No description available.

Thesis (M.S.)--Brigham Young University. Dept. of Geology, 2005. / Includes bibliographical references (p. 61-64).

The Eureka Lilly fault zone provides an impermeable barrier for groundwater flow in the East Tintic mining district. The fault zone separates two distinct groundwaters that have different temperatures, compositions, and potentiometric surfaces. The damage zone of the fault is an extensive network of interconnected open fractures and fault intersections that provide conduits for groundwater flow in otherwise impermeable units. The fault core breccia has been re-cemented and mineralized, which eliminates porosity in the rock by creating a thick impermeable zone, which has compartmentalized groundwaters across the fault zone. The compartmentalization of groundwater shows that fault zone variability (from strain partitioning and multiple deformation episodes) make traditional basin flow concepts inaccurate and difficult to apply in this area.

Historical archaeologists are turning more and more attention to the study of capitalism in post-Industrialist nations. Rhoda Halperin's concept of householding considers networks of families or other groups that operate outside of the mainstream capitalist economy. The concept is most often applied in anthropological contexts, but may be a useful tool in the study of homesteading in the American West. At Benmore, a small homesteading community in southern Rush Valley, Tooele County, Utah, 20 families sought to survive by dry farming in a marginal environment. The enthusiasm of such residents as Israel Bennion, whose journal provides deep insight into the town's short existence, may have united the community under the ideology of self-sufficiency and resulted in an example of householding in early twentieth century Utah. This thesis utilizes surface data from Benmore, compared to surface and excavation data from Tintic Junction—a railroading town approximately 20 miles away from Benmore—to consider whether Benmore fits Halperin's concept of householding and the extent to which the community operated outside of the mainstream economy. The data is considered both in order to better define the community of Benmore and to determine whether Halperin's concept may be applicable to future homesteading studies throughout the American West. I argue that the specific questions considered in identifying householding are useful but that a broader theoretical approach is necessary to fully consider the dynamics of homesteading towns in Utah and the West.

Voluminous Eocene to Oligocene intermediate to silicic volcanic rocks related to subduction erupted throughout the Great Basin and were supplanted by bimodal eruptions of basalt and rhyolite related to extension in the Miocene. Locally, in the northern East Tintic Mountains of central Utah, this important transition is marked by a distinctive package of mafic alkaline magmas that reveal important details about the nature of this fundamental change. A late Oligocene anorthoclase-bearing shoshonite lava in the Boulter Peak quadrangle contains megacrysts of anorthoclase, with phenocrysts of olivine, clinopyroxene, magnesiohastingsite, magnetite, and apatite. The anorthoclase grains occur as glomerocrysts with irregular, resorbed edges, indicating they are not in equilibrium with the mafic phenocrysts in the shoshonite. They are interpreted to be xenocrysts incorporated into an ascending mafic magma that came into contact with a partially crystallized syenite. The mafic magma involved was probably derived by partial melting of the lithospheric mantle based on its high Mg/Fe ratios, magnesian phenocrysts, high water content, and high ratios of lithophile to high field strength elements. The syenite body likely crystallized from a highly differentiated melt. The 40Ar/39Ar age of the shoshonite is 25.35±0.04 Ma, and appears to represent the transition from subduction before the onset of extension (Christiansen et al., 2007). Other Oligocene mafic units in the area may represent different variations of the mafic alkaline endmember for the mixing process. The Gardison Ridge dike, a potassic alkaline basalt with an 40Ar/39Ar age of 26.3±0.3 Ma, contains olivine and clinopyroxene phenocrysts that are compositionally very similar to those found in the shoshonite. Other mafic dikes have even higher alkalis. All of these dikes have similar trace element patterns, with negative Nb and positive Pb anomalies, and high Ba and K concentrations. The minette of Black Rock Canyon (28.45±0.13 Ma) also contains high alkalis, particularly K, and its trace element pattern shows positive Ba and negative Nb anomalies. The clinopyroxene phenocrysts in the minette are also very similar to those found in the other alkaline rocks. The high water contents of these units are evidenced by amphibole in the shoshonite, phlogopite in the minette, and the lack of plagioclase phenocrysts in the basaltic dikes. The ages, mineral assemblages, and chemical compositions show that these late Oligocene alkaline magmas formed after a shallowly subducting oceanic slab peeled away from the overlying continental lithosphere and rolled back. Hot asthenosphere flowed in to replace the subducting plate and caused partial melting of the variably metasomatized lithospheric mantle. These alkaline magmas include the shoshonite, mafic alkaline dikes, and minette of Boulter Peak; they mark the transition from older subduction-related magmatism to Miocene magmatism caused by lithospheric extension.

