Post on 29-Jan-2016
description
transcript
What is Newberry Volcano?
Julie Donnelly-Nolan, USGS Menlo Park CA,
Tim Grove, MIT, & Rick Carlson, Carnegie Institution
View of Newberry edifice from the northeast
view south of the Newberry edifice from Bend, Oregon
Cascades or not? High Lava Plains volcano?
Is it a volcanic field, not a volcano?
Cascades arcnot equal to Cascade Range
Newberry Volcano Sited at the Intersection of the Cascadesand the High Lava Plains Magmatic Province
Oregon
Idaho
Montana
Wyoming
Nevada
CaliforniaUtah
Arizona
WashingtonBasalt
Andesite
DaciteRhyolite
< 5 5-10 10-17 Ma
Colored Regions Show Volcanic Deposits Younger than 17 Million Years (Smith and Luedke, 1984)South Sister, Oregon
Diamond Craters
Cascades
Newberry
ThreeSisters
Newberry margin
Newberry edifice
Newberry lavascover ~3000 km2
For comparison,MSH
10 m DEMFocused onNewberry Caldera
view from Paulina Peak
At least 3 calderas, 300 ka - 80 ka
View of Paulina Peak from Paulina Lake
Highest point on caldera rim is Paulina Peak atnearly 8000 ft.,~4000 ft. higherthan surroundingterrain
Slide courtesy of Mike Poland
Medicine Lake volcano
Newberry Volcano
Newberry Volcano
Medicine Lake volcano
Geologic Map of Newberry VolcanoBy MacLeod, Sherrod,Chitwood, & Jensen
Qba
Scanned map courtesy of Templeton, Taylor, Giles,& Rowe (WOU, OSU)
~35 mapped Newberry units
field assistant
& Mazama
Field challenges --
& lots of similar rocks
The Subduction Contribution
87Sr/86Sr = 0.70317187Os/188Os = 0.1518
87Sr/86Sr = 0.70382187Os/188Os = 0.1922
Sr = 1124 ppm
Sr = 300 ppm
~4% H2O
(Carlson data)
(Carlson isotope data)
What is the “Subduction Component”?
(Carlson data)
He isotope data
Graham, et al.JVGR 2009
NV
Grove et al. model
WVF
Figure adapted from B. Jordan PhD thesis
than HLP rhyolites
Newberry rhyolites are lower in SiO2
Newberry Volcano
• A subduction-related volcano, not an HLP volcano• Calc-alkaline basalts as well as HAOT-type basalts• Is isotopically like Cascades lavas• Lies behind the arc axis = rear-arc volcano• Extensional terrain; strong magmatic focus• Edifice with central caldera eruptions; not a volcanic field
Tectonic settingOf Newberry:interaction of tectonism and volcanism akey feature
High Lava Plains
Crater Lake
Mt. Jefferson
WVF
From Donnelly-Nolan et al., JVGR 2008
Fore-arc, arc axis, & rear-arc volcanoes
Behind-the-arc Quaternaryvolcanism
Interpretation:
Preliminary version of Newberry geologic mapping will be ondisplay Monday at poster booth 288
View of Newberry edifice from the southeast
Acknowledgments: with thanks to Robert Jensen, Dave Ramsey, Duane Champion,Andy Calvert, Marvin Lanphere, Larry Chitwood