Tepeoba-havran (balıkesir) Porfiri Cu-mo Sahasının Jeolojisi, Cevher Mineralojisi Ve Yüzey Jeokimyasının İncelenmesi

Abstract

Çalışma alanı Balıkesir ili Havran ilçesinin 8 km kuzeyinde (Tepeoba) olup 52 km2’ lik bir alan kaplamaktadır. Tepeoba sahası bölgedeki jeoloji ve jeokimyasal etütler çalışmalar sonucunda MTA tarafından ortaya çıkarılan sahalardan biridir. Sahanın Triyas öncesi temelini, çoğunlukla fillat olmak üzere, düşük dereceli metamorfik kayalardan oluşan Kalabak Formasyonu oluşturmaktadır. Bunun üzerine ise tektonik dokanakla metasedimanter ve metabazik kayaçlardan oluşan Alt Triyas yaşlı Karakaya Formasyonu gelmiştir. Granit-granodiyorit bileşimli Eybek Granitoyidi ile onun asidik ve bazik damar kayaçları Tersiyer yaşlıdır. Eybek Granitoyidi, çalışma sahasında Karakaya Formasyonuna ait metasedimanter-metabazik kayaçları ve Kalabak formasyonuna ait şistleri kontakt metamorfizmaya uğratmıştır. Kalabak formasyonu parlak yüzeyli, ince taneli, iyi foliasyona sahip, sarımsı gri, koyu gri, gümüşi gri fillatlardan, belirgin foliasyonlu, orta taneli, sarımsı gri renkli ve kuvars bantlı şistlerden, yer yer mermer seviyelerinden oluşmaktadır. Karakaya Formasyonu metabazit-metasedimanter kayaçlardan ve Permo-Karbonifer yaşlı kireçtaşı bloklarından oluşmaktadır. Çalışma sahasında Karakaya Kompleksini oluşturan kayaçların haritalanmasında ayrıntıya girilmemiş olup, birim Karakaya Formasyonu olarak haritalanmıştır. Metabazik kayaçlar bu çalışmada ayrı bir formasyon olarak adlandırılmamış, Karakaya Formasyonunun Metabazit Üyesi olarak haritalandırılmıştır. Metabazik kayaçlar arazide genellikle metaserpantin-metadiyabaz mineralojisinde olup yeşilimsi siyah renklidirler. Eybek Granitoyidi bu çalışmada granitik ve granodiyoritik kayaçlardan oluşan ve asidik-bazik damar kayaçları tarafından kesilen intrüzif olarak saptanmıştır. Tepeoba sahasında, Eybek Granitoyiti metasedimanter ve metabazik kayaçlardan oluşan Karakaya Formasyonu’nu ve Kalabak şistlerini kontak metamorfizmaya uğratmıştır. Çalışma alanının genel minerolojik, petrografik çalışmalarının yanında, cevher örneklerinden parlak kesitler ve granitoyitik kayaçlardan XRF ve ICP-MS analizleri de yapılarak elde edilen verilerin jeokimyasal olarak çok yönlü değerlendirilmesi sağlanmıştır. Değerler kullanılarak elde edilen regrasyon grafikleri kullanılarak iki elementin birlerine göre uyumluluğu incelenmiştir. Bu çalışmaların neticesinde anomali haritaları, detaylı jeoloji haritası ile karşılaştırılarak bölgedeki cevherleşmenin niteliği ve bölgesel cevherleşme konusunda daha doğru tespitlere ulaşmak hedeflenmiştir. Yayla tepe, Kırca Tepe ve Karayüksek Mevki arasında mineralize zonların yoğunluğu tespit edilmiştir. Sahanın “porfiri tip Cu-Mo-Au” cevherleşmelerine benzerlik gösterdiği saptanmıştır. Cevherleşmenin kontak metamorfik kayaçlar ve granit içinde breşik, ağsal damar, damarcık ve dissemine şekillerde görülmesi, Cu-Mo-Au elementleri arasında jeokimyasal olarak güçlü pozitif korelasyon, ‘porfiri tip Cu-Mo’ sahası teşhisini destekler niteliktedir. Eybek Granitoyidi’nden alınan kayaç örneklerinin çoğunlukla granitik kayaçlar olduğu görülmüştür. Diyagramlarda görülen pozitif ve negatif korelasyonların fraksiyonel kristalleşme süreci ile açıklanmıştır. Kayaçların subalkali ve tipik kalkalen özellik gösterdiği saptanmıştır. Regresyon grafikleri ile elementler arasında yüksek pozitif korelasyon görülmektedir. Bu da element birlikteliğini destekler niteliktedir. Sistematik kayaç örnekleri sonucu çizilen anomali haritaları da elde edilen sonuçlarla uyumludur.

