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See detailSource constraints on the genesis of Danubian granites in the South Carpathians Alpine Belt (Romania)
Duchesne, Jean-Clair ULiege; Laurent, Oscar; Gerdes, Axel et al

in Lithos (2017), 294-295

The pre-Alpine basement of the Lower Danubian nappes in the South Carpathians is made up of two Precambrian terranes (Drăgşan and Lainici-Păiuş) that were intruded by Pan-African/Cadomian and Variscan ... [more ▼]

The pre-Alpine basement of the Lower Danubian nappes in the South Carpathians is made up of two Precambrian terranes (Drăgşan and Lainici-Păiuş) that were intruded by Pan-African/Cadomian and Variscan granitoid massifs. We focus on the major and trace element geochemistry (1) in the Drăgşan terrane, of the Variscan Retezat and Parâng intrusions; (2) in the Lainici-Păiuş terrane, of the Variscan Furcǎtura, Petreanu and Frumosu intrusions and of the Pan-African Vârful Pietrii, Şuşiţa and Olteţ granites and granitic leucosomes of migmatites; and (3) in the Upper Danubian nappes basement, of the Variscan Muntele Mic, Sfârdin, Cherbelezu and Ogradena intrusions. For each intrusion, in which a range of composition is observed, we decipher the differentiation mechanisms (fractional crystallization, hybridization, melt laden with restite minerals, etc.) in order to define the parental liquid compositions. The latter are calc-alkaline to alkali-calcic (except Olteţ that is calcic) and medium to high-K in composition. With [La/Yb]N>10 and Sr/Y >15, most melts display the so-called “continental adakite” affinities. The parental melt compositions are compared with experimental data to determine the melting conditions and the nature of the source rock. When the P-T conditions can be estimated, the temperatures range between 850°C and 875°C and the pressure between 5 and 15 kbar regardless of the ages of the granites and the terrane in which they have intruded. The source rock composition is dominated by a variety of mafic igneous compositions or metasediments rich in volcanic components. Clay-rich (pelitic) protoliths have not been identified. We confirm a Variscan age (c. 300 Ma) for the Frumosu intrusion granite and inherited Precambrian ages (c. 1.7-1.9 and 2.6-2.9 Ga) for the Motru dyke swarm. Thus, both Drăgşan and Lainici-Păiuş together with the Upper Danubian basement terranes were affected by Variscan post-collisional granitic plutonism. In the South Carpathians, both Pan-African and Variscan granites were generated in a crust thickened by stacking of terranes. The source of the Pan-African granites in Lainici-Păiuş is different from that of the Variscan granites (from Lainici-Păiuş and Drăgşan terranes and from the Upper Danubian nappe basement), but all these sources were notably depleted in metapelite component. [less ▲]

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See detailDyke swarms in the Pan-African basement from the Alpine Danubian window : new field and geochemical investigation in southern Carpathians (Romania)
Femenias, Olivier; Demaiffe, Daniel; Liégeois, Jean-Paul ULiege et al

in Journal of Conference Abstracts (2001), 6

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See detailGeochemistry of granitoids from the south Carpathians: A review
Berza, Tudor; Andar, Petre; Tatu, Mihai et al

in Anuarul Institutului Geologic al României (2000), 71

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See detailThe Neoproterozoic Pan-African basement from the Alpine Lower Danubian nappe system (South Carpathians, Romania)
Liégeois, Jean-Paul ULiege; Berza, Tudor; Tatu, Mihai et al

in Precambrian Research (1996), 80

The South Carpathians, which were thrust to the Moesian platform in the Alpine orogeny (Late Cretaceous to Tertiary), include the Danubian nappe system. The Danubian pre-Alpine basement comprises two ... [more ▼]

The South Carpathians, which were thrust to the Moesian platform in the Alpine orogeny (Late Cretaceous to Tertiary), include the Danubian nappe system. The Danubian pre-Alpine basement comprises two Variscan nappes, each one made up of partially retrogressed amphibolite facies rocks intruded by granitoids and capped by an Ordovician-Devonian volcano-sedimentary cover. No lithological correlation can be established between the pre-Ordovician basements of these two units. The metamorphic basement from the first Variscan nappe, the Drãgºan Group, is composed of banded amphibolites with some augen and aluminous gneisses intruded by granodioritic to tonalitic plutons. The banded structure of the amphibolites, together with their geochemistry, suggests a volcano-sedimentary sequence. Zircon U-Pb data on an intercalated augen gneiss have given an age of 777 ± 3 Ma for the emplacement of the protolith of this gneiss. Nd model ages (TDM) for the amphibolites range from 717 Ma to 817 Ma. At 777 Ma, Nd values cluster is at +8.3 to +9.8 and Sr initial ratios range between 0.7007 and 0.7023, indicating an oceanic origin without continental crust contamination. Major and trace elements from the Drãgºan amphibolites consistently display an island arc signature, with three differentiation trends evolving from an early tholeiitic trend to a more differentiated low-K calc-alkaline one. The Drãgºan terrane is similar to the Early Pan-African juvenile terranes of the Sahara. The basement of the second Variscan nappe, the Lainici-Pãiuº Group, is made up of metasedimentary rocks (mainly quartzites, marbles and graphitic mica gneisses) cut by early leucogranitic dykes, medium-K calc-alkaline and alkali-calcic (mainly granitic) plutons, and late medium-K porphyry diorite dykes. This magmatism can be bracketed between 588 Ma and 567 Ma (U-Pb zircon ages). The best preserved pluton (Tismana, 567 Ma old), displays a composite alkali-calcic (very high-K calc-alkaline) magmatic sequence, ranging from gabbro-diorite to monzogranite, including an ultramafic pod. Ages and geochemical signatures resemble the Saharan Late Pan-African granitoids. The existence of Late Precambrian partly juvenile terrains is thus confirmed within the basement of South Carpathians, which renders then a segment of the European Alpine belt that can be successfully compared to the Pan-African Trans-Saharan belt. [less ▲]

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