Rock Canyon near Provo, Utah County: A Geologic Field Laboratory

Rock Canyon near Provo, Utah is an ideal outdoor laboratory. The canyon has been known and explored for many years by scientists and students for its fascinating geology, biology, and botany. It is also a favorite location for rock climbers, hikers, and other outdoor enthusiasts. Facilities near the mouth of the canyon including parking, restrooms, a lecture amphitheater, and a covered pavilion with picnic tables provide an ideal location for visitors. Geology is the focal point of this beautiful canyon with a history that stretches from the Precambrian (about 700 million years ago) to the Wasatch fault and Lake Bonneville, which covered much of western Utah at its peak roughly 18,000 years ago. Excellent exposures of the rocks allow visitors to see features clearly and piece together the history of the canyon. The oldest rocks are glacial deposits of the Mineral Fork Tillite. The tillite is overlain by a thick section of Paleozoic rocks of Cambrian to Permian age, all of which have been deformed into an asymmetric, overturned fold formed during the Sevier orogeny, a roughly 140 to 50 million year old mountain building event. The upper reaches of the canyon were sculpted by glaciers during the Pleistocene and deposits of the Provo and Bonneville levels of Lake Bonneville are found at the mouth of the canyon, now cut by a recent alluvial fan. Also, at the mouth of the canyon are excellent exposures of features associated with the Wasatch fault.

Petrogenesis of Mesozoic, Peraluminous Granites in the Lamoille Canyon Area, Ruby Mountains, Nevada, USA

Two groups of closely associated, peraluminous, two-mica granitic gneiss were identified in the area. The older, sparsely distributed unit is equigranular (EG) with initial εNd ∼ − 8·8 and initial 87Sr/86Sr ∼0·7098. Its age is uncertain. The younger unit is Late Cretaceous (∼80 Ma), pegmatitic, and sillimanite-bearing (KPG), with εNd from −15·8 to −17·3 and initial 87Sr/86Sr from 0·7157 to 0·7198. The concentrations of Fe, Mg, Na, Ca, Sr, V, Zr, Zn and Hf are higher, and K, Rb and Th are lower in the EG. Major- and trace-element models indicate that the KPG was derived by muscovite dehydration melting (<35 km depth) of Neoproterozoic metapelitic rocks that are widespread in the eastern Great Basin. The models are broadly consistent with anatexis of crust tectonically thickened during the Sevier orogeny; no mantle mass or heat contribution was necessary. As such, this unit represents one crustal end-member of regional Late Cretaceous peraluminous granites. The EG was produced by biotite dehydration melting at greater depths, with garnet stable in the residue. The source of the EG was probably Paleoproterozoic metagraywacke. Because EG magmatism probably pre-dated Late Cretaceous crustal thickening, it required heat input from the mantle or from mantle-derived magma.