Çobanisa (ısparta) Yöresine Ait Rezidüel Oluşumlardaki Nadir Toprak Element Potansiyelinin Belirlenmesi

Abstract

Bu çalışmanın amacı, Isparta şehir merkezinin kuzeydoğusunda bulunan Davraz Dağı kuzeybatısında bulunan, Gölcük volkanizması kaynaklı oldukça ayrışmış piroklastik oluşumların NTE potansiyelinin araştırılmasıdır Piroklastik oluşumların depolandığı alan topoğrafik olarak sert rölyefler oluşturan Mesozoyik yaşlı kireçtaşları ve kuzeybatı ve güneydoğu kesimlerinde normal faylar ile sınırlandırılmıştır. Çalışma sırasında bu bölgede yer alan birimler litolojik özelliklere göre ayırt edilerek yaklaşık 66 km2 bir alanda arazi çalışması gerçekleştirilmiş ve inceleme alanının özel ölçekli bir jeoloji haritası hazırlanmıştır. Çalışma bölgesi Isparta M25a3 paftasında yer almaktadır. Çalışma genel olarak Çobanisa Köyü güneybatısında yer alan ayrışmış piroklastik oluşumlar üzerinde yoğunlaşmakla beraber sınırları oluşturan kireçtaşları da örneklenmiştir. Çalışma alanının özellikle kuzey-kuzeydoğu ve güneybatı kesimlerinde yer alan temel kayaçlar Orta-Geç Triyas yaşlı Dolomitik Kireçtaşları , Triyas-Jura yaşlı neritik kireçtaşları, Geç Kretase yaşlı pelajik kireçtaşlarıdır Temeli teşkil eden bu kayaçlar Pliyo-Kuvaterner yaşlı piroklastik oluşumlar tarafından uyumsuz olarak örtülmüştür. Kireçtaşlarının özellikle kuzeybatı ve güneydoğu mostralarında oldukça altere kısımlara rastlanmıştır. Piroklastik oluşumlar ise oldukça ayrışmış olup boyutları 10 cm’ye kadar çıkabilen volkanik çakıllar içermektedir. Bölgedeki piroklastiklerin Gölcük volkanı kaynaklı olduğu düşünülmektedir. Bu çalışmadaki laboratuvar incelemeleri çalışma alanından sistematik olarak alınan örnekler üzerinden yapılmıştır. Mineralojik ve petrografik analizler gerçekleştirilmiştir. Derlenen tüm örneklerin jeokimyasal (Major ve İz elementler) analizleri yapılmış ve elde edilen veriler kullanılarak Harker, jeokimyasal sınıflama diyagramları ve spider diyagramları çizilmiştir. Buna ek olarak gerçekleştirilen jeokimyasal analizlerde yüksek miktarda Nadir Toprak Elementi içeren örneklerin 5 adedinde XRD analizleri yapılmıştır. Yapılan XRD çalışmalarında özellikle Nadir Toprak Elementlerininin kaynağı olan minerallerin varlığı difraktogramlarda bulunmaya çalışmış, bunun yanısıra bileşimi oluşturan diğer mineraller de analiz edilmiştir. Bu çalışmalara ek olarak, jeokimyasal analizlerde yüksek ve orta derecede Nadir Toprak Element anomalisi içeren iki adet örnek üzerinde yapılan farklı elek çapları kullanılarak yapılan çalışmalar ile Nadir Toprak Elementlerinin hangi fraksiyonlarda zenginleşmiş olduğu belirlenmeye çalışılmıştır. Çalışma sırasında alınan örneklerin Nadir Toprak Elementleri, Th ve Nb elementlerinin jeokimyasal analizleri kullanılarak ortalama bir tenör değeri elde edilmiş ve çalışma sahasının alanı hesaplanarak bir jeolojik rezerv hesaplanmıştır.

