Sunday, March 31, 2013

The occurrence of tin-Tungsten mineral deposits

In Myanmar, the occurrence of tin-Tungsten mineral deposits can be traced along the length in the eastern half of the country form south to north. In Kayah State, a world famous huge deposit of tin-tungsten mineral occurs at Mawchi. The distribution of of the deposits are spread out around Mawchi. Closely packed occurrence of tin-tungsten mineral deposits are found on the both side of the Shan-Yamethin boundary in the hilly region where granite intrusive occur among the sediments.
Veins quartz, grasin and pegmatite containing minerals of tin and tungsten occurs along the length of Myanmar from south to north. In all these areas, the occurrences of these mineral veins are closely associated with the intrusions of coarse grained biotite granite which constitute apportion Ranges in the Indo-Malayan mountain system. The granite bosses are distributed in the eastern half of Myanmar starting from Kawthaung the southern most extremity, wide-spreading abundantly in Mergui and Tavoy districts, Mokpalin, Yamethin and Kyaukse districts. To the East the occurrence is traced in Kayah State and western part of Shan State adjunct to Pyinmana Township. The mineralization of Tin and Tungsten are found in or around the intrusions.  These minerals occur in veins of quartz, greisens and pegmatite that traverse the granite bodies and the adjoining sedimentary rocks. Sometimes the constitute accessory minerals of some portion of granite. The denudation of these primary deposits produces eluvial deposits near the sources and alluvial deposits at distance places from the sources.












1. Primary Deposits
                a. Quartz veins and stringers traversing the granite and sedimentaries.
                b. Decompossed pegmatites containing muscovite and tourmaline and
                c. as a sergregation in greisens.
2. Secondary Deposits
                d. Elluvial deposits on the slopes of hills near the primary deposits
                e. Stream deposits and alluvial flats
                f. Deposits along the lower courses of the river.
Greisen bands are found are formed at the contact of quartz vein and the granite. The mineral constituents of the veins are cassiterite, wolframite, and other sulphide minerals such as pyrites, chalcopyrite, arsenopyrite, molybdenite, stibnite and galenite. Generally, more mineralization is found in thinner veins, sometimes, huge quartz veins and pegmatite veins are practically barren. The portion of tin and wolfram varies with the locality. But generally, the content tin decreases and that of wolfram increases with the approach to the north.
 
The Mawchi Mine
 The Mawchi mine is located at Latitude 18º 49’ 24.8”N and Longitude 97º 9’ 22.1”E in the Balhke Destrict, Hparsaung Township, Kayah State, Myanmar. It is situated 95 miles from south of Loikaw in Kayah State, at elevation of 3000 feet. The mine is round about 19 miles from Hparsaung and is situated in the Hilly region. It lies on one inch topographic map sheet of 94 F/1. The existence of the occurrence is known since the last 100 years. Several technologist had estimated the reserves from 500,000 to 700,000 tons of ore with an average content of 1 to 2% tin and wolfram.
A coarse-grained biotite granite had intruded the sedimentary rocks which were metamorphosed and termed as Mawchi series. There are the argillites, sandstone and limestone. The intrusion of granite causes the tourmalinisation of granite itself the formation of quartz veins carrying wolfram and tin and tourmalinisation of adjoining country rocks. About 70 quartz veins containing ore minerals are known to occur in the area striking from north to south and dipping vertical. These veins ate from a few inches to 8.37 feet wide and occur both in granite and the adjoining sedimentaries.  Through, G.V Hobson assumed that the Mawchi limestone is a limit of the northern extension of the veins, U Kyaw Nyein has reported the northern continuation of these veins beyond the limestone in 1963. He also traced the considerable occurrence of alluvial cassiterite along the down stream of Kempyu village.
Mining is tributie system and underground methods. The average annual production in the post war ranges to about 30 tons concentrate of 60% tin. The mineralization could possibly occur at Sawalo and Khodogale on the north and Parsalo, Mosaki and Sawkokedo on the south. The property is being operated by by Mineral Development Corporation since January, 1963. At present, the mine production was continued by M.E.H.Company, Myanmar.






Produce From: Review of Tin and Tungsten  deposits of Myanmar. (U Tin Aye and U Kyaw Nyein