Uludağ volfram yatağındaki cevher ve mineral türlerinin tesbiti ve değerlendirme olanaklarının araştırılması

Abstract

ÖZET Bu çalışma, Uludağ volfram yatağında bulunan cevher ve mineral türlerinin tesbiti ve değerlendirme olanaklarını araştırmak için yapı lan incelemeler ve sonuçlarını içermektedir. Mineralojik incelemeler sonucunda, Uludağ cevherleri içinde, hammarit, gladit, tetradimit, bizmutit, beyerit, nabit altın, desklo zit, stannit, vulfenit ve beril mineralleri ile Hg3TeS2 bileşiminde yeni bir karışım mineralinin varlığı ilk kez bu araştırma sonucunda tesbit edilmiştir. Deneysel çalışmalar, volfram içerikleri ve mineralojik bileşim leri birbirlerinden farklı granitik cevher, skarn cevheri ve manye tit li skarn cevheri olmak üzere üç ayrı cevher numunesi üzerinde yürü tülmüştür. Cevherler üzerinde yapılan mikroskop incelemeleri ve tane sayımları sonucunda, mineral bileşimleri ve miktarları ile şelitin faz boyut dağılımları ve ekonomik serbestleşme boyutu saptanmıştır. Ayrıca, gravite yöntemleri ile ön zenginleştirme olanaklarını araş tırmak için değişik boyut gruplarında sarsıntılı masa deneyleri yapıl mıştır. Deneylerden üretilen ürünlerde manyetik ayırma, sülfür ve şelit flotasyonu ile bu üç yöntemin farklı kombinezonlarını içeren zenginleştirme deneyleri yapılmıştır. Sarsıntılı masa devresinden üretilen kaba konsantrenin sülfür flotasyonu ve manyetik ayırma deneyleri sonucunda, granitik cevherde, girenin % 0.11 'i oranında konsantrenin % 66.91 W03 içeriği, % 29.87 W0o kazanma verimi ile. skarn cevherinde, girenin % 0.19' u oranında konsantrenin % 70.05 W0- içeriği, % 27.24 W03 kazanma verimi ile man- yetitli skarn cevherinde.girenin % 0.19'u oranında konsantrenin ise % 68.44 W03 içeriği ve % 21.52 W0~ kazanma verimi ile üretilebileceği anlaşılmıştır. Değişik cevherlerden sarsıntılı masa ile elde edilen ürünler üzerinde yapılan sülfür flotasyonu, manyetik ayırma ve şelit flotas- yon deneyleri sonucunda granitik cevherden girenin % 0.57 'si oranın da şelit konsantresi % 25.20 W03 içeriği, % 58.30 W03 verimi ile skarn cevherinden girenin % 0.94' ü oranında şelit konsantresinin % 39.85 W03 içeriği, % 76.68 W03 kazanma verimi ile, manyetitli skarn cevherinden girenin % 1.85' i oranında şelit konsantresinin ise, % 22.78 W03 içeriği ve % 69.75 W03 kazanma verimi ile üretilebileceği anlaşılmıştır. X111

SUMMARY DETERMINATION OF ORE AND MINERAL TYPES OCCURRING IN ULUDA? TUNGSTEN ORE-BODY AND INVESTIGATIONS OF CONCENTRATION POSSIBILITIES FOR EVALUATION It is known that tungsten occurs in small proportion on the Earth Crust with a total reserve of 2.8 million tonnes of tungsten metal in ore deposits and distributed in 32 Countries in the world. 55.8 % of the tungsten reserve is possessed by U.S.S.R., People's Republic of China and North Korea i^e. Socialist Countries. Turkey has a reserve of 65 thousand tonnes of tungsten metal forming 2.3 % of the world reserve. 95 % of the tungsten reserve in our country occurs in Bursa-Uludağ deposit. In spite of increased field of industrial application in recent years, historical evolution indicates undulating market for tungsten. Owing to the economic difficulties prevailing in the world the consumption of tungsten has been recently reduced in many countries. In developed countries like U.S.A., the consumption of tungsten has been affected by the use of uranium instead of tungsten for the military purposes and the utilization of molybdenum and other heavy metals comparatively cheaper than tungsten in the manifacture of high speed steels. Considering the adverse factors above it is forecast that the demand for tungsten will be in the increase in the forth coming years due to the superior physical proporties of this metal. In the recent years, some radical changes have taken place in the mining of tungsten ore. Previously, the grade of exploited tungsten are bodies was in the range of 0.7-2 % W03. Today orebodies have lower grades with a range of 0.1 - 0.7 % W03 In the development stage for minning. Large-scale underground minning methods have been started to apply to wolfram minning as in the case of other underground mines with a result of increased mine mechanisation. With the new production trends W03 content of the ore is decreased with the increase of minning cost. In order to evercome increased minning cost the attention has been given to the cheaper ore-beneficiation methods like pro-concentration. The methods applied in the tungsten ore beneficiation depend on the structure of tungsten mineral as well as associated minerals. If tungsten mineral occurs in coarse grain size, gravity methods are the obrious choice as experienced in many concentration plants in the world owing to the high specific gravity of tungsten minerals. Due to the friable nature of tungsten minerals, the tungsten loss xivtakes place in the gravity concentration circuit because of the excessive fines produced in the conminution circuit. The tungsten concentrate obtained from the gravity circuit has lower grade because of the inclusion of