Research On Material Composition And Contamination Transmission Of Tailings In Tin-polymetallic Mine Of Gejiu

With the increasing beneficiation and smelting capacity and the environmental awareness of the public, it has been acknowledged that numerous mine tailings are characterized by re-exploitation and environmental pollution under the pressure of resource shortages and environmental degradation. The tin-exploitation history of the Tin-polymetallic Mine in Gejiu in Yunnan province dates back to 200 years ago. Not only being famous for its tin mines, Gejiu is also rich in 27 associated useful compositions. After beneficiation, these compositions are into tailings dams. There are altogether 31 tailing dams in Gejiu, accumulating 190 million tons of tailings and 390 thousand tons of tin. For such a huge volume of potential resources and contamination, it is essential for tailings to evaluate resource availability and contamination transmission to ecological environment.For more than 10 tailings dams in Gejiu area, Using multiple methods of artificial heavy minerals analysis, major elements testing, X-ray powder diffractometry and trace elements testing etc. , has comprehensive studied characteristics of the chemical components, the mineral components, contents and occurrence of valuable elements etc.; By means of follow- up investigation of sulfide ore beneficiation process and reelection process of the tailings, it has been analyzed that are dispersion and enrichment regularity of components of sulfide ore and tailings during the beneficiation process, and the feasibility of tailings exploitation; Discussing the characteristics of contamination transmission along the chain of rock(ore)- concentrator-water-tailings-soil-plant; these study have reached the following conclusions:(1) It is found that the major one is the type of low Si(1.41%-32.22%) content and high Fe(9.16%-66.38%) content;it is showed distribution characteristics of paragensis and associated component(W、Bi、Cu、Pb、Zn、Ga、Cd and so on), such as Yang Badi tailings dam showed that paragensis and associated component is dominated by (Cu3226×10-6-13242×10-6) and combinated by Cu, Bi, Pb, Zn and W; the REE in the tailings keeps the characteristics of the original mine; sulfide ore tailings takes on the distribution of V curve; the tailings of oxide ore and placer ore takes on a right-leaning curve.(2) Among crystalline mineral , the contents of mica(13.00%-48.80%) and fluorite(3.68%-17.6%) in some tailing dams appears relatively high, which have potential development value; In the tailings, occurrence of Cu, Sn, Pb, Ti, As, Fe, and Mn etc. have been found: the occurrence of W is scheelite; in the Tian Wan tailings dam, the content of W in some samples have reached the cutoff grade of tungsten depoit, and the elements of W and Sn could be exploitated. The occurrence of Bi is bismuthite, but the recovery bismuthite is hard to realize int he beneficiation at present.(3) The integrated workshop serve as the grinding-floating-dehydration process to reconcentrate the bulk flotation tailings in Ka Fang mine, and beneficiate S, Bi, and W-Sn concentrates. It further recycles the associated and paragensis components of cooper mines. In the industrial experiment of AXizhai tailing reconcentration, drawing from the“coarse flow”of the slime system, actual yield of Sn is 14.96%, paragensis and associated component of Cu、W、Bi、In、Pb、Zn has futher low actural yield. Cost input is 132077 yuan RMB, obtaining 7.425t tin concentrate with 7.47% Sn grade, it could be found that input outclass output.(4)In Axizhai tailings dam, it has been found that contents of Pb, As and Cu in rhizosphere far exceed national gradeⅡstandard on soil environmental quality of China (GB 15618-1995). The soil contamination index of Pb, As and Cu, which are all high-grade polluted, are 41-49, 158-173, 22-29 respectively. It also has been found that crops living in the tin tailings suffer the contamination of heavy metals. The contents of Pb, As and Cu in edible parts of patatos and peas are 152 and 38.5 times, 17.4 and 1.2 times, 2 and 0.95 times higher than the upper limit of national criteria for food sanitation in China. Therefore , the remediation of soil based on geochemical distribution characteristics of heavy metal in the tailings is demanded. And avoiding crops-planting in the tailings to reduce the diffusion of heavy metal contamination in food chain of mining area is necessary.