Phanerozoic magmatic activity in the northwestern part of the Trans-European Suture Zone

In northwestern Iran, magmatic activity occurred during three main intervals: The Cretaceous, Eocene, and Miocene-Quaternary. The first two phases of magmatic activity are more consistent with arc-type magmatism on an active continental margin; whereas the last phase, which has calc-alkaline and alkaline affinities, shows more similarity to postcollisional magmatism. Magmatic belts are mostly situated in the northern and eastern parts of the Oshnavieh–Salmas–Khoy ophiolite belt (OSK-Ophiolite) in northwestern Iran. The OSK-Ophiolite is known as the Neotethys, an ocean remnant in northwestern Iran, and extends to eastern Turkey and surrounds the Van area. This configuration shows that the Van microplate and surrounding ocean have played an important role in the evolution of magmatic activity in northwestern Iran, eastern Turkey, and the Caucasus since the Cretaceous. The Van microplate is situated among the Arabian plate to the south, northwestern Iran to the east, and Armenia to the north. The subduction of the northern branch of the Neotethys oceanic lithosphere beneath southern Eurasia has been critical in flare-up magmatism in the southern Caucasus since the Late Cretaceous. Considering the Van area as a new microplate makes understanding the geodynamic evolution of this area easier than in the many tectonic models that have been suggested before. When regarding the Van microplate, the main suture zone, which is known as the Bitlis–Zagros zone, should be changed to the Zagros–Khoy–Sevan–Akera suture zone, which extends to the eastern and northern Van microplate and western Iran.

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High-temperature acid magmatic rocks from the Late Cretaceous suture zone between European plate and Adria microplate (Croatia)

10.5194/egusphere-egu2020-10088 ◽

2020 ◽

Author(s):

Petra Schneider ◽

Dražen Balen

Keyword(s):

High Temperature ◽

Late Cretaceous ◽

Suture Zone ◽

Age Dating ◽

Magma Source ◽

Northwestern Part ◽

Magmatic Complex ◽

Magmatic Rocks ◽

The Village ◽

European Plate

The Late Cretaceous magmatic rocks within the southwestern part of the Pannonian Basin basement (Croatia) occur in two areas: Vo&#263;in volcanic mass (VVM) at the northwestern part of Mt. Papuk (near town of Vo&#263;in, covering the area of ~10km2) and volcanic mass of Mt. Po&#382;e&#353;ka Gora (PVM, area of ~30 km2). Both volcanic masses consist of basalts and rhyolites, and in lesser extent of pyroclastic material. Granite can be found it the PVM. Interconnection of this two masses and Late Cretaceous ages have been proposed based on the petrography and mineralogical features of previously studied samples and rather arguable data: K-Ar dating on basalts from VVM (~73&#8722;52 Ma) and Rb-Sr isochron age on granite and rhyolite from PVM (~72 Ma). The age has been recently refined with the zircon LA-ICP-MS age dating (~82 Ma), but the magma source of this bimodal formation, geotectonic position, setting and its regional importance still have not been explained in detail.In order to conduct preliminary research, two localities with acid effusive rocks were sampled from the VVM (Rupnica geosite and Tre&#353;njevica quarry), and three more from PVM (near the village of Vesela, Pakao Creek and the granite from quarry near the village of Gradski Vrhovci).Acid rocks are characterized by a highly siliceous composition (up to 75 wt.% SiO2), enrichment in alkalies (high-K calc-alkaline towards to shoshonite series) and aluminium (peraluminous affinity), followed by high FeOT/(FeOT+MgO) ratios matching ferroan magmas. They classify as rhyolites or alkali-rhyolites/granite. Microelements including REE show that studied rocks have characteristics of A2-type of post-collisional/post-orogenic acid rocks, most common A-type of rocks formed during rifting caused by extension and thinning of continental crust. According to geotectonic classification diagrams, rocks from PVM show geochemical signature of volcanic arc, while VVM shows signature of within plate environment.External zircon morphology seems to be uniform with prevailing J3&#8722;J5-type for rhyolites and D-type for granite and with average ratio of 2.2:1. Those types are characteristic for the high-temperature magmas (confirmed with the calculated Zr-saturation temperature of 850&#8722;930&#176;C) originating from the lower crust or even upper mantle. Inclusions of hematite, F-apatite and anatase have been detected with Raman spectrometry in zircon from all samples, with the most significant findings of kumdykolite and kokchetavite inclusions detected in samples from Vesela and Gradski Vrhovci. Latter inclusions are metastable phases crystallized from enclosed melt and are indicators of a rapid cooling of the host magma.According to the results presented here, acid rocks show rather uniform geochemistry, which speaks in favor of the early ideas of the unique magmatic complex, although today at the surface they are separated by ~35 km in distance. Those rocks show potential to be of great regional importance bearing new information about the evolution in the Late Cretaceous in the area of Sava Zone, a suture zone between Tisia Mega-Unit (European plate) and Adria microplate, which spatially and temporally marks the closure of the Neotethys Ocean.Support by the Croatian Science Foundation (IP-2014-09-9541) is acknowledged.

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