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Zircon record of the plutonic-volcanic connection and protracted rhyolite melt evolution

Chad D. Deering, Brenhin Keller, Blair Schoene, Olivier Bachmann, Rachel Beane and Maria Ovtcharova
Zircon record of the plutonic-volcanic connection and protracted rhyolite melt evolution
Geology (Boulder) (February 2016) Pre-Issue Publication


The potential petrogenetic link between a crystal-poor rhyolite (the Rhyolite Canyon Tuff) and its associated subvolcanic intrusion and crystal-rich post-caldera lavas from Turkey Creek, Arizona (USA), is examined using zircon chemical abrasion-thermal ionization mass spectrometry U-Pb geochronology and inductively coupled plasma mass spectrometry trace element analyses. U-Pb ages indicate that zircon growth within the rhyolite and the dacite-monzonite porphyry magmas was coeval over approximately 300 k.y. prior to the large eruptive event. Trends in zircon trace elements (Hf, Y/Dy, Sm/Yb, Eu/Eu (super *) ) through time in the dacitic-monzonitic units and rhyolite reflect melt evolution dominated by crystal fractionation. Importantly, the Y/Dy ratio in zircons in both units remains mostly similar for the first approximately 150 k.y. of the system's evolution, but the dominant population in the rhyolitic unit diverges from that of the dacite-monzonite porphyry approximately 150 k.y. before eruption. We interpret this divergence in trace element composition to record the assembly time of the melt-rich cap within its intermediate mush zone in the upper crustal reservoir. These results are consistent with (1) a connection between plutonic and volcanic realms in the upper crust, (2) a protracted time scale for constructing an intermediate mush large enough to hold 500 km (super 3) of rhyolite, and (3) the prolonged extraction of that melt prior to eruption.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: Pre-Issue Publication
Title: Zircon record of the plutonic-volcanic connection and protracted rhyolite melt evolution
Affiliation: Michigan Technological University, Department of Geological and Mining Engineering and Sciences, Houghton, MI, United States
Published: 20160224
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 27
Accession Number: 2016-025830
Categories: Geochemistry of rocks, soils, and sedimentsIgneous and metamorphic petrologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2016081
Illustration Description: illus. incl. geol. sketch map
N31°19'60" - N32°22'60", W110°28'00" - W109°04'00"
Secondary Affiliation: Princeton University, USA, United StatesETH Zuerich, CHE, SwitzerlandBowdoin College, USA, United StatesUniversity of Geneva, CHE, Switzerland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201613
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