The Coles Hill uranium deposit is located in

Pittsylvania County, Virginia Pittsylvania County is a county located in the Commonwealth of Virginia, United States. At the 2020 census, the population was 60,501. The county seat is Chatham. Pittsylvania County is included in the Danville, VA Micropolitan Statistical ...

, in the Smith River

allochthon upright=1.6, Schematic overview of a thrust system. The hanging wall block is (when it has reasonable proportions) called a window. A klippe is a solitary outcrop of the nappe in the middle of autochthonous material. An allochthon, or an alloc ...

of southern Virginia. The deposit is located east of US Highway 29 between the towns of Chatham and Gretna, Virginia, divided into a north and south ore body. A part of Virginia's Western Piedmont Province, the uranium deposit is bounded by the Chatham fault to the east, where it borders the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

Danville basin. Uranium minerals are found in the footwall of the Chatham fault, in healed fractures where

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

crystallized from high-temperature hydrothermal water in the Leatherwood

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

mylonite Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a ...

. The site was discovered during uranium prospecting in the 1970s, inspired by the Ambrosia Lake deposit in Canada, with exploration led by the Marline Oil Corporation. Uranium is found within a structural trap, surrounded by

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...

gneiss Gneiss (pronounced ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. This rock is formed under p ...

, with staining from

hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...

overlying the Fork Mountain

schist Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced ''schistosity'' (named for the rock). This means that the rock is composed of mineral grains easily seen with a l ...

. Hematite staining on the ground surface is related to the weathering of the Fork Mountain schist. The exact origin of this uranium deposit is unclear. One model suggests that uranium was dissolved and "mobilized" from the neighboring Triassic basin by rainwater, while a different interpretation suggests mineralization occurred because of hydrothermal fluids flowing through the rock during the emplacement and cooling of the Leatherwood granite.

References

{{Geology of the United States by political division Geology of Virginia

Virginia Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...

See also

References