Preservation of an extreme transient geotherm in the Raft River detachment shear zone

Gottardi, Raphaël; Teyssier, Christian; Mulch, Andreas; Vennemann, Torsten; Wells, Michael L.

doi:10.1130/g31834.1

Cited by 43 publications

(102 citation statements)

References 29 publications

(54 reference statements)

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“…23 Ma, when the exhumed hydrothermal system ceased, the brittle-ductile interface at the transient hanging wall-footwall interface stopped to be an effective means of rapid heat advection and that subsequently extensional strain was localized through brittle deformation mechanisms. Together with results from metamorphic core complexes in the northern North American Cordillera (e.g., Shuswap and Kettle ; Raft River [Gottardi et al, 2011]) microstructural and isotopic evidence summarized in this paper demonstrates that meteoric hydrothermal systems represent key features of extensional detachments that involve lateral and vertical mass transfer, denudation, and ultimately Cenozoic development of topography in the North American Cordillera Mix et al, 2011].…”

Section: Discussionsupporting

confidence: 71%

“…Deciphering the spatial pattern of fluid migration and its relationship to strain localization processes and assessing the isotopic composition, and therefore the origin of fluids within extensional shear zones, provide invaluable information on crustalscale fluid flow and the thermal and mechanical implications of large-scale extension [e.g., Mulch et al 2006;Gottardi et al, 2011]. These studies also inform about the paleo- topography of the region undergoing extension [e.g., since the hydraulic head generated in high-relief areas may be an important driving force for hydrothermal fluid circulation in detachment systems [Person et al, 2007].…”

Section: Discussionmentioning

confidence: 99%

“…If the 40 Ar/ 39 Ar ages within the top 188 m of the detachment indeed reflect recrystallization and ductile non-coaxial top-to-east shearing, hot footwall material was advected at relatively high rates leading to strongly compressed isotherms in the NSRD footwall while at the same time protracted normal faulting and denudation at the Earth's surface continuously exhumed parts of the footwall. In such a continuously exhuming system, shearing rocks in the detachment footwall cool owing to the combined effects of exhumation and hydrothermal activity [Gottardi et al, 2011]. As a result, ductile deformation microstructures freeze, and the deformation-recrystallization front moves downward.…”

Section: Fluid Flow In Exhuming Detachment Systemsmentioning

confidence: 99%

“…The mylonitic footwall of such detachments represents a zone of high strain that varies in thickness from 10s to 100s of meters and separates the cool upper crust from the hot middle crust. While active, this zone of localized deformation hosts very large temperature gradients [Rey et al, 2009a[Rey et al, , 2009b that may be transient [Mulch et al 2006;Gottardi et al, 2011].…”

Section: Introductionmentioning

confidence: 99%

“…Backscattered electron (BSE) diffraction on the scanning electron microscope has become an important tool for the combined study of microstructures in crystalline materials. It is possible to measure complete crystallographic orientations of single crystallites with direct reference to the microstructure [Neumann, 2000;Heidelbach et al, 2000]. EBSD is based on the automatic analysis of diffraction patterns.…”

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confidence: 99%

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Oligo‐Miocene extensional tectonics and fluid flow across the Northern Snake Range detachment system, Nevada

Gébelin¹,

Mulch²,

Teyssier

et al. 2011

Tectonics

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[1] The Northern Snake Range (Nevada) represents a spectacular example of a metamorphic core complex and exposes a complete section from the mylonitic footwall into the hanging wall of a fossil detachment system. Paired geochronological and stable isotopic data of mylonitic quartzite within the detachment footwall reveal that ductile deformation and infiltration of meteoric fluids occurred between 27 and 23 Ma. 40 Ar/ 39 Ar ages display complex recrystallization-cooling relationships but decrease systematically from 26.9 ± 0.2 Ma at the top to 21.3 ± 0.2 Ma at the bottom of footwall mylonite. Hydrogen isotope (dD) values in white mica are very low (−150 to −145 ‰) within the top 80-90 m of detachment footwall, in contrast to values obtained from the deeper part of the section where values range from −77 to −64 ‰, suggesting that time-integrated interaction between rock and meteoric fluid was restricted to the uppermost part of the mylonitic footwall. Pervasive mica-water hydrogen isotope exchange is difficult to reconcile with models of 40 Ar loss during mylonitization solely by volume diffusion. Rather, we interpret the 40 Ar/ 39 Ar ages of white mica with low-dD values to date syn-mylonitic hydrogen and argon isotope exchange, and we conclude that the hydrothermal system of the Northern Snake Range was active during late Oligocene (27-23 Ma) and has been exhumed by the combined effects of ductile strain, extensional detachment faulting, and erosion.

