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Rhyolitic Volcanism of the Central Snake River Plain: a Review

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Rhyolitic Volcanism of the Central Snake River Plain: a Review View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by RERO DOC Digital Library Bull Volcanol (2013) 75:745 DOI 10.1007/s00445-013-0745-y REVIEW ARTICLE Rhyolitic volcanism of the central Snake River Plain: a review B. S. Ellis & J. A. Wolff & S. Boroughs & D. F. Mark & W. A. Starkel & B. Bonnichsen Received: 5 April 2013 /Accepted: 24 June 2013 /Published online: 20 July 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract The central Snake River Plain (CSRP) of southern signature; with >20,000 km3 of rhyolite exhibiting this deple- Idaho and northern Nevada, USA, forms part of the Columbia tion, the CSRP represents the largest low-δ18Oprovinceon River–Yellowstone large igneous province. Volcanic rocks of Earth. The low-18O nature of the rhyolites requires assimila- the province are compositionally bimodal (basalt–rhyolite), tion of hydrothermally altered materials which may be from and the rhyolites produce a broadly time-transgressive record altered Eocene batholithic rocks or from down-dropped intra- of a hotspot which is currently located under Yellowstone. caldera tuffs. The wide range of crustal assimilants, with Snake River Plain rhyolites represent hot (>850 °C), dry highly variable radiogenic isotope characteristics, available magmas and have field characteristics consistent with high in the CSRP is permissive of a variety of petrogenetic models emplacement temperatures. Individual ignimbrite sheets reach based on radiogenic isotopic data. 1,000 km3 and exhibit little to no compositional zonation on a large scale but reveal considerable complexity on a crystal Keywords Snake River Plain . Rhyolite . Bimodal . scale, particularly with regard to pyroxene compositions. Ignimbrite . Low δ18O Multiple pyroxene compositions may exist in a single ignim- brite which, along with multiple glass compositions in widely dispersed fallout tephra, suggests complex storage of rhyolite Introduction prior to eruption. Unlike most igneous rocks, the mineral cargo of the CSRP rhyolites exhibits little isotopic variability, For the past ~16.7 Ma, the inland northwest of North America with unimodal 87Sr/86Sr values returned from plagioclase has been the site of a large igneous province. Activity began grains inferred to represent the combination of strong crys- with the voluminous outpouring of basalt in the Columbia tal–melt coupling and rapid diffusional re-equilibriation. All River Basalt Group from sources in eastern Oregon, prior to the rhyolites within the CSRP have a characteristic low-δ18O rapid northward migration and the development of a fissure system on the Idaho–Oregon and Idaho–Washington borders (Swanson et al. 1979; Swisher et al. 1990; Geist and Richards Editorial responsibility: S. Self 1993;Camp1995; Hooper et al. 2002; Camp and Ross 2004; B. S. Ellis (*) Wolff et al. 2008). Although basaltic volcanism in Washington Institute for Geochemistry and Petrology, ETH Zurich, and northern Idaho continued up to ~6 Ma (Reidel et al. 2013), NW Clausiusstrasse 25, 8092 Zurich, Switzerland the majority of material was erupted between ~16.7 and e-mail: [email protected] 16 Ma in the Steens, Imnaha and Grande Ronde Formations J. A. Wolff : S. Boroughs : W. A. Starkel (Hooper et al. (2007) and references therein; Jarboe et al. School of the Environment, Washington State University, 2008; 2010). Broadly synchronously, silicic magma was Pullman, WA 99164, USA erupting over a wide region of southern Oregon and northern D. F. Mark Nevada (Brueseke et al. 2008; Shervais and Hanan 2008; NERC Argon Isotope Facility, Scottish Universities Environmental Brueseke and Hart 2009; Coble and Mahood 2012). Silicic Research Centre (SUERC), Rankine Avenue, East Kilbride, volcanism remained dispersed until ~14 Ma when it became Scotland G75 0QF, UK more focussed along the near-linear track, extending from B. Bonnichsen southwesternmost Idaho along the central and eastern Snake 927 East 7th Street, Moscow, ID, USA River Plain and culminating in the present-day Yellowstone 745, Page 2 of 19 Bull Volcanol (2013) 75:745 plateau (Fig. 1). During its development, the central Snake from the cratonic margin (Camp and Ross 2004;Jordanetal. River Plain (CSRP) likely was extending in an ENE–WSW 2004). direction, parallel to the elongation of the Yellowstone–east- Silicic volcanism is currently focussed at the Yellowstone ern Snake River Plain hotspot trend and to the proposed drift volcanic field, which sits some 600 m higher than the sur- direction of the North American continent. Evidence for this rounding Rocky Mountains and is associated with a heat flow includes numerous normal faults and basalt dikes with NNW anomaly some 30–40 