Sofia University “St. Kl. Ohridski”, Faculty of Geology and Geography, Department of Mineralogy, Petrology and Economic Geology, 15 Tsar Osvoboditel Blvd., 1504 Sofia, Bulgaria; E- mails: [email protected] ORE DEPOSITS OF NORTH-EASTERN GREECE AND SOUTH-EASTERN BULGARIA - SOFIA UNIVERSITY SEG STUDENT CHAPTER FIELD TRIP – 2019 1 CONTENTS Introduction .................................................................................................... 2 “Khan Krum” (Ada Tepe) Deposit .............................................................. 3 Perama Hill Deposit ....................................................................................... 4 Xylagani VMS Deposit ................................................................................. 5 Maronia Deposit ............................................................................................. 6 Intrusion-related mineralization in Palea Kavala area ............................ 7 Stratoni, Skouries and Olimpias deposit (Kassandra mines) ................... 8 Vourinos Ophiolite Complex (Grevena Geopark) ..................................... 9 Acknowledgments ........................................................................................ 10 2 Introduction This year during 23-29th of May, 2019 Sofia University SEG Student Chapter organized six day field trip in North-Eastern Greece and South-Eastern Bulgaria. The aim of the trip was to visit and examine the regional geology and metallogeny of the area. In the trip twenty students (Fig.1.) with different degrees of education take a part from bachelors to PhD students. The visited deposits were “Khan Krum” (Ada Tepe) deposit, Perama Hill deposit, Maronia deposit, Palea Kavala deposit, Olimpias and Stratoni deposits (Kassandra mine), Skorious deposit and Vourinos ophiolite complex (Grevena Geopark). The main activities during our visitations were examine drillcore, examine on the field characteristics of the different types of mineralization, holding discussions on the formation of the deposits and many other fieldwork activities. The leaders of the field trip were Professors K. Bogdanov and N. Botoucharov from Sofia University and V. Melfos from Aristotle University of Thessaloniki and Dr Anne Ewing Rassios. Fig.1. Sofia University SEG Student Chapter members and other students. “Khan Krum” (Ada 3 Tepe) Deposit During the first day we visited “Khan Krum” (Ada Tepe) deposit in South-Eastern Bulgaria operated by Dundee Precious Metals. We had introductory presentation (Fig.2.) about the deposit is attached to large metamorphic complex in Eastern Rhodopes that suffered extension during Upper Cretaceous period that formed detachment faulting with orientation N-NE (10°-15°) and sedimentary basins in which occurs terrestrial and marine sediments. The deposit is typically epitermal low-sulphidation Au-Ag deposit with erosion features and Paleogene age. There are no evidence for the mineralization to be related to the volcanism. The origin of the fluid that is bearing the mineralization is metamorphic. Due to construction activities at the mine we were only able to visit the drillcore shelter (Fig.3.) where we examine the quartz Au bearing veins (Fig.4.). The mining will be with open-pit method and conventional processing methods, including crushing, grinding, and flotation processing will be employed for extracting gold. The Ada Tepe deposit is estimated to contain approximately 6.2Mt of ore and it is estimated to contain 800,000oz of gold grading 4.03g/t Au and it will operate at least 8 years. Fig.3. Тhe typical quartz Au bearing veins. Fig .2. Presentation on the metallogeny and genesis of the deposit. Fig.4. Introducing the students to the basic mineralization in the deposit. 4 Perama Hill Deposit Next day, we visited Perama Hill deposit operated by “Eldorado Gold”. It is a high- to intermediate-sulfidation Au-Ag-Te-Se epithermal system located in the Petrota graben (Fig.5.). The mineralization forms ore veins in the Oligocene silicified and argillic-altered andesite and oxidized Au-rich mineralization in the overlying sedimentary rocks. The deposit evolved from an early stage silica-pyrite rock and argillic alteration followed by the deposition of sulfide-, sulfosalt- and telluride-bearing quartz-barite veins (Fig.6.) and stockworks. There are to stages of mineral deposition: 1) high sulfidation stage – with gangue minerals pyrit, coveline, energit, tetradymite, tellurides and etc.; 2) intermidiate sulfidation stage – with quartz-barite veins composed of tennantite, Au, electrum, telurites, bismuth and etc. The presence of energit indicates the high sulfidation stage and tennantite is indicative for the intermidiate sulfidation stage. Also the presence of tellurides and selenides presume