Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

Abstract

-The Mt Cer Pluton, Serbia, is a complex laccolith-like intrusion (∼ 60 km 2 ), situated along the junction between the southern Pannonian Basin and northern Dinarides. It intrudes Palaeozoic metamorphic rocks causing weak to strong thermal effects. Based on modal and chemical compositions, four rock-types can be distinguished: (1) metaluminous I-type quartz monzonite/quartz monzodiorite (QMZD); (2) peraluminous S-type two-mica granite (TMG), which intrudes QMZD; (3) Stražanica granodiorite/quartz monzonite (GDS); and (4) isolated mafic enclaves (ME), found only in QMZD. 40 K-39 Ar dating and geological constraints indicate that the main quartz monzonite/quartz monzodiorite body of Mt Cer was emplaced not later than 21 Ma, whereas the emplacement ages of the Stražanica granodiorite/quartz monzonite and two-mica granites are estimated at around 18 and 16 Ma, respectively. The Mt Cer pluton is similar to the Mt Bukulja pluton, some 80 km southwestwards. Genesis of QMZD cannot be interpreted by fractional crystallization coupled with mixing or assimilation. It is best explained by a convection-diffusion process between mantle-derived minette/leucominette magmas and GDS-like magmas followed by two end-member magma mixing. The composition of GDS rocks suggests that GDS-like magmas could have formed by melting of lower crustal lithologies similar to amphibolite/metabasalts. The geochemistry of TMG is reproduced by an Assimilation/Fractional Crystallization model with a ratio of rate of assimilation to rate of fractional crystallization of 0.4, using the compositions of the least evolved TMG of the Bukulja pluton and adjacent metamorphic rocks as proxies for the parental magma and contaminant, respectively. The origin and evolution of the Mt Cer and adjacent Mt Bukulja plutons provide new constraints on the Tertiary geodynamics of the northern Dinarides-southern Pannonian region. The quartz monzonite/quartz monzodiorite is interpreted as a result of the Oligocene post-collisional Dinaride orogen-collapse, which included a limited lithosphere delamination, small-scale mantle upwelling, and melting of the lower crust. By contrast, the two-mica granite magmas formed through melting in shallower crustal levels during the extensional collapse in the Pannonian area.

Cenozoic granitoids in the Dinarides of southern Serbia: age of intrusion, isotope geochemistry, exhumation history and significance for the geodynamic evolution of the Balkan Peninsula

“…10 East-West profile sketches illustrating the migration of magmatism from the upper plate (Tisza-Dacia and Rhodopes) into the lower plate (present-day Dinarides due to delamination of the lower plate (Adriatic) lithospheric mantle, possibly associated with slab break-off. Present-day geometry is that provided by the mantle tomography (Piromallo and Morelli 2003) and a by a crustal transect Miocene magmatic activity in the Dinarides The Miocene Polumir intrusion (18 Ma) is part of a larger group of S-type granitoids in the Dinarides that includes a part of the Cer intrusive (albeit within an older I-type quartz monzonite; an age around 16 Ma (K-Ar) is reported for the S-type two-mica granite; Koroneos et al 2010) and the twomica Bukulja intrusion (20-17 Ma are reported for the twomica granites; Cvetković et al 2007b). It is uncertain, however, if the somewhat older I-type Golija intrusion with high-K affinity also belongs to this same suite.…”

“…Fig. 9), Koroneos et al (2010) and Cvetković et al (2007b) proposed emplacement during the early stages of extension related to the formation of the Pannonian basin, the Bukulja intrusion being located in the footwall of a major core complex exhumed in early Miocene times (Marović et al 2007). Hence, the location of these S-type granites at the southern margin of the Pannonian basin, their Early Miocene age, and their association with core complex formation all argue for them being located in the backarc area of the W-directed subduction of the European lithosphere beneath the Carpathians, widely invoked to explain extension and magmatism in the main part of the Pannonian basin (Csontos 1995;Seghedi et al 2004).…”

“…Bukulja and Mt. Cer in northern Serbia have been studied by Karamata et al (1992), Cvetković et al (2007a), and Koroneos et al (2010), and their petrogenesis has been attributed to the Pannonian extension. However, the Cenozoic granitoids in southern Serbia that are subject of this study remained very poorly studied in terms of their age and geodynamic significance.…”

“…'Miocene' and 'pre-Miocene' zircon ages are unpublished data from Int J Earth Sci (Geol Rundsch) Paleogene Periadriatic intrusions of the Alps (Periadriatic intrusions s.str.) can be followed into the Mid-Hungarian fault zone and/or into the internal Dinarides and whether these intrusions represent the back-arc magmatism with respect to only one or two different subduction zones (Kovács et al 2007), or alternatively, whether they are related to post-orogenic collapse of an overthickened crust in the internal Dinarides (Koroneos et al 2010), mantle delamination and/or to extension in the Pannonian basin (e.g. Cvetković et al 2007a).…”

Geochronology, geochemistry and isotope tracing of the Oligocene magmatism of the Buchim–Damjan–Borov Dol ore district: Implications for timing, duration and source of the magmatism

“…The Late Eocene-Oligocene magmatic belt evolved from K-rich trachybasalts (34 Ma) via shoshonites, calc-alkaline and high-K calcalkaline basalts (33 to 31 Ma) to alkaline basalts (28-26 Ma; Marchev et al, 2004Marchev et al, , 2005Cvetković et al, 2000;Prelević et al, 2005). The origin of this very heterogeneous magmatism has generally been explained to be related to the postcollisional collapse of the Dinaride orogen (Late Oligocene) followed by the extension in the Pannonian basin (Miocene) and in the Aegean area (Pliocene) (Cvetković et al, 2000(Cvetković et al, , 2004Koroneos et al, 2011;Prelević et al, 2005;Schefer et al, 2011;Van Hinsbergen and Schmid, 2012). It was also demonstrated that the mafic magmas resulted from the melting of depleted mantle metasomatized by earlier subduction processes.…”