Cenozoic Tectonics, Magmatism, and Stratigraphy of the Snake River Plain– Yellowstone Region and Adjacent Areas themed issue Geochemistry and geochronology of the Jim Sage volcanic suite, southern Idaho: Implications for Snake River Plain magmatism and its role in the history of Basin and Range extension Alexandros Konstantinou1,*, John Valley2, Ariel Strickland2, Elizabeth L. Miller1, Chris Fisher3, Jeffrey Ver- voort3, and Joseph Wooden1,4 1Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA 2Department of Geoscience, University of Wisconsin, 1215 W. Dayton Street, Madison, Wisconsin 53706, USA 3School of the Environment, Washington State University, Pullman, Washington 99164-2812, USA 4U.S. Geological Survey, Menlo Park, California 94025, USA ABSTRACT (without the large calderas inferred for the Bryan, 2007), yet their origin is one of the SRP rhyolites) implies that there might be fundamental debates in igneous petrology and The Jim Sage volcanic suite (JSVS) an alternative mechanism for the formation geodynamics. This debate is long standing due exposed in the Jim Sage and Cotterel Moun- of the low-δ18O signature other than the pro- to the complex nature of how large silicic mag- tains of southern Idaho (USA) consists of two posed assimilation of hydrothermally altered matic systems are generated and magma stored volcanic members composed of ~240 km3 caldera blocks. One suggestion is that the for large periods of time in heterogeneous con- of Miocene rhyolite lavas separated by an north to south propagation of SRP-type low- tinental crust. Understanding the origin and interval of lacustrine sediments. It is capped δ18O rhyolitic melt along the Albion fault led longevity of large silicic complexes is of great by rheomorphic ignimbrite and as much as to off-axis magmatism. Another possibility is importance because this magmatic activity 100 m of basaltic lava fl ows probably derived that there was prior and widespread (across is often associated with mineral deposits and from the central Snake River Plain (SRP) a region wider than the SRP) hydrothermal because silicic caldera-forming supereruptions province to the north. The occurrence of vol- alteration of the crust related to its earlier pose major safety and economic risks to society. canic vents in the JSVS links the lava fl ows magmatic and faulting history. In the western United States, the Snake River to their local eruptive centers, while the adja- The eruption of SRP-type lavas in the Plain–Yellowstone (SRP-Yellowstone) vol- cent Albion–Raft River–Grouse Creek meta- hanging wall of an evolving metamorphic canic province is a prominent feature, defi ned morphic core complex exposes ~3000 km2 of core complex helps us outline the role of the by low-relief topography extending ~750 km once deep-seated rocks that offer constraints SRP magmatic province in the extensional from northwestern Nevada to Yellowstone on the composition of the potential crustal evolution of the northeastern Basin and National Park (Wyoming, Montana, and Idaho; sources of these rhyolites. U-Pb zircon ages Range. The lavas of the JSVS imply the addi- Fig. 1 inset; e.g., Pierce and Morgan, 1992, from the rhyolite lavas of the JSVS range tion of basalt, related to the SRP hotspot, to 2009; Coble and Mahood, 2012). It is one of from 9.5 to 8.2 Ma. The Miocene basalt of the crust beneath the Raft River Basin that the most productive young silicic igneous prov- 87 86 the Cotterel Mountains has an Sr/ Sri provided a heat source for crustal melting inces on Earth, active from ca. 16.5 Ma to the composition of 0.7066–0.7075 and εNd(i) = and weakening of the deep crust; this led present day, generating large volumes (tens –3.7, and the rhyolite lavas of the JSVS have to a vertical component of crustal fl ow and of thousands of cubic kilometers) of mostly 87 86 Sr/ Sri = 0.7114–0.7135 and εNd(i) values doming during extension, after the erup- basaltic and rhyolitic magmas (e.g., Christian- that range from –6.7 to –7.1. Zircon from the tion of the 9.5–8.2 Ma JSVS rhyolites. This sen, 2001). Petrologic investigations of silicic, 18 rhyolites of the JSVS range in δ Ozr (Vienna younger than 8.2 Ma component of vertical intensely welded outflow ignimbrites (e.g., standard mean ocean water, VSMOW) from motion during faulting of the Miocene strati- Branney et al., 2008) surrounding the SRP have –0.5‰ to 5.7‰ and have εHf(i) values ranging fi ed sequence of the Raft River Basin and demonstrated that the SRP-Yellowstone prov- from –0.8 to –6.8. Based on geochronology, the rotation of the Albion fault to shallower ince is capable of producing large volumes of whole-rock major elements, trace elements, angles collectively resulted in the subhorizon- rhyolitic