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Durham Research Online Deposited in DRO: 15 September 2016 Version of attached le: Accepted Version Peer-review status of attached le: Peer-reviewed Citation for published item: Moritz, R. and Melkonyan, R. and Selby, D. and Popkhadze, N. and Gugushvili, V. and Tayan, R. and Ramazanov, V. (2016) 'Metallogeny of the Lesser Caucasus : from arc construction to post-collision evolution.', in Special publications of the Society of Economic Geologists. , pp. 157-192. Special publications. (19). 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Durham University Library, Stockton Road, Durham DH1 3LY, United Kingdom Tel : +44 (0)191 334 3042 | Fax : +44 (0)191 334 2971 https://dro.dur.ac.uk Manuscript Click here to download Manuscript Metallogeny Lesser Caucasus Revised version.pdf 1 1 Metallogeny of the Lesser Caucasus: From arc construction to post-collision evolution 1 2 3 2 4 5 3 6 7 1,a 2 3 4 8 4 Robert Moritz , Rafael Melkonyan , David Selby , Nino Popkhadze , 9 10 4 2,* 5,** 11 5 Vlademir Gugushvili , Rodrig Tayan and Vagif Ramazanov 12 13 6 14 15 16 7 1 Department of Earth Sciences, University of Geneva, Rue des Maraîchers 13, 1205 Geneva, 17 18 8 Switzerland 19 9 20 21 10 2 Institute of Geological Sciences, National Academy of the Republic of Armenia, 22 23 11 Baghramyan Avenue 24, 0019 Yerevan, Armenia 24 12 25 3 26 13 Department of Earth Sciences, University of Durham, DH1 3LE United Kingdom 27 14 28 4 29 15 A. Djanelidze Institute of Geology of I. Javakhishvili Tbilisi State University, Politkovskaia 30 16 St. 5, 0186 Tbilisi, Georgia 31 32 33 5 Geological Department, Baku State University, Z. Khalilov St. 23, Az1145, Baku, 34 17 35 18 Azerbaijan 36 37 19 38 20 39 40 21 * deceased March 25th 2016 41 th 42 22 ** deceased May 7 2014 43 44 23 45 24 46 47 25 48 26 a corresponding author: Robert MORITZ, University of Geneva, Rue des Maraîchers 13, 1205 49 50 27 Geneva, Switzerland; e-mail: [email protected] 51 28 52 53 54 29 55 30 56 57 58 31 59 60 61 62 63 64 65 2 32 Abstract 1 33 This contribution reviews the metallogenic setting of the Lesser Caucasus within the framework of the 2 3 34 complex geodynamic evolution of the Central Tethys belt during convergence and collision of Arabia, 4 5 35 Eurasia and Gondwana-derived microplates. New rhenium-osmium molybdenite ages are also 6 36 presented for several major deposits and prospects, allowing us to constrain the metallogenic evolution 7 8 37 of the Lesser Caucasus. The host rock lithologies, magmatic associations, deposit styles, ore controls 9 10 38 and metal endowment vary greatly along the Lesser Caucasus as a function of the age and tectono- 11 magmatic distribution of the ore districts and deposits. The ore deposits and ore districts can be 12 39 13 40 essentially assigned to two different evolution stages: (1) Mesozoic arc construction and evolution 14 15 41 along the Eurasian margin, and (2) Cenozoic magmatism and tectonic evolution following late 16 17 42 Cretaceous accretion of Gondwana-derived microplates with the Eurasian margin. 18 19 43 The available data suggest that during Jurassic arc construction along the Eurasian margin, i.e. the 20 44 Somkheto-Karabagh belt and the Kapan zone, the metallogenic evolution was dominated by 21 22 45 subaqueous magmatic-hydrothermal systems, VMS-style mineralization in a fore-arc environment or 23 24 46 along the margins of a back-arc ocean located between the Eurasin margin and Gondwana-derived 25 47 terranes. This metallogenic event coincided broadly with a rearrangement of tectonic plates, resulting 26 27 48 in steepening of the subducting plate during the middle to late Jurassic transition. 28 29 30 49 Typical porphyry Cu and high-sulfidation epithermal systems were emplaced in the Somkheto- 31 50 Karabagh belt during the late Jurassic and the early Cretaceous, once the arc reached a more mature 32 33 51 stage with a thicker crust, and fertile magmas were generated by magma storage and MASH processes. 34 35 52 During the late Cretaceous, low-sulfidation type epithermal deposits and transitional VMS-porphyry- 36 53 epithermal systems were formed in the northern Lesser Caucasus during compression, uplift and 37 38 54 hinterland migration of the magmatic arc, coinciding with flattening of the subduction geometry. 39 40 41 55 Late Cretaceous collision of Gondwana-derived terranes with Eurasia resulted in a rearrangement of 42 56 subduction zones. Cenozoic magmatism and ore deposits stitched the collision and accretion zones. 