Bull Volcanol DOI 10.1007/s00445-007-0142-5 RESEARCH ARTICLE Diverse mid-Miocene silicic volcanism associated with the Yellowstone–Newberry thermal anomaly Matthew E. Brueseke & William K. Hart & Matthew T. Heizler Received: 1 February 2005 /Accepted: 8 March 2007 # Springer-Verlag 2007 Abstract The Santa Rosa–Calico volcanic field (SC) of primarily focused along its eastern and western margins. At northern Nevada is a complex, multi-vent mid-Miocene least five texturally distinct silicic units are found in the eruptive complex that formed in response to regional western Santa Rosa–Calico volcanic field, including abun- lithospheric extension and flood basalt volcanism. Santa dant lava flows, near vent deposits, and shallow intrusive Rosa–Calico volcanism initiated at ∼16.7 Ma, concurrent bodies. Similar physical features are found in the eastern with regional Steens–Columbia River flood basalt activity portion of the volcanic field where four physically distinct and is characterized by a complete compositional spectrum units are present. The western and eastern Santa Rosa– of basalt through high-silica rhyolite. To better understand Calico units are characterized by abundant macro- and the relationships between upwelling mafic magmatism, microscopic disequilibrium textures, reflecting a complex coeval extension, and magmatic system development on petrogenetic history. Additionally, unlike other mid-Mio- the Oregon Plateau we have conducted the first compre- cene Oregon Plateau volcanic fields (e.g. McDermitt), the hensive study of Santa Rosa–Calico silicic volcanism. Santa Rosa–Calico volcanic field is characterized by a Detailed stratigraphic-based field sampling and mapping paucity of caldera-forming volcanism. Only the Cold illustrate that silicic activity in this volcanic field was Springs tuff, which crops out across the central portion of the volcanic field, was caldera-derived. Major and trace element geochemical variations are present within and Editorial responsibility: M. McCurry between eastern and western Santa Rosa–Calico silicic This paper constitutes part of a special issue dedicated to Bill units and these chemical differences, coupled with the Bonnichsen on the petrogenesis and volcanology of anorogenic rhyolites. observed disequilibrium textures, illustrate the action of Electronic supplementary material The online version of this article open-system petrogenetic processes and melt derivation (doi:10.1007/s00445-007-0142-5) contains supplementary material, which is available to authorized users. from heterogeneous source materials. The processes and styles of Santa Rosa–Calico silicic magmatism are linked to * M. E. Brueseke ( ) three primary factors, local focusing of and thermal and Department of Geology, Kansas State University, Manhattan, KS 66506-3201, USA material contributions from the regional flood basalt event, e-mail: [email protected] lithospheric extension within the northern portion of the Northern Nevada rift, and interaction of mid-Miocene W. K. Hart silicic magmas with pre-Santa Rosa–Calico lithosphere. Department of Geology, Miami University, 114 Shideler Hall, Similar processes and styles of mid-Miocene silicic Oxford, OH 45056-2473, USA volcanism likely occurred across the Oregon Plateau in e-mail: [email protected] regions characterized by both focused lithospheric exten- sion and localized mafic magmatism. M. T. Heizler New Mexico Bureau of Mines and Mineral Resources, New Mexico Tech, 801 Leroy Place, Socorro, NM 87801, USA Keywords Miocene . Oregon plateau . Owyhee–Humboldt . e-mail: [email protected] Santa Rosa–Calico . Silicic . Steens basalt . Yellowstone Bull Volcanol Introduction information comes from the McDermitt volcanic field, also often cited as the “ground zero” of the Yellowstone–Snake Nowhere is volcanism associated with the Yellowstone– River plain volcanic system (Pierce and Morgan 1992). Newberry mantle upwelling more diverse than in the However, numerous other large and small, dominantly silicic Oregon–Idaho–Nevada tri-state region, the southeastern Ore- mid-Miocene volcanic systems are present across the Oregon gon Plateau. Continuous mafic volcanism from ∼16.7 Ma to Plateau (Fig. 1b), including the Santa Rosa–Calico volcanic the present as well as the only silicic volcanism associated field (SC) of northern Nevada. The SC lies at the junction of with the initial manifestation of the upwelling is found across the Northern Nevada rift and Owyhee Plateau (Fig. 1b), an this region. Recent studies dealing with mid-Miocene north- ideal location to further investigate the relationships between western United States volcanism have focused on the Steens mid-Miocene flood basalt volcanism, magmatic system and Columbia River flood basalts, their relationship to development, and tectonism. In this paper, we present a younger regional Cenozoic volcanism, and its relationship to portion of the results of the first comprehensive field, mid-Miocene mineralization and rift-development (Fig. 1a; chronostratigraphic, geochemical, and petrologic study of Zoback et al. 1994; Wallace and John 1998; Cummings et al. the SC, focusing on the silicic components (>64 wt% SiO2). 