Main Lode, Tyuya-Muyun Cu-V-U deposit, Tyuya-Muyun Massif, Aravan District, Osh Region, Kyrgyzstani

Regional Level Types
Main Lode	Vein
Tyuya-Muyun Cu-V-U deposit	Deposit
Tyuya-Muyun Massif	Massif
Aravan District	District
Osh Region	Region
Kyrgyzstan	Country

The Maine Lode, also known as Glavanaya vein or Fersman Cave (the largest cave in the Tyuya-Muyun massif) consists of a vertically extensive (>220 m) complex cave channel. The cavity was originally filled with a suite of epigenic cave sediments and flowstone as well as a suite of hypogene gangue (calcite, baryte) and ore (U, V, and Cu) minerals. Four new minerals: tangeite, turanite, tyuyamunite, and 'alaite' (a hydrated vanadium oxide not yet fully characterised) were discovered here in 1909-1926. Ores contained also various amounts of malachite, descloizite, vanadinite, carnotite, and uraninite. Most of the U minerals are the result of oxidation of the primary ore composed of colloidal pitchblende (uraninite).

The site was probably worked in the Bronze Age, since a stone hammer (of diorite) was found in the old workings; later, it was exploited for copper by the Chinese, as early as the second century BC to the second century AD. Uranium was discovered here in 1899 and mining operation begun in 1904, primarily aimed at recovering radium. Between the years 1904 and 1914 the mine yielded ca. 1,000 tons of ore, from 700 tons of which 2-3 grams of metallic radium was recovered. Operations were interrupted by World War I in 1914, the Russian Revolution of 1917, and the ensuing period of turmoil. The Main Lode was mined again for Ra in 1924–1928. In 1928, water inflow into the "mine cave" disrupted mining activities. The final exploitation period, which lasted from 1948 until 1954, included the construction of a 2200-m-long drainage adit from the River Aravan to the Main Lode. As its mineral content was removed, this complex karstic ore body became a cave again. During mining, in addition to the 219.4-m-deep vertical main shaft, numerous exploratory galleries, drifts and winzes were excavated at different levels, so that the now abandoned Tyuya-Muyun mine is presently a complex three-dimensional arrangement of natural and artificial underground passages with total length of ca. 4580 m.

The "mine cave", which originally was almost completely filled with gangue and ore minerals, starts with the Central pipe (a vertical hole located at an elevation of 1296 m, level 0.0 m), the West crawlway (-1.5 m) and the Chinese entrance (-5.2 m). These openings lead to the upper part of two subparallel shafts measuring ca. 35 m in depth and 3-8 m in diametre. Due to the abundance on the walls of tyuyamunite (prior to modern mining), this part of the cave was named the Yellow Cave (Zheltaya Cave; Жёлтая пещера). It was exploited as a copper deposit by the Chinese as early as the second century BC (and probably already worked in the Bronze Age). Going more deeply into the cave, carbonates and ores evenly filled the tubular cavity; only in separate sectors of the cave, the wall of the cavity diverged, leaving an open space in the axial part of the cave. As the extraction work proceeded, an enlarged sector, named the Green Cave (Zelenaya Cave; Зелёная пещера) because of the abundance of turanite, tangeite and malachite, was discovered. At level -39 m the Yellow and Green caves join together and turn into a steeply inclined shaft having a diameter of 3-7 m. Another enlarged sector was discovered at level -80 m. It looked as a real cave, because of the absence of the typical carbonate-ore filling, and was named the White Cave [Белая пещера] (due to the abundance of snow-white fibrous gypsum crystals on the walls). The gypsum substratum was a thin calcite layer, which coated a layer of crystalline zoned baryte up to 1.5 m thick. The enlarged part, located below level -125 m and rich in uranium ore, was named Fersman Cave [пещерой академика Ферсмана; пещера Ферсмана] by the personnel of the uranium mine. Later, this name was used to designate the entire system of natural and artificial passages inside the "mine cave". At -147 m the cave branches into two tubes: one going to the north and terminated, after 25 m, by a vertical pit ending at level -184 m (North stope; Северный забой); the other to the south up to level -220 m (South stope; Южный забой), where ore mining was stopped due to heavy water inflow. Drilling at the bottom of the South stope showed the depth continuity of the karst ore body to at least 100 m below this level.

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