Geology and Geochemistry of the Volcanics from the Eastern Part of Pertek Tunceli

Çalışma sahası Pertek doğusunda yer almaktadır ve Solhan Volkanitleri'nin bir parçası niteliğindedir. Çalışmanın asıl konusunu oluşturan lav akıntılarının, petrografik ve jeokimyasal değerlendirmeler sonucunda, tümü ile bazaltlardan oluştukları belirlenmiştir. Bazaltlar, plajiyoklaz, olivin, klinopiroksen ve nefelin gibi ana mineraller ile opak ve ikincil kalsit ve serpantin minerallerinden oluşmaktadırlar. Bazaltların çoğunluğu alkalen, daha azı subalkalen karakterdedir. Subalkalen örnekler ise kalkalkalen-toleyitik geçiş özelliği göstermektedirler. Tümü ile aynı köken özellikleri gösteren alkalen ve subalkalen bazaltların, spinel lerzolitik bir kaynaktan yaklaşık %5-35 arasında bir kısmi ergime ile oluştukları düşünülmektedir. Volkanitlerin levha içi bazalt özelliğinde olduğu jeotektonik sınıflama diagramları kullanılarak ortaya çıkarılmıştır. Söz konusu volkanitler Doğu Anadolu Sıkışma Bölgesi içerisinde yer almaktadır. Bu bölgede doğrultu atımlı faylar önemli miktarda deformasyonu üzerinde toplamıştır. Bu fayların denetiminde, bölgede lokal gerilme alanları oluşmuştur. Çalışılan volkanitlerin bu lokal gerilme alanları içerisinde yer alan derin kırık sistemleri boyunca, muhtemelen Üst Miyosen-Pliyosen aralığında, yüzeye çıktıkları düşünülmektedir. Anahtar Kelimeler: Levha içi bazalt, petrografi, jeokimya, Tunceli. ABSTRACT: The study area, a part of the Solhan Volcanics, is located in the eastern part of Pertek. The lava flows, which are the main subject of this study, in basaltic composition based on the petrographical and geochemical studies. The essential minerals of the basalts are plagioclase, olivine, clinopyroxene and nepheline. Beside these, opaque and secondary minerals such as calcite and serpentine are observed in minor amount. Although the most of basalts show alkaline character, small amount of them plots into sub-alkaline area. The sub-alkaline samples demonstrate transition from tholeiitic to calc-alkaline suite. It is thought that, the alkaline and sub-alkaline basalts, which have same origin, were generated by approximately %5-35 of the partial melting of a spinel lherzolithic source. Within plate basalt character was determined for the volcanic rocks by using geotectonic discrimination diagrams. The studied volcanic rocks are located in East Anatolian Compressional Region where strike slip faults caused substantially deformation. The local tension regions occurred under the control of these faults. The studied volcanic rocks, highly possible, came to the surface along the deep fracture systems in the local tension regions during the late Miocene-Pliocene

Geochemistry of the post-collisional Miocene mafic Tunceli Volcanics, Eastern Turkey: Implications for the nature of the mantle source and melting systematics

The East Anatolian Accretionary Complex (EAAC) comprises an ideal example of post-collisional volcanism within the Africa-Eurasia collision zone. The Miocene mafic Tuncell Volcanics, as a part of this post-collisional volcanic system, are located in the western termination of EAAC. The mafic Tunceli Volcanics are characterized by mildly alkaline and tholeiitic basalts, in which olivine, clinopyroxene and plagioclase characterize the main mineralogy. The role of fractional crystallization (FC) and assimilation combined with fractional crystallization (AFC) processes appear to be negligible in the petrogenesis of the primitive mafic Tunceli Volcanics. Relative enrichment in large ion lithophile elements (LILE), Th and La over high field strength elements (HFSE) and heavy rare earth elements (HREE) suggest contribution from a metasomatized mantle source. The wide range of ratios displayed by these elements also calls for some asthenospheric input for the genesis of these volcanics. The metasomatizing agents can be attributed to a past subduction event, probably during the closure of Neotethys. Considering also the geophysical constraints, which limits the lithospheric thickness to about 70-75 km around the region, a melt mixing between lithospheric and asthenospheric melts generated at different depths appear to be an important process in the petrogenesis of these lavas. The combined geochemical and geophysical data, therefore, necessitate a geodynamic model with some remnant lithospheric mantle underlying the Eastern Anatolian region

Preliminary results about the Quaternary activity of the Ovacık Fault Eastern Turkey

