Gold Resources in Mongolia
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資源地質,66(2), 89 ~94, 2016 特集:モンゴルの鉱物資源 資源情報 Gold resources in Mongolia by S. JARGALAN* Abstract: Mongolia has considerable reserves and resources of gold in both placer and primary deposits. Gold has been mined in the country since ancient times, but recently it plays main role on country’s mining activity as well as economic development. Placer gold deposits are studied much and most of them are now under mining activity. Pri- mary gold deposits are studied weakly and only Boroo gold deposit is mined and other deposits are under development study level. Distribution of gold deposits and occurrences depends on mineralization type, but generally shows linear form along the independent geotectonic units, or bigger fault zone. The data of various geological reports of gold metallogenic and gold bearing belts of Mongolia suggest that there are 17 belts containing total amount of 2,100 tons of gold. 1. Introduction development study level. Geological background for the gold deposits is given in Mongolia has considerable reserves and resources of gold Jargalsaihan et al. (1996). Distribution of gold deposits and in both placer and primary deposits. Gold has been mined in occurrences depends on mineralization type, but generally the country since ancient times (Dejidmaa, 1996; Ochirbat, shows linear form along the independent geotectonic 1999), but recently it plays main role on country’s mining units, or bigger fault zone. According to general trend and activity as well as economic development. Placer gold distribution of gold deposits and occurrences, a number of deposits are studied much and most of them are now under potential gold metallogenic belts and gold-bearing belts are mining activity. Primary gold deposits are studied weakly and identified (Fig. 1). only Boroo gold deposit is mined and other deposits are under Gold mineralization took place, with varying intensity Fig. 1 Distribution of gold deposits in Mongolia (Mineral resources map of Mongolia, 2002). 2015 年 8 月 3 日受付,同年 10 月 26 日受理 * Mongolian University of Science and Technology, Ulaanbaatar, Mongolia (Corresponding author, E-mail: [email protected]) Key words: gold, vein, porphyry, placer, fault-controlled, Boroo mine 89 90 S. JARGALAN 資源地質: in Neo Proterozoic, Early Cambrian, Early Paleozoic, with powerful machines and latest technology quickly Middle Paleozoic and Late Paleozoic, Early Mesozoic, grew into a modern settlement having all the needed social Late Mesozoic and Cenozoic metallogenic periods. The infrastructure. By 1990, there were two joint ventures intensity of mineralization increases from older to younger operating gold. One is Mongolian-Soviet Joint Venture age. Gold mineralization is represented by three economic “Mongolsovtsvetmet” in the Tolgoit gold district of North types: veins, mineralized zones and placers. Hentii gold belt, and another one is Mongolian-Bulgarian Joint Venture in the Bayanhongor gold belt. From 1974 to 2. Gold mining history 1990 these two Joint Venture companies produced total of 9084.8 kg of gold, from which 4183.95 kg were exported Historical records and archaeological findings suggest to the USSR (former) and Bulgaria. that the gold mining on the territory of Mongolia began 1990-Recent: There was big change on society and since ancient times. Before the establishment of the politics of Mongolia, in early 90’s. The country has Great Mongolian Empire in 12th century, the territory of embarked to a market economy, which caused much Mongolia was inhabited by numerous tribes and there is economic difficulties. To recover this economic crisis an evidence that they were extracting gold for jewelers Mongolian government made a decision to develop mining and, in some instances, to sue as pay off if defeated in of gold and initiated“ Gold-2000” program. According tribal conflicts. The scientific survey of gold deposits, to this program gold operating and mining activity has prospecting and estimation of reserves as well as industrial abruptly increased, and once it was a lot of mining; now mining of gold began only after the People’s Revolution there are almost 130 companies, engaged on this business. in 1921. The history of gold exploitation in the territory of Mongolia can be divided into 4 main stages: 1901-1921; 3. Distribution of gold 1939-1954; 1974-1990 and 1990-Recent. 