Chapter 27 Lead–zinc–silver deposits of Myanmar

Before 1960 the Pb–Zn–Ag mines in Myanmar were an important source of foreign exchange. Almost the entire output of lead and zinc came from the Bawdwin Mine which, before 1942, was ranked as the sixth-largest producer of lead in the world (Ministry of Mines 1970). In 1938 Myanmar’s output of refined lead, zinc concentrates and silver was 76 590 tons, 65 928 tons and 6 230 000 ounces, respectively. By 1986 output levels had fallen to 5948 tons of lead, 7393 tons of zinc and 576 000 ounces of silver. These figures represent a dramatic decline in production from the Bawdwin Mine and Namtu Processing Plant, which Soe Win (1994) has considered to be due to the failure to identify new reserves and inadequate investment in mine facilities. In the past, the Namtu–Bawdwin mining complex produced refined silver, lead and zinc concentrates, copper matte, nickel speiss and antimonial lead. The rich sulphide ore, previously mined underground at Bawdwin and treated at Namtu, yielded a lead concentrate averaging 51.3% Pb, 14.1% Zn and 1.16% Cu and a zinc concentrate averaging 26.1% Zn and 18.1% Pb. Currently, the oxide ore (‘halo ore’) from the open pit only is processed at Bawdwin, to yield a concentrate averaging 41.73% Pb, 9.03% Zn and 3.06%Cu. The lower ore grades present a problem for the old Namtu smelter, which was designed for processing sulphide ore and requires lead concentrates to have a minimum content of 57% Pb with 10–15% Zn and 1– 2%Cu. A new blast furnace has been installed capable of smelting lead concentrates as low as 40% Pb, with a tolerance of up to 8% Zn and 3% Cu and with a rated capacity of 50 tons/day (Than Htay 2002). In addition, a zinc fuming plant will produce zinc oxide from zinc slags. The zinc oxide will be transported via the Namtu–Lashio–Muse–Kunming Highway to a zinc smelter in Yunnan Province in China. In 1961 a United Nations Special Fund was requested to assist the Geological Survey in Myanmar to reverse the decline in lead production at Bawdwin, and to initiate exploration to identify additional resources. As a result of this initiative, during the succeeding years the main lead–zinc areas in Myanmar have been mapped at a scale of 1:24 000 and individual lead– zinc deposits at a scale of 1:2400. Many investigations were undertaken, including by the Canadian International Development Agency (CIDA) in 1973 and 1974, German Geological Mission (BGR) between 1974 and 1976 and Australian Mineral Development Laboratory (AMDEL) project between 1985 and 1987. Mining ventures following from these works included a production-sharing joint venture (PSC) from August 1996 between the ME-1 (Mining Enterprise No. 1 of the previous Ministry of Mines) and the Hawsaing Mining Co. in the Namlon–Namhwe area, Muse township and Kho Mone area, Kutkai township in the Shan State. Up until October 1999 only 293 tons of galena ore grading 20% Pb had been extracted (Than Htay 2000). In 2006 this PSC, including an additional area, was transferred to the Shwe Li Grade Mining Co. A total of 30 000 tons of ore@ 5.51% Pb, 1.03% Zn and 0.03%Cu had been estimated in two mining blocks (AK-Associates 2006). Mining Enterprise No. 1 also operates the Bawsaing lead– zinc mine on a PSC basis, producing both lead sulphide (galena) and lead carbonate (cerussite) ores and concentrates, and the Yadanatheingi Mine, which produces lead sulphide ores and concentrates. Sulphide ores and concentrates from both mines contain a certain quantity of silver. As at the Bawdwin Mine, production in both these mines is currently in decline. The Mawkmai (Mawkhi) and Longh Keng mines also have PSC contracts with ME-1 for zinc carbonate ore production; these operations have however been suspended at the time of writing.