Vladica Cvetković

The Miocene granitoid rocks of Mt. Bukulja (central Serbia): evidence for pannonian extension-related granitoid magmatism in the northern Dinarides

The study presents evidence about the origin and evolution of the Miocene (20–17 Ma) granitoid pluton of Mt. Bukulja, situated within the southern Pannonian/northern Dinarides region (central Serbia, south-central Europe). The pluton is composed of slightly peraluminous two-mica granite (TMG), metaluminous hornblende-biotite and biotite-bearing (H-BG) granite and rare aplite granite. A lamprophyre dyke (BLD) similar in composition and age to other Serbian primitive minettes has been found in the vicinity of Mt. Bukulja. The available and newly determined radiometric age suggests that the TMG was emplaced around 20 Ma whereas the age of the H-BG is inadequately constrained. TMG and H-BG show similar petrographic characteristics but evidence of open system magma processes is found only in the H-BG. In comparison to the H-BG, the TMGs are less enriched in most trace elements, including REE, and have a more fractionated REE-pattern and stronger negative Eu-anomaly. The TMGs display a wider range of initial Sr-Nd isotope ratios (87Sr/86Sr20 Ma = 0.70652–0.71368 and 143Nd/144Nd20 Ma = 0.51223–0.51283) than the H-BG (87Sr/86Sr20 Ma = 0.70768–0.70781 and 143Nd/144Nd20 Ma = 0.51242–0.51256). Geochemical modeling suggests that the H-BG could have derived from a BLD-like melt by mixing plus fractionation processes assuming a batch of TMG-like magma as the acid end-member. On the other hand, the geochemical variability of the TMG is reproduced by an AFC model with an assimilation/fractionation ratio ( r ) of 0.5 and with high amount of crustal component (~20–50 %) starting from the least evolved TMG rocks. In the modeling, the average composition of the least evolved TMG samples was used to represent the parental magma composition whereas the composition of adjacent metamorphic rocks was adopted as possible contaminant. The composition of the least evolved TMG implies that the TMG parental magma likely originated by melting of a mafic lithology such as earlier basalts underplating in the lower crust. The high proportions of crustal assimilation along with other geochemical and geological evidence suggest that the Mt. Bukulja TMG originated within the same geotectonic setting as acid volcanics of the north Pannonian Basin. The results of this study support the hypothesis that the Mt. Bukulja pluton is related to tectonomagmatic events controlled by the early extensional phases in the opening of the Pannonian basin.

The analcime problem and its impact on the geochemistry of ultrapotassic rocks from Serbia

Abstract Tertiary ultrapotassic volcanic rocks from Serbia occasionally display low levels of K2O and K2O/ Na2O. In these rocks, analcime regularly appears as pseudomorphs after pre-existing leucite microphenocrysts. The process of leucite transformation in Serbian ultrapotassic rocks is very thorough: fresh leucite survives only in ugandites from the Koritnik lava flows as well as in rare inclusions in Cpx. This paper focuses on the impact of ‘analcimization’ on the mineralogy and geochemistry of the Serbian ultrapotassic rocks, using the samples where leucite survived as a monitor for the process. Analcimization has had a great impact on the geochemistry of the rocks, but affects only a restricted number of chemical parameters. These are the falsification of the original K2O/Na2O ratio, the decoupling of large-ion lithophile elements resulting in considerable depletion of Rb and K2O, but not of Ba, and sporadic, but extreme enrichment of Cs in some analcime-bearing samples (up to 900 ppm). Analcimization is also recognized by an increase in whole-rock S18O values of ~3‰ compared to fresh rocks, which correlates with the level of whole-rock hydration. Finally, the 87Sr/86Sr enrichment at nearly constant 143Nd/144Nd demonstrated by some rocks can also be explained by the analcimization of leucite. For samples with variable 87Sr/86Sr from the same lava flow, 87Sr/86Sr values correlate with modal analcime abundance (ex-leucite), loss on ignition of whole-rock and whole-rock δ18O values. The extreme depletion in K and enrichment in Na, together with modification of other geochemical parameters, may have led to the misinterpretation of the origin and geodynamic affiliations of the Serbian ultrapotassic rocks, had the effects of analcimization not been taken into account.

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

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.

