Başköy (Murgul-Artvin) cevher oluşumunun mineralojik ve jeokimyasal araştırması
Mineralogical and geochemical study of Başköy (Murgul-Artvin) ore formation
Yazar: KAMAL BAKOUR
Danışman: PROF. DR. EMİN ÇİFTÇİ
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Jeoloji Mühendisliği Ana Bilim Dalı / Jeokimya ve Maden Yatakları Bilim Dalı
Derece: Yüksek Lisans, 2022
Konu: Jeoloji Mühendisliği = Geological Engineering
Dizin: Artvin-Murgul = Artvin-Murgul ; Cevher mineralojisi = Ore mineralogy ; Jeokimyasal özellikler = Geochemical features

Özet:
Bugüne kadar Doğu Karadeniz Bölgesi'nde birden fazla yüksek tenörlü yatak keşfedilmiş olup, bu yataklardan bakır, kurşun, çinko, altın ve gümüş içeren cevherler çıkarılmaktadır. Doğu Karadeniz Bölgesi'nde birden fazla yatak hali hazırda işletilirken, ekonomik olabilecek birçok saha araştırılmaktadır. Bu sahalardan biri daha önce kısa bir süreliğine işletilmiş ve daha sonra işletilmesine ara verilmiş olan Başköy (Murgul-Artvin) maden sahasıdır.
Başköy (Murgul-Artvin) Cevher Oluşumunun Mineralojik ve Jeokimyasal Araştırması konulu bu yüksek lisans tez çalışmasının amacı; bölgedeki bakır cevherleşmesinin karakteristik özelliklerini, jeokimyasını, mineral parajenetik sekansını, mineral oluşum koşullarını araştırmayı ve bölgedeki VMS yatakları ile benzerlik ve farklılıklarını ortaya koymayı hedeflemektedir.
Bu tez, çalışma hedefleri doğrultusunda sahadan alınan örnekler; cevher mikroskobu, sıvı kapanım, CLM, kükürt izotop, oksijen izotop ve EPM analiz yöntemleri kullanılarak hazırlanmıştır.
Doğu Pontidlerdeki cevherler genellikle dasitler içinde bulunmaktadır. Bu dasitler iki farklı seviyeye ayrılmaktadır. Bunlar 90'dan fazla masif ve damar tipi cevherleşmeyi kapsamakta olup, Alt Dasitik serinin yaşı Üst Kretase-Senoniyen, Üst Dasitik serisini yaşı ise Paleosen-Tersiyer-Eosen'dir. Bu iki seriyi birbirinden ayıran Maastrihtiyen yaşlı bazik kayalardır. Başköy sahası Üst Dasitik serisinin içinde yer almaktadır. Bu serinin yaşı Paleosen ile başlayıp, Eosen ile sona ermektedir. Bu seri filiş ve bezner sedimenterler ile başlamakta, orta kesimlerini cevheri barındıran dasitik ve andezitik tüfler teşkil etmekte olup, andezit kayaçları ile örtülmektedir.
Başköy maden sahasının cevher örneklerinin mikroskop incelenmesi sonucunda, cevherleşmenin 3 birincil safhada oluştuğu, çok zayıf bir süperjen safha yaşadığı dokusal ilişkilerden ortaya konmuştur. Ayrıca yatağın Cu-Zn tipi VMS yatağı mineral parajenezine sahip olduğu tespit edilmiştir.
Yapılan duraylı oksijen izotop analizi neticesinde; cevheri oluşturan çözeltilerin deniz suyu ve magmatik su karışımı olabileceği düşünülmüştür. Yapılan duraylı kükürt izotop analizleri sonucunda elde edilen izotop oranları diğer Doğu Pontidler VMS yatakları kükürt izotop referans oranları ile mukayese edilmiştir. Elde edilen kükürt oranları magmatik kükürt değerlerine yakın dağılım göstermektedir. EPMA sonucunda; bir alanda daha önce Doğu Pontidler VMS yataklarında rapor edilmeyen stannit mineralinin varlığı belirlenmiştir.
Yapılan bu incelemeler sonucunda Başköy cevherlemesine startigrafik olarak yaş verilmiştir.

Abstract:
VMS (Volcanogenic Massive Sulfide) ore deposits in Turkey are generally considered to be the most important source of Cu-Pb-Zn elements and one of the sources of Au-Ag elements as by-products. These deposits are distributed in 3 different tectonic regions of Turkey; (I) Kuroko Type VMS deposits are in the Eastern Pontite Tectonic Belt (EPTB); (II) Cyprus-Type VMS deposits in Küre (Kastamonu) and Bitlis-Zağos Suture Zone, and (III) Beşi-Type VMS beds in Hanönü-Taşköprü (Kastamonu) region.
Genesis and formation of the Kuroko-type VMS ore deposits in the Eastern Pontide Tectonic Belt can only be recognized thorough understanding of it tectonic evolution. The Eastern Pontide Tectonic Belt evolved during the subduction of the Afro-Arabian plate beneath the Euro-Asian plate and the form closure of the northern branch of Tethys Ocean and lies within a tectonic corridor stretching from southern Georgia and northern Armenia to Bulgaria and Romania, where a large number of similar deposits occur.
