Tavşanlı (yaylacık) Ofiyolitindeki Manyezit Cevherlerinin Oluşumu Ve Ekonomisi

Abstract

Türkiye'deki ofiyolitlerin benzer bir örneğini teşkil eden Tavşanlı (Yaylacık) ofiyoliti içindeki serpantinitlere bağlı olarak oluşmuş manyezit cevherlerinin kökenini ve oluşum sartlannın.incelendiği bu çalışma giriş te dahil olmak üzere yedi bölümden oluşmaktadır. Birinci bölümde, oldukça önemli bir endüstriyel hammadde olan manyezit ve onun ilişkili olduğu mineraller incelenmiştir. Üçüncü bölümde, sahanın genel özellikleri çerçevesinde saha tanıtılmıştır. Ocakların durumu incelenmiştir. Dördüncü bölümde ise, manyezitin detaylı olarak jeolojisi incelendikten sonra sahadan elde edilen çeşitli verilerle, manyezitleri ve onların oluşumu ve kökeni hakkında detaylı olarak çalışılmıştır. Bu bölümde manyezitlerin içinde oluştuğu kayaçlann jenezi ile manyezitlerin ilişkisi detaylı olarak ele alınmıştır. Beşinci bölümde ise, manyezitlerden ve ilişkili oldukları kayaçlardan 16 tane örneğin ince kesiti yapılarak içindeki mineraller incelenmiştir. Buna göre serpantin + kuvars(kalsedon), serpantin + manyezit parajenezinin varlığı ispatlanmıştır. Ayrıca bu parajenezlere metamorfik bir mineral olarak bilinen talk'ında girdiği gözlenmektedir. Altıncı bölümde, detaylı olarak kimyasal analizlere yer verilmiştir. Bunların sonuçlarından gidilerek kayaçlann kökeni bulunmuştur. Manyezitlerden alınan 16 adet örneğin içindeki safsızlık oranları tayin edilip jeoistatistik olarak incelemeleri yapılmıştır. Bazik ve ultrabazik kayaçlardan 8 tane örnek alınarak ana element ve iz element analizleri yapılmıştır. Yedinci bölümde, manyezitlerin ekonomisine yer verilmiştir. Manyezit üretiminin Türkiye'de ve Dünyada artan bir trende sahip olduğu çeşitli tabloların sonuçlarında yorumlanmıştır. Aynı zamanda Türkiye'nin manyezit cevheri ihracat trendinin de artma eğiliminde olduğu gözlenmektedir. Sonuç ve öneriler kısmında ise tez ana hatlarıyla yorumlanarak yararlı bilgiler verilmiştir.

