Preliminary Precambrian basement map of Colorado – A geologic interpretation of the aeromagnetic anomaly map

Cripple Creek and other alkaline-related gold deposits in the southern Rocky Mountains, USA: influence of regional tectonics

“…7A; Karlstrom and Humphreys 1998). Major blocks include the: (1) Archean craton, with protoliths and deformation dated between 2.5±3.5 Ga; (2) a 1.76±1.72-Ga juvenile arc terrane that constitutes the Yavapai Province (termed the Colorado Province in Colorado; Sims et al 2001); and (3) Mazatzal province, 1.7±1.6-Ga supracrustal rocks on unknown basement (Karlstrom and Bowring 1988). No major shear zone that might represent a discrete suture between the Yavapai and Mazatzal provinces has been identi®ed (Karlstrom and Humphreys 1998;Shaw and Karlstrom 1999).…”

“…Deformation during the Mesoproterozoic was of regional extent and expressed by superposed folds and abundant northeast-trending ductile shear zones (Hildenbrand et al 2000;Sims et al 2001). The northwest and southeast margins of the CMB are marked by major Mesoproterozoic structures (shear zones), and in southern Colorado, the southwestward projection of the Arkansas shear zone marks the southwestern limit of the CMB (Sims et al 2001).…”

“…The northwest and southeast margins of the CMB are marked by major Mesoproterozoic structures (shear zones), and in southern Colorado, the southwestward projection of the Arkansas shear zone marks the southwestern limit of the CMB (Sims et al 2001). In addition to known prominent shear zones in Colorado, the interpretation of magnetic data implies the presence of abundant northeast-trending shear zones throughout the entire southern Rocky Mountain region (Carol Finn, personal communication, 2001).…”

“…In addition to known prominent shear zones in Colorado, the interpretation of magnetic data implies the presence of abundant northeast-trending shear zones throughout the entire southern Rocky Mountain region (Carol Finn, personal communication, 2001). These shear zones were reactivated repeatedly in the Phanerozoic, as shown by mylonitic shear fabrics, late faulting and brittle fracturing, and by alignment of younger intrusions and structural and topographic features (Sims et al 2001). In addition to having been a major factor in localizing the CMB, several speci®c features can be shown to be aligned along major Mesoproterozoic shears.…”

“…Deformation during the Mesoproterozoic was of regional extent and expressed by abundant northeast-trending ductile shear zones (Sims et al 2001). In addition to having been a major factor in localizing the CMB, the Cripple Creek district is located on or near the projection of the Arkansas shear zone, and near the major northeastern boundary (marked by the northernmost edge of 1.65-Ga deformation) separating the Yavapai and Mazatzal provinces (Fig.…”