Institute of Earth Sciences

The south-central part of the Greater Caucasus region, Georgia Republic, represents an extremely prospective region for significant orogenic gold deposits. Gold-bearing quartz veins are concentrated in two extensive WNW-trending belts, the Mestia-Racha and Svaneti districts, within the northern margin of the Southern Slope Zone of the Great Caucasus orogen. This metalliferous region is dominated by Early to Middle Jurassic slates, which are part of a terrane that likely accreted to the continental margin from late Paleozoic to Jurassic. The slates were subsequently intruded by both Middle to Late Jurassic and Neogene granitoids. Quartz veins in the more carbonaceous slate units are most consistently enriched in As, Au, Hg, Sb, and W, and show mineralization styles most consistent with typical orogenic gold deposits. Quartz veins in the Mestia-Racha district were mined in Soviet times for As, Sb, and W, but many of these are now being recognized as gold resource targets. The veins occur in the footwall of a thrust fault between the Southern Slope zone and an earlier accreted terrane, the Main Zone, to the north. Many veins in the district continue along strike for N 1 km and some cut Neogene intrusions, constraining ore formation to the most recent 4 to 5 million years. Gold deposition thus correlates with final collision of the Arabian plate to the south and uplift of the ore-hosting Greater Caucasus. The Zopkhito deposit, previously mined for antimony, contains an estimated 55 t Au at a cutoff grade of 0.5 g/t. The veins are localized in an area where smallerorder structures show a major change in strike from N-S to more E-W trends. A pyrite-arsenopyrite ore stage includes gold concentrated in both sulfide phases; it is overprinted by a later stibnite-dominant stage. Fluid-inclusion studies of ore samples from the Zopkhito deposit indicate minimum trapping temperatures of 300 to 350°C and 200 to 300°C for the two stages, respectively, and minimum trapping pressures of 0.2 to 0.5 kbar. Ore-forming fluids, with approximately 5 to 20 mol% non-aqueous gas, evolved from N 2-dominant to CO 2-dominant during evolution of the hydrothermal system. δ 34 S values of +1 to +4‰ for ore-related sulfides at Zopkhito are consistent with a sedimentary rock source for the sulfur, and δ 18 O quartz measurements of 16 to 21‰ are consistent with either a magmatic or metamorphic fluid. More than 60 gold-bearing lodes and placers in the Svaneti district occur along the thrust between the Southern Slope and Main Zones. Lode gold potential was first recognized in the historic placer district in the 1980s, with many auriferous quartz veins cutting Middle Jurassic igneous rocks. Brecciated veins in the 18 t Au Lukhra deposit cut a small granodioritic to dioritic stock; the latter intrudes Devonian schist immediately north of the thrust. Presently, there are three recognized ore zones in the deposit, with the most significant occurring over an area 140 m in length and 12 m-wide, with typical grades of 7 to 9 g/t Au. Reconnaissance fluid-inclusion studies of ore samples from the Lukhra deposit indicate minimum trapping temperatures of 220°C. Measurements of δ 18 O quartz of about 10‰ suggest buffering of isotopic composition by the igneous host rocks.

According to Greek mythology and historical sources the ancient Georgian Kingdom of Colchis was rich of "gold sands" and the natives mined this metal from the rivers, using special wooden vessels and sheepskins. Modern geological research conducted by us in the Svaneti region (Greater Caucuasus) has shown that this area is the province of the former Colchis Kingdom where it was possible to obtain abundant gold from the mountain rivers using the methods unique to this region. We think, from our investigations, that the bedrock and placer gold contents of this region give grounds to believe that there was enough gold in this region to describe Svaneti as "the country rich of this noble metal". After comparing the geological data, artifacts, myths and historical sources, we share the viewpoint of the Roman historian Apian Alexandrine (90e170 AD) and suppose that the myth about expedition of Argonauts in quest of the "Golden Fleece" to the Colchis Kingdom was a real event and that the main purpose of this mission was to obtain gold and sheepskin (fleece) technique of gold mining. Though there are a lot of varients of the explanation of the "Golden Fleece" phenomena in historical literature. According to one of the theories the "Golden Fleece" phenomena as a symbol of Colchian gold, was not confined solely to representations of actual gold mining. Other theorists saw the "Golden Fleece" as a symbol of the wealth of the Colchis, famed since antiquity for the abundance of their precious metals. The phenomena of the "Golden Fleece" according to our research, is connected with the sheepskin technique of recovering placer gold. The end result of this technique of gold recovery river gravels was a gold imprinted sheepskin, giving rise to the romantic and unidentified phenomena of the "Golden Fleece" in the civilized world.

