Hot faults: Iridescent slip surfaces with metallic luster document high-temperature ancient seismicity in the Wasatch fault zone, Utah, USA

Geology ◽  
2014 ◽  
Vol 42 (7) ◽  
pp. 623-626 ◽  
Author(s):  
James P. Evans ◽  
Mitchell R. Prante ◽  
Susanne U. Janecke ◽  
Alexis K. Ault ◽  
Dennis L. Newell
Keyword(s):  
High Temperature ◽  
Fault Zone ◽  
Metallic Luster ◽  
Slip Surfaces ◽  
Wasatch Fault

scholarly journals Seismicity recorded in hematite fault mirrors in the Rio Grande rift

Geosphere ◽  
2021 ◽  
Author(s):  
M.L. Odlum ◽  
A.K. Ault ◽  
M.A. Channer ◽  
G. Calzolari
Keyword(s):  
High Temperature ◽  
Fault Zone ◽  
Temperature Rise ◽  
Rio Grande ◽  
Fault Slip ◽  
Fault Reactivation ◽  
Rio Grande Rift ◽  
Seismogenic Zone ◽  
Size Dependent ◽  
Slip Surfaces

Exhumed fault rocks provide a textural and chemical record of how fault zone composition and architecture control coseismic temperature rise and earthquake mechanics. We integrated field, microstructural, and hematite (U-Th)/He (He) thermochronometry analyses of exhumed minor (square-centimeter-scale surface area) hematite fault mirrors that crosscut the ca. 1400 Ma Sandia granite in two localities along the eastern flank of the central Rio Grande rift, New Mexico. We used these data to characterize fault slip textures; evaluate relationships among fault zone composition, thickness, and inferred magnitude of friction-generated heat; and document the timing of fault slip. Hematite fault mirrors are collocated with and crosscut specular hematite veins and hematite-cemented cataclasite. Observed fault mirror microstructures reflect fault reactivation and strain localization within the comparatively weaker hematite relative to the granite. The fault mirror volume of some slip surfaces exhibits polygonal, sintered hematite nanoparticles likely created during coseismic temperature rise. Individual fault mirror hematite He dates range from ca. 97 to 5 Ma, and ~80% of dates from fault mirror volume aliquots with high-temperature crystal morphologies are ca. 25–10 Ma. These aliquots have grain-size–dependent closure temperatures of ~75–108 °C. A new mean apatite He date of 13.6 ± 2.6 Ma from the Sandia granite is consistent with prior low-temperature thermochronometry data and reflects rapid, Miocene rift flank exhumation. Comparisons of thermal history models and hematite He data patterns, together with field and microstructural observations, indicate that seismicity along the fault mirrors at ~2–4 km depth was coeval with rift flank exhumation. The prevalence and distribution of high-temperature hematite grain morphologies on different slip surfaces correspond with thinner deforming zones and higher proportions of quartz and feldspar derived from the granite that impacted the bulk strength of the deforming zone. Thus, these exhumed fault mirrors illustrate how evolving fault material properties reflect but also govern coseismic temperature rise and associated dynamic weakening mechanisms on minor faults at the upper end of the seismogenic zone.

Rupture characteristics of normal faults: an example from the Wasatch fault zone, Utah

1987 ◽  
Vol 28 (1) ◽  
pp. 337-353 ◽  
Author(s):  
Ronald L. Bruhn ◽  
Pamela R. Gibler ◽  
William T. Parry
Keyword(s):  
Fault Zone ◽  
Normal Faults ◽  
Wasatch Fault

scholarly journals On the geothermal potential of crustal fault zones: a case study from the Pontgibaud area (French Massif Central, France)

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Hugo Duwiquet ◽  
Laurent Arbaret ◽  
Laurent Guillou-Frottier ◽  
Michael J. Heap ◽  
Mathieu Bellanger
Keyword(s):  
High Temperature ◽  
Fault Zone ◽  
Hydrothermal System ◽  
Numerical Models ◽  
Thermal Anomaly ◽  
Fault Zones ◽  
French Massif Central ◽  
Predictive Tool ◽  
Massif Central ◽  
Geothermal Potential

Abstract The present study aims to understand the potential of a new and novel type of geothermal play system for high temperature and electricity production: crustal fault zones (CFZ). According to geological and geophysical data, the Pontgibaud fault zone (French Massif Central) is suspected to host an active hydrothermal system at a depth of a few kilometers. The deep geometry of the fault zone and the permeability distribution are the main unknown parameters that are required to assess the geothermal potential of the Pontgibaud site. Structural and thin-section observations, laboratory permeability and connected porosity measurements and X-ray micro-tomography observations suggest that the hydrothermal system behaves like a double matrix-fracture permeability reservoir. Numerical modeling in which we varied the fault dip and the ratio between the fault zone permeability and host rock, R, was performed. Results indicate that three main convective regimes can be identified (weak convection, single cellular-type convection and bicellular convection). For a sufficiently high fault zone permeability (> 1 × 10−15 m2), buoyancy-driven flow creates a positive thermal anomaly of several tens of °C at a depth of 2–5 km. For a vertical fault zone, the thermal anomaly is larger for higher R values. Numerical models, then applied to the geologically constrained Pontgibaud fault zone, show that a temperature of 150 °C at a depth of 2500 m can be obtained for a fault zone permeability of 1.6 × 10−14 m2. Based on a multi-disciplinary approach, this work establishes a potential predictive tool for future high-temperature geothermal operations within basement rocks hosting large-scale fault systems.

scholarly journals Reevaluation of Holocene faulting at the Kaysville site, Weber segment of the Wasatch fault zone, Utah

Tectonics ◽  
1994 ◽  
Vol 13 (1) ◽  
pp. 1-16 ◽  
Author(s):  
James P. McCalpin ◽  
Steven L. Forman ◽  
Mike Lowe
Keyword(s):  
Fault Zone ◽  
Wasatch Fault
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