Large-volume, low-delta super 18 O rhyolites of the central SnakeRiver plain, Idaho, USA 
Reference Number:
Publication Year:
GeoREF Number:
2005-074680 (View Original Data File)
Boroughs, Scott; Wolff, John; Bonnichsen, Bill; Godchaux, Martha;Larson, Peter
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
Geology Boulder, vol.33, no.10, pp.821-824, Oct 2005
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.
With GSA Data Repository Item 2005162
GeoRef, Copyright 2005, American Geological Institute. Referenceincludes data supplied by the Geological Society of America, Boulder,CO, United States

Sample Summary:
Sample ID: Major Data: Trace Data: Isotope Data:
I-3487 No No Yes
I-3488 No No Yes
02SB-39 No No Yes
02SB-40 No No Yes
I-3410 No No Yes
S-487 No No Yes
I-404 No No Yes
I-3388 No No Yes
I-3388 No No Yes
I-1122 Yes Yes Yes
I-1100 Yes Yes Yes
I-841 Yes Yes Yes
X-214 Yes Yes Yes
X-72 Yes Yes No
X-116 Yes Yes No
X-174 Yes Yes Yes
X-20 Yes Yes Yes
X-37 Yes Yes No
I-810 Yes Yes Yes
I-569 No No Yes
I-3868 No No Yes
I-1060 Yes Yes Yes
I-496 Yes Yes Yes
I-529 Yes Yes Yes
I-3843 No No Yes
02SB-45 Yes Yes Yes
02SB-46 Yes Yes Yes
02SB-47 Yes Yes No
02SB-48 Yes Yes Yes
02SB-49 Yes Yes No
02SB-50 Yes Yes No
02SB-51 Yes Yes No
02SB-56 No No Yes
02SB-57 No No Yes
I-2132 No No Yes
I-1143 Yes Yes Yes
01SB-27 Yes Yes No
01SB-28 Yes Yes Yes
01SB-29 Yes Yes No
01SB-30 Yes Yes Yes
01SB-31 Yes Yes No
01SB-32 Yes Yes No
01SB-33 Yes Yes No
01SB-35 Yes Yes No
I-688 Yes Yes Yes
I-1037 Yes Yes Yes
I-1214 Yes Yes Yes
I-1350 No No Yes
I-1260 Yes Yes Yes
02SB-76 No No Yes
I-1056 Yes Yes Yes
01SB-10 Yes Yes No
01SB-6 Yes Yes No
01SB-7 Yes Yes No
01SB-8 Yes Yes No
01SB-05 No No Yes
01SB-1 Yes Yes No
01SB-3 Yes Yes No
01SB-4 Yes Yes Yes
01SB-5 Yes Yes No
02SB-61 No No Yes
02SB-65 No No Yes
I-2863 No No Yes
I-1074 Yes Yes Yes
I-1197 Yes Yes Yes
I-3425 No No Yes
I-1631 No No Yes
I-2207 No No Yes
I-1138 Yes Yes Yes
I-2475 No No Yes
I-1269 Yes Yes No
01SB-11 Yes Yes No
01SB-12 No No Yes
01SB-13 Yes Yes No
01SB-15 Yes Yes No
01SB-19 Yes Yes No
01SB-21 Yes Yes Yes
02SB-85 No No Yes