The aim of this study is to investigate the REE potential of highly altered pyroclastic occurances originating from the Golcuk volcano, located in the hillside of the Davraz Mt at the northeastern part of Isparta city center. The area where the pyroclastic occurrences deposited is bordered by the Mesozoic aged limestones which are forming topographically hard reliefs and normal faults in the northwest and southeast zones. During the study, the units located in this area were distinguished according to the lithological features and a field study of approximetely 66 km2 was carried out and a special scale geological map of the study area was prepared. The study area is located in Isparta M25a3 sheet. In general, the study focused on the altered pyroclastic occurrences located to the southwest of Çobanisa village but some samples also taken from the limestones. The preliminary results of the TUBITAK/CAYDAG project Determination of Rare Earth Elements potential along the residual formations along the southern Anatolide-Tauride zone’ used to select the study field of this thesis. The basement rocks in the north-northeast and southwest parts of the study area are Middle-Late Triassic dolomitic limestones, Triassic-Jurassic neritic limestones, Late Cretaceous pelagic limestones. These basement rocks are unconformably covered by Plio-Quaternary pyroclastic occurrences. In the northwestern and southeast outcrops of the limestones, lots of altered zones are encountered. The occurrences are very altered and contain volcanic pebbles sizes up to 10 cm. The pyroclastic occurences in the region are thought to be originated from the Golcuk volcano. This volcano is the most significant example of the well known post collisional, Afyon-Isparta potassic-ultrapotassic volcanic province in southwestern Turkey. Partial melting of oceanic crust and subcontinental lithospheric mantle causes the formation of K, Na, Ba and Sr rich potassic-ultrapotassic magma. The crystallization of REE bearing florocarbonates and Nb bearing pyrochlore group minerals from such magma, resulted the LREE enrichment in Gölcük volcanics. Extrusive rocks are mainly trachyandesites, augite-trachytes, porphyry trachytes and tephriphonolite dikes which are formed in several eruptive cycles. The third (and the last) eruptive cycle caused the formation of ultrapotassic tephriphonolite dikes and pyroclastic flows which moves across the flanks of the volcano towards to the study field. The LREE enrichment for alkaline-potassic rocks are also observable in various locations beneath the Isparta angle. One the main aim of this thesis is to search and find the volcanic rock particles located at the study field. For better understanding of the nature of golcuk originated volcanic rocks and their REE content laboratory studies in this study were made on samples taken systematically from the study area. Mineralogical and petrographic analysis were carried out on both limestones and volcanic rock samples. Lots of Golcuk extrusive rocks are defined by the use of petrographic-polarised microscope. Geochemical (Major and Trace elements) analyzes of all collected samples were made. The major element content is obtained by a XRF analysis and trace element analysis is carried out by the use of an ICP-MS device. Some trace element data also determined by XRF analysis because of the enrichment of some trace elements (because of the limitation of ICP-MS). Harker, geochemical classification diagrams and spider diagrams were drawn using the obtained data. The geochemical classification diagrams verifes that the volcanic rock samples are potassic-ultrapotassic volcanic rocks. Spider diagrams clearly shows that there is an enrichment in LREE (especcialy in low silica high alkaline contents). HREE’s have a rather horizontal pattern in most of the spider diagrams. Most of the HREE content is depending on the element Y. Ba and Sr enrichments in volcanic rock samples also compatible with the oceanic crust contribuiton to the magma composition. The enrichments of Nb and Th elements are also compatible with LREE content. Eu/Eu*, (La/Sm)n, (Gd/Yb)n LREE/HREE values also calculated. In addition to these studies, XRD analyzes of 5 samples containing high amounts of Rare Earth Element were carried out. In the XRD studies performed, the presence of REE minerals, which are the sources of rare earth elements, were tried to be found in diffractograms, as well as other minerals that consists in the composition. According to the XRD analysis lots of REE bearing minerals identified (lanthanite, pyrochlore, betafite, pretulite, polymignite, xenotime etc.) The mineral which hast the most intensity in XRD analysis is Lanthanite. The presence of such mineral suggests that there must be some florocarbonate minerals (e.g Bastnasite, Huanghoite etc.) and during the deposition process the undetermined florocarbonate minerals transfoms to it. As a matter of fact most of the LREE and Th enrichment can be explain by the presence of the mineral Lanthanite. Nb and Ti enrichments are also deretemined by geochemical analysis. XRD analysis shows lots of Ti and Nb bearing minerals exsists in the study field (perovskite, fergusonite, pyrochlore etc. ) Most of the Nb enrichment can be explained by the existence of such minerals . The geochemical analysis also indicates that the difference between rock and altered pyrcolastics in terms of REE is very low. That results suggests that the REE bearing minerals are relatively durable in atmospheric conditions and can protect their crystal structures in contrast to the high levels of weathering. The lack of low pH hydrothermal alteration, immobile behaviour of the REE’s and the other HFSE at atmospheric conditions, and specified structural geology of the study area are also playing a big role in enrichment process. In addition to these studies it has been tried to determine which fractions the REE’s are enriched, by using different sieve diameters on two specimens with high and medium rare earth element anomalies. Two samples are indeed altered samples and one of the selected sample have the highest REE content. The results show that there is a slight enrichment in REE especially LREE in the smallest sieve sizes. This results are compatible with the mineral sizes of carbonatite type REE deposits like Bayan-Obo. Most of the REE’s are enriched by this sieving process except the element Sc. After the sieving process LREE/HREE results are calculated once more and calculations show that the HREE bearing minerals are relatively more enriched in smaller Sieve size. With the usage of the spatial and geochemical data, an avarage grade of REE determined. By using the avarage grade REE and the area of the study field probable reserves of REE, Th and Nb are calculated. Under the financial conditions of the date which this thesis has been wrote, the REE production from the study field is rather difficult. But the rising of the REE prices in near future may differs the importance of the study field