a Map of the northwestern USA depicting select Cenozoic tectonomagmatic features. Shaded region is the approximate extent of mid-Miocene flood basalt volcanism (after Hart and Carlson 1985; Camp and Ross 2004). Also shown are major flood basalt dike swarms/eruptive loci (black lines), Oregon–Idaho graben and magnetic anomalies in Nevada corresponding to zones of lithospheric extension/mafic magma emplacement (black dotted-dashed lines; Cummings et al. 2000; Glen and Ponce 2002), major volcanic fields of the Yellowstone–Snake River plain province (dashed circles); BJ, Bruneau–Jarbidge (∼12.5–<11 Ma); TF, Twin Falls (∼10–8.6 Ma); PC, Picabo (∼10 Ma); HS, Heise (∼6.7–4.3 Ma); and YS, Yellowstone (<2.5 Ma), and age isochrons (dashed black lines, ages in Ma) of Oregon High Lava Plains silicic volcanism (N Newberry Volcano; after Jordan et al. 2004). The SC lies between the initial 87Sr/86Sr 0.706 and 0.704 isopleths (after Armstrong et al. 1977; Kistler and Peterman 1978; Leeman et al. 1992; Crafford and Grauch 2002). b Shaded relief map of the southern Oregon Plateau illustrating the locations of major mid-Miocene silicic volcanic systems. SC Santa Rosa–Calico volcanic field, MD McDermitt volcanic field, LO Lake Owyhee volcanic field, NWNV Northwest Nevada volcanic field (e.g. Virgin Valley, High Rock, Hog Ranch, and unnamed calderas), HVLM Hawks Valley–Lone Mountain dome complex, SI Silver City–DeLamar dome complex, JM Juniper Mountain volcanic center, CC Circle Creek volcanic center, J Jarbidge Rhyolite loci, SS Snowstorm Mountains dome complex. Unnamed black circles are other rhyolite dome complexes/eruptive loci/shallow intrusive bodies. HLP High Lava Plains, SM Steens Mountain, OIG Oregon–Idaho graben, WSRP western Snake River Plain, OP Owyhee Plateau, NNR Northern Nevada rift and related lineaments. Mid-Miocene extensional features from a are also depicted
Recent studies dealing with mid-Miocene northwestern United States
volcanism have focused on the Steens and Columbia River flood
basalts, their relationship to younger regional Cenozoic volcanism,
and its relationship to mid-Miocene mineralization and
rift-development (Fig. 1 a; Zoback et al.
However, numerous other large and small, dominantly silicic
mid-Miocene volcanic systems are present across the Oregon Plateau
(Fig. 1 b), including the Santa Rosa–Calico volcanic field
(SC) of northern Nevada.
The SC lies at the junction of the Northern Nevada rift and Owyhee
Plateau (Fig. 1 b), an ideal location to further investigate
the relationships between mid-Miocene flood basalt volcanism,
magmatic system development, and tectonism.
These mid-Miocene systems were characterized by multiple eruptions
of extensive ash-flow sheets and subsequent rhyolite dome formation
(Fig. 1 b).
Less well documented are the abundant rhyolite dome complexes that
also formed during the mid-Miocene (Fig. 1 b).
The interplay between volcanism and focused extensional tectonism
suggested for the SC may help to better understand the origin of
Miocene silicic volcanism on the adjacent Owyhee Plateau
(Fig. 1 b).
Across the Owyhee Plateau, numerous, small silicic eruptive centers
and shallow intrusive bodies are present and must reflect multiple
eruptive loci (Fig. 1 b).
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