ignimbrite (>1000 km3) that can travel isotopes (Sr and Nd), and in situ zircon O tal detachment structure imaged seismically over great distances (e.g., Andrews and Bran- and Hf isotopic compositions, we infer that beneath the Raft River Basin. ney, 2011; Ellis et al., 2011). Individual silicic the JSVS is genetically related to the central eruptive centers in the central portion of the SRP SRP province. The eruption of the low-δ18O INTRODUCTION are largely inferred because they are mostly bur- rhyolites of the JSVS, outside of the main ied beneath younger basalt fl ows, making them topographic extent of the SRP province Large silicic igneous complexes are com- inaccessible for direct study. Ongoing borehole monly associated with continental fl ood basalt drilling studies within the SRP are trying to provinces (e.g., Paraná-Etendeka and North address some of these problems by sampling the *Email: [email protected]. Atlantic igneous provinces; Bryan et al., 2002; volcanic section directly (e.g., Shervais et al., Geosphere; December 2013; v. 9; no. 6; p. 1681–1703; doi:10.1130/GES00948.1; 14 fi gures; 2 tables; 6 supplemental tables. Received 15 May 2013 ♦ Revision received 6 September 2013 ♦ Accepted 4 October 2013 ♦ Published online 13 November 2013 For permission to copy, contact [email protected] 1681 © 2013 Geological Society of America Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1681/3346267/1681.pdf by guest on 30 September 2021 Konstantinou et al. Columbia River Basalt Paleocene-Eocene volcanic rocks 20 Km Mesozoic plutons Yellowstone Met. Core complex 02010 Idaho 45°N Batholith 16.6– 15.6 Ma 6.6– N 4.4 Ma Cotterel OR ID 12.7– 10.5– 10.2– Mts 10.5 Ma 8.5 Ma 8.0 Ma NV Snake River Plain ID ARG Ruby NV UT Albion Mts n Basin and Range Snake Range 40°N n 0100 200 Jim Sage Km Mts n n Middle Mtn. gneiss Figure 2 Middle Mtn. n Raft River extent of 32–27 Ma Basin 20° Black plutonic complex Almo Pine Mts pluton n IDAHO 42° UTAH n n n n n n n n Vipoint n n n pluton n n n n 10° n Raft River n UTAH Mts n n n n n n n n n Quaternary alluvium and basalt n Red Butte <8.2 Ma Basalt of Cotterel pluton Grouse Cenozoic Basin Miocene ignimbrite Creek Mts 8.2 Ma Upper Jim Sage lava n Middle unit (sedimentary rocks) JSVS n 9.5 Ma Lower Jim Sage lava Detachment fault, n teeth on the upper Cenozoic sedimentary rocks n plate Fault or unconformity Emigrant High-angle normal 32–25 Ma Cenozoic plutons Pass plutonic fault, ball on the 42–31 Ma Cenozoic plutons complex down thrown side Phanerozoic metasedimentary units Middle Mountain Fault shear zone Metamorphic lower plate rocks Raft River Unconformity 113°45′ Detachment Archean Crystalline basement Figure 1. Generalized geologic map of the Albion–Raft River–Grouse Creek Mountains. Box (dashed lines) indicates the location of Figure 2. Inset indicates the location of the Albion–Raft River–Grouse Creek metamorphic core complex (ARG) in the western U.S. and relative to the inferred eruptive centers in the Snake River Plain. Modifi ed from Konstantinou et al. (2012) and references therein. 1682 Geosphere, December 2013 Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/9/6/1681/3346267/1681.pdf by guest on 30 September 2021 Geochemistry and geochronology of the Jim Sage volcanic suite 2006; Project HOTSPOT, http:// www .usu .edu Basin and Range province, few studies have assimilation (e.g., Taylor, 1986) or remelting /geo /shervais /Shervais -USU -Geology /Project tried to explain how Basin and Range exten- (e.g., Bindeman and Valley, 2001) of low-δ18O _Hotspot .html). sion is accommodated in and across the SRP- (2‰ to <–3‰) hydrothermally altered rock. Fewer studies have focused on the smaller Yellowstone province (e.g., Rodgers et al., The occurrence of low-δ18O rhyolite in Yellow- (<300 km3) eruptive centers adjacent to the 1990, 2002; Anders and Sleep, 1992; Parsons stone has been explained by the remelting of SRP province that are not associated with cal- et al., 1998; Fig. 1). In addition, there have older collapsed hydrothermally altered cal- dera-forming eruptions but are more accessible been very few studies focused on the relation dera blocks (e.g., Taylor, 1986, Bindeman and to study. One of the best examples of such an of magmatic addition from the SRP-Yellow- Valley , 2001). This model was then adopted for eruptive center is the Jim Sage volcanic suite stone province to the deep and shallow part the central SRP, where large-scale remelting of (JSVS; Fig. 1), developed within the evolving of the crust in the region of the Basin and buried caldera blocks resulted in the formation Miocene Raft River Basin (Konstantinou et al., Range province and/or its effects on the exten- of low-δ18O rhyolites (e.g., Bindeman et al., 2012).