Abstract The Jurassic to Early Cretaceous magmatic and metallogenic evolution of the Lesser Caucasus and Eastern Pontides segment of the Central Tethyan orogenic belt is still poorly understood. This study reports an investigation about the link between ore formation and magmatic evolution in the major Gedabek porphyry-epithermal mining district, which is located in the Somkheto-Karabagh belt, Azerbaijan. Long-lasting magmatic arc evolution of ~50 m.y., from the Middle Jurassic to the Early Cretaceous, is supported by new U-Pb zircon ages between 164.3 ± 0.7 and 125.1 ± 0.5 Ma. Middle Jurassic magmatic rocks have a dominantly tholeiitic to transitional and primitive island-arc composition, whereas Late Jurassic to Early Cretaceous magmatic rocks are calc-alkaline to shoshonitic and have mature island-arc compositions. Radiogenic isotopes document a higher mantle contribution during petrogenesis of the Late Jurassic-Early Cretaceous magmatic rocks. The combined data document progressive magmatic arc maturation and crustal thickening from the Middle Jurassic to the Early Cretaceous, accompanied by slab roll-back and asthenospheric upwelling. This evolution is shared by other areas of the Somkheto-Karabagh belt and its southern extension in the Kapan block, which also host porphyry-epithermal mining districts. Muscovite and K-feldspar from a porphyry Cu-related potassic alteration assemblage at the Gedabek deposit (overprinted by a younger intermediate- to high-sulfidation epithermal system) have yielded 40Ar/39Ar ages between 140.1 ± 1.0 and 136.3 ± 0.9 Ma. Together with a previous Re-Os molybdenite age, they document formation of the porphyry-epithermal systems at the end of the long magmatic arc maturation of the Gedabek district. Although ore-forming events were diachronous along the arc, the relative timing of magmatic evolution and ore formation at Gedabek is shared by the other Late Jurassic to Early Cretaceous mining districts of the Somkheto-Karabagh belt and the Kapan block. Our study demonstrates that long arc maturation and crustal thickening has taken place along the southern Eurasian margin from a Middle Jurassic nascent arc to an Early Cretaceous evolved arc. This evolution is in line with the essential prerequisites for the genesis of porphyry-epithermal systems in orogenic belts. It also provides evidence that Middle Jurassic to Early Cretaceous magmatic fertile systems and porphyry-epithermal centers have been preserved in this belt.

Abstract This contribution reviews the metallogenic setting of the Lesser Caucasus within the framework of the complex geodynamic evolution of the Central Tethys belt during convergence and collision of the Arabia-, Eurasia-, and Gondwana-derived microplates. New rhenium-osmium molybdenite ages are also presented for several major deposits and prospects, allowing us to constrain the metallogenic evolution of the Lesser Caucasus. The hostrock lithologies, magmatic associations, deposit styles, ore controls, and metal endowment vary greatly along the Lesser Caucasus as a function of the age and tectono-magmatic distribution of the ore districts and deposits. The ore deposits and ore districts can essentially be assigned to two different evolution stages: (1) Mesozoic arc construction and evolution along the Eurasian margin, and (2) Cenozoic magmatism and tectonic evolution following Late Cretaceous accretion of Gondwana-derived microplates with the Eurasian margin. The available data suggest that during Jurassic arc construction along the Eurasian margin, i.e., the Som-kheto-Karabagh belt and the Kapan zone, the metallogenic evolution was dominated by subaqueous magmatic-hydrothermal systems, VMS-style mineralization in a fore-arc environment or along the margins of a back-arc ocean located between the Eurasian margin and Gondwana-derived terranes. This metallogenic event coincided broadly with a rearrangement of tectonic plates, resulting in steepening of the subducting plate during the Middle to Late Jurassic transition. Typical porphyry Cu and high-sulfidation epithermal systems were emplaced in the Somkheto-Karabagh belt during the Late Jurassic and the Early Cretaceous, once the arc reached a more mature stage with a thicker crust, and fertile magmas were generated by magma storage and MASH processes. During the Late Cretaceous, low-sulfidation-type epithermal deposits and transitional VMS-porphyry-epithermal systems were formed in the northern Lesser Caucasus during compression, uplift, and hinterland migration of the magmatic arc, coinciding with flattening of the subduction geometry. Late Cretaceous collision of Gondwana-derived terranes with Eurasia resulted in a rearrangement of subduction zones. Cenozoic magmatism and ore deposits stitched the collision and accretion zones. Eocene porphyry Cu-Mo deposits and associated precious metal epithermal systems were formed during subduction-related magmatism in the southernmost Lesser Caucasus. Subsequently, late Eocene-Oligocene accretion of Arabia with Eurasia and final closure of the southern branch of the Neotethys resulted in the emplacement of Neogene collision to postcollision porphyry Cu-Mo deposits along major translithospheric faults in the southernmost Lesser Caucasus. The Cretaceous and Cenozoic magmatic and metallogenic evolutions of the northern Lesser Caucasus and the Turkish Eastern Pontides are intimately linked to each other. The Cenozoic magmatism and metal-logenic setting of the southernmost Lesser Caucasus can also be traced southward into the Cenozoic Iranian Urumieh-Dokhtar and Alborz belts. However, contrasting tectonic, magmatic, and sedimentary records during the Mesozoic are consistent with the absence of any metallogenic connection between the Alborz in Iran and the southernmost Lesser Caucasus.

