Çukur (Kayseri) bölgesi siyenitik kompleksinin petrolojik etüdü

Abstract

Kayseri -Felahiye-Cukur Nahiyesi 'nd eki bu çalışmada 'bölgenin jeolojisi ile birlikte ülkemizde ender raslanan oluşumlardan olan feldispatoldli siyenitler ve birlikte oluştuğu diğer mağmatik kompleksin üyeleri olan alkali siyenitler ve granodioritlerin petrografisi ve petrolojiei ayrıntılı olarak incelenmiştir. Bölgede ana formasyon birimleri olarak metamorfikler (gnays, mikaşist, kuvarsit ve mermerler).sedimanter oluşumlar (tüfler.alüv yonlar ve Neojen çökelleri) İle mağmatikler (granodiori t, alkali siyenit ve f eldispatoidli siyeniti er )bulunmaktadır. Metamorfikler bölgenin en eski birimleri olmakla birlikte, yaşları üzerinde çalışmalarda bulunan Brinkman(1976) (16).genelde Orta Anadolu metamorfiklerinin Devonien, hatta Ordovsien olduğunu ileri, sürerken, Ketin(1959) (14) metamorfik serilerin büyük bir kısmının Mesozoike ait olduğunu belirtmiştir. Halen Orta Anadolu `da ki metamorfiklerin oluşum yaşı konusunda birleşme yoktur. Çukur bölgesi mağmatiklerininde yer aldığı Orta Anadolu plütonik kompleksinin yaşları konusunda çalışmalarda bulunan Ayan(1959)(12),Çiçekdağı-Kaman arasındaki granitik kayaçların yaşlarına 54 milyon sene olarak vermiştir. Ataman(1981) (13) ise, Kırşehir civarındaki Cefalık Dağ-Kaman arasındaki granitik int rüzyonun yaşını 71 milyon yıl olarak saptamıştır. Ketin(1961) (8), jeolojik verilerden giderek Orta Anadolu kristalen masiflerinin Eosen veya Paleosan (Alpln Orojenezind'e) olduğunu belirtmektedir. Genel olarak birleşilen kanı, Orta Anadolu Kristalen masiflerinin Üst Kretase sonunda oluştuğudur. Çalışma sahasındaki intrüsif kayaçları asit ve nötür bile şimli olarak iki guruba ayırmak olasıdır. Asit karektere sahip ve siyeni tik kayaçlara göre çok daha küçük alan işgal eden granitin bileşimi kayacın yapılan modal analiz çalışmaları sonucunda, ortalama mineralojik bileşimlerinin granodiorite tekabül ettiği görülmüştür. Kuzeyden Güneye doğru gittikçe asit bileşimden nötür bileşime geçilmektedir. Alkali siyenit ve f eldispatoidli siyenit lerde hakim olan feldispat ortozdur. Ortozlar büyük ölçüde kalsit leşmişlerdir.Kayaçta ikincil kalsite herzaman raslanırken, oldukça geniş çaplı bir kontaminasyonuda izlemek olasıdır. IV Feldispatoidli siyenitlerde kayaca hakim olan mineral ortozdur.Feldiepatoid gurubu minerali olarak kayaçta bulunan nefelinin yer yer kankrinite ve sodalite dönüşüm gösterdiği izlenmektedir. Siyenitik kayaçların mermerlerle olan kontaklarına yaklaş tıkça, genellikle gröna, enirin ve manyetite oldukça sık Taşlan maktadır. Çatlaklarda ise çoğunlukla fluorit oluşumları yer almaktadır. Bölge kayaçlarının yapılan petrokimyasal çalışmaları sonu cunda magmatik kayaçlarda 56 SiO2 oranı 53.91-68.06 arasında deği şirken, %Na20 0.28-5.27 ve % KgO 0.98-9.90 arasında değişim gös termektedir. Ketamorfiklerde ise kontağa yakın bölgelerde İt CaO, Fe20,,TeO ve HnO değerlerinde bir artış İzlenmektedir.Metamor fiklerin kökeninin sedimanter olduğunu söylemek olasıdır. Olduk ça fazla silis içeren Bedlmentlerin metamorf izması sonucunda, metamorfiklerln oluşmuş olması düşünülebilir. Magmatik kayaçlar, alkalice normalden biraz daha zengin bir magmaya tekabül ederler ve tümü salik bölgeye düş er. Bunların normal bir dif eransiyasyon sürecini izi ediği, fakat zaman zaman kristalleşmeler esnasında süreksizliklerin varlığı gözlenmektedir. Köken olarak magmatik kayaçları oluşturan magmanın slalik olduğu kanısına varılmıştır. Granodioritlerin, alkali siyenitlerin ve feldispatoidli siyenitlerin oluşumu konusunda granitik magma nın desilikasyonu, diferansiyel ergime, metasomatizm.kristalizasyon -dif eransiyasyon ve kalker sinteksisi gibi değişik görüşler orta ya atılmış tır. Ancak gerek sahanın Jeolojisini incelerken, gerekse petrografik ve petrokimyasal çalışmalar sonucunda, Çukur bölgesin deki granodiorit ve siyenitlerden oluşan ve incelemede siyenitik kompleks olarak bahsedilen i ntrüzy onun, magmanın kalker asimilas yonu sonucunda oluştuğu kanısına varılmıştır. Magmatik kayaçlarda yapılan iz element tayinleri (Rb,Iİ,Ba ve Sr),Niggli parametreleri ve C.I.P.W.norm hesaplamaları birbir lerini bir uyum içerisinde desteklemektedir ve bu verilerle intrüzyonun petrolojjisi ortaya konmaya çalışılmıştır. Çalışma alanının Batısına doğru geniş bir uzanım gösteren skarn oluşumlarında many eti t, hemati t ve olijist gibi cevher mine ralleri bulunmaktadır.Bunlar yer yer % 50.54 Pe2°3 içerirler. Ayrıca bölgede plroluait( 5I 29.04 MnO) ve Fluorit mostralarınada raalanılmaktadır. 2 Bölgede yaklaşık 30 km lik bir alanda 1.25-1.50 m kalınlık gösteren pembe ve gri tüf ler, geniş çapta yapı elemanı olarak bölge halkı tarafından kullanılmaktadır.