43 44 57 Eocene porphyry Cu-Mo deposits and associated precious metal epithermal systems were formed 45 46 58 during subduction-related magmatism in the southernmost Lesser Caucasus. Subsequently, late 47 59 Eocene-Oligocene accretion of Arabia with Eurasia and final closure of the southern branch of the 48 49 60 Neotethys resulted in the emplacement of Neogene collision to post-collision porphyry Cu-Mo 50 51 61 deposits along major translithospheric faults in the southernmost Lesser Caucasus. 52 53 62 The Cretaceous and Cenozoic magmatic and metallogenic evolutions of the northern Lesser Caucasus 54 55 63 and the Turkish Eastern Pontides are intimately linked to each other. The Cenozoic magmatism and 56 57 64 metallogenic setting of the southernmost Lesser Caucasus can also be traced southwards into the 58 65 Cenozoic Iranian Urumieh-Dokhtar and Alborz belts. However, contrasting tectonic, magmatic and 59 60 61 62 63 64 65 3 66 sedimentary records during the Mesozoic are consistent with the absence of any metallogenic 1 67 connection between the Alborz in Iran and the southernmost Lesser Caucasus. 2 3 4 68 5 6 69 Introduction 7 8 70 The Lesser Caucasus is a major segment of the Tethyan belt, which extends from the Black Sea to the 9 71 Caspian Sea, across Georgia, Armenia and Azerbaijan (Figs 1 and 2). This mountain belt links the 10 11 72 Western and Central metallogenic Tethys belts with their extensions into Asia (Jankovic, 1977, 1997; 12 13 73 Richards, 2015). The Lesser Caucasus was formed as a consequence of convergence and collision of 14 74 Eurasia, Gondwana-derived terranes and Arabia, and it evolved from a Jurassic nascent subduction- 15 16 75 related magmatic arc environment to a Neogene post-collisional setting (Fig. 3). This geodynamic 17 18 76 evolution resulted in episodic ore formation in response to particular tectonic and magmatic events 19 across the entire belt (Figs 1, 2 and 3). 20 77 21 22 78 In this contribution, we focus on ore deposit belts and districts from the Lesser Caucasus only (Figs 1 23 79 and 2), and discuss their genetic link with adjoining metallogenic provinces in eastern Turkey and 24 25 80 northern Iran. While the metallogenic aspects of the Tethyan segments along Turkey and Iran have 26 27 81 been relatively well addressed in recent contributions (e.g. Yigit, 2009; Kusçu et al., 2013; Aghazadeh 28 82 et al., 2015), there is only fragmentary information available about the Lesser Caucasus in reviews 29 30 83 about Tethyan metallogeny and Tethyan porphyry belts (e.g. Tvalchrelidze, 1980, 1984; Cooke et al., 31 32 84 2005; Richards, 2015). We deliberately restrict this review to the Lesser Caucasus, because of its 33 85 particular position as a link between the Turkish and Iranian mountain belts, and to keep this report to 34 35 86 a reasonable length. We are aware that the metallogenic evolution of this part of the Tethys belt goes 36 37 87 beyond the geographic limits of the Lesser Caucasus, such as the Greater Caucasus for example 38 88 (Tvalchrelidze, 1980, 1984), which includes orogenic gold-style mineralization (Kekelia et al., 2008), 39 40 89 intrusion-related gold and polymetallic style mineralization (Okrostsvaridze et al., 2015), and black 41 42 90 shale-hosted gold and polymetallic deposits, such as the famous Filizçay and Kızıldere deposits 43 91 (Markus, 2002; Kekelia et al., 2004). 44 45 46 92 The main host rock, alteration, ore characteristics, and ages of the ore districts and deposits described 47 48 93 in this review are presented in Figures 1 and 2, summarized in Table 1, and set in a geodynamic 49 94 scheme in Figure 3. New Re-Os molybdenite ages obtained for several ore deposits and occurrences 50 51 95 are summarized in Table 2. The host rock lithologies, magmatic associations, deposit styles, ore 52 53 96 controls and metal endowment vary greatly along the Lesser Caucasus as a function of the age and 54 97 tectono-magmatic distribution of the ore districts and deposits. The mineral districts of the Lesser 55 56 98 Caucasus can be grouped and discussed according to their distribution among the major tectonic and 57 58 99 magmatic zones of this mountain belt (Fig. 2). The first group includes mineral districts associated 59 100 with the Mesozoic subduction-related, magmatic evolution of the Eurasian margin, which are hosted 60 61 62 63 64 65 4 101 by the Kapan zone, the Somkheto-Karabagh belt and its northern Georgian extension, named the 1 102 Artvin-Bolnisi zone (Fig.