Geochemical study of Cenozoic mafic volcanism in the west-central Great Basin, western Nevada, and the Ancestral Cascades Arc, California

Timmermans, Ann C.; Cousens, Brian; Henry, Christopher D.

doi:10.1130/ges01535.1

Cited by 4 publications

(2 citation statements)

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“…S1 [footnote 1]). All analyzed samples are consistent with a subduction zone setting (e.g., Pearce, 2008;Pearce and Peate, 1995) based on their trace element data (i.e., Nb depletion and Sr, K, and Ba enrichment) and are broadly similar to other studied volcanic rocks associated with the Ancestral Cascade arc around the greater Reno, Nevada, region (Cousens et al, 2008;du Bray and John, 2011;Timmermans et al, 2020). Therefore, we infer that volcanism in the Pine Nut Mountains was related to the Ancestral Cascade arc and preceded Basin and Range bimodal volcanism in the area (e.g., Say and Zuza, 2020).…”

Section: Local Stratigraphy With Age Constraintssupporting

confidence: 75%

Heterogenous late Miocene extension in the northern Walker Lane (California-Nevada, USA) demonstrates vertically decoupled crustal extension

Say

Zuza

2021

Geosphere

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The spatial distribution and kinematics of intracontinental deformation provide insight into the dominant mode of continental tectonics: rigid-body motion versus continuum flow. The discrete San Andreas fault defines the western North America plate boundary, but transtensional deformation is distributed hundreds of kilometers eastward across the Walker Lane–Basin and Range provinces. In particular, distributed Basin and Range extension has been encroaching westward onto the relatively stable Sierra Nevada block since the Miocene, but the timing and style of distributed deformation overprinting the stable Sierra Nevada crust remains poorly resolved. Here we bracket the timing, magnitude, and kinematics of overprinting Walker Lane and Basin and Range deformation in the Pine Nut Mountains, Nevada (USA), which are the westernmost structural and topographic expression of the Basin and Range, with new geologic mapping and 40Ar/39Ar geochronology. Structural mapping suggests that north-striking normal faults developed during the initiation of Basin and Range extension and were later reactivated as northeast-striking oblique-slip faults following the onset of Walker Lane transtensional deformation. Conformable volcanic and sedimentary rocks, with new ages spanning ca. 14.2 Ma to 6.8 Ma, were tilted 30°–36° northwest by east-dipping normal faults. This relationship demonstrates that dip-slip deformation initiated after ca. 6.8 Ma. A retrodeformed cross section across the range suggests that the range experienced 14% extension. Subsequently, Walker Lane transtension initiated, and clockwise rotation of the Carson domain may have been accommodated by northeast-striking left-slip faults. Our work better defines strain patterns at the western extent of the Basin and Range province across an approximately 150-km-long east-west transect that reveals domains of low strain (~15%) in the Carson Range–Pine Nut Mountains and Gillis Range surrounding high-magnitude extension (~150%–180%) in the Singatse and Wassuk Ranges. There is no evidence for irregular crustal thickness variations across this same transect—either in the Mesozoic, prior to extension, or today—which suggests that strain must be accommodated differently at decoupled crustal levels to result in smooth, homogenous crustal thickness values despite the significantly heterogeneous extensional evolution. This example across an ~150 km transect demonstrates that the use of upper-crust extension estimates to constrain pre-extension crustal thickness, assuming pure shear as commonly done for the Mesozoic Nevadaplano orogenic plateau, may not be reliable.

