Home
Register
Login
Album list
Last uploads
Last comments
Most viewed
Top rated
By date
My Favorites
Search
Monument Valley Upgrader (Monument 2 Mine)
Location: The former Monument Valley upgrader site is on Navajo Nation land in Cane Valley, Apache County, Arizona, about 20 miles south of Mexican Hat, San Juan County, Utah.
Background: The Monument Valley uranium district is in the southern part of the Monument Upwarp, a north-trending, broad asymmetrical anticline (fold structure) in northeastern Arizona and southeastern Utah. The Upwarp's thick cover of fluvial and eolian strata has been deeply eroded to expose principally sandstone and shale of Permian, Triassic, and Jurassic age. Nearly all known uranium deposits in the district occur in fluviatile conglomerate and sandstone beds of the Shinarump Member, the basal unit of the Chinle Formation (Late Triassic age). The Shinarump was deposited on the Moenkopi Formation (Early and Middle(?) Triassic age). Throughout the southeastern Utah region, the two rock units are separated by the Middle Triassic unconformity. The individual paleostream channels eroded channels into the underlying Moenkopi beds can be up to several hundred feet wide and more than 100 feet deep. These channels are filled with coarse sediments that locally host uranium deposits, typically in "trashy," cross-bedded, conglomeratic, clayey sandstone with considerable fossilized and carbonized wood.
Uranium ore occurs in the Shinarump scattered at various levels. Ore is also present locally in the upper few feet of the Moenkopi and De Chelly Member (Early Permian) beds where either unit and the Shinarump ore-bearing channel strata are in contact. Ore bodies are generally elongate, lenticular, and follow the trend of the hosting paleochannel strata. The ore occurs mostly in smaller channels but is not known to completely fill any channel. Most ore bodies are about 100 by 50 feet horizontally and average about 5 feet in thickness, though some larger deposits range up to 20 feet in thickness. Uranium mineralization tends to be concentrated in high grade pockets associated with carbonized woody trash, the whole being surrounded by sub-ore grade to sparsely mineralized rock. The uranium-bearing ores in the Shinarump beds are described, based on metal content, as either vanadium-uranium ore, copper-uranium ore, or uranium ore containing minor amounts of vanadium and copper.
In the Monument Valley district, ore production from individual mines ranged from a few tons of ore to near 800,000 tons. For the district, the median production for 54 mines was about 25,300 tons of ore that averaged 0.32 percent U3O8 and 0.91 percent V2O5. The Monument 2 mine was a large vanadium-uranium ore deposit hosted by Shinarump strata that filled a large and deep erosional swale in the unconformity surface atop the Moenkopi Formation. At the mine, Shinarump channel beds are several hundred feet wide and extend for about 1.3 miles along the axis of the swale. A small amount of ore was reportedly mined for vanadium in 1943 from the Monument 2 mineral claim, first staked in 1942. Large-scale mining of the deposit for uranium ore was begun in early 1948 by Vanadium Corporation of America (VCA). In the mid 1950s, underground methods were used to mine pods of higher grade ore through multiple (about 15) short adits or shafts. Overall underground ore production averaged 125 tons of ore per day (TPD). Lower grade and higher grade ores were blended to maintain a minimum-grade, direct-shipping ore containing about 0.30 percent U3O8 and 1.40 percent V2O5. In this phase of mining the Monument 2 deposit, the ore was shipped 185 miles to the company's mill at Durango, Colorado.
In June 1954, stripping operations were begun for openpit mining at the south end of the Monument 2 deposit. Both the underground mines and openpit mine continued to produce until the summer of 1957, when underground mining ended. Openpit operations were continued until the mine was closed in June 1964. The open-pit mine average production rate was about 750 TPD. In its early years, the openpit yielded both higher grade ore along with considerable low grade ore. Later, the openpit yielded only low grade ore. Mined high grade ore was shipped directly to a mill, while low grade ore was stockpiled onsite for later processing to concentrate the uranium and vanadium values. An upgrader plant (1955-1964), a batch-leach plant (1964-1967), and a heap-leaching operation (1966-1967)were used to raise the mine-run, low grade ore to a shipping grade product. All U3O8 recovered from milling of the final products obtained from the upgrader, batch-leach, and heap-leaching plants was purchased by the U.S. Atomic Energy Commission (AEC).
