Abstract
Late Miocene to Pleistocene volcanism within the Vardar zone (North Macedonia) covers a large area, has a wide range in composition, and is largely connected to the tectonic evolution of the South Balkan extensional system, the northern part of the Aegean extensional regime. The onset of the scattered potassic to ultrapotassic volcanism south from the Scutari-Peć transverse zone occurred at ca. 8.0 Ma based on this study. Here, we focused on three volcanic centers located on deep structures or thrust faults along the western part of the Vardar zone, for which there is none to very little geochronological and geochemical data available. Pakoševo and Debrište localities are represented as small remnants of lava flows cropping out at the southern edge of Skopje basin and at the western edge of Tikveš basin, respectively. Šumovit Greben center is considered as part of the Kožuf-Voras volcanic system, and it is located on its westernmost side, at the southern edge of Mariovo basin, which is largely composed of volcaniclastic sediments. We present new eruption ages applying the unspiked Cassignol-Gillot K–Ar technique on groundmass, as well as petrological and geochemical data, supplemented with Sr and Nd isotopes to complement and better understand the Neogene-Pleistocene volcanism in the region. Eruption ages on these rocks interlayered between sedimentary formations allow to better constrain the evolution of those sedimentary basins. Rocks from the three volcanic centers belong to the high-K calc-alkaline–shoshonitic series based on their elevated K content. The oldest center amongst these three localities, as well as other Late Miocene centers within the region, is the trachyandesitic Debrište, which formed at ca. 8.0 Ma, and exhibits the highest Nd and lowest Sr isotopic ratios (0.512441–0.512535 and 0.706759–0.706753, respectively). The basaltic trachyandesite Pakoševo center formed at ca. 3.8 Ma and its Nd and Sr isotopic ratios (0.512260 and 0.709593, respectively) bear the strongest signature of crustal contamination. The rhyolitic Šumovit Greben center is a composite volcanic structure formed at ca. 3.0–2.7 Ma. Its youngest eruption unit has a slightly higher Nd and lower Sr isotopic ratios (0.512382 and 0.709208, respectively) representing a magma with a lesser extent of crustal assimilation than the other samples from this center. The overall trend through time in the Sr and Nd isotopic ratios of the Late Miocene to Pleistocene mafic volcanic centers in the region implies an increasing rate of metasomatism of the lithospheric mantle.
Highlights
Extensive volcanism characterized the entire Balkan Peninsula since Late Cretaceous–Paleogene times, closely related to the complex tectonic evolution of the Alpine–Mediterranean region (e.g., Boev and Yanev 2001; Cvetković et al 2004; Harangi et al 2006; Lustrino and Wilson 2007; Burchfiel et al 2008)
Since the three sampling localities differ in character, we present the basic volcanological features, K–Ar ages and the obtained petrographic, whole-rock geochemistry and Sr–Nd isotopic results for each locality separately
Pakoševo (Dumurdzanov et al 2004). The age of this volcanic center was assigned to Pleistocene based on its stratigraphic position and correlation with similar settings in the neighboring basins, as indicated by the geological mapping and description of Karajovanovik and Hadži-Mitrova (1982)
Summary
Extensive volcanism characterized the entire Balkan Peninsula since Late Cretaceous–Paleogene times, closely related to the complex tectonic evolution of the Alpine–Mediterranean region (e.g., Boev and Yanev 2001; Cvetković et al 2004; Harangi et al 2006; Lustrino and Wilson 2007; Burchfiel et al 2008). The most intense phase of the volcanism in the central parts of the peninsula occurred during Oligocene times, related to the Dinaride collapse and the retreating Aegean subduction zone (e.g., Boev and Yanev 2001; Cvetković et al 2004; Pe-Piper and Piper 2007). The northern boundary of this extensional regime is marked by the Scutari-Peć transverse zone (Fig. 1) This tectonic framework induced a change in the features of volcanism of the region leading to the development of small-volume centers along fault lines and/or boundaries of nappe structures. These volcanic centers concentrated within the Vardar zone and south from Scutari-Peć zone since ca. These volcanic centers concentrated within the Vardar zone and south from Scutari-Peć zone since ca. 6.6 Ma
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