Title:
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Large-volume, low-delta super 18 O rhyolites of the central SnakeRiver plain, Idaho, USA
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Reference Number:
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1989
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ISSN:
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0091-7613
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Publication Year:
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2005
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GeoREF Number:
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2005-074680 (View Original Data File)
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Authors:
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Boroughs, Scott; Wolff, John; Bonnichsen, Bill; Godchaux, Martha;Larson, Peter
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Descriptors:
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Bruneau-Jarbridge volcanic field; calderas; Cenozoic; crust;eruptions; feldspar group; framework silicates; geochemistry;hydrothermal alteration; Idaho; Idaho Batholith; igneous rocks;isotope ratios; isotopes; Jacks Creek volcanic field; lava; magmatism;major elements; melting; metasomatism; meteoric water; Miocene;Neogene; O-18/O-16; oxygen; pyroclastics; quartz; rhyolite tuff;rhyolites; silica minerals; silicates; Snake River plain; southwesternIdaho; stable isotopes; Tertiary; trace elements; Twin Falls volcanicfield; United States; volcanic features; volcanic fields; volcanicrocks; volcanism; volume; welded tuff; Yellowstone Hot Spot
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Source:
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Geology Boulder, vol.33, no.10, pp.821-824, Oct 2005
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Abstract:
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The Miocene Bruneau-Jarbidge and adjacent volcanic fields of thecentral Snake River Plain, southwest Idaho, are dominated byhigh-temperature rhyolitic tuffs and lavas having an aggregate volumeestimated as 7000 km super 3 . Samples from units representing atleast 50% of this volume are strongly depleted in super 18 O, withmagmatic feldspar delta super 18 O sub VSMOW Vienna standard meanocean water values between -1.4ppm and 3.8 ppm. The magnitude of thesuper 18 O depletion and the complete lack of any rhyolites withnormal values 7 ppm-10 ppm combine to suggest that assimilation ormelting of a caldera block altered by near- contemporaneoushydrothermal activity is unlikely. Instead, we envisage generation ofthe high-temperature rhyolites by shallow melting of Idaho Batholithrocks, under the influence of the Yellowstone hotspot, affected byEocene meteoric-hydrothermal events. The seeming worldwide scarcity ofstrongly super 18 O-depleted rhyolites may simply reflect a similarscarcity of suitable crustal protoliths.
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Notes:
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With GSA Data Repository Item 2005162
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Copyright:
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GeoRef, Copyright 2005, American Geological Institute. Referenceincludes data supplied by the Geological Society of America, Boulder,CO, United States
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