Kütahya kuzeyindeki hidrotermal alterasyon ve etkinlikleri

Abstract

Bu çalışmada Kütahya-Eskişehir arasında yer alan, yaklaşık 144 km2 lik bir çalışma sahasının stratigrafik ve tektonik özelliklerini belirleyen 1:25000 lik jeolojik haritası sunulmuştur. Araziden toplanan kayaç örnekleri mineralojik ve petrografik yöntemlerle incelenmiştir. X-ışınları laboratuarında, örneklerin X-ışınları dif raktogramları çekilmiş ve kil mineralleri belirlenerek dağılımları incelenmiştir. Volkanitlere ve tüflere ait örneklerin kimyasal analiz değerleri, volkanitlerin özelliklerini belirlemek ve hidrotermal alterasyonun kayaç kimyasındaki etkilerini araştırmak için kullanılmıştır. Konuya duyulan ilgi bilimsel amaçlı olmakla birlikte, hidrotermal alterasyon çalışmalarının, cevher oluşum süreçlerini aydınlatma, cevher yataklarının saptanması ile genelleştirilmesinde bir araç olması ve jeotermal depolarla ilgili uygulamalarda konuya katkılı yaklaşımından dolayı, önemini vurgulamak amacıyla incelenmiştir.

The area under study is in West Anatolia Region, lying on the North-East of Kütahya-Eskişehir highway. It is 30 kms away from Kütahya, 35 kms away from Eskişehir and has Sabucupinar as its center. Fig. 2 shows the generalized stratigraphic section of the study area on the columnar section of Sabuncupinar. Several former investigations have been carried out in the vicinity of the study area, in order to find out the basic geological problem of the region and its tectonic and stratigraphic character. Other studies aiming at coal mining and exploitation of meerschaum and other ore reserves with an economical value have also been worked out by public and private enterprises. The volcanic rock series of Western Turkey, mostly calc-alcaline and partly alcaline in character, have been one of the most frequently studied topics by both domestic and foreign researchers. In this study, within the frame of the general geological structure and tectonic characteristics of the region, the stratigraphical and tectonic evolution of the study area has been summarized. The chemical and petrographic analyses of the volcanics have been reported and their genetic interpretations have been given. The region partly covers the southernmost edge of the Pontides as well as the northernmost section of the Anatolides. During different periods of volcanic activity, rocks of different composition had been formed. Neogene-Quaternary volcanic activities are common in this region. The results of the chemical analyses of samples suggest that they are calc-alcaline in character. Classification of volcanic rock samples according to alkali-silica contents as well as v - distribution of samples in AFM diagram and Gottini diagram of the volcanics have been presented. The volcanic rocks in the study area show a successsion as Dacite, Ruyodacit and Basaltic. The rock associations in concern are formed from different source materials. Based on their chemical properties, young volcanisms of this area are found to belong essentially to two groups, namely mantle originated and crustal originated. Petrographic definitions have been suggested from the samples of the study area. With samples of Neogene tuffs which show a wide dispersion in the study area, several investigations such as mineralogic and petrographic analyses, X-ray diffraction analyses and chemical analyses have been carried out. The existence of hydrothermal alteration which is thaught to have developed in relation with strike-slip faults and diagonal fissures has been shown and the effects of hydrothermal alteration on Neogene tuffs, such as mineralogic and chemical changes, have been determined. Tectonic structures of the investigated area depend on NE-SW directions and hydrothermal alteration occurs at this structure. Hydrothermal alteration can be defined as changes in the chemical and mineralogical character of the host rocks due to a heated geothermal fluid which circulates within the rocks. As a result of this process, compositional changes do occur and new minerals form. During the alteration, several physical features of the environment, such as colour and texture, also change and it is always helpful to determine the physical changes in the environment while studying the effects of the hydrothermal alteration in a given area. vi - The study of hydrot hernial alteration has some practical outcomes such as the clarification of the process of ore deposits and applications related with hot-water type geothermal reservoirs. One of the principal objectives of this study was to establish criteria which would guide the search for ore deposits, based on certain features of the hydrothermally altered rocks with which many ore deposits are associated. Much has been written about hydrothermal alteration and the compositional changes induced by it in the wallrocks of mineral deposits. Several schemes and criteria have been used by different authors to systematize the types of hydrothermal alterations and various classification systems have been offered. A classification based on the conditions of occurence of alteration has been proposed as well as several based on mineral assemblages which are the end products of the hydrothermal alteration. The fact that hydrothermally altered rocks show great variance within short distances proves the complexity of altered rocks. Certainly the mineralogy and chemistry of such rocks are not as simple as most people would like, but a good classification scheme, such as Creasey's, clarify most of the complexities. The results obtained from the chemical analyses of the samples of the area have been plotted on Creasey's compatibility diagrams for potassic and argillic alterations. The following are the end results of the X-ray diffraction analyses of the samples: E5 Montmorillonite + Illite + Kaolinite + Y-Crystobalite + K-Feldespar Rg Illite + Kaolinite + Calcite 83 Illite + Kaolinite + K-Feldespar + Calcite VI I 85 Muscovite + Illite + Kaolinite + Feldespar + Magnetite It is difficult to prepare a complete list of minerals which may develop on the wall rocks as a result of chemical processes during hydrothermal alteration. It has been determined that thermal fluids and acidic solutions which came out at the last phase of the volcanism have been dispersed through some tuff levels and kaolinized them. Besides it was seen that acidic hydrothermal solutions which had moved upward during the acidic or basic rock contact caused the togetherness of kaolin and bentonite deposits. In the area of study whose detailed investigation has not been completed yet, field observations supported by the analytic laboratory data yielded possible evidence of kaolin and bentonite formation with hydrothermal origins. A vital point not to be overlooked is the overwhelming evidence that hydrothermal alteration and ore formation are genetically related processes. But apparently the almost ubiquitous association of alteration with ore is not reciprocal such that hydrothermal alteration is a necessary but not sufficient condition for ore formation. Alteration areas always show different zones with various mineral assemblages. A detailed analysis of alteration layers may guide the search and mining of industrial raw materials such as quartz, alunit, zeolit, kaolin and bentonite. But to achieve all these goals, more comprehensive and detailed studies are needed. These may require core sampling from the surfaces and microscopic examination, mineralogical determination through detailed X-ray studies and further chemical analyses of the drill samples. Hopefully this kind of detailed research may provide - V I I I added insight into processes of hydrothermal systems and their relationship with ore deposits.