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Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Section: Fluid Flow In Exhuming Detachment Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Oligo‐Miocene extensional tectonics and fluid flow across the Northern Snake Range detachment system, Nevada

Gébelin¹,

Mulch²,

Teyssier

et al. 2011

Tectonics

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Titanium concentration in quartz as a record of multiple deformation mechanisms in an extensional shear zone

Nachlas

Teyssier

Bagley

et al. 2014

Geochem. Geophys. Geosyst.

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Results of high precision analysis of Ti concentration ([Ti]) in quartz representing different recrystallization microstructures in a suite of progressively deformed quartzite mylonites show the effect of recrystallization on distribution of Ti in quartz. Petrographic observations and ion microprobe analysis reveals three texturally and geochemically distinct quartz microstructures in mylonites: (1) cores of recrystallized quartz ribbons preserve the highest [Ti] and are interpreted to have recrystallized via grain boundary migration recrystallization, (2) recrystallized rims and grain margins preserve a lower and more variable [Ti] and are interpreted to reflect the combined influence of subgrain rotation and bulging recrystallization, and (3) neocrystallized quartz precipitated in dilatancy sites has low ( 1 ppm) [Ti], reflecting the Ti content of the syndeformational fluid. Muscovite in nonmylonitic quartzite (at the base of the sampling traverse) is compositionally zoned, whereas muscovite in mylonitic quartzite shows a progressive decreasing in zoning in higher strain samples. Threedimensional phase distribution mapping using X-ray computed tomography analysis of rock hand samples reveals that Ti-bearing accessory phases are less abundant and more dispersed in higher strained mylonites compared to nonmylonitic quartzite. This study demonstrates the influence of dynamic recrystallization on Ti substitution in quartz and evaluates the Ti buffering capacity of aqueous fluids (meteoric versus metamorphic/ magmatic) as well as the distribution and reactivity of Ti-bearing accessory phases in a deforming quartzite. Results of this study suggest that Ti-in-quartz thermobarometry of deformed quartz is a sensitive technique for resolving the multistage history of quartz deformation and recrystallization in crustal shear zones.

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Eocene and Miocene extension, meteoric fluid infiltration, and core complex formation in the Great Basin (Raft River Mountains, Utah)

et al. 2015

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Metamorphic core complexes (MCCs) in the North American Cordillera reflect the effects of lithospheric extension and contribute to crustal adjustments both during and after a protracted subduction history along the Pacific plate margin. While the Miocene‐to‐recent history of most MCCs in the Great Basin, including the Raft River‐Albion‐Grouse Creek MCC, is well documented, early Cenozoic tectonic fabrics are commonly severely overprinted. We present stable isotope, geochronological (40Ar/39Ar), and microstructural data from the Raft River detachment shear zone. Hydrogen isotope ratios of syntectonic white mica (δ2Hms) from mylonitic quartzite within the shear zone are very low (−90‰ to −154‰, Vienna SMOW) and result from multiphase synkinematic interaction with surface‐derived fluids. 40Ar/39Ar geochronology reveals Eocene (re)crystallization of white mica with δ2Hms ≥ −154‰ in quartzite mylonite of the western segment of the detachment system. These δ2Hms values are distinctively lower than in localities farther east (δ2Hms ≥ −125‰), where 40Ar/39Ar geochronological data indicate Miocene (18–15 Ma) extensional shearing and mylonitic fabric formation. These data indicate that very low δ2H surface‐derived fluids penetrated the brittle‐ductile transition as early as the mid‐Eocene during a first phase of exhumation along a detachment rooted to the east. In the eastern part of the core complex, prominent top‐to‐the‐east ductile shearing, mid‐Miocene 40Ar/39Ar ages, and higher δ2H values of recrystallized white mica, indicate Miocene structural and isotopic overprinting of Eocene fabrics.

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Preservation of an extreme transient geotherm in the Raft River detachment shear zone

Cited by 43 publications

References 29 publications

Oligo‐Miocene extensional tectonics and fluid flow across the Northern Snake Range detachment system, Nevada

Oligo‐Miocene extensional tectonics and fluid flow across the Northern Snake Range detachment system, Nevada

Titanium concentration in quartz as a record of multiple deformation mechanisms in an extensional shear zone

Eocene and Miocene extension, meteoric fluid infiltration, and core complex formation in the Great Basin (Raft River Mountains, Utah)

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