Abstract We present arguments for an innovative tectonic set-up just prior to the Northern Neotethys obduction event in the NE Anatolian and Lesser Caucasus area. Along the Northern Neotethyan suture (the Ankara–Erzincan–Amasia–Sevan–Akera suture zone), relicts of the northern branch of the Neotethys oceanic domain outcrop as preserved unmetamorphosed slivers obducted over the northern edge of the South Armenian Block (SAB) and Taurides–Anatolides Platform (TAP) margins. Recent studies have shown that the ophiolitic bodies are formed of similar lithologies of Middle Jurassic age, all bearing mid-ocean ridge basalt chemical compositions enriched in large ion lithophile elements. This extensive database supports a model in which these ophiolites are derived from a single obducted nappe. This model is supported by the metamorphic pressure–temperature–time paths of the sole lithologies under the outcrops of the suture zone ophiolites. Palaeontological dating of sediment deposits directly under or sealing the obduction contact also support this model by temporally linking the emplacement of distant ophiolite outcrops. General emplacement during early Late Cretaceous time has been determined. A south-dipping subduction under the SAB shortly predating obduction has recently been proposed from the metamorphic and magmatic evolution preserved in the SAB crystalline basement, founding a model featuring opposite-direction subduction from at least late Middle Jurassic to Early Cretaceous times. The emplacement of alkaline pillow basalts directly on the oceanic crust is dated as Early to mid-Cretaceous. These dates argue the existence of abnormal mantle heat flows which may be responsible for a decrease in the density of the 80 Ma-old oceanic lithosphere prior to its obduction onto the SAB–TAP. We present a detailed review of recent data to further constrain the structural and geodynamic evolution of this sector and to define the tectonic set-up just prior to the obduction event.

Abstract In the Lesser Caucasus three main domains are distinguished from SW to NE: (1) the autochthonous South Armenian Block (SAB), a Gondwana-derived terrane; (2) the ophiolitic Sevan–Akera suture zone; and (3) the Eurasian plate. Based on our field work, new stratigraphical, petrological, geochemical and geochronological data combined with previous data we present new insights on the subduction, obduction and collision processes recorded in the Lesser Caucasus. Two subductions are clearly identified, one related to the Neotethys subduction beneath the Eurasian margin and one intra-oceanic (SSZ) responsible for the opening of a back-arc basin which corresponds to the ophiolites of the Lesser Caucasus. The obduction occurred during the Late Coniacian to Santonian and is responsible for the widespread ophiolitic nappe outcrop in front of the suture zone. Following the subduction of oceanic lithosphere remnants under Eurasia, the collision of the SAB with Eurasia started during the Paleocene, producing 1) folding of ophiolites, arc and Upper Cretaceous formations (Transcaucasus massif to Karabakh); 2) thrusting toward SW; and 3) a foreland basin in front of the belt. Upper–Middle Eocene series unconformably cover the three domains. From Eocene to Miocene as a result of the Arabian plate collision with the SAB to the South, southward propagation of shortening featured by folding and thrusting occurred all along the belt. These deformations are sealed by a thick sequence of unconformable Miocene to Quaternary clastic and volcanic rocks of debated origin.