Temporal Changes in Deformation Mode: From Failure to Flow in the Colorado River Extensional Corridor

Campbell-Stone, Erin; John, Barbara E.

doi:10.2747/0020-6814.44.6.512

Cited by 13 publications

(11 citation statements)

References 43 publications

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“…The connections between crustal extension and magmatic activity within the CREC are controversial [e.g., Gans et al, ; Lister and Baldwin , ; Spencer et al, ; Gans and Bohrson , ; Campbell‐Stone and John, ]. Much of the debate stems from uncertainties regarding the precise timing of plutonism and volcanism relative to the inception and duration of extensional faulting in the region.…”

Section: Discussionmentioning

confidence: 99%

Dike emplacement, footwall rotation, and the transition from magmatic to tectonic extension in the Whipple Mountains metamorphic core complex, southeastern California

Gans

Gentry

2016

Tectonics

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The Chambers Well dike swarm and associated plutonic/volcanic rocks in the western footwall of the Whipple Detachment Fault (WDF) provide key insight into the evolution of this metamorphic core complex. New structural and geochronologic data suggest that the western 12–15 km of exposed footwall is steeply tilted to the SW, providing a cross‐sectional view of the upper crust, from the Miocene erosion surface to the top of the coeval mylonitization. Ages and compositions of dikes are indistinguishable from adjacent thick volcanic successions. Several kilometers of early Miocene extension (~20.5 to 19.0 Ma) were accommodated by magmatic accretion but transitioned to rapid extensional faulting and tilting at 19.0–18.5 Ma. The subhorizontal WDF in this area initiated as a northeast dipping high‐angle (50–60°) normal fault that breached the surface locally, not in a breakaway tens of kilometers to the west. Large‐scale tilting and differential uplift of the western footwall was in part coeval with mylonitization and dike emplacement and was accomplished by block rotation in the hanging wall of additional normal faults, isostatic uplift, and flow of lower crust from beneath less extended regions to the west. The WDF is likely a composite surface with a western segment that had ceased moving by ~18.5 Ma, cut by successively younger and steeper fault(s) to the east. Perhaps, the most important difference between seismogenic high‐angle normal faults and low‐angle “detachment faults” characteristic of metamorphic core complexes is one of magnitude and rate of total accumulated slip, not of initial failure conditions.

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Section: Discussionmentioning

confidence: 99%

Dike emplacement, footwall rotation, and the transition from magmatic to tectonic extension in the Whipple Mountains metamorphic core complex, southeastern California

Gans

Gentry

2016

Tectonics

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“…The paleo-earthquakes documented in northern Norway also occurred 10-20 km deeper and at temperatures 200-300 °C higher than the predicted brittleductile transition. Locally, strength in the lower crust must be suffi cient for repeated coseismic rupture, even in feldspar-rich lithologies (mangerite and anorthosite), and at temperatures where rocks should be weakest at inferred regional shear strain rates (10 −14 to 10 −16 s -1 ; Campbell-Stone and John, 2002).…”

Section: Depth-temperature-strength Considerationsmentioning

confidence: 99%

Direct calculation of rupture depth for an exhumed paleoseismogenic fault from mylonitic pseudotachylyte

Moecher

Steltenpohl

2009

Geology

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Multiple generations of pseudotachylyte within granulite-facies orthogneiss (northern Norway Caledonides) are cut by ultramylonitic shear bands that contain the mineral assemblage garnet + clinopyroxene + plagioclase + quartz. Mineralogic thermobarometry yields pressure (P) = 950 ± 150 MPa at temperature (T) = 625-675 °C for equilibration conditions of the ultramylonite assemblage, requiring minimum depths of 35 ± 5 km for coseismic slip that generated pseudotachylyte. These depths are well below the base of the standard seismogenic zone (15-20 km). Ambient temperatures are 200-300 °C higher than those commonly cited for the onset of ductile creep in quartzofeldspathic rocks, but they are similar to those in modern intraplate settings of higher than average heat fl ow that have experienced deep crustal earthquakes. The occurrence of overprinting mylonites and pseudotachylytes requires tens of kilometers of dynamic downward rupture propagation from the brittle-frictional regime into the ductile regime. Plastic instabilities do not explain the relationship between ultramylonites and mylonitized pseudotachylytes in this setting.on August 4, 2015 geology.gsapubs.org Downloaded from

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“…Extrusive magmatism in the CREC also records an evolution in composition during extension; the oldest volcanic deposits comprise a heterogeneous suite of basaltic, intermediate, and minor felsic rocks, whereas the youngest volcanism is basaltic or bimodal in composition (Gans et al, 1989;Gans and Bohrson, 1998;Foster and John, 1999). Although a significant volume of the documented syntectonic magmatism in the CREC is extrusive, plutons and dikes were also emplaced prior to, during, and after peak slip on low-angle normal faults associated with the core complexes (Davis et al, 1982;Campbell and John, 1996;Campbell-Stone et al, 2000;Campbell-Stone and John, 2002;Singleton and Mosher, 2012). Dikes characteristic of the early syntectonic magmatism in the CREC are exposed in the Whipple, Mohave, Chemehuevi, and Sacramento mountains (Howard and John, 1987;John, 1987b;Lister and Davis, 1989;Nielson and Beratan, 1995;Sherrod and Nielson, 1993).…”

Section: Paleogene-neogene Magmatism In the Colorado River Extensionamentioning

confidence: 99%

“…1; Howard and John, 1987). These core complexes offer a wealth of information on extensional processes from inception to cessation of large-slip normal faults, often including associated magmatism (e.g., John, 1987b;Lister and Davis, 1989;Campbell-Stone and John, 2002). The original orientation of large-offset low-angle normal faults in the CREC (and elsewhere) remains the subject of significant debate due to the apparent incompatibility with Andersonian mechanics (Axen, 2007).…”

Section: Introductionmentioning

confidence: 99%

Synextensional dike emplacement across the footwall of a continental core complex, Chemehuevi Mountains, southeastern California

2017

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Temporal Changes in Deformation Mode: From Failure to Flow in the Colorado River Extensional Corridor

Cited by 13 publications

References 43 publications

Dike emplacement, footwall rotation, and the transition from magmatic to tectonic extension in the Whipple Mountains metamorphic core complex, southeastern California

Dike emplacement, footwall rotation, and the transition from magmatic to tectonic extension in the Whipple Mountains metamorphic core complex, southeastern California

Direct calculation of rupture depth for an exhumed paleoseismogenic fault from mylonitic pseudotachylyte

Synextensional dike emplacement across the footwall of a continental core complex, Chemehuevi Mountains, southeastern California

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