Magnesium, the eighth most abundant element in the earth's crust, is found widely distributed in a variety of minerals. Among the more commercially important ones are magnesite (MgC03), brucite (Mg(OH)2), dolomite (CaMg(C03)2), and the salts magnesium sulfate and chloride often found in natural brines. The other important magnesium minerals are olivine ((MgFe)2 Si04), talc H2 Mg3(Si03)4 and serpentine (H4Mg3Si209). These are valuable because of desirable characteristic given to them by the magnesium content and its placement in the particular crystal structure. These minerals are the raw materials for a host of products including magnesium metal and several grades of magnesia or magnesia containing materials for refractors, fluxes, fillers, insulation, cements, decolornts, fertilizers and chemicals. Magnesite, when pure, contains 47.8 % MgO and 52.2 % C02. The pure mineral is some times rarely, found as transparent crystals resembling calcite, but, preponderantly, magnesite contains variable amounts of the carbonates, oxides, and silicates of iron, calcium manganese, and aluminum. Magnesite (MgC03) was the first suggested by J.E. Delantherie in 1975, and later discovered in nature by C.F. Ludwing in 1803. It exhibits as crystalline and microcrystalline textures in limestones and dolomites, and as amorphous in ultramafic rocks. Magnesitization process, even today, is still subject of scientific arguments, which can be explained by various theories based on experimental studies. According to these studies, magnesites have occured with the reaction of atmospheric and magmatic (probably coming from deep sources) during serpentinization origin of CO2 rich waters (ascending or descending theories), on the ultramafic rocks, together with shale-shaly limestone sequences in lacustrin environments, as a result of metasomatism within the limestones and associated with anhydrite as crystalline texture in salt deposits. Magnesite may be either crystalline or amorphous. The crystalline form has a hardness of 3.5 to 4.0. The color may range from white to black with shades of yellow, blue, red, or gray. The color is not a fundamentally significant.indicator of purity, but in a given deposit, an experienced person can often roughly grade magnesite by assessing color and crystallinity. The crystalline form of magnesite occurs in relatively few but large deposit where as the cryptocrystalline variety tends to occur in many but small deposits. Cryptocrystalline magnesite is massive with no cleavage and is sometimes descriptively called bone magnesite. The fracture is usually conchoidal, and hardness IX is 3.5 to 5.0. The color is normally white, but it can be tints of yellow, orange, or buff. Accessory siliceous minerals such as serpentine, quartz, or chalcedony are usually present. Also these minerals were found in the study area. Calcium minerals are usually absent or in low concentration in cryptocrystalline magnesite as contrasted to their almost invariable presence and higher concentration in the crystalline variety. Magnesite dissociates upon heating to form magnesia (MgO) and carbon dioxide. When heated sufficiently, magnesia develops a crystal structure identical with that the natural mineral percales. The mineral percales occurs only rarely in nature and not in any known, commercially workable deposits. Brucite is another mineral which can be directly reduced to periclase through the application of heat. Brucite has been mined for the production of magnesia, but is no longer an important an important source. The mineral is associated with limestone, but almost commonly with magnesite. Cryptocrystalline or "amorphous" magnesite is an alteration product of serpentine or allied magnesium rocks which have been subjected to the action of carbonate waters. The serpentine which lies near or surrounds the magnesite is itself an alteration product of the ultramafic rocks. The mode of formation of the magnesite usually limits the amount of impurities to small amounts of iron, lime and silica. Occurrences of this type of magnesite are fairly common throughout the world, but because of their usually limited size, few - with notable exceptions of those in Greece, Turkey, and Australia- are worked commercially. The action of surface water containing carbon dioxide percolating down through serpentinized fissures can convert serpentine to magnesite and other minerals Also, waters rising through fissures could produce magnesite. In both cases, the relation ship between temperature and carbon dioxide pressure is very critical to the formation of magnesite. The zones closer to the earth's surface are more favorably situated for the reaction. Therefor, most of the deposits of this type of magnesite are found near the surface and have limited extent in dept. Tavşanlı (Yaylacık) area is on the ultramafic massive rocks that hosted magnesite. In the area, ultramafic rocks have been decomposed in the form of serpentine. Be cause of tectonic activity, serpentine have been altered. At the end of the processes magnesite have been formed. In the field the weather is cold in winter and hot, dry in summer. Ridges have 1000 to 1350 m high, so the communication is very difficult. This study has been by supported by COMAG (AS) which has been working in the area since 1963. The research has been carried out using one of COMAG Erna-Foral extraction equipment and the results obtained are given. The structure and the texture of magnesites and hosted rocks(ophiolit rocks) have been carefully studied and their origin and formation has been found. Magnesites are formed during the compression-expansion process of ophiolit rocks due to the dual movement of tectonic forces. The formation of magnesium structure is function of ore type such as vein, lens, massive etc... For the quality of magnesium purity is very important, therefore, 16 different samples have been selected and their individual quality compared. These results are showed in Table 1. The Fe203 and CaO, C02 in the magnesium have been found to be not related. Thus, the impurities in the magnesium have been carefully controlled because the quality effect is very important Tablet At the same time 16 thin sections of ultramafic and magnesite samples have been selected and their mineral content has been analyzed in the microscope. The paragenesis of serpentine, quartz, and talc in the thin sections have been then determined. The finding of the talc mineral shows the conditions of a metamorphism environment. So microscope studies is very benefit. The other samples of rocks were carefully analyzed to found main elements and trace elements (Table 2) According to the results of this study, Basic intrusive rocks were found in island arc toleyite zone. It was analyzed to find the origin of the ultramafic rocks and They were found in ultramafic cumulate zone (table 2). XI First magnesite production in Turkey began in 1850' s. Estimated total reserve are about 160 million tons and Turkey is fourth country with the above reserve after China, North, Korea, and Soviet Union. Also Turkey is ninth country in production and export in the world. *., " Table 2. The study region is located in Anatolia and this have very high magnesite potential in terms of quality and reserves. Kütahya Eskişehir - Bursa area, Which contains 28 % of total reserves (65 million tons) of Turkey, is second important area after Konya, and it is first area in terms of number producing openpits. In Yaylacık ultramafic rocks, serpantinization is very important for magnesitization. In this area ultramafic and basic intrusive rocks are named Tavşanlı ophiolites. The ophiolites have been effected by tectonic forces after that have been fractured. The faults have been occured on it. Ultramafic rocks in the ophiolit group generally form in two type rocks, first one harzburjit, second one dunit, The both have greenish color. In the study area, the samples were taken from harzburgits and dunits. They contains mafic mineral that has amount of Mg that is source of magnesite ore is extracted near the serpentine rock. The structure of the magnesite that is various that may be found vine, lense and massive. The production of magnesite is rising toward 2000 years. The most important productive countries, Greece, ABD, China, Turkey etc. (tabled). Magnesite economy is connected by all reserve of the countries. Turkey have been commercially produced magnesite since 1950. But the foreign companies have been extracted magnesite from Turkey. Unfortunately the amount of Turkish companies are not enough.