/XXXXX The eastern part of the Caucasus orogen, termed the Georgian segment, is mainly underlain by highly deformed Lower-Middle Jurassic shales, sandstones, and volcaniclastic rocks, and cut by numerous intrusive bodies of various compositions. All units contain a variety of mineral deposit types and their surrounding zones of hydrothermal alteration. Detailed geological and metallogenic research, after 30 years stagnation, has led to important new information regarding the evolution of this region. Three main stages of magmatic activity are now clearly distinguished. The oldest magmatism comprises early Jurassic events, related to extensional tectonism, with volcanism and subvolcanic plutonism that ranged from rhyolitic, through dacitic and andesitic, and to basaltic. Additional extensional processes (in Bajocian times) were characterized by intrusion of a gabbro and diorite dike system into slightly older late Early Jurassicearly Middle Jurassic formations. The final magmatic event was associated with Middle Jurassic folding and uplift during which multiphase diorite plutons were emplaced. Intense hydrothermal activity related to this latest magmatism was responisble for important polymetallic mineralization including more than 100 historically recognized outcropping occurrences. A detailed study of 11of the more significant of these occurrences has indicated anomalous concentrations of base metals as well as gold, thorium, yttrium, cobalt, cadmium, and bismuth. In addition, several new and potentially significant mineral occurrences were discovered, including two designated here as Gelia and Lechuri.

Kakheti and Tusheti regions (Eastern Graeter Caucasus), of the Georgia Republic are mainly underlain by highly deformed Lower-Middle Jurassic shales, sandstones, and volcaniclastic rocks, intruded by numerous intrusive bodies of various compositions. All units contain a variety of ore mineral deposit types and their surrounding zones of hydrothermal alteration. Continued geological and metallogenic researches in the past 30 years have led to important new information regarding the evolution of this region. Three main stages of magmatic activity are now clearly distinguished. Oldest magmatism comprises Early Jurassic events, related to extensional tectonism, which ranged from rhyolitic, through dacitic and andesitic, and to basaltic magma. Additional extensional processes (in Bajocian) were characterized by intrusion of a gabbro and diorite dike system into recently deposited late Early Jurassic-early Middle Jurassic formations. The final magmatic event was associated with Middle Jurassic folding and uplift during which multiphase diorite plutons were emplaced. Related intense hydrothermal activity was responsible for important polymetallic mineralization, with more than 100 recognized outcropping ore occurrences. A detailed study of 11 of these ore occurrences has indicated anomalous concentrations of gold, thorium, yttrium, cobalt, cadmium, and bismuth. In addition, several new and potentially significant ore mineral occurrences were discovered.

ВУЛКАНОГЕННЫЕ МЕСТОРОЖДЕНИЯ ЦВЕТНЫХ МЕТАЛЛОВ ПАЛЕООСТРОВОДУЖНЫХ СООРУЖЕНИЙ И ПРОБЛЕМЫ ГЕНЕЗИСА РУД (на примере рудных обьектов Грузии, Армении и Турции) (Рекомендовано членом редакційної колегії д-ром геол.-мінерал. наук, проф. В.М. Загнітком) Цель: изучение околорудного пространства вулканогенных месторождений цветных металлов палеоостроводужных сооружений (на примере Маднеульского месторождения) и определение условий их формирования с использованием геохимических и термобарогеохимических исследований. Методы: выполнено картирование карьера Маднеульского месторождения, определены содержания редких и рассеянных элементов на приборе ICP-MS, в Геологической службе США и Кавказском институте минерального сырья проведены термобарогеохимические исследования и определён изотопный состав кислорода и водорода в рудах. Результаты: выявлены структурные особенности месторождения, характер околорудного пространства, определён минеральный состав метасоматитов и доказана многоэтапность формирования месторождений. Научная новизна: высказаны соображения о генезисе вулканогенных месторождений альпийских палеоостроводужных сооружений с учётом выполненных авторами термобарогеохимических исследований, а также с привлечением существующих в научном мире представлений о генезисе месторождений. Практическая значимость: описанные особенности околорудного пространства могут быть с успехом использованы в других регионах в процессе поисков месторождений вулканогенного класса.

The Greater Caucasus represents a Phanerozoic collisional orogen which is formed along the Euro-Asian North continental margin between the Black and Caspian Seas, and is accreted to the south margin of the Euroasian continent. The Kakheti region is located on the eastern part of the southern slope of the Greater Caucasus and is mainly formed of strongly folded Lower Jurassic clay-shales and mafic volcanic-sedimentary formations. Ore mineralization is related to hydrothermally altered zones, which are significantly enriched in rare metals – thorium and bismuth, and also in gold, zinc, lead and cobalt. The studied area is underlain with highly deformed Lower-Middle Jurassic sediments and volcaniclastic rocks, associated with numeorus intrusive bodies. The rocks contain variety of mineralization types and hydrothermal alteration. The largest outcrop of felsic hypo-abyssal dykes is Speroza massif, which has a lenticular shape with a length of 14 km. It represnets the area of mesothermal...

