Chalaka Boron Deposit in Ge'gyai County(3)
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发布时间：2022-11-16 15:22
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时间：2024-12-02 16:15
The Chalaka boron deposit is administered by the Yagra Village of Ge＇-gyai County，Ali Prefecture.There is a simply-built highway on the east side of Chalaka.It runs 1 0 km southwards to the Yagra Village，70 km northwards to Xungba.Then linking with the Heihe（Nagqu）-Ali highway it goes 1500 km further eastwards to the Amdo County.The transportation is inconvenient.
The Chalaka deposit is overall a NNW-elongated egg-shaped semi-arid saline lake，covering an area of about 6 square kilometers.The west and south parts are the mirabilite cover；the northeast part is water-accumulated.The water area is 3.1 3 square kilometers at a depth ranging 0.05-0.8 m in rainy season，while in dry season it is only 1.17 square kilometers.The alti-tude of the lake area is 4570 m.
The lacustrine facies sediments can be classified into three layers.The up-per layer consisting of gray borax mirabilite，lenticulated，0.1 2-4.25 m in thickness，is the principal boron-bearing orebed.The middle layer is made up of black silt，horizontally bedded，0.58-7.2 m thick，and steadily distributed；of which the upper part is made up of borax carbonaceous clay band with minor small saccharoidal borax crystals and is traditionally the principal horizon for boron exploitation，with boron decreasing downward.The lowermost layer is composed of gray-black lake-facies pebbly sandstone over 0.25 m thick.The commercial reserves of solid boron amounted to 700000 tons and the temporar-ily unusablereserves were 200000 tons.Besides boron，the lake water con-tains also 515 mg/L lithium chloride，2867 mg/L potassium chloride and 0.45 mg/L iodine.
In 1956，the No.841 Geological Party of the TBG，based on the report by local people，concted a two-day reconnaissance survey in Chalaka and reached at a conclusion that the area was worth further investigation.
In 1961，the Tibet Comprehensive Expedition Team under the CAS led by Leng Bing came to Tibet.Zheng Mianping，a member of the party asssigned by the MGMR，went on a reconnaissance survey with some of his colleagues.Altogether 6 shallow boreholes and 7 shallow wells were operated and the study of mineralogical composition was done in much detail.The reserves of boron they submitted amounted to 62000 tons.In September the same year Liu Tingrong，Wang Yongkun and others with the No.1 Reconnaissance Sub-party of the Zangbei Geological Party of the TBG carried out a more standard-ized reconnaissance survey；the Surveying Party of the TBG concted topo-graphic and engineering survey.A total of 46 shallow boreholes of 233.5 m were drilled and the orebody was controlled with shallow pits.A 1 5.5 km long section of Quaternary geology was mapped，and the geological sketch map of Quaternary and the Quaternary topographic-geologic map of the lake area were compiled.In May 1963 the“Report of reconnaissance survey of the Chalaka boron deposit”was submitted.In 1975 the party performed a certain amount of work in the area which upgraded the control of the deposit.The economic re-serves verified by the Geological Bureau amounted to 762300 tons which indi-cate a medium-size deposit；the temporally subeconomic ones were 141100 tons.
In 1985 the Ali Administrative Office of Tibet organized the villagers to exploit the Chalaka boron deposit by local methods.In a two years＇time about 2000 tons of boron crystals were mined.
