David A. John, 1998. "Day One Road Log: Mid-Tertiary Igneous Rocks and Mineral Deposits in the Central Wasatch Mountains, Utah", Geology and Ore Deposits of the Oquirrh and Wasatch Mountains, Utah, David A. John, Geoffrey H. Ballantyne
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Today's field trip examines late Eocene and Oligocene granitoid intrusions, cogenetic volcanic rocks (Keetley Volcanics), and associated hydrothermally altered and mineralized rocks in the central Wasatch Mountains. Because of late Cenozoic tilting related to Basin and Range extension, a continuum of mid-Tertiary paleodepths is exposed that ranges from about 11 km on the west side of the Little Cottonwood stock to the actual paleosurface on the east side of the range (Fig. 1; John, 1989a). Consequently, we will see a wide variety of textures and styles of emplacement in the intrusive rocks, and a correspondingly wide variety of hydrothermal...
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Geology and Ore Deposits of the Oquirrh and Wasatch Mountains, Utah
The Oquirrh and Wasatch Mountains lie at the eastern edge of the Basin and Range province in north-central Utah. North-central Utah has had a long and complex deformational history, including two compressional events and two extensional events in the Mesozoic and Cenozoic, respectively. The ranges host three major mining districts largely containing pluton-related mineralization. The districts are aligned along the east-west trending Uinta-Cortez axis that is a manifestation of an Archean-Proterozoic suture. The axis is the fundamental control on pluton emplacement and related metallogeny. The major intrusions in the districts are Paleogene in age and were emplaced in an extensional stress regime with a NW-SE least principal stress direction. Within the mining districts mineralization is controlled by Mesozoic compressional structures and NE-striking faults and fractures.
The Wasatch and Oquirrh Mountains lie in north-central Utah at the eastern edge of the Great Basin. The mountain ranges host three major mining districts, including the world-class Bingham mining district (Fig. 1 ). Because of the location of the districts, this discussion will only focus on the Oquirrh and the central Wasatch Mountains. North-central-Btah has had a long and complex structural history that has direct bearing on the distributionof plutonic rocks and the metallogenic evolution of the two mountain ranges. This paper will briefly review the structural history of the region followed by a discussion of the structural controls on plutonism and metallogeny.
The structural control of plutonism and metallogeny in north-central Utah has been recognized for more than 7 5 years. Most of the previous work has focused on the importance of the Uinta trend, an east-west trend of intrusions and structures in the eastern Great Basin, which was first noted by Butler et al. (1920). Stokes (1968) statistically examined the relationship between fault trends and mineralization in the eastern Great Basin, and noted that mineralization is dominated by east and northeast trends. Erickson (1974) summarized the evidence for the Uinta trend and emphasized its economic importance. Within the Wasatch and Oquirrh Mountains, several studies have addressed the structural control in the respective mining districts and will be cited below.
The southern margin of the Archean Wyoming Province strikes east-west through north-central Utah. The edge of the Archean craton is represented by thesouthernmost exposure of the Farmington Canyon Complex in the central Wasatch Mountains (Bryant, 1988). The suture between the Archean Wyoming Province to the north and the Proterozoic Yavapai Province