search Abstract Bulk assimilation of small (millimeters to ∼1 km) fragments of crust—driven and (ultimately) masked by reactions during xenolith melting and magma crystallization—is an important mechanism for crust-mantle mixing. Xenoliths containing mica or amphibole undergo dehydration melting when incorporated into a host magma, yielding mainly plagioclase, pyroxene, Fe-Ti oxides, and hydrous melt. The xenolith is physically compromised by partial melting and begins to disintegrate; xenolithic melt and crystals are mixed into the host magma. Xenocrystic zircon is liberated at this stage. The cryptic character of assimilation is greatly enhanced in any hydrous magma by hydration crystallization reactions (the reverse of dehydration melting). All pyroxenes and oxides (phenocrysts, xenocrysts, or crystals having a hybrid signature) will be subject to these reactions, producing feldspars, amphiboles, and micas that incorporate material from several sources, a particularly effective mixing mechanism. Implicit in the model is a reduced energy penalty for bulk assimilation—much of the assimilant remains in solid form—compared to melt-assimilation models. A large role for bulk assimilation supports stoping as a credible mechanism for the ascent of magmas. While the assimilation of low-density crust and concomitant fractionation provide the isostatic impetus for ascent, the wholesale incorporation and processing of crustal rocks in the magma chamber helps create the room for ascent. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.