Placing this history in a global context suggests that Hadean-Eoarchean crust formed in diachronous and spatially diverse environments that were both plume-like e. Geological Survey Professional Paper 1317, 37 p. Constraints from the surface geology and forward models indicate that the Tecolote fault has ~2. In all units, the evidence for metasomatism e. Comment Type: Geology Comment: Structure Most Upper Jurassic and older basement rocks of the northern Sierra Nevada were metamorphosed and deformed during the Jurassic-Cretaceous Nevadan Orogeny. Considered to be Late Triassic Carnian and Norian Stages based on fossil assemblage Vallier, 1977. MacBoyle 1919 reported an ore shoot that extended at least 400 feet down-dip and had a length on the vein of about 160 feet.
Deeply buried rocks became exposed in Miocene time when crustal extension resulted in the development of a regional detachment fault. Geological Survey Miscellaneous Geologic Investigations Map I-752, scale 1:48,000. Major minerals include 8-32 percent hornblende, 0-20 percent biotite, 0-5 percent epidote, 10-25 percent quartz, and 0-5 percent K-feldspar. Metamorphism and crustal evolution of the western United States. Pliocene-Pleistocene westward uplift of the Sierra Nevada caused existing drainages to carve deep river gorges. The base of this unit is poorly defined and appears gradational with rocks of the underlying Wild Sheep Creek Formation. Evidence for silicification and alkali exchange also occurs in greenschist and amphibolite facies units.
The oldest Tertiary units are basal Eocene auriferous gravels, preserved in basement paleochannels, and associated bench gravels deposited by the predecessors of the modern Yuba and American Rivers. Vein and host-rock mineralogy and whole-rock compositions demonstrate large-scale chemical redistribution, especially of Si and alkali elements. Comment Type: Geology Comment: Stratigraphy The northern Sierra Nevada basement complex has a history of both oceanic and continental margin tectonics recorded in sequences of oceanic, near-continental, and continental volcanism and sedimentation that have been divided into four lithotectonic belts; the Western Belt, Central Belt, Feather River Peridotite Belt, and Eastern Belt Day and others, 1988. A clean-up operation at the property was ordered by the U. A regional geologic map covering the area is the 1:250,000-scale Chico Quadrangle compiled by Saucedo and Wagner 1992. Scientific Investigations Report 2007—5012 U. Notes: Papers presented at the Rubey Colloquium, held at the University of California, Los Angeles, Jan.
Lu-Hf systematics of the 3. Robert Dawson, and Clay E. In the Middle Proterozoic St. Miller, 1988, Pb isotopic evidence for the formation of Proterozoic crust in the southwestern United States; pp. Synkinematic and postkinematic veins record fluid transport and metasomatism during prograde metamorphism and uplift. Outcrop of mylonite granite in the Cougar Creek intrusive complex, Upper Pittsburg Landing. Regional orogenesis occurred in the Late Jurassic and Early Cretaceous, which included intrusion of quartz diorite, diorite, and gabbro plutons and andesite dikes, folding, faulting and cleavage formation, and uplift and exhumation.
Geological Survey Open-File Report 02-406. Slightly deeper emplacement levels ~10. The record of subduction-zone mass transfer in the Catalina Schist is compatible with the record inferred for greater depths from geochemical and petrologic studies of arc magmatism. Geological Survey Open-File Report 91-109, scale 1:24,000. For example, at depth within the California Coast Ranges, high-P phases are currently being destroyed. Cordilleran metamorphic core complex, Funeral Mountains, California: Geology, v.
General stratigraphy of Wallowa terrane. Silica ± carbonate addition, consistent with the majority of veins observed, is likely the consequence of cooling ± decompression whereas sodic ± silica-undersaturated assemblages would be expected for rarer, but geologically plausible up-T fluid flow paths. Geological Survey Open-File Report 73-57, scale 1:24,000. Subsequent mining was accomplished through a vertical shaft that reached 1,750 feet in 1940 the current depth may be about 1,900 feet. Metamorphism and crustal evolution of the western United States. Crystalline Basement-Rock Studies Ague, J. Geological Survey Professional Paper 1439, p.
O, 1977, Rb-Sr and K-Ar geochronometry of Mesozoic granitic rocks and their Sr isotopic composition, Oregon , Washington , and Idaho : Geological Society of America Bulletin, v. Outcrop of massively-bedded volcaniclastics with characteristic red color in Doyle Creek Fm. Geological Survey, 2006, Annual water data report, 2005: U. Evidence exists for mass transfer, at both local and larger scales, via mechanical mixing, diffusional, and fluid-mediated transfer processes. Geological Survey Bulletin 1995-R, p. Jurassic Coon Hollow Formation Rocks of the Coon Hollow Formation lie in angular unconformity on older Triassic and Jurassic sequences. The deposit described here refers to that on the Blue Canyon quadrangle.
Schweickert, Charles Merguerian, and Nicholas L. These are Permian to Triassic fragments of oceanic island arcs, continental fringing arcs, and various subduction-related mélange that were amalgamated, and underwent Late Triassic metamorphism and Triassic-Jurassic sedimentation, before collision with the North American margin. The ore deposit consists of a quartz vein-dike complex that is emplaced in slate wallrock. Many of the intrusive granitic plutons of the Sierra Nevada were also part of this compressive episode. Through much of Phanerozoic time, subduction of Pacific Ocean plates beneath North America has resulted in the accretion of crustal fragments to the western margin of the continent.
The exposed rocks belong to a 13-km thick sedimentary sequence of Neoproterozoic to Mississippian age. The crust thickens from 34 to 37 km, and the lower crust increases in density 2. Rock assemblages include mostly mélange and blocks of island-arc crust of Devonian to Late Triassic age consisting of igneous and sedimentary rocks that have mostly been metamorphosed to greenschist grade. Comment Type: Commodity Comment: Ore Materials: Native gold, native silver, and auriferous sulfides pyrite, galena Comment Type: Commodity Comment: Gangue Materials: Quartz Comment Type: Deposit Comment: The deposit at the Herman Mine is typical of sulfide-bearing gold-quartz veins found in the Sierra Nevada metamorphic belt. Oxygen isotope relationships in plutonic igneous rocks of the Peninsular Ranges batholith, southern and Baja California.