1901-1921:First stage of gold exploitation was conducted At present, in the territory of Mongolia a number of by Mongol-Or association on the Yeroo, Shariin Gol, potential gold metallogenic and gold-bearing belts are Haraa, Yamaat, Nyalkh, and Tolgoit river area at the North identified. The data of various geological reports of gold Khentei gold belt. At that time gold was mined mostly by metallogenic and gold bearing belts of Mongolia suggest foreign investors. In many cases, historical records reflect that there are 17 belts containing total amount of 2,100 facts of gold smuggling out of the country, therefore, it tons of gold. Seven of them are considered to be as high can be estimated that the total gold production was 9346.4 gold potential belts: North Khentii, Bayanhongor, Hangai, kg. In 1923, the Mongolian government issued the mining Jid, South Khentii, Ulziit, and Urgamal belts. Economic regulations which declared the land and underground deposits and potentially economic occurrences belong mineral resources should belong to people. In accordance mainly to the gold-sulfide-quartz and gold-quartz ore to this, all coal and gold mines were nationalized. formations. 1939-1954: Mongolian Government set up“ Mining and The Northern Hentii belt occupies the territory of Mineral Resources Trust” which is charged for the task of Tov, Selenge, and Bulgan prefecture, covering total of surveying and exploring natural resources. That time gold 400km long and 30-100 km wide area (Fig. 2). This belt is mining was limited and there was small mines at the Boroo limited by two deep faults: Bayangol fault on its northern deposit of North Hentii gold belt and Bayanhongor gold border and Yoroo on its southern border. This belt can belt. Mining of placer gold deposit at the Bayanhongor be divided into five districts in terms of gold deposits, area started in 1939 and gold production reached 22.3kg in content and geological setting specifics: Zaamar, Yoroo, 1939; 38 kg in 1940; and 40.1 kg in 1941. It continued for Boroo, Tsaidam and Tseel. Geologically this belt is studied 15 years and altogether 695.4 kg of gold was produced. In well and the most of gold mining activity is in progress the Boroo area during 1943-1954 gold mining operation there. The belt contains well-known big deposits like was carried out on auriferous quartz veins and the Narantolgoi, Sujigtei, Boroo and Bumbat (Fig.2). production was 20000 m3 ore and 300 kg of gold. The Bayanhongor belt is second biggest after the 1974-1990: Gold mining sector received a strong impulse North Hentii in terms of its potentiality, and locates at by setting up the first Mongolian-Soviet Union Joint the western part of central Mongolia, occupying territory Venture at the Tolgoit placer deposit. The mine equipped of Bayanhongor prefecture. It is 250 km in length and 66(2), 2016 Gold resources in Mongolia 91 Fig. 2 Geologic outline of the western Hentii belt. 60-90 km in width. This belt is characterized by wide The belt consists of wide spread rocks of volcanogeno- spread rocks of volcanogeno-sedimentary, sedimentary, sedimentary, sedimentary, and metamorphic rocks metamorphic and magmatic rocks. The belt can be divided intruded by Paleozoic and Mesozoic granitoids. This into 2 main zones: Baidrag river and Tuin river basins. belt can be divided into 4 gold bearing districts: Balj gol, Most prospected and operating deposits are located in the Terelj, Modot, and Janchivlan. Balj gol district is direct Baidrag river basin, Burd valley and Jargalant mountainous continuation of gold belt in Russia. Terelj district has range . several placer gold deposits and some of them are mined The Jid gold-bearing belt is located almost in the most in 1902-1910 years. Modot district is characterized by northern part of Mongolia near the boundary of Russia. auriferous quartz veins and sulfidized veinlets. This is The territory of this belt is occupied by deep forests and known for tin and tungsten mineralization. There are because of its improper road network the area was not several placer deposits in Janchivlan district and the mining surveyed properly. The belt is composed of variable rocks of activity has started since 1990. volcanogenic, sedimentary, metamorphic, intrusive and dike The Ulziit belt occupies territory of Omnogobi rocks. Gold mineralization occurs in quartz veins, skarns, and Dundgobi prefectures. The area of this belt is not greisens and sulfidized zones and they associated with silver, economically utilized and has limited reserves of water copper mineralization. There are some gold containing and fuel. The belt is composed of rocks of sedimentary, tungsten, molybdenum and lead zinc mineralizations. volcano-sedimentary and volcanogenic rocks. There are The South Hentii belt is located at the central part of some positive perspectives to discover primary ore of gold. Mongolia, and has considerably good economical and The Hangai belt is located at the Hangai mountainous geographical conditions comparing to the other gold belts. range, occupying the territory of Arhangai, Ovorhangai ad 92 S. JARGALAN 資源地質: Zavhan prefectures. There are some placer gold deposits in found in the deposit area. Seven large veins are 100-800 the valley of the mountainous range. Recently one big gold m in length, with average thickness ranging from 0.8 m to placer has been discovered in the valley of Khavtsgait, Olt, 3.2 m. These are identified down to 100-200m in depth. Zuun Sodot and Baruun Sodot. Average gold content ranges from 7 to 30 g/ton.