No description available.

This work was a case study of historical ecological change in Tintic Valley, Juab County, Utah, an area historically impacted by mining and ranching activities common to much of the American West. The temporal framework for the study was approximately 120 years, the period of direct Euroamerican influence. In recognition of the ecological implications of cultural change, however, the impacts of prehistoric and protohistoric human activity on study area landscape patterns and processes were also explicitly addressed. The study included a narrative description of historic land uses and ecological change in Tintic Valley, and examined the changes in landscape patterns and processes so revealed within the context of the state and transition model of rangeland dynamics. The case of Tintic Valley thus served as a test of the heuristic utility of the theory of self-organization in ecological systems, within which the state and transition model is embedded. This theoretical framework in turn was used to gain insight into the present state of the Tintic landscape, how that state has changed over time, and the nature of those forces leading to transitions between system states in the historic period. The study employed archival research, personal interviews, repeat photography, field surveys, aerial photographs, and a geographic information system (GIS) to identify, describe, and quantify historic-era change in Tintic Valley landscape level patterns and processes. The analysis revealed dramatic change in both the landscape vegetation mosaic and the channel network of the study area over time. Evidence was found for direct anthropogenic influence in precipitating those changes, primarily through tree harvesting associated with mining and ranching activities and through the effects of historic roads and railroads on the Tintic Valley gully network. Results supported the working hypothesis of a change in system state in the Tintic Valley landscape in the historic period. Taken together, historical narrative and theoretical context permitted a degree of prediction with respect to potential future conditions for the study area under different management scenarios. Future research directions and implications of the research results for ecosystem management are also discussed.

In many ore deposits throughout the world, brecciation often accompanies or occurs in association with mineralization (Sillitoe, 1985). Such is the case in the Tintic Mining District (Ag-Pb-Zn) of north-central Utah, where unique breccia features called pebble dikes occur alongside significant mineralization. Pebble dikes are tabular bodies of breccia, which consist of angular to rounded clasts of quartzite, shale, carbonate, and minor igneous rock cemented in a fine-grained clastic matrix. All clasts now lie above or adjacent to corresponding source rocks. Dikes are thin, typically less than 0.3 m wide to as much as 1 m, and can exceed 100 m in length. The average of the largest clast sizes is less than 3 cm but correlates positively with pebble dike width. Contacts are sharp and an envelope of fine breccia surrounds roughly half of the dikes. Pebble dikes are mostly hosted in an Eocene rhyolite lava flow, which displays argillic to silicic alteration when in contact with a pebble dike, but are also hosted in an assortment of folded Paleozoic sedimentary rocks. The dikes show a strong northeast trend in orientation, following a regional fabric of northeast-trending strike-slip and oblique-slip faults.The formation of pebble dikes has been historically attributed to the intrusion of the Silver City Stock, the Tintic District's main productive intrusion (Morris and Lovering, 1979; Hildreth and Hannah, 1996; Kim, 1997; Krahulec and Briggs, 2006). However, pebble dikes are spatially associated with a previously unrecognized porphyritic unit, informally named the porphyry of North Lily, which is texturally, mineralogically, and chemically distinct from the Silver City Stock, and like pebble dikes, is emplaced in northeast-trending plugs and dikes. Pebble dikes show a strong spatial correlation to outcrops of the porphyry of North Lily. Additionally, clasts of the porphyry of North Lily have been found in pebble dikes, while pebble dike quartzite clasts have been found as xenoliths in the porphyry of North Lily. These similarities and interactions suggest simultaneous formation. Low-grade alteration associated with pebble dikes indicates that they formed at elevated temperatures (<150°C). Stable isotope characteristics of rhyolite altered during the emplacement of pebble dikes suggests that the dikes formed in the presence of heated groundwater, with little to no magmatic water association. The overall physical, spatial, and chemical characteristics of pebble dikes of the Tintic Mining District suggest that they formed by the mobilization of breccia in the explosive escape of groundwater that had been heated by the porphyry of North Lily. This escape occurred along pre-existing northeast-trending faults and fractures. Pebble dikes then became pathways for later ore fluids, easing the creation of the district's abundant mineral resources.