other heavy minerals like pyrite, magnetite and sulphide minerals. Heavy minerals present in the tungsten concentrate can be separated individually or in groups by the application table-flotation, sulphide-flotation, magnetic separation, magnetic roasting-magnetic separation and electrostatic separation methods. In this way, the grade of tungsten concentrate is improved in addition to the production of other heavy minerals as by products. In some concentration plants, flotation is applied to gravity middling products and slimes in order to reduce tungsten loss. The direct flotation finds a wide field of application to low grade and fine grained scheelite ores which are treated in difficulty by gravity methods. Scheelite flotation concentrate has low W03 content because of the presence of calcite, dolomite, apatite and floorite having common calcium cation as scheelite. Their W03 contant can be improved by the application of slime tables or acid leaching depending on the minerological composition of tungsten concentrate. Nowadays APT is produced from a concentrate w ith 5-40 % WO- through chemical methods so that a high tungsten recovery has been maintained. The most important tungsten reserve in Turkey occurs in Uludağ scheelite deposit so that all the mineral content of the scheelite ore must be evaluated economically and the concentration plant must be operated in parallel with the latest technology to produce other mineral concentrate suitable for final utilization. Bearing this in mind, the aim of this thesis is to determine ore and mineral types occurring in Uludağ. Tungsten One-Body and to investigate concentration possibilities of scheelite ores with different mineral composition for evaluation. Uludağ tungsten deposit forms a big metal logenic provence having different ore types and a large number of mineral assemblages. Recent studies have indicated that the main mineralization is related to the skarn zone and there are five different mineralization with a little or extensive variation in mineral distribution in the mine. Minerological studies carried out on the representative samples taken in the ore zones of the mine have shown that new important mineral types in addition to ones forming minerals have not been encounterd. The determination of probable minerals in the scheelite concentrate is rather difficult, as the only small amount of concentrate can be obtained after concentrating very low grade scheelite ore. So that mineralogical determinations were executed on the selected samples, taken from different ore zones as well as middling and final products of concentration plant. X-ray diffraction and X-ray fluoresence methods were applied to determine elements and mineral composition of concentrate, middlings, tailings and slimes samples taken from Uludağ Concentration Plant. In addition, screen analyses and chemical analyses for tungsten bismuth, copper and zinc contents of these products of the concentrations plant were also carried out. Trace-element analysis xvwas also done on certain products of concentration plant. At the end of minera logical studies, the existence of the following minerals was determined in the final scheelite concentrate: Bismutite, beyerite, pcwellite, wulfenite, desclozite, monazite, native gold and chromite. Native gold is associated particulary in bismutite grains and scheelite concentrate rich in bismutite contains 8.5 g/t gold. Heavy medium separation, magnetic separation and flotation methods were applied to samples obtained from different ore zones and concentrates were studied by X-ray diffraction and microprobe analysis. At the end of mineralogical investigations hammarite, gladite, tetradymite, bismutite, beyerite, nativ gold, descloizite, stannite, wulfenite and beryllium minerals were determined in Uludağ Tungsten Ores.Basides a new mineral assemblage with a composition of Hg3TeS2 was determined first time through this research work. Laboratory test work was carried out on granitic, skarn and magnetitic skarn ores with different W03 content and mineralogical composition. The share of the reserve of these three different ores in the total reserve is 94.6 % with an average grade of 0.43 % WO.,. Thinsections were prepared from ore samples and grain size mesurement were made on these sections. The average volume-moment size for scheelite was 0.39 mm. in granitic ore, 0.58 mm. in skarn ore and 0.52 mm. in magnetitic skarn ore. The scheelite grain size distribution by volume was 25 % minus 0.3 mm. in granitic ore, 22 % minus 0.4 mm. in skarn ore and 20 % minus 0.4 mm. in magnetitic skarn ore. Ore samples reduced to minus 1 mm. and 0.5 mm. in size were subjected grain-counting by the use stereo-microscope and short wave ultra-violet rays in various size fractions. Liberation studies executed on various ores have shown that 75-80 % liberation taves place in 0.106-0.150 mm. in granitic and magnetitic skarn ores and 0.210-0.300 mm. in skarn ores. The ores reduced to minus 1 mm. and minus 0.5 mm. in size have free