View, in 1953, of Mount Holmes in the Henry Mountains with a core of diorite and upturned Jurassic beds along the flanks. Photo courtesy of USGS.
Cartoon showing an idealized laccolith intruding into sedimentary rocks.
After Gilbert’s work geologists then begin to describe other laccolithic centers in the Colorado Plateau.—the La Sal, Abajo, Carrizo, Ute Mountains, Navajo Mountain, Ophir-San Miguel-Klondike Ridge (Mutschler and others, 1997). All of these laccoliths have the igneous rocks exposed in the center with the exception of Navajo Mountain on the Utah-Arizona state line. At that locality, which is a single domed peak (10,388feet), the overlying sedimentary rocks have not been eroded away to expose the underlying igneous rocks.
Navajo Mountain with part of Lake Powell in the foreground. Public Domain photo courtesy of G. Thomas.
Tomichi Dome, a Tertiary laccolith located in Gunnison County about 20 miles east of Gunnison, Colorado. The dome is situated just south of Waunita Hot Springs and their water temperature may be related to the heat of this igneous intrusion.
Immediately to the south of the La Sal Mountains is Lisbon Valley containing the Lisbon Valley Anticline, a large salt anticline where the dipping beds are due to movement/solution of salt in the subsurface. Several of these salt structures are found in the greater Paradox Basin (an evaporate basin in Utah and Colorado near the Four Corners). Although the Valley has several tens of producing gas wells, the most active mineral commodity has been the numerous uranium mines (earliest report in 1913) and the area is undergoing uranium resurgence today. Target zones have been, and still are, the Cutler Formation/Group (Permian), the Moss Back Member of the Chinle Formation (Triassic), and the Salt Wash Member of the Morrison Formation (Jurassic) found along the flanks of the anticline.
Satellite image, oblique view, of Lisbon Valley looking northwest down the strike of the Lisbon Valley Anticline. Photo courtesy of Mesa Uranium Corporation.
Besides the abundance of azurite, other minerals collected from the claims and mines include: Wulfenite, Tyrolite, Tenorite, Tennantite, Sphalerite, Quartz, Pyrite, “psilomelane”, Olivenite, Malachite, Kaolinite, Goethite, Enargite, Djurleite, Diginite, Cuprite, Covellite, Cornwallite, Copper, Conichalcite, Clinoclase, Chrysocolla, Chalcopyrite, Chalcopyrite, Chalcophyllite, Chalcocite, and Calcite. Information in this paragraph came from an article by Arnold G. Hampson (1993).
Azurite crystal cluster bottom (3 x 2.6 cm) from Blue Grotto Prospect, La Sal/Lisbon Valley District. Photo courtesy of Kevin Conroy. Azurite blueberries, top. Photo courtesy of Blue Crystal Mine.