The mineral resources of the Tintic Mining District are influenced by three major events in its geologic history; the Mesozoic Sevier Orogeny, Paleogene volcanism and Late Neogene Basin and Range extension. In this paper a detailed analysis of each these geologic events is presented to help us understand the structural host, mineralization and exhumation of the Tintic Mining District ore. A kinematic analysis of the faults was completed to determine the origin of NE-trending faults, Sevier Orogeny or Basin and Range extension, in the northern part of the East Tintic Mountains in Allens Ranch 7.5' quadrangle, near the eastern margin of the Great Basin of central Utah. The structural history of the NE-trending faults found in the quadrangle was reconstructed to determine stress directions and fault kinematics. Maximum paleostress direction for the East Tintic fold and thrust system is between 80º–100º with fold axes oriented at ~350º. For example, the Gardison Ridge and Tintic Prince faults are NE-trending right-lateral transverse faults that formed at ~30º to paleostress directions similar to those of the Sevier Orogeny. The dominant NE-trending faults in the region are likely due to (1) differential shortening during progressive orocline development, (2) the pre-deformational Pennsylvanian-Permian Oquirrh basin geometry, and (3) the influence of the Leamington transverse zones of the Provo salient. Conversely, mixed paleostress directions for the north-trending Tintic Davis Canyon fault show it is a Basin and Range extension-related normal fault that may have originated as a Sevier related fault. Other N-trending faults within the quadrangle are only related to Basin and Range extension. However, large offset, range-bounding faults are buried by valley fill throughout the quadrangle and no young fault scarps are identified cutting Lake Bonneville deposits. An Oligocene to Miocene suite of extrusive volcanic units in the quadrangle correlates well with those of the East Tintic and Soldiers Pass volcanic fields. The Paleogene volcanic section is dominated by a suite of high-K calc-alkaline extrusive rocks (35 to 32 Ma). This intermediate to silicic sequence was followed by eruption of the mildly alkaline Mosida Basalt during the Miocene (19.5 Ma) marking the transition from subduction-related intermediate and silicic volcanism to extension-related mafic volcanism in the eastern Great Basin.

Geologic structures within the Birdseye 7.5 minute quadrangle Utah County, Utah have been related by previous workers to both the Jurassic Arapien Shale diapirism and to the mid-Cenozoic extensional collapse of the Charleston-Nebo Thrust. Whichever model proves valid, it will have implications for oil exploration and interpretation of the subsurface geologic structure in the region. A detailed map of the quadrangle was constructed to better constrain which mechanism was responsible for the deformation. Exposures of Arapien Shale near, and within the Birdseye quadrangle show no evidence of diapiric movement. Arapien involvement in the deformation of Tertiary rocks in the center of the quadrangle is therefore unlikely. Changes in the pattern of sedimentation of Eocene age rocks suggest a change in tectonics during this time. Restoration of the Eocene strata shows that the most plausible mechanism for this deformation is extension along reactivated thrusts in the Arapien Shale, Thaynes Formation, and Woodside Shale, related to Basin and Range extension. The Moroni Formation, a prominent Tertiary volcanic unit present throughout the Birdseye quadrangle, has been used to justify Eocene extension. Deformation with the formation was found to be present only along the Thistle Canyon normal fault, constraining movement along the fault to the Eocene and later. Dip and facies relationships present within the formation mainly are a result of paleotopography rather than extension. Several distinctive units were mapped within the formation, including lahar and fluvial deposits, as well as two different ash-flow tuffs. A depletion in nickel and chromium, an unusually ferroan composition, and distinctive Fe/Ti ratios suggest that the volcaniclastic rocks of the Moroni Formation are similar to volcanic rocks in the Slate Jack Canyon and Goshen quadrangles which lie about 35 km to the west. This implies that the ignimbrites and volcanic clasts in the Moroni Formation were sourced from the East Tintic volcanic center. It further implies that any mid-Tertiary extension between the East Tintic center and the Birdseye quadrangle did not create barriers to sedimentation and was limited in extent.