scheelite grains as in the following respectively 41.7 % and 59.7 % in granitic ore, 64.3 % and 82.4 % in skarn ore, 39.6 % and 63.5 % in magnetitic skarn. In order to study preconcentration by gravity method, cone crushed ore sample was reduced in size to minus 0.5 mm. instages by the use of a laboratory type roll crusher. The roll crushed product was screened to obtain 0.500+0.210 mm., 0.210+0.106 mm. and 0.106+0.025 mm. fractions after controlled desliming. The three fractions were treated on a standard w i If ley shaking table separately to obtain a concentrate and tailings. The tailings were fed to the shaking table once more to discard tailings with a lew W03 content. Tabling tests resulted in three products namely, concentrate, midd lings and tailings from each fraction. Microscopic studies on midd lings of 0.500+0.210 mm. fraction have shown that liberation was incomplete, consequently the middlings were ground to minus 0.210 mm. and jointed with middlings of the other two fractions. These midd lings were treated on the shaking table twice to obtain concentrate, middlings and tailings. This concentrate was added to the concent rate of the run of mine ore and treated twice on the shaking table xvito obtain two middlings and a concentrate, which was cleaned twice by tabling to produce final concentrate and middlings. Tabling tests on three ore types gave the following results: A concentrate with grades of 35.14 % WO, and 1.285 % Bi and recoveries of 30.16 % and 22.52 % respectively, middlings having grades of 0.51 % WO, and 0.018%Bi and recoveries of 37.70 % and 26.97 % and tailings with grades of 0.07 % W03 and 0.006 % Bi and recoveries of 18.61 % and 32.56 % were obtained from granitic ore. Scarn ore resulted in a concentrate having grades of 55.54 % W03 and 2.334 % Bi and recoveries of 27.21 % and 33.27 % respectively middlings having grades of 1.36 % W0, and 0.035 % Bi and recoveries of 45.35 % and 34.23 % and tailings having grades of 0.11 % W0, and 0.004 % Bi and recoveries of 15.52 % and 16.42 %. A concentrate with grades of 9.10 % W03 and 0.36 % Bi and recoveries of 22.50 % and 30.06 % respectively; middlings with grades of 1.73 % WO, and 0.328 % Bi and recoveries of 49.08 % and 34.85 % and tailings with grades of 0.14 % WO, and 0.05 % Bi and 15 % and 18.09 % Bi were obtained from magnetic skarn ore. In order to improve the grades of table concentrates, flotation and magnetic separation were applied resulting in products with a grade of 66.91 % W0, and a recovery of 29.87 % from granitic ore; a grade of 70.09 % W0X and a recovery of 27.24 % from skarn ore and a grade of 68.44 % W0X and a recovery of 21.52 % from magnetitic skarn ore. Slimes and table-middlings ground to minus 0.106 mm. were subjected to sulphide flotation followed by scheelite flotation where 0MC 377 of Henkel Co. was used as scheelite collector. The results of flotation experiments have shown that it is possible to obtain a concentrate with a grade of 15.23 % W0, and a recovery of 28.43 % from skarn ore a grade of 32.20 % W0, and a recovery of 49.44 %. Flotation tests of magnetitic skarn ore was carried out on the sample obtained by mixing middlings, tailings and slimes. gave a concentrate with a grade of 11.3 % W0, and recovery of 16.27 %. Flotation middlings can be recirculated to improve the recovery slightly. Overall concentration test results can be expressed as in the following: Final concentrate with a grade of 25.20 % W0, and a recovery of 58.3 % can be produced from granitic ore and discarded tailings resulted in a grade of 0.08 % W0, and a loss of 28.50 %. Skarn ore xviigave a final concentrate with a grade of 39.85 % W03 and a recovery of 76.68 % and discarded tailings contained a grade of 0.1 % WOg and a loss of 18.50 %. Final concentrate of magnetitic skarn ore had a grade of 22.78 % W03 and a recovery of 69.75 % and discarded tailings gave a grade of 0.06 % W03 and a loss of 5.83 %. The results obtained on the completion of gravity concentration experiments carried out with different ore-types have indicated that differences in scheelite particle size distributions and variable mineralogical compositions are closely related to concentration criteria. It is extremely difficult to apply selective mining in Uludağ Tungsten Mine for uniform ore production due to the present underground mining methods applied in to-day's conditions. When the mine production is done in the present panels underground according to the production schedule, it would be extremely difficult to supply the Concentration Plant with the uniform ore-feed. When Concentration Plant is not fed uniformly, the performance of the Plant is affected adversely. ît is observed during studies that tungsten losses on a large scale occur in slimes of very fine sizes produced in the process of comminution of the ore. In order to improve W03 recovery in the Plant, middlings of gravity circuit together witn the slimes must be treated by flotation to maintain up to date beneficiation practice in Uludağ. xvm