times that of the surrounding non- to WNW strikes within the CSRP, approximately perpendic- volcanic regions (Lowenstern and Hurwitz 2008). A deep- ular to the eastern Snake River Plain elongation, and to the seated seismic low-velocity zone, interpreted by many workers NE–SW direction in which the western SRP rift was being as a mantle plume, has been imaged beneath Yellowstone at the widened as the CSRP developed. eastern terminus of the province (Yuan and Dueker 2005; The Snake River Plain represents one of the best known Schutt et al. 2008; Obrebski et al. 2010; Schmandt et al. compositionally bimodal (basalt–rhyolite) volcanic prov- 2012), in addition to a shallow, hot, sheet-like upwelling be- inces, with silicic volcanism broadly time-transgressive from neath the Snake River Plain for much of its length (Wagner southern Idaho to Wyoming (Armstrong et al. 1975; Pierce et al. 2010; James et al. 2011;Schmandtetal.2012). A mantle and Morgan 1992), although this relationship is not perfectly plume has been both invoked and refuted as the source for the monotonic in detail (Bonnichsen et al. 2008), and there are Columbia River basalts (e.g. Hooper et al. 2007 and the ensu- major exceptions to the age progression such as the Arbon ing discussion-in-print). A number of studies have questioned Valley Tuff (Kellogg et al. 1994) and the Magic Reservoir the nature and even existence of the proposed plume beneath Eruptive Centre (Leeman 1982; Honjo and Leeman 1987). the Yellowstone volcanic field; on the basis of inferred mantle Despite the broad-scale relationship between age and longi- temperature, Leeman et al. (2009) suggested that the thermal tude of silicic volcanism, basaltic volcanism in the Snake anomaly under Yellowstone was significantly less than those River Plain (SRP), which generally followed silicic volca- under other ‘hotspots’. Via numerical modelling, Manea et al. nism at any location, does not exhibit the same time- (2009) concluded that solely plume-driven thermal erosion of transgressive behaviour (Bonnichsen and Godchaux 2002). the lithosphere would be insufficient to cause decompression To the east, the High Lava Plains of central Oregon show a melting and preferred Snake River magmas to be derived from similar trend of time-transgressive behaviour in silicic volca- melting of the subcontinental lithospheric mantle. Using seis- nic rocks, although with younging occurring to the west which mic imaging, James et al. (2011) inferred that the breakup of has been attributed to the flow of plume material westward the subducting Farallon slab and subsequent mantle upwellings Fig. 1 Location of the Snake River Plain. a Regional map showing the CRB dike swarms. b Location of the central Snake River Plain (black extent of the Columbia River–Yellowstone magmatic province (after square) in southern Idaho and northern Nevada. Abbreviations relate to Perkins and Nash (2002)). The dotted square represents the location of areas where the rhyolitic successions have been studied: AM Albion the DEM in b. CRB Columbia River basalts, OHLP Oregon High Lava Mountains, BB Browns Bench, BJ Bruneau–Jarbidge, CM Cassia Moun- Plains, IB Idaho batholith. The red shapes represent the proposed eruptive tains, EB East Bennett Mountains, ESRP Eastern Snake River Plain, GE centres of silicic volcanism along the Snake River Plain, the orange Grasmere Escarpment, JM Juniper Mountain, JR Jarbidge Rhyolite, RG shapes represent some of the early silicic volcanism associated with the Rogerson Graben, RM Rough Mountain, TF Twin Falls, WB West Ben- Columbia River–Yellowstone province, the green area represents the nett Mountains, WSRP Western Snake River Plain. The location of the extent of the Columbia River flood basalts and the grey lines represent McDermitt caldera is shown in Fig. 13 Bull Volcanol (2013) 75:745 Page 3 of 19, 745 around the fragmented slab were the cause of SRP volcanism. lithofacies are summarised here—see Branney et al. (2008) Alternatively, non-plume explanations include unusually for a comprehensive treatment. copius back-arc volcanism, regional extension and other dom- The ignimbrites exhibit a bimodality of welding with both inantly upper mantle origins related to plate tectonics (Carlson intensely welded and non-welded ignimbrites present (Fig. 2), and Hart 1988;Smith1992; Christiansen et al. 2002; Hales but moderately welded, eutaxitic ignimbrites are absent. The et al. 2005; James et al. 2011; Liu and Stegman 2012; Long welded ignimbrites are of high grade and commonly intensely et al. 2012). The ultimate cause of volcanism within the welded throughout; even in cases where they are thin to only a Yellowstone–Snake River Plain province as a whole remains few metres (e.g. Castleford Crossing Ignimbrite, House Creek contentious and addressing all the arguments in detail is be-
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