The formation in the area of district of which is about 70 kilometers from Kayseri in central region of Turkey appear worth of interest geologically. In this studv.the petrography and petrochemistry of feldapathoidal syenites.alkalen syenites and granodiorites which one accomponied in formation are investigated in details. The investigations in the Central Anatolia go back aB far as 1840' a. More detailed researcere have worked on the. geology and petrography of the Central Anatolia. The geologies of the Central Anatolia and Çukur area are very closley related with each other. In this area, as the main formation unites, metamorphicB(gneİ8B,micaechist,quart2ite and marbles), Neogen, tuffs, alluvions and magmatlc rocks are exist. Although metamorphice are the oldest unites in the region. Brinkmann(1976) who worked on their ages has claimed that the Central Anatolian metamorphicses would be Devolen or even Ordoveien Ketin(1959) Investigating metamorphice series on the basis of geological data in points that these Beries in below to Meao*zoic. There is no aggrement on the age of metamorphic formations among the Investigators who have worked on the age of the Central Anatolian metamorphic complexes. While doing the geological study of the formation of Neogen, the fosil " Helix Ramondi " waB found which a lake Gastropoda belongs to Upper Miosen. Yalçınlar-îzbırak(1959) »who had studied previously on the field of Heogen in the Central Anatolia have also found the teeth and bones of the "Hipparion Gracile" a vertebrate animal belonging to Upper Miosene.Both the Neogen of Central Anatolia and those of Çukur area of the lake origin. VII The thickneBB of tuffs formed by the Erciyes volcanism rises up to 70-100 meters in the Urgüp-Göreme region in the Central Anatolia, to 1.25-2.00 meters in Cukur.Frech(1914) who did researcher concerning the Erciyes volcaniBm reveals the fact that Erciyes 1b still continuing its volcanic actions intermit- lentley to its craters. The analyes of tuffs in Çukur have revenled that they consist of 71 percent SiOp.In their microscopic investigations due to its suddenly zonal plagloclase has been observed, in addition to orthoclase. The alluvions of Kızılırmak River consist of gravels, sands clays and travertens belonging to Quaterner. Their wldes range to 70-100 meters in Borne locations. On the subject of the ages of the Central Anatolion plutonic complex where in the magmatlce of Çukur are also located, Ayan(1959) Ketln(196l) and Ataman(1981) has inquiries of them,Ayan(1959) estimated the ages of granitic rocks lying between Çiçekdağı and Kaman as 54 million years. On the basis of geological data, Ketin(196l) states that the crystallne massif of Central Anatolia might have been formed during Eosen or Paleosen.Ataman(1981) ooncluded that the age of granitic intrüsyons which lies between Cefalikdağ and Kaman around Kırşehir might be 71 million years. The other writers having research on the age of granite plutons in the Central Anatolia have also come 'to a common opinion that the Central Anatolian crystalline massifs might have been formed rate in the Upper Cretaceous. The intrrusif rocks in the field of research can be classified under two groups as those silica saturated containing and intermediate ones. In the region of Çukur. the granites with silica containing components, cover a smaller area than the alkalen syenites and feldepatholdal syenites with intermediate components. According to the result of the point counter investigation of the rock with silica saturated components, it waB discovered that the mineralogic components of the rock correspond to granodiorite. If we follow along the At Creek crossing exactly in the midBt of a line passing the north to south direction of the district of Çukur, The phenomenon of passing from silica saturated components can be seen clearly. The minerals that dominantes on the alkalen Till Byenites and feldspatholdal syenites la feldspar orthoclase.Pure, clean orthoclaae.ia seen very rarely. The greatest part of orthoclasea near its whole Is calclfled.lt is always possible to see the secondary calcite.In the case of feldspatholdal syenites the mineral dominating the rock are feldspars..As the alterating minerals are cancrinlta and aodalite take place If one follows from syenites to the contact of marble, garnet, aegirlne and magnetite are seen more frequently in the syenitic rocks. On tne other hand.fluorlte is seen along the line of joints and craks in syenites, magnetite and pyrite exist as the accessory minerals generally. In the petrochemical inquiries of such rocks the percentages of Si02 in the magmatic rocks has show a change from 53-91 to 68.06.The percentages of Ka20 and K20 have demonstrated a variation of 0.28 - 5.27 and 0.98 - 9.90 respectively likewise as we progressed to the contacts of marbles, the percentage values of FeO and Fe20, have indicated increases. In the metamorphic