The study area is located to the 8 km north of Havran, Balıkesir and covers an area around 52 km2. The basement of the area is presented by Kalabak Formation which consists of, dominantly phyllite, low-grade metamorphic rocks. On top of that formation, there is Lower Triassic Karakaya Formation including metasedimentary and metabasic rocks as tectonic contact. Eybek Granitoid, granite-granodiorite composition, and its acidic and basic vein rocks are Tertiary aged. The Eybek Granitoid causes contact metamorphism of metasedimentary and metabasic rocks of Karakaya Formation and schists of Kalabak Formation. Kalabak formation consists of glossy surface, fine-grained, yellowish gray-dark gray-silvery gray phyllites with a good foliation, and clear foliation, medium-grained, yellowish gray, banded quartz schists and the marble levels. Karakaya Formation consists of metabasalts-metasedimentary rocks and Permo-Carboniferous limestone blocks. In this study, Metabasic rocks mapped as a member of the Karakaya Formation. Metabasic rocks have the mineralogy of greenish-black colored metaserpantin-metadiabase. Eybek Granitoid is an intrusive composing granitic-granodioritic rocks and its acidic and basic vessels. Biotite phyllites are located near breccia zones. They are exposed to contact metamorphism. This leads to formation of andalusite fels. The effects of potassic alteration are determined with biotite veins, pyrites and quartzs in breccia zones. Asidic vein rocks are fine-grained white-cream-pink colored dykes which intruded contact metamorphic rocks. In optical studies samples of these rocks is called granophyre in this study. Basic vein rocks are dark green which intruded Oligo-Miocene granitoid rocks. Its mafic minerals transformed into epidote, pyrite and calcite. They are granular textured and fine granular textured. Disseminated and veinlets pyrite are observed in the rock which has epidote and calcite. This vein rocks are the last stage of basic products of Eybek Granitoid. The west side of the study area, Eybek Granitoid causes contact metamorphism by intrusion to the Karakaya Formation leading to weak sericitic alteration. There are hydrotermal breccias as a result of the effect of contact metamorphism. The east side of the study area, Kalabak Formation is exposed to contact metamorphism. Especially, the effcet of contact metamorphism is very clear in marbles. In order to determine the mineralogical and petrographic properties of rocks in the area, 36 thin sections was prepared from 56 samples. Microscopic examination of thin sections was carried out on the basis of the observations made in the field. As a result of the optical inspection 9 different rock types presence were determined. These are granite, granophyre, quartz monzonite, biotite phyllite, quartz-sericite schist with some quartz-mica schist, chlorite-schist, marble and amphibolite. Granite has a holocrystalline hypidiomorphic granular texture in general. The mineralogical composition is plagioclase, quartz, alkali feldspar, biotite, amphibole and opaque minerals. The main minerals of granophyres are quartz and alkali feldspar. There is graphitic texture because of interbadded growth between quartz and alkali feldspar. This form of structure reveals the crystallization of phenocrystal at the same time with the matrix. Quartz monzonite has a holocrystalline hypidiomorphic and xenomorphic granüler texture. The main minerals of quartz monzonite are feldspar and plagioclase. The minerals of this rock are quite large. Xenomorphic quartzs fill the large alkali feldspar. It shows a typical perthitic texture. Quartz-sericite schist’s basic minerals are quartz and sericit. Sericitization is very obvious and common in schists. Some samples includes zircon. Amphibolite shows high pleochroism and fine anhedral grained. Chlorite-schist minerals are quartz, epidote, chlorite and calcite. Marble minerals are mainly calcites. Orientated biotites, quartz, albit twinning plagioclase are minerals of biotite phyllites. Quartz-mica schist has lamination and composing of anhedral quartzs and mica scales. Besides general mineralogical and petrographic studies, the polished section of ore samples, XRF and ICP-MS analyses in granitoid rocks provide multi-faceted evaluation of geochemical datas. Ore samples were taken for ore microscopy examination to determine ore minerals types, abundances, the formation stages and their relations with each other. Accordingly, pyrite, chalcopyrite, molybdenite, magnetite, sphalerite and ilmenite are formed as metallic minerals in the first phase, in the the second stage of formation the hematite, limonite, goethite minerals are formed. The results of geochemical analysis of soil samples collected from the area were statistically evaluated and the maximum, minimum, average, and standard deviation values of elements were calculated and presented in table form. The histogram plots were used for the determination of element regularly dispersed or not. According to statistical data and descriptive results of a systematic analysis of geochemical anomaly maps, the basic value and anomoly locations were drawn for each element The compatibility of two elements with each other were examined using regression graphics. According to the graphs Cu has positive relationship with Mo, Au and Zn elements. The relationships with Pb is a very low negative correlation. Also these datas supports the elements association in common anomaly maps. As a result of these studies, anomaly maps were compared with detailed geological map of the region to reach the more accurate determinations of ore mineralization of its nature. In main element geochemistry, SiO2 concentration of samples is ranged from approximately 58 to 75%. In diagrams, SiO2 has a positive correlation only with the value of K2O whereas P2O5, Al2O3, MgO, CaO, K2O, TiO2, MnO, Fe2O3 values have negative correlation with SiO2. This kind of positive and negative correlations is illustrated by the fractional crystallization process. Approximately half of the samples are peralüminyum and the other half of the samples metalüminyum characterized. In trace element geochemistry, SiO2 has low positive correlation with Th and Rb, secondary negative correlation with Sr and Nb highly negative correlation with Ba, Zr, V, and Y. There is spoon shaped in the chondrite normalized spider diagrams. Such pattern is generally known as a result of fractionation of amphibole. In this study, samples are categorized granites, monzonite, quartz monzonite and syenite in total alkali silica diyagram. Except three of all samples have subalkaline and a typical calc-alkaline characteristic. Biga Peninsula has rich reserves as metallic minerals, industrial raw materials, coal, geothermal and natural waters. In study area the origin of Cu-Pb-Zn mineralization is contact hydrothermal mineralization and hydrothermal origin. Cu-Mo mineralization deposits as veins and veinlets in intrusives and contact metamorphic zones. The study area is Cu-Mo-Au porphyry-type mineralization according to observations in the field.