2000;JohnandWallace2000;Johnetal.2000;John2001; This contribution will (1) distinguish the SC from contem- Camp et al. 2003; Wallace 2003; Camp and Ross 2004; poraneous Oregon Plateau volcanic systems (e.g. McDermitt, Jordan et al. 2004). While these studies have focused Owyhee–Humboldt), (2) formally define the SC as a locus of attention on regional mafic volcanism and silicic volcanism mid-Miocene volcanism and potential source for regionally peripheral to the loci of mid-Miocene activity (the Oregon exposed tephra, (3) detail the spatial, temporal, physical, and Plateau), the details of mid-Miocene Oregon Plateau silicic bulk chemical characteristics of the silicic magmatic prod- activity remain poorly understood. The most comprehensive ucts, and (4) provide first-order constraints on the petroge- Fig. 1 a Map of the northwestern USA depicting select Cenozoic Peterman 1978;Leemanetal.1992; Crafford and Grauch 2002). tectonomagmatic features. Shaded region is the approximate extent of b Shaded relief map of the southern Oregon Plateau illustrating the mid-Miocene flood basalt volcanism (after Hart and Carlson 1985; locations of major mid-Miocene silicic volcanic systems. SC Santa Camp and Ross 2004). Also shown are major flood basalt dike Rosa–Calico volcanic field, MD McDermitt volcanic field, LO Lake swarms/eruptive loci (black lines), Oregon–Idaho graben and mag- Owyhee volcanic field, NWNV Northwest Nevada volcanic field netic anomalies in Nevada corresponding to zones of lithospheric (e.g. Virgin Valley, High Rock, Hog Ranch, and unnamed calderas), extension/mafic magma emplacement (black dotted-dashed lines; HVLM Hawks Valley–Lone Mountain dome complex, SI Silver Cummings et al. 2000; Glen and Ponce 2002), major volcanic fields City–DeLamar dome complex, JM Juniper Mountain volcanic of the Yellowstone–Snake River plain province (dashed circles); BJ, center, CC Circle Creek volcanic center, J Jarbidge Rhyolite loci, Bruneau–Jarbidge (∼12.5–<11 Ma); TF, Twin Falls (∼10–8.6 Ma); SS Snowstorm Mountains dome complex. Unnamed black circles are PC, Picabo (∼10 Ma); HS, Heise (∼6.7–4.3 Ma); and YS, Yellowstone other rhyolite dome complexes/eruptive loci/shallow intrusive (<2.5 Ma), and age isochrons (dashed black lines, ages in Ma) of bodies. HLP High Lava Plains, SM Steens Mountain, OIG Oregon High Lava Plains silicic volcanism (N Newberry Volcano; Oregon–Idaho graben, WSRP western Snake River Plain, OP after Jordan et al. 2004). The SC lies between the initial 87Sr/86Sr Owyhee Plateau, NNR Northern Nevada rift and related lineaments. 0.706 and 0.704 isopleths (after Armstrong et al. 1977; Kistler and Mid-Miocene extensional features from a are also depicted Bull Volcanol netic processes active within the SC. Isotopic studies now during the mid-Miocene (Fig. 1b). Regionally, the eruptive underway will allow for a more detailed petrogenetic products of these mid-Miocene systems are best represented treatment and will be presented elsewhere in the context of in the tephra fall record and numerous studies have been the entire suite of SC magmatic products. performed to better characterize these deposits (Perkins et al. Field sampling and mapping, major and trace element 1998; Perkins and Nash 2002). geochemical data, and 40Ar/39Ar radiometric dating provide a comprehensive examination of the physical, chemical, General geology and temporal diversity of SC silicic units. A detailed discussion of the specific techniques employed and the The Santa Rosa–Calico volcanic field is located in north- chronologic results are presented as Appendix 1 in central Humboldt County, Nevada, overlapping with the Electronic supplementary material. Supplemental figures northern portion of the Santa Rosa mountain range, which and a table of representative major and trace element forms its western boundary (Fig. 2a). The eastern SC geochemical data that are discussed in the text are found as boundary is defined by the Calico Mountains and the Appendix 2 in Electronic supplementary material. southern SC boundary is defined by the basin bounding normal fault at the northern end of Paradise Valley; the northern boundary is less well defined physically (Fig. 2a, The Santa Rosa–Calico volcanic field: regional overview b). The northern Santa Rosa Range and the Calico and geologic setting Mountains help delineate the central SC, an oval topographic