The Caucasus is a central segment of the Mediterranean Alpine-Himalayan collisional orogenic system and consists of the Greater and Lesser Caucasus orogens and intermountain depression. There are numerous layers of volcanic ashes in the late Miocene marine sediments (dated paleontologically) of the Eastern Caucasus intermountain depression. The ashes consist primarily of hornblende, pyroxene, and volcanic glass (Skhirtladze, 1964). The thickness of the layers varies between 5 m to several decimeters, while their distribution area is wide and includes the Kartli and Kakheti regions in Georgia and the western region of Azerbaijan

Magmatism and Mineral Occurrences of the Eastern Greater Caucasus, Georgian Segment N. GAGNIDZE, A.OKROSTSVARIDZE, K. AKIMIDZE, S. L. CHUNG Ilia state University, Tbilisi 0162, Georgia, (*correspondence:[email protected]) Javakhishviuli State University, Tbilisi 0138, Georgia ([email protected]) 3 Institute of Earth Science, Academia Sinica, Taipei 11529, Taiwan ([email protected])

The authors’ aim was determination of estimated gold resources on the basis of the geological data analysis. The following methods were used for calculation of resources: parameters of ore bodies at gold occurrences, data of geochemical anomalies, geological evidence indicating existence of ore bodies in the depth. The territory of Georgia includes part of the Alpine-Himalayan mountain-fold belt, which is a result of interaction of the Scythian and South Caucasus microplates geologically developed in the marginal area of the Eurasian continent. Four gold bearing complexes are found on the territory of Georgia: 1) Activated in Middle Jurassic south Caucasus microcontinent slope and slope root zones, which are built by Palaeozoic Middle-Early Jurassic marginal sea flischoid-terrigenous sediments (potential in Middle Jurassic deposits in granite stocks Lukhra and in carbonaceous suite Arshira, Lasilli, on Svaneti ridge; 2) The Greater Caucasus southern slope suture zone (“main thrusts”...

The Greater Caucasus represents a Phanerozoic collisional orogen which is formed along the Euro-Asian North continental margin between the Black and Caspian Seas and is extended over 1200 km distance between the Black and Caspian seas, and considered as a terrane of the first order, which is accreted to the south margin of the Euroasian continent. The Kakheti segment is located on the eastern part of the southern slope of the Greater Caucasus and is mainly formed of strongly folded Lower Jurassic clay-shales and mafic volcanic-sedimentary formations. According to geophysical data these sediments are located on oceanic or transitional crust. Ore mineralization is related to hydrothermally altered zones, which are significantly enriched by rare metals – thorium and bismuth, and also by gold, copper, zinc, lead and cobalt.

Metallogenic features of Pontides – Lesser Caucasus microplates (part of active paleomargin of Eurasian microplate are determined by copper, copper-molibdenium porphyry, iron-scarn, volcanic nonferrous, precious metals, auriferous and manganese ore deposits. Their orebearing fluid systems occurred consistently on various stages of development of the region and were correlated with geological processes on the border of convergental and divergental interaction of mic¬roplates. The above mentioned types of ore deposits display clear areal and temporary bonds with certain composites of lithogeodynamic complexes (which are presented in mountain folding systems of relics of ancient geomorphological structures) - geological formations. Different geologic-genetical models are suggested for each type of deposits, characterizing possible sources of ore substance, causes of rise and functions of fluid systems, in addition to ore formation environment. It may be said that different genetic grou...

The Caucasus represents a Phanerozoic collisional orogeny, that formed along the Eurasian North continental margin, extends over 1200 km from the Caspian to Black Sea. Georgian republic is situated in the central part of Caucasus Region. Here are marked 3 ore occurrences of thorium : 1-in the Greater Caucasus (Th concentrations vary between 51g/t 3882g/t); 2in the Dzirula massif (Th concentrations vary between 117 g/t -266 g/t); 3in Vakijvari orefield (Th concentrations vary between 185 g/t 428 g/t). Based on these data thorium ore occurrences found in Georgia should be treated as prospective resources.

The paper presents brief characteristics of geological environments of ore deposit occurrences in Turkey, Georgia and Armenia. They can be attributed to Kuroko-type deposits, being distinguished by the character of ore accumulation. To the west, in Turkey, there are epigenetic and hydrothermal-sedimentary copper-zinc deposits that were formed in deep restricted basinal settings. An example of the latter is the Chayeli deposit.To the east, in the Caucasus, we have predominantly only epigenetic deposits. Besides, in the Bolnisi mining district (Georgia) there is the Madneuli deposit which represents an example of polyformational deposit. Here, within the restricted territory, have been concentrated:barite, barite-polymetallic, gold-bearing secondary quartzite, large-scale stockworks of copper ores. Judged by the 87Sr/86Sr ratios, some volcanites which are spatially associated with ores, might have been products of the “differentiation” of undepleted mantle, or other magmas that were g...