Background: The Monument Valley uranium district is in the southern part of the Monument Upwarp, a north-trending, broad asymmetrical anticline (fold structure) in northeastern Arizona and southeastern Utah. The Upwarp's thick cover of fluvial and eolian strata has been deeply eroded to expose principally sandstone and shale of Permian, Triassic, and Jurassic age. Nearly all known uranium deposits in the district occur in fluviatile conglomerate and sandstone beds of the Shinarump Member, the basal unit of the Chinle Formation (Late Triassic age). The Shinarump was deposited on the Moenkopi Formation (Early and Middle(?) Triassic age). Throughout the southeastern Utah region, the two rock units are separated by the Middle Triassic unconformity. The individual paleostream channels eroded channels into the underlying Moenkopi beds can be up to several hundred feet wide and more than 100 feet deep. These channels are filled with coarse sediments that locally host uranium deposits, typically in "trashy," cross-bedded, conglomeratic, clayey sandstone with considerable fossilized and carbonized wood.
Uranium ore occurs in the Shinarump scattered at various levels. Ore is also present locally in the upper few feet of the Moenkopi and De Chelly Member (Early Permian) beds where either unit and the Shinarump ore-bearing channel strata are in contact. Ore bodies are generally elongate, lenticular, and follow the trend of the hosting paleochannel strata. The ore occurs mostly in smaller channels but is not known to completely fill any channel. Most ore bodies are about 100 by 50 feet horizontally and average about 5 feet in thickness, though some larger deposits range up to 20 feet in thickness. Uranium mineralization tends to be concentrated in high grade pockets associated with carbonized woody trash, the whole being surrounded by sub-ore grade to sparsely mineralized rock. The uranium-bearing ores in the Shinarump beds are described, based on metal content, as either vanadium-uranium ore, copper-uranium ore, or uranium ore containing minor amounts of vanadium and copper.
In the Monument Valley district, ore production from individual mines ranged from a few tons of ore to near 800,000 tons. For the district, the median production for 54 mines was about 25,300 tons of ore that averaged 0.32 percent U3O8 and 0.91 percent V2O5. The Monument 2 mine was a large vanadium-uranium ore deposit hosted by Shinarump strata that filled a large and deep erosional swale in the unconformity surface atop the Moenkopi Formation. At the mine, Shinarump channel beds are several hundred feet wide and extend for about 1.3 miles along the axis of the swale. A small amount of ore was reportedly mined for vanadium in 1943 from the Monument 2 mineral claim, first staked in 1942. Large-scale mining of the deposit for uranium ore was begun in early 1948 by Vanadium Corporation of America (VCA). In the mid 1950s, underground methods were used to mine pods of higher grade ore through multiple (about 15) short adits or shafts. Overall underground ore production averaged 125 tons of ore per day (TPD). Lower grade and higher grade ores were blended to maintain a minimum-grade, direct-shipping ore containing about 0.30 percent U3O8 and 1.40 percent V2O5. In this phase of mining the Monument 2 deposit, the ore was shipped 185 miles to the company's mill at Durango, Colorado.
In June 1954, stripping operations were begun for openpit mining at the south end of the Monument 2 deposit. Both the underground mines and openpit mine continued to produce until the summer of 1957, when underground mining ended. Openpit operations were continued until the mine was closed in June 1964. The open-pit mine average production rate was about 750 TPD. In its early years, the openpit yielded both higher grade ore along with considerable low grade ore. Later, the openpit yielded only low grade ore. Mined high grade ore was shipped directly to a mill, while low grade ore was stockpiled onsite for later processing to concentrate the uranium and vanadium values. An upgrader plant (1955-1964), a batch-leach plant (1964-1967), and a heap-leaching operation (1966-1967)were used to raise the mine-run, low grade ore to a shipping grade product. All U3O8 recovered from milling of the final products obtained from the upgrader, batch-leach, and heap-leaching plants was purchased by the U.S. Atomic Energy Commission (AEC).
1 files on 1 page(s)