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Section: Local Stratigraphy With Age Constraintssupporting

confidence: 75%

Heterogenous late Miocene extension in the northern Walker Lane (California-Nevada, USA) demonstrates vertically decoupled crustal extension

Say

Zuza

2021

Geosphere

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“…The normalized incompatible element plots for the mafic to intermediate rocks of the SCF region (Figure 62) indicate that the mafic magmatism is subduction-related as they mimic the pattern of subduction-related volcanic arc rocks of Eocene through Pliocene age elsewhere in northern Nevada (Cousens et al, 2019;Timmermans et al, 2020) that are more similar to those of a mantle source that is older (Precambrian?) and/or more enriched than a modern upper mantle source (White, 2014;Wooden & Mueller, 1988) (Figure 76).…”

Section: -Mantle Source For the Scf-related Volcanic Rocksmentioning

confidence: 99%

The Stone Cabin Formation, Nevada, USA: Geochemical and Isotopic Indicators of Magma Sources and Crustal Influence in an Eocene Caldera System

Chan

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The 35.8 Ma Stone Cabin Formation (SCF) ignimbrites and related Eocene volcanic rocks of this study are located in eastern Nevada within the Central Nevada Volcanic Field. The SCF is a part of the mid-Cenozoic, subduction-related, primarily intermediate to silicic volcanic event termed the Ignimbrite Flareup. This project aims to determine the magma source or sources of the SCF and determine the existence/extent of crustal contamination during petrogenesis using whole-rock major element, trace element, and Pb-Sr-Nd-Hf isotopic analysis. The source of SCF ignimbrites is the White River caldera southwest of Ely, NV. The caldera includes SCF intracaldera tuffs, low-Si to high-Si rhyolite lavas, and andesite lava flows.

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Tectonic controls on the origin and segmentation of the Cascade Arc, USA

Humphreys

Grunder

2022

Bull Volcanol

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The magmatic response above subducting ocean lithosphere can range from weak to vigorous and from a narrow zone to widely distributed. The small and young Cascade Arc, riding on the margin of the tectonically active North American plate, has expressed nearly this entire range of volcanic activity. This allows an unusually good examination of arc initiation and early growth. We review the tectonic controls of Cascade-related magmatism from its inception to the present, with new considerations on the influences of tectonic stress and strain on volcanic activity. The Cascade Arc was created after accretion of the Siletzia oceanic plateau at ~ 50 Ma ended a period of flat-slab subduction. This (1) initiated dipping-slab subduction beneath most of the northern arc (beneath Washington and Oregon) and (2) enabled the more southerly subducting flat slab (beneath Nevada) to roll back toward California. As the abandoned flat slab fragmented and foundered beneath Oregon and Washington, vigorous extension and volcanism ensued throughout the northwest USA; in Nevada the subducting flat slab rolled back toward California. Early signs of the Cascade Arc were evident by ~ 45 Ma and the ancestral Cascade Arc was well established by ~ 35 Ma. Thus, from ~ 55–35 Ma subduction-related magmatism evolved from nearly amagmatic to regional flare-up to a clearly established volcanic arc in two different tectonic settings. The modern Cascades structure initiated ~ 7 Ma when a change in Pacific plate motion caused partial entrainment of the Sierra Nevada/Klamath block. This block pushes north and west on the Oregon Coast Ranges block, breaking the arc into three segments: a southern extensional arc, a central transitional arc, and a northern compressional arc. Extension enhances mafic volcanism in the southern arc, promoting basalt decompression melts from depleted mantle (low-K tholeiites) that are subequal in volume to subduction fluxed calcalkaline basalts. Compression restricts volcanic activity in the north; volcanism is dominantly silicic and intra-plate-like basalts cluster close to the main arc volcanoes. The transitional central arc accommodates dextral shear deformation, resulting in a wide volcanic arc with distributed basaltic vents of diverse affinities and no clear arc axis.

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Geochemical study of Cenozoic mafic volcanism in the west-central Great Basin, western Nevada, and the Ancestral Cascades Arc, California

Cited by 4 publications

References 157 publications

Heterogenous late Miocene extension in the northern Walker Lane (California-Nevada, USA) demonstrates vertically decoupled crustal extension

Heterogenous late Miocene extension in the northern Walker Lane (California-Nevada, USA) demonstrates vertically decoupled crustal extension

The Stone Cabin Formation, Nevada, USA: Geochemical and Isotopic Indicators of Magma Sources and Crustal Influence in an Eocene Caldera System

Tectonic controls on the origin and segmentation of the Cascade Arc, USA

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