Search results for "Massif"
showing 10 items of 112 documents
Geochemistry, tectonic setting and geodynamic significance of late orogenic dikes in the Melibocus Massif, Bergsträsser Odenwald
2001
The Melibocus