The Erzincan Basin and the surrounding region have a complex structure, which is formed by the interaction of the North Anatolian Fault (NAF), the Northeast Anatolian Fault (NEAF), the Pülümür Fault (PF), and the Ovacık Fault (OF). The region has been shaked many times by devastating earthquakes throughout both the instrumental and the historical periods. The infamous 26 December 1939 Erzincan Earthquake (M~7.9) is the largest event, which was instrumentally recorded along the NAF. Moreover, the eastern continuation of the surface rupture of this earthquake, "the Yedisu Segment", is known as one of the two seismic gaps on this dextral shear zone. We started multi-disciplinary studies on the OF, which has relatively very limited data. Even though some researches think about this tectonic feature as a non-active fault, recent GPS measurements point strain accumulation along it. In addition to that 1992 Erzincan and 2003 Pülümür earthquakes loaded additional stress on the neighboring faults, including the OF. The OF elongate between the SE Erzincan Basin and Kemaliye (Erzincan) about 110 km with a general strike of N60E. The clear morphological expression of the fault is especially observed around Ovacık, Tunceli. The OF delimits the Jurassic aged Munzur limestone in the north and the Miocene volcanoclastics and Permo-Carboniferous schist in the south in this vicinity. We identified many offset features, such as wash plains, moraines, alluvial fans and inset terraces in our preliminary morphological maps. The measured displacements change from 20 to 350 m, which may play a critical role in the calculation of the geological slip-rate. Moreover, we used morphological indices, such as topographic profiling, hypsometric integral, basin asymmetry, and the mountain front sinuosity to quantify the activity of the OF. Our preliminary results clearly point out the necessity of future studies, which may help to understand the earthquake potential of this poorly known tectonic feature

New Petrological Data from the Western Termination of East Anatolian Accretionary Complex EAAC Eastern Turkey

Geodynamic characteristics of the East Anatolian Accretionary Complex (EAAC) have been one of the major research topic for last a few decades. The models hitherto try to interpret the role of Teritiary volcanism in EAAC were not wealthy, due to the few geochemical, isotopic and radiometric age data. Furthermore, since boundary of EAAC is delimited by geophysical methods, discussion about relationship between EAAC volcanism and other volcanics, which is close proximity with EAAC, is not sufficiently examined. To provide new data, this study focused to western termination -Tunceli Teritiary volcanic rocks- of EAAC. The most important reason for this target is the lack of analytical studies and insufficient data about petrographic-petrologic characteristics of the Tunceli Teritiary volcanic rocks. Volcanic rocks of these study area classified into two main groups; Lavas and Pyroclastics. Lavas include only basalts in the study area. Pyroclastics rocks consist of tuff, lapilli tuff and blocks. According to petrographical studies, basalts include three main minerals; plagioclase, olivine and clinopyroxene. Pyroclastic rocks formed by andesitic and basaltic clasts. In the study area the most dominant textures of the lavas are porphyritic and intergranular textures. Almost all of the volcanic rocks have suffered alterations which gave rise to the formation of secondary minerals such as sericite, serpentine and iddingsite. According to the petrochemical evidences, the characters of magma are identified into two series; alkaline and calc-alkaline. Some of the samples have a tendency to potassium enrichment; probably these results indicate a crustal contamination. Major and trace element analysis of thirty samples, revealed the volcanic arc and WIP characteristics of Tunceli volcanic rocks. According to the N-type MORB normalized trace element diagrams, these volcanic rocks are enriched by LIL elements while HFS elements are relative depleted. In addition, negative Nb and Ti anomalies indicate that this situation have resulted from subduction-related events or crustal contamination. All in all, these data clearly indicate that volcanic rocks in Tunceli have great correlation with Teritiary volcanic rocks of EAAC. Ongoing isotopes and age determination studies will be more starkly put forward the relationship between volcanic rocks of EAAC and Tunceli