The basement of the region consists of a mafic volcanic complex, "Lower Basic Complex", which is intruded by a number of igneous bodies that have numerous ages from the early Cretaceous to Eocene. Except for a few outcrops in the northern zone of the region, they are mostly exposed in the southern zone. These rocks would have served as source rock, particularly for copper through the hydrothermal circulation. This is the main reason for the formation of Cu-rich Kuroko-type deposits in the region.
The Eastern Black Sea Region of Turkey geotectonically occurs in The Eastern Pontide Tectonic Belt which part of The Alpine-Himalayan Orogenic Belt. Therefore, The Eastern Black Sea Region hosts various amounts of VMS ore deposits. VMS-type ore deposits are one of the most important economic resources of the Eastern Black Sea Region of Turkey. Thus, the region has been explored and mined by many local and foreign mining companies for the last 8 decades. Till nowadays, several high-grade deposits have been explored, investigated and mined such as Murgul-Anayatak, Murgul-Damar, Çayeli Madenköyü, Akarşen, and Lahanos. These deposits contain numerous ores such as copper, lead, zinc, gold, and silver ores. At this time, various amounts of ore deposits are being mined in Eastern Black Sea Region while many other potential sites are being researched in the same region. One of the currently under research sites is Başköy (Murgul-Artvin) site.
The area of Başköy (Murgul-Artvin) was investigated and samples were gathered from the field. Later on, a couple of geological and geochemical analyses were applied in local and international laboratories in order to finalize this thesis study.
Mineralogical and Geochemical Study of Başköy (Murgul-Artvin) Ore Formation MSc thesis aims to light on; the characteristic features, the geochemical features, the mineral paragenetic sequence, and the mineral formation of the copper ores of Başköy. It also aims basically to reveal the similarities and differences between Başköy mineralization and the other VMS deposits in the Eastern Black Sea Region of Turkey.
According to the thesis study objectives, the samples that were gathered from the Başköy field were inspected and analyzed with an ore microscope, fluid inclusion microscope, cathodoluminescence microscope (CLM), sulfur isotope, oxygen isotope, and electron probe micro (EPM) analysis methods.
The ores in the Eastern Pontides are generally located in the dacites series. These dacites are divided into two different series which are the lower and the upper series. These two series host more than 90 massive and vine types of mineralization, the age of the lower dacitic series is Upper Cretaceous-Senonian, while the age of the upper dacitic series is Paleocene-Tertiary-Eocene. Both dacites series are separated from each other by Maastrichtian aged basic rocks. Başköy ore formation is located in the upper dacitic series. In addition to that, the age of this series starts with Paleocene and ends with Eocene. The upper dacitic series starts with flysch and similar sediments, the ore host rock is dacitic andesitic tuff located in the middle of the series, over and above it's covered by andesitic rocks.
As a result of microscopic examination of the ore samples of Başköy ore formation; the ore formation occurred in 3 primary stages and a very weak supergene phase has been demonstrated. Additionally, hydrothermal replacement textures were extensively observed while some hydrothermal displacement textures were barely observed in pyrite and chalcopyrite, colloform texture was observed in pyrite and chalcopyrite and chalcopyrite disease texture was observed in some sphalerite also. Moreover, the ore formation of Başköy mainly formed from pyrite, chalcopyrite, sphalerite, tetrahedrite, and secondary from bornite, covellite, goethite, and quartz as a gang mineral, consequently, it was determined that Başköy ore formation has Kuroko-Cu-Zn VMS ore deposit type mineral paragenesis.
A comparison was conducted between Başköy ore formation and the other deposits in the Eastern Pontide Region (Murgul-Anayatak, Murgul-Damar, Çayeli Madenköyü, Akarşen, and Lahanos), this comparison showed that the paragenetic sequence of Başköy ore formation is slightly different from the paragenetic sequences of the other deposits in Eastern Pontide Region.
The CLM analysis showed that sphalerite has geochemical zoning which can prove that the chemical composition of the hydrothermal solution formed sphalerite was changed during its formation. In addition, dark and non-luminescent zones were detected in some sphalerite micro areas during the CLM analysis. Since Fe+2 CL is a quenching element, it was concluded that black or non-luminescent zones are rich in this element.
As a result of the stable oxygen isotope analysis; the hydrothermal solution forming the Başköy ore formation could be from two different aquifers which is a mixture of seawater and magmatic water. The stable oxygen isotope analysis results of the Başköy ore formation were compared to the stable oxygen isotope analysis results. This comparison showed that the hydrothermal solution forming Başköy ore formation has a different origin from the other hydrothermal solution that laid to
Murgul-Anayatak, Murgul-Damar, Çayeli Madenköyü, Akarşen, and Lahanos deposits formation.
The stable sulfur isotope analyses were applied on pyrite and chalcopyrite samples and the ratios obtained results of the stable sulfur isotope analysis were compared with the sulfur isotope reference ratios of other Eastern Pontides VMS deposits. The sulfur ratios obtained are fitted with the stable sulfur isotope ratios of the Eastern Pontides VMS deposits and it shows a distribution close to the magmatic sulfur values.
EPM analysis were applied on 3 different micro areas where pyrite, sphalerite, and 2 different types of sulfosalt minerals are located. The EPM analysis results show the first sulphosalt is tetrahedrite and it contains 0.67% of silver while the second sulfosalt is stannite. Stannite mineral has never been reported in any Eastern Pontides VMS deposits study before.
A stratigraphical age was determined for Başköy ore formation.