Title: Magmatic processes associated with caldera collapse at Ossipee ring dyke, New Hampshire
Abstract: Research Article| January 01, 2007 Magmatic processes associated with caldera collapse at Ossipee ring dyke, New Hampshire Ben Kennedy; Ben Kennedy 1Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 2A7, Canada Search for other works by this author on: GSW Google Scholar John Stix John Stix 1Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 2A7, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Ben Kennedy 1Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 2A7, Canada John Stix 1Department of Earth and Planetary Sciences, McGill University, 3450 University Street, Montreal, Quebec H3A 2A7, Canada Publisher: Geological Society of America Received: 24 Jan 2006 Revision Received: 23 Jun 2006 Accepted: 10 Aug 2006 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 GEOLOGICAL SOCIETY OF AMERICA GSA Bulletin (2007) 119 (1-2): 3–17. https://doi.org/10.1130/B25980.1 Article history Received: 24 Jan 2006 Revision Received: 23 Jun 2006 Accepted: 10 Aug 2006 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Ben Kennedy, John Stix; Magmatic processes associated with caldera collapse at Ossipee ring dyke, New Hampshire. GSA Bulletin 2007;; 119 (1-2): 3–17. doi: https://doi.org/10.1130/B25980.1 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 A detailed textural and chemical study of a section through the 121 Ma Ossipee ring dyke in New Hampshire provides a comprehensive record of magmatic and volcanic events during caldera formation. Phenocryst-rich quartz syenite is the main rock type; syenite, rhyolite, and basalt form small mingled dykes, xenoliths, and magmatic enclaves. Enclaves of fine-grained syenite have positive Eu anomalies, are more mafic, and are depleted in crystals relative to host quartz syenite. Anorthoclase phenocrysts in enclaves have compositions similar to the bulk enclave; high CaO contents in the crystals indicate magmatic temperatures up to 1050 °C. Rhyolite in the ring dyke is texturally and chemically equivalent to ignimbrite inside the caldera. Basalt occurs both as xenoliths and megabreccias from earlier volcanoes and as dykes that mixed and mingled with rhyolitic dykes during eruption. We suggest the following sequence of events: (1) Convection, crystal settling, and filtration of melt away from solidification fronts formed a zoned magma chamber containing voluminous rhyolite overlying crystal-rich quartz syenite and cumulate syenite. (2) Basalt partially melted the anorthoclase syenite cumulate at the base of the chamber to form a hot mobile syenitic liquid, now represented by enclaves in the ring dyke. (3) Continued intrusion of basalt replenished and rejuvenated the Ossipee chamber, driving large eruptions of rhyolitic ignimbrite that ponded in the caldera as the chamber roof collapsed. (4) Caldera collapse stirred the chamber, mingling and mixing rhyolitic, quartz syenitic, and syenitic magma. Vortices around subsiding blocks during caldera collapse caused the mixing and mingling. (5) Quartz syenite, rhyolite, and small volumes of basalt magma were intruded simultaneously into the ring dyke, causing the basalt and rhyolite to mingle explosively. The rejuvenation of the magma chamber and subsequent subsidence of the caldera produced a mixed and mingled crystal mush now preserved in the ring dyke. The ring dyke represents residual magma from a caldera-forming eruption. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Publication Year: 2007
Publication Date: 2007-01-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 46
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