In addition, he was a wonderful person to discuss ideas with, and helped me understand the historical context of the Hartberg problem. This thesis addresses some of the uncertainty regarding two specific detachments, the Mormon Peak detachment in Nevada and the Heart Mountain detachment in Wyoming and Montana. Constraints on the geometry and kinematics of emplacement of the Mormon Peak detachment are provided by detailed geologic mapping of the Meadow Valley Mountains, along with an analysis of structural data within the allochthon in the Mormon Mountains.
Identifiable structures suitable for constraining the kinematics of the detachment include a recently mapped monoclinal bend of Sevier age in the hanging wall of the detachment. Fault rocks from about 1 m from the Mormon Peak detachment, including veins, breccias, gouges, and host rocks, were analyzed for carbon, oxygen, and lumped isotope measurements. The data indicate that much of the carbonate breccia and burrow material along the detachment is comminuted host rock, as expected.
There is ample textual evidence of the important role of fluids during detachment via pressurized solution.
Introduction
Geologic mapping in Chapter 3 provides constraints on the displacement of the Mormon Peak detachment (is it part of a crustal extensional fault system, or a landslide?), which is a critical first step in explaining its mechanics of slip. A study of the textures of fault rocks along and near the Hartberg detachment is presented in Chapter 4. Determine whether sliding occurred during one catastrophic event or more. implications for both slip rate and dynamics. Volcanic or magmatic processes are commonly used to facilitate slip, and temperature measurements of the associated fault rocks are important to evaluate that possibility.
5 Eksempel fra Heart Mountain Slide Block, Wyoming og Montana, U.S.A: The Journal of Geology, v. H., og Losh, S., 2013, Mode I microfracturing and fluid flow in damage zones: Nøglen til at skelne fejl fra dias : Journal of Structural Geology, v. E., Felger, T.J., Diehl, S.F., Page, W.R., Workman, J.B., 2010, Integration af tektoniske, sedimentære og geohydrologiske processer, der fører til en lille udvidelsesmodel for Mormonbjergene nord for af Lake Mead, Lincoln County, Nevada, i Umhoefer, P. Eds.), red., Miocene Tectonics of the Lake Mead Region, Central Basin and Range, Geological Society of America Special Paper 463, s. L., 1972, Low-Angle (Denudation) Faults, Hinterland of the Sevier Orogenic Belt, Eastern Nevada og Western Utah: Geological Society of America Bulletin, v. J., 1993, Ramp-flat detachment faulting and low-angle normal reactivation af Tule Springs thrust, southern Nevada: Geological Society of America Bulletin, v. J., 1990, Mesozoic and Cenozoic tectonics of the Sevier thrust belt in the Virgin River valley area, southern Nevada Basin and Range extensional tektonik nær breddegraden Las. Vegas, Nevada: Geological Society of America Memoir, v. P., 2005, Catastrophic placement of Heart Mountain block slide, Wyoming og Montana, USA: Geological Society of America Bulletin, v. Architecture and evolution of the collaps of an eocæn vulkanic system, nordvest Wyoming: Rocky Mountain Geology, v. Collettini, C., 2011, The mechanical paradox of low-angle normal faults: Nuværende forståelse og åbne spørgsmål: Tectonophysics, v. H., 2012, Vertical injectites of detachement carbonate ultracataclasite at White Mountain, Heart Mountain detachment, Wyoming: Geology, v. R., 2009, Dynamics of the placement of Heart Mountain allochton at White Mountain:. Begrænsninger fra calcit-twinning-stammer, anisotropi af magnetisk følsomhed og termodynamiske beregninger: Geological Society of America Bulletin, v. J., 1979, Geologisk udvikling af Cordilleran metamorfe kernekomplekser: Geology, v. F., Anderson, R.E., og Humprey, J.D., , 2010, Væskestrøm, opløsningskollaps og massiv opløsning ved løsrivningsforkastninger, Mormon Mountains, Nevada, i Umhoefer, P. Eds.), red., Miocene Tectonics of the Lake Mead Region, Central Basin and Range, Geological Society of America Special Paper 463, s.
A., 1985, Gravity-Spreading origin of the Heart Mountain allochthon, Northwestern Wyoming: Geological Society of America Bulletin, v.
Temperatures and Fluids on Faults Based on Carbonate Clumped–Isotope Thermometry
In eastern areas of exposure, the detachment cuts across Middle and Upper Cambrian strata of the thrust allochthon. We collected samples from 4 locations relatively evenly spaced across this transect (fig. 1A), generally within 1 m of the detachment plane. An important member of the cold suite is the calcite-spar breccia sample ES10-27 (fig. 3A) mentioned above.
Shawe et al. (1988) suggested that such a pluton may be present at depth, based on (1) an aeromagnetic anomaly along the western flank of the range, and (2) the presence of a small igneous body ( 200 m2) in the northern part of the range they interpreted as an intrusive. This suggests that brecciation occurred after the deposition of the calcite spar in the clast. Oxygen composition of the fluid is calculated from measured δ18O and temperature of each sample (see text for discussion).
These values are calculated from each sample based on temperature and δ13C composition of the carbonate, provided.
Geologic map of the east-central Meadow Valley
Mountains, and implications for reconstruction of the Mormon Peak detachment fault, Nevada
Here we use geologic maps in the Meadow Valley Mountains to define the geometry and kinematics of the emplacement of the Mormon Peak allochthon, the hanging wall of the Mormon Peak detachment. Although previous suggestions that the detachment's initiation corner in the central Mormon Mountains c. The Mormon Mountains are a topographical and structural dome veneered by cliffs of the Mormon Peak detachment (Figure 1).