rocks an Increase has been observed in the percentages values of CaO,Fe20,,FeO and MnO and it is possible to state that metamorphices are of sedlmantary origin. It is likely that the metamorphic rocks formed by sediments, it contains silica in very large proportion. These magmatic rock correspond to a magma, richer than normal m alkalen.All the magmatic rocks are located in the aalic region. A normal dlff erantiation process might have been taken place during the formation of magmatic rocks, However, it might be strongly possible that they might have been cut at times during the crystallization. Possibly, in the magma which formed the magmatic rocks is sialic origin. Though we can say it in certain on the subject of the formation of rocks with acid and intermadiate components, situated close intervals in the same region, variously hypotheses have been developed as desillcation of granitic magma by limestone assimilation, Crystallisation Differentiation, Differential Fusion, Metasomatism and also Feldispatoldal Rocks Associated with Carbonatites.In our geological, petrographic and petrochemical study of the Çukur region, we have come to the conclusion that it is possible that the pluton called the syenitic complex, consist of granodiorite.alkalen syenites and feldspatholdal II syenites might been formed as the result of assimilation of limestone by magma. It is diffucult to say something in certainly about the origin the magmatlc rocks show a coexisting formation. In the region the field Investigations and diagrams in fig.10 and fig.ll may illustrate only the fast that the magma indicates differation though interruptedly in some places. Although a first possibility to come to mind from the fact of coexistence of silica saturated and intermediate rocks is that two magmas may exist.it appear to be a very least probable possibility for the time being. The studies under taken in the nearly areas out of the Çukur region demonstrate that granodloritic and feldispatoidal syenitic ro'cks cut each other no where. That is.it is an exteremly distant possibility that two magmas of different origins might exist. The coexistence of syenites and granodiorltes become a syenitic compound as it goes downward the upper parts of the granodiorite containing magma at the end of limestone assimilation. There are aegirine and alternated nepheline and aodalite in siyenites.At the end of the reactions between magma and carbonated rocks show. A transformation from granodiorltes to syenites in a form of line as we go near the contacts of magmatic rocks with marbles the existence of such calcium silicated minerals as garnet, sfen, and tremolite illustrate good txamplea for on interactional formation between magma and marbles. This interpretation is in aggreement with the conclusion of Dally(1930),Hyes(1930) and Shand(1939).. There are skarn formations in a large field located from the area between Çomaklı-Giniglni Hills in the west of research. site towards the Tuğlaeah Village. In the chemical analyses of skarn specimens picked up from the different places in the area it has been discovered that there axist the locations containing 50.54 percent of Fe-O, scatteredly.Magnetite and hematite are ore minerals most frequently seen in skarn. Of silicate minerals, epldote exist in, the largest proportion and garnet in a smaller proportions. Tremolite is seen very rarely. It 1b rather intermediate to see pyrite near the contacts. In the modal analyses of magmatic rocks, it has teen found out that such rocks demonstrate a tendency from a granodioritic composition to a monzonitic one. The analyses of 52 specimens (of them, 11 specimens belong to the magmatic rocks) of the rocks of the region have been carried out. In this study, and we have tried to realize such subdimensions of our investigation as the magmatic rocks analyses the parameters of Niggli and their transformation into the parameters of Burrie C.I.P.W. norm calculation and the petrology of intrusion. According to the result of the petrographlc investigation of the lamprofire vein which cuts the alkalen syenites vertically. It was indicated that. it might be Kersantite and their geochemical analyses were done. In addition, the specificaton of Rb,Li,Ba and Sr which are seen in the magmatic rocks, have been done and interpreted through diagrams. In the concluding part, it has been indicated that the magma is richer than normal is alkali, a magma with silica components shown differantion and it happens intermittenly at times during this formation process. The alkalen and f eldspathoidal syenites in region can be put into production economically, However before hand it requires a more through and concrete detailed investigation of area. I have to emphasize the fact that the pyroluslte.fluorlte and the ores of magnetite and hematite in the zone of skarn, in the region dont appear to be economically useful in mining at present.