that under the high sulfidation zone there is porphyry magmatic intrusion. The proven and probable reserves are 975,000 oz Au 3.14 g/t (Eldorado Gold 2016), but it cannot proceed to the operational stage because of legislative and environmental obstacles. Fig.5. Discussion with students about geological features of Petrota graben. Fig.6. Surface telluride-bearing quartz-barite veins and stockworks. Xylagani (VMS) 5 Deposit On the next day we visited Xylagani Mesozoic gold-bearing Fe-Cu volcanogenic massive sulfide (VMS) deposit (Fig.7.). The mineralization shares common characteristics with the Cyprus-type mineralizations. The mineralization is hosted in Mesozoic lavas and tuffs which belong to the Circum Rhodope belt and have been metamorphosed to low grade stage with prehnite and pumpellyite. The silicified mineralized bodies are hosted in the metavolcanic rocks. The main the hydrotermall alteration is chlorite-sericite alteration and the fluids extracted basic metals (Au, Cu, Zn and etc.) from the host rocks. There are five types of mineralization: thin layered, disseminated, disseminated to massive and massive sulfide (pyrite or chalcopyrite-pyrite) mineralizationc (Fig.8.) as well as quartz veins poor in sulfides. The ore mineral assemblage consists of pyrite, chalcopyrite, sphalerite, galena, pyrrhotite, tennantite and gold. The main gangue minerals are quartz, white mica and chlorite. Fig.7. Field work and discussion about volcanogenic massive sulfide (VMS) deposit. Fig.8. Massive sulfide (pyrite or chalcopyrite- pyrite) mineralization. 6 Maronia Deposit In our third day in Greece after a long march and an introduction to the history of the area we visited porphyry Cu-Mo deposit in the Maronia area (Fig.9.), which belongs to the Rhodope metallogenic province. The geology of the area is dominated by metamorphosed sediments and volcanic rocks and by Tertiary plutonic and subvolcanic intrusions. The metamorphic rocks belong to the Makri Unit of the Circum Rhodope Belt and consist mainly of marbles and schists. The marbles and schists of the Makri Unit are intruded by detachemnt fault the Oligocene Maronia pluton of gabbro-monzogabbro-monzonitic composition. Chalcopyrite-pyrite-molybdenite mineralisation, concentrated mainly in the silicified zones and associated with areas of phyllic and propylitic alteration, occurs as disseminations, veinlets and segregations. The marbles are cross-cut by hematite and goethite veins that are near normal fault footwall type (Fig.10.) along to the sea side that is very typicall for detachment fault. A high temperature skarn is formed at the contact zone of the Maronia pluton with the calcareous schists and the marbles. The Maronia skarn is Ca- and Al-rich. The main minerals observed are wollastonite, larnite, calcite, grossular-andradite garnet, diopside, vesuvianite, clinopyroxene, augite, sodalite and etc. The probable reserves are 1.32 Mt of ore at an average grade of 15.1 g/t Au. Fig.10. Surface manifestation of the normal fault footwall type, typicall for detachment faults. Fig.9. Approaching the field of Maronia with beautiful view. Intrusion-related 7 mineralization in Palea Kavala area During the fourt day we visited intrusion-related Palea Kavala area, which is composed of metamorphic rocks of the Pangeon which is large metamorphic core complex that was exhumed and later Kavala pluton was intruded along the detachment fault Kavala- Komotini. The Kavala pluton (Fig.11.) has the characteristics of an I-type intrusion and is dominantly composed of amphibole-biotite granodiorite with subordinate amounts of diorite, tonalite, monzogranite, and monzodiorite. A total of 150 minor and major base and precious metal occurrences. These metal occurrences have a magmatic-hydrothermal origin and are found within the Kavala pluton (Fig.12.), as well as in the surrounding metamorphic rocks. Variable metal assemblages that consist of weathered and oxidized Fe-Mn-Au bodies are localized in marbles, whereas Fe-As-Au, FeCu-Au, and Bi-Te-Au are hosted in gneisses and granitoids. Fig.12. Student examine the mineralization of Kavala pluton rocks. Fig.11. Presentation of Kavala pluton its mineralization and time of its intrusion. Stratoni, Skouries and 8 Olimpias Deposits (Kassandra mines) During our fifth day we visited the Kassandra mining area operated by “Eldorado Gold” and comprises the Skouries Au-Cu porphyry and the Stratoni and Olympias massive sulphide deposits. We were welcomed by the geology staff who presented us at a presentation about the local geology and characteristics of the deposits. We also examine the common mineral association for the deposits in the drillcore shelter (Fig.13). The Skouries deposit is a typical sub-alkaline Cu-porphyry deposit. The alteration zones at