In the central part of the area, the Middle Cambrian strata of the Mormon Thrust Plate are thrust over the Mississippian strata. The Meadow Valley Mountains, immediately west of the Mormon Mountains, contain two structurally distinct domains. Faults within the mapped areas of the Meadow Valley Mountains (Fig. 4) are predominantly high-angle normal faults trending from NE to NNW, with moderate offsets (10 s to 100 s meters).
Orientations of bedding in the hanging wall of the Mormon Peak section show an abrupt transition from predominantly easterly dips to predominantly westerly dips in both the Meadow Valley Mountains and the Mormon Mountains (Figure 3). The hanging wall of the Mormon Peak section is divided into 8 subdomains (including the eastern Meadow Valley Mountains), with each subdomain indicated by differently colored and numbered enclosures (Figure 3). The geology of the Mormon Mountains and Tule Springs Hills in the footwall of the Mormon Peak detachment is taken from Axen et al.
In Figure 8c, the bedposts for 90 measured stands in Tertiary units on the hanging wall of the Mormon Peak detachment are shown, along with domain averages (Figure 3). Twenty-six lineaments on or near the detachment plane, widely distributed over the surface trace of the Mormon Peak detachment in the Mormon Mountains, are shown in Figure 9 (Walker, 2008). Throughout the eastern half of the topographic and structural dome, the subducting detachment is the Mormon thrust plate.
The third marker below the detachment is the top of the thrust slope, which is easily visible in the Tule Springs Hills near Jumbled Mountain. This suggests that the Mormon Peak detachment is closely parallel to the Mormon thrust ramp, at least in the northern part of the Mormon Mountains. A single (?) aphanitic flow as much as 4 m thick, exposed near Hackberry Canyon, lies between the Hiko Tuff (Th) and the crystal tuff (Tku) of the Kane Wash Tuff.
D., 1971, Style and evolution of thrusts in the area of the Mormon Mountains, Nevada [Ph.D: University of Utah, 213 p.
Episodic(dissolution,(precipitation(and(slip(along(
We suggest that displacement along the detachment near the base of the carbonates initiated as localized patches of viscous yielding, caused by pressure solution. Faulting and sliding on shallow dipping detachments is one of the longest debated mysteries in tectonics. The borders of the dykes can be either level and parallel to each other, or highly irregular.
In the footwall of the detachment at Jim Smith Creek, re-brecciation (Figure 6c) included examples that record the formation of three distinct textures of breccia (Figure 6d). There is no clear pattern regarding the size or composition of the striped grains versus 'normal' grains. In general, however, the darkest layer in the stripes is at the outer edge of the grain.
Surrounding grains in the ∼100 μm range exhibit tangential flattening parallel to the edge of the core grain. A later, more iron-rich liquid led to crystallization of the en-echelon structure in Figure 6b. This loading can have the effect of locally rotating the principal stress directions in the vicinity of the fault, enabling brittle failure on the detachment surface (Figure 12a).
Many detachment-related rocks show fault-zone texture and wall deformation that indicate a complex deformation history. Pressure solution features are common, must have formed during embrittlement events, and probably play a role in the cyclic deformation of the Heart Mountain offset. P., 2005, Catastrophic emplacement of the Heart Mountain block slide, Wyoming and Montana, USA: Geological Society of America Bulletin, v.
R., 2009, Dynamics of the emplacement of the Heart Mountain allochhon at White Mountain: Constraints from calciet twinning strains, anisotropy of. K., 1983, Heart Mountain: blokke in 'n reuse vulkaniese rotsgletser: 34th Annual Field Conference Guidebook of the Wyoming Geological Association, p.
Fluid Flow, Brecciation, and Shear Heating on Faults
Insights from Carbonate Clumped-Isotope Thermometry
Both the Heart Mountain and Mormon Peak detachments developed synchronously with regional magmatism, the former during the development of the Eocene Absaroka Volcanic. In contrast, the Mormon Peak solution and allochthon developed further away from magmatism, about 30–40 km SE of the Kane Springs Wash caldera. Exposures of the detachment span an east–west distance of more than 20 km, corresponding to footwall paleodepths of ∼2 to 7 km.
We collected samples from 6 locations relatively evenly spaced across this transect (Figure 3a), usually within 1 m of the detachment plane. In the case of the Heart Mountain samples, it is clear that this fault experienced many episodes of slip, with gog overprint breccia, only to be incorporated as clasts into a later breccia. It may have formed immediately post-slip, during cooling of the slip event, or it may have formed in the fault zone at 1-2 km depth, depending on the local geothermal gradient.
This difference is reflected in the temperatures of the hottest veins, with the hottest vein at Heart Mountain recording a temperature of 65°C, much colder than the 165°C vein temperatures from the footwall of the Mormon Peak allochthon. The preservation of the heating signal appears to be better in hanging-wall faults, which were not sampled in Mormon Mountain, but both areas have samples above 200°C. Summary of the three types of material found in fault breccias and gouges associated with the Heart Mountain (HM) and Mormon Peak (MP) detachments.
Figure(3.!Structural!map!and!schematic!cross-section!of!the!Mormon!Mountains,!(Nevada.!(a),!map!showing!the!sample locations.!MVM,!Meadow !Valley!Mountain ;!MP,.
