Carlin Unconformity
Encyclopedia
The Carlin Unconformity or Carlin Trend is a geologic feature in northeastern Nevada
which represents a period of erosion or non-deposition likely associated with a collision between a tectonic
crustal block called a terrane
and the North American Plate
. The collision occurred during the Mississippian Period, about 350 million years B.P. The collision is associated with the Antler Orogeny
.
The collision induced higher crustal temperatures and pressures which produced numerous hot springs along the suture zone. Several episodes of subsurface magmatism are known to have occurred subsequent to the collision, associated with tectonic forces affecting the entire Basin and Range
. During each of these episodes, and particularly during the Eocene
epoch, hot springs brought dissolved minerals toward the surface, precipitating them out along fissures. Among these minerals were gold
and silver.
The Carlin Gold trend is one of the world's richest gold mining districts. It is a belt of gold deposits, primarily in Paleozoic
limy sediments, that is about 5 miles wide and 40 miles long, extending in a north-northwest direction through the town of Carlin, Nevada
. Gold was first discovered in the area in the 1870s, but there was very little production until 1909, and only about 22,000 ounces was produced through 1964. By 2008, mines in the Carlin Trend had produced over 70 million ounces of gold, worth around US$85 billion at 2010 prices.
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
which represents a period of erosion or non-deposition likely associated with a collision between a tectonic
Tectonics
Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures.Tectonics is concerned with the orogenies and tectonic development of...
crustal block called a terrane
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
and the North American Plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...
. The collision occurred during the Mississippian Period, about 350 million years B.P. The collision is associated with the Antler Orogeny
Antler orogeny
The Antler orogeny is a mountain-building episode that is named for Antler Peak, at Battle Mountain, Nevada. The orogeny extensively deformed Paleozoic rocks of the Great Basin in Nevada and western Utah during Late Devonian and Early Mississippian time...
.
The collision induced higher crustal temperatures and pressures which produced numerous hot springs along the suture zone. Several episodes of subsurface magmatism are known to have occurred subsequent to the collision, associated with tectonic forces affecting the entire Basin and Range
Basin and Range
The Basin and Range Province is a vast physiographic region defined by a unique topographic expression. Basin and Range topography is characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins...
. During each of these episodes, and particularly during the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
epoch, hot springs brought dissolved minerals toward the surface, precipitating them out along fissures. Among these minerals were gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
and silver.
The Carlin Gold trend is one of the world's richest gold mining districts. It is a belt of gold deposits, primarily in Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
limy sediments, that is about 5 miles wide and 40 miles long, extending in a north-northwest direction through the town of Carlin, Nevada
Carlin, Nevada
Carlin is a city located near the western border of Elko County in northeast Nevada, west of the city of Elko. It is part of the Elko Micropolitan Statistical Area. Carlin sits along Interstate 80 at an elevation of approximately . As of the 2000 census, its population was 2,161...
. Gold was first discovered in the area in the 1870s, but there was very little production until 1909, and only about 22,000 ounces was produced through 1964. By 2008, mines in the Carlin Trend had produced over 70 million ounces of gold, worth around US$85 billion at 2010 prices.
See also
- Carlin-type gold deposit
- John LivermoreJohn LivermoreJohn Sealy Livermore is an American geologist who has discovered or helped to discover four major gold deposits in northern Nevada. The Carlin deposit, from which the current Nevada gold-mining industry grew, was his first discovery. In 1961, after reading an article by Ralph J...
- Ralph J. RobertsRalph J. Roberts (geologist)Ralph J. Roberts was an American geologist and research scientist with the USGS. He is credited with the discovery of the Carlin and Battle Mountain Gold Belts, which make up the richest gold-mining region in Nevada as well as the United States....
- Gold mining in NevadaGold mining in NevadaGold mining in Nevada, a state of the United States, is a major industry, and one of the largest sources of gold in the world. Nevada currently mines 79% of all the gold in the United States, which is equivalent to in 2009. Total gold production from Nevada recorded from 1835 to 2008 totals ,...