Mafic alkaline metasomatism in the lithosphere underneath East Serbia: Evidence from the study of xenoliths and the host alkali basalts

Abstract Effects of mafic alkaline metasomatism have been investigated by a combined study of the East Serbian mantle xenoliths and their host alkaline rocks. Fertile xenoliths and tiny mineral assemblages found in depleted xenoliths have been investigated. Fertile lithologies are represented by clinopyroxene (cpx)-rich lherzolite and spinel (sp)-rich olivine websterite containing Ti–Al-rich Cr-augite, Fe-rich olivine, Fe–Al-rich orthopyroxene and Al-rich spinel. Depleted xenoliths, which are the predominant lithology in the suite of East Serbian xenoliths, are harzburgite, cpx-poor lherzolite and rare Mg-rich dunite. They contain small-scale assemblages occurring as pocket-like, symplectitic or irregular, deformation-assisted accumulations of metasomatic phases, generally composed of Ti–Al- and incompatible element-rich Cr-diopside, Cr–Fe–Ti-rich spinel, altered glass, olivine, apatite, ilmenite, carbonate, feldspar, and a high-TiO2 (c. 11 wt%) phlogopite. The fertile xenoliths are too rich in Al, Ca and Fe to simply represent undepleted mantle. By contrast, their composition can be reproduced by the addition of 5–20 wt% of a basanitic melt to refractory mantle. However, textural relationships found in tiny mineral assemblages inside depleted xenoliths imply the following reaction: opx+sp1 (primary mantle Cr-spinel) ±phlogopite+Si-poor alkaline melt=Ti–Al-cpx+sp2 (metasomatic Ti-rich spinel)±ol±other minor phases. Inversion modelling, performed on the least contaminated and most isotopically uniform host basanites (87Sr/86Sr=c. 0.7031; 143Nd/144Nd=c. 0.5129), implies a source that was enriched in highly and moderately incompatible elements (c. 35–40× chondrite for U–Th–Nb–Ta, 2× chondrite for heavy rare earth elements (HREE), made up of clinopyroxene, carbonate (c. 5%), and traces of ilmenite (c. 1%) and apatite (c. 0.05%). A schematic model involves: first, percolation of CO2- and H2O-rich fluids and precipitation of metasomatic hydrous minerals; and, second, the subsequent breakdown of these hydrous minerals due to the further uplift of hot asthenospheric mantle. This model links intraplate alkaline magmatism to lithospheric mantle sources enriched by sublithospheric melts at some time in the past.

Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26Al, 36Cl, 3He, and 21Ne)

Abstract This paper focuses on constraining the erosion rate in the area of the Allchar Sb‐As‐Tl‐Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long‐term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ∼165 m/Ma. The samples from four locations (L‐8 CD, L1b/R, L1c/R, and L‐4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo‐depths for the ore body Centralni Deo from 4.3 Ma to the present are 250–290 and 750–790 m, respectively, whereas the upper limit of paleo‐depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo‐depth values allow estimating the relative contributions of 205Pb derived from pp‐neutrino and fast cosmic‐ray muons, respectively, which is an important prerequisite for the LOREX experiment.

The recent fault kinematics in the westernmost part of the Getic nappe system (Eastern Serbia): Evidence from fault slip and focal mechanism data

Abstract In this study we performed a calculation of the tectonic stress tensor based on fault slip data and all available focal mechanisms in order to determine the principal stress axes and the recent tectonic regime of the westernmost unit of the Getic nappe system (Gornjak-Ravanica Zone, Eastern Serbia). The study is based on a combined dataset involving paleostress analyses, the inversion of focal mechanisms and remote sensing. The results show dominant strike-slip kinematics with the maximal compression axis oriented NNE-SSW. This is compatible with a combined northward motion and counterclockwise rotation of the Adria plate as the controlling factor. However, the local stress field is also shown to be of great importance and is superimposed on the far-field stress. We managed to distinguish three areas with distinct seismic activity. The northern part of the research area is characterized by transtensional tectonics, possibly under the influence of the extension in the areas situated more to the northeast. The central and seismically most active part is dominated by strike-slip tectonics whereas the southern area is slightly transpressional, possibly under the influence of the rigid Moesian Platform situated to the east of the research area. The dominant active fault systems are oriented N-S (to NE-SW) and NW-SE and they occur as structures of either regional or local significance. Regional structures are active in the northern and central part of the study area, while the active fault systems in the southern part are marked as locally important. This study suggests that seismicity of this area is controlled by the release of accumulated stress at local accommodation zones which are favourably oriented in respect to the active regional stress field.