Tunceli' deki Cevherleşmeler ve Madencilik Faaliyetlerinin Su Sistemine Etkileri

Tunceli, yılda yaklaşık 2.2 hm3 yeraltısuyu ve 3112 hm3 yüzey suyu rezervi, bazı metalik madenler ile endüstriyel hammadde yatakları bakımından önemli potansiyele sahiptir. İldeki cevherleşmelerin ve madencilik faaliyetlerinin çoğunluğu, ilin en önemli iki akarsuyunu oluşturan Munzur ve Pülümür çaylarının drenaj alanlarında yer almaktadır. Munzur çayı drenaj alanında henüz işletmeye açılmamış Au, Cu, Mo, Pb ve Ag ile Pülümür çayının drenaj alanında ise Cu yataklarının varlığı bilinmektedir. Munzur çayı drenaj alanında işletme faaliyetine ara verilmiş kömür, Pülümür çayı drenaj alanında ise işletilmekte olan alçıtaşı, tuzla, kireçtaşı, bazalt ve kum-çakıl ocakları bulunmaktadır. İldeki Cr yataklarının önemli bir bölümü ilin kuzeyinde yine Munzur ve Pülümür çaylarının drenaj alanında yer almaktadır. Bu yataklarda zaman zaman açık işletme yöntemiyle cevher alınmakta ve bazı yıllarda işletme faaliyetlerine ara verilmektedir. Sanayinin neden olabileceği kirletici etkinin yok denecek kadar az olduğu Pülümür ve Munzur çaylarından alınan sediman örneklerinde kirletici etkiye sahip bazı toksik elementlerde zenginleşmeler tespit edilmiştir. Yine her iki çayın sediman örneklerinde asbest grubu minerallerin varlığı da belirlenmiştir. Pasalardaki asbest grubu mineraller ve kromit, ilin kuzeyinde mevcut olan aktif ve terk edilmiş açık işletmelerden drene olan sular tarafından Munzur ve Pülümür çaylarına taşınmaktadır. Bu işletmelerden taşınan sedimanlar Birleşik Devletler Çevre Koruma Ajansının (EPA) belirlediği sediment kalite kriterlerine göre Cr ve Ni’ce kirletilmiştir. İlaveten bu alanlardan drene olan sular da Pb ve Zn bakımından “Su Kirliliği Kontrol Yönetmeliği”ne göre, kıta içi 1. kalite su olma özelliğini kaybetmiştir. Ancak, kirlenmiş bu drenaj suları Munzur ve Pülümür çaylarına karışınca, kirlilik seyrelmektedir. Henüz endüstriyel faaliyetlerce kirletilmemiş Tunceli ilinin doğal ortamını temsil etmesi açısından, bu sediman ve su analiz sonuçları önemli güncel kayıtlardır. Munzur ile Pülümür çaylarının drenaj alanlarında var olan ve henüz işletmeye açılmamış maden sahalarında yüzey, yeraltısuyu, toprak ve bitki sistemleri analiz edilerek kirletici elementlerin kaynağı belirlenmelidir. Sağlıklı çevre koşullarının sürdürülebilmesi ve mevcut ekosistemin korunması için, ildeki ilgili kurumların var olan veya faaliyete başlayacak maden işletmelerine gerekli tedbirleri aldırması büyük önem arz etmektedir

DEPLETED TO REFERTILIZED MANTLE PERIDOTITES HOSTING CHROMITITES WITHIN THE TUNCELI OPHIOLITE, EASTERN ANATOLIA (TURKEY): INSIGHTS ON THE BACK ARC ORIGIN

The Tunceli Ophiolite, which represents the eastern part of the Izmir-Ankara-Erzincan Suture Belt (IAESB), hosts several chromite mines. The petrological characteristics of these deposits and their host rocks were investigated here for the first time. This ophiolite includes serpentinized peridotites, harzburgites, dunites, gabbros, sheeted dykes, pillow lavas and mudstones. The chromite occurrences are hosted in the mantle peridotites. The spinel group minerals in the ore and in ultramafic samples were sampled in seven different chromite mines (Yildirim, Aksu, Hasangazi, Atilla, Eskigedik, Isikvuran and Oymadal). The chromitite spinels display podiform characteristics. The Cr# = (0.39-0.89) and Mg# = values (0.43-0.74) of these spinel group minerals mainly correspond to magnesiochromite and chromite compositions. The silicate assemblage of the cpx-poor harzburgites include Mg-rich olivine (Fo(91)), enstatite and diopside. The occurrence of Ti-enriched secondary clinopyroxenes likely reflect refertilization processes which may have originated by interaction between Ti-rich melts and highly depleted peridotites. The average Cr2O3 (15.46 % wt) and Sigma PGE (92.10 pbb) contents of the chromitites from the Tunceli ophiolite are lower than those of other chromitite-bearing ophiolites in Turkey. The consistent geochemical and mineral chemistry data from the mantle peridotites and chromitites within the Tunceli Ophiolite suggest formation in an intra-oceanic back-arc basin which may have been active during the closure of northern branch of the Neotethyan ocean