Geology of South-Eastern Europe

The region of South-Eastern Europe (SEE) occupies an important segment of the Alpine–Himalayan collisional orogenic belt and consists of several Phanerozoic mobile belts. The SEE region inherits its geology from the evolution of the Vardar Tethys ocean, which existed in-between the Eurasian (Europe) and Gondwana (Africa) continental plates and which relicts presently occur along the Vardar–Tethyan mega-suture. This synthesis, therefore, consists of (1) pre-, (2) syn- and (3) post-Vardar–Tethyan geology of SEE. Pre-Vardar–Tethyan geology on the European side is reflected by geological units formed from Precambrian to Mesozoic times and include the Moesian platform, the Dacia mega-unit and the Rhodopes. On the Gondwana side, it is represented by the External Dinarides, the Dalmatian-Ionian Zone and Stable Adria (Apulia), all principally formed from Paleozoic to Mesozoic times. The Syn-Vardar–Tethyan units encompass the bulk of the geological framework of SEE. They are a physical record of the former existence of the Mesozoic oceanic lithosphere, being represented dominantly by ophiolites and trench/accretionary wedge (melange) assemblages, which originated and were reworked during the life-span of the Vardar Tethys. The Post-Vardar–Tethyan geological evolution refers to the time period from the final closure of the Vardar Tethys until present. It comprises all rocks that stratigraphically overlie the Vardar–Tethyan mega-suture and seal the contacts between the mega-suture and the surrounding geological units. This is the time characterized by rapid extension coupled with exhumation of the lower crustal material, high heat flow, both intrusive and extrusive magmatism and considerable lithosphere thinning.

Investigation of the microbial diversity of an extremely acidic, metal-rich water body (Lake Robule, Bor, Serbia)

An investigation of the microbial diversity in the extremely acidic, metal-rich Lake Robule was performed using culture-dependant and culture- independent (T-RFLP) methods. In addition, the ability of the indigenous bac- teria from the lake water to leach copper from a mineral concentrate was tested. T-RFLP analysis revealed that the dominant bacteria in the lake water samples were the obligate heterotroph Acidiphilium cryptum (≈50 % of the total bacte- ria) and the iron-oxidizing autotroph Leptospirillum ferrooxidans (≈40 %) The iron/sulfur-oxidizing autotroph Acidithiobacillus ferrooxidans was reported to be the most abundant bacteria in the Lake in an earlier study, but it was not detected in the present study using T-RFLP, although it was isolated on solid media and detected in enrichment (bioleaching) cultures. The presence of the two bacterial species detected by T-RFLP (L. ferrooxidans and A. cryptum) was also confirmed by cultivation on solid media. The presence and relative abundance of the bacteria inhabiting Lake Robule was explained by the physio- logical characteristics of the bacteria and the physico-chemical characteristics of the lake water.

The Upper Cretaceous ophiolite of North Kozara – remnants of an anomalous mid-ocean ridge segment of the Neotethys?

Abstract This study sheds new light on the origin and evolution of the north Kozara ophiolite, a part of the Sava-Vardar Zone. The Sava-Vardar Zone is regarded as a relict of the youngest Tethyan realm in the present-day Balkan Peninsula. The north Kozara ophiolite consists of a bimodal igneous association comprising isotropic to layered gabbros, diabase dykes and basaltic pillow lavas (basic suite), as well as relicts of predominantly rhyodacite lava flows and analogous shallow intrusions (acid suite). The rocks of the basic suite show relatively flat to moderately light-REE enriched patterns with no or weak negative Eu-anomaly, whereas those of the acid suite exhibit steeper patterns and have distinctively more pronounced Eu- and Sr- negative anomalies. Compared to the known intra-ophiolitic granitoids from the Eastern Vardar Zone, the acid suite rocks are most similar to those considered to be oceanic plagiogranites. The new geochemical data suggest that the basic suite rocks are similar to enriched mid-ocean ridge basalts. The geochemical characteristics of the acid suite rocks indicate that their primary magmas most probably originated via partial melting of gabbros from the lower oceanic crust. Our study confirms the oceanic nature of the north Kozara Mts rock assemblage, and suggests that it may have formed within an anomalous ridge setting similar to present-day Iceland.

Status and New Data of the Geochemical Determination of the pp-Neutrino Flux by LOREX

LOREX (LORandite EXperiment) addresses the determination of the solar (pp) neutrino flux during the last four million years by exploiting the reaction with an incomparably low-energy threshold of 50 keV for the capture of solar neutrinos. The ratio of 205Pb/205Tl atoms in the Tl-bearing mineral lorandite provides, if corrected for the cosmic-ray induced background, the product of the flux of solar neutrinos and their capture probability by 205Tl, averaged over the age of lorandite. To get the mean solar neutrino flux itself, four problems have to be addressed: (1) the geological age of lorandite, (2) the amount of background cosmic-ray-induced 205Pb atoms which strongly depends on the erosion rate of the lorandite-bearing rocks, (3) the capture probability of solar neutrinos by 205Tl and (4) the extraction of lorandite and the appropriate technique to “count” the small number of 205Pb atoms in relation to the number of 205Tl atoms. This paper summarizes the status of items 1 (age) and 3 (neutrino capture probability) and presents in detail the progress achieved most recently concerning the items 2 (background/erosion) and 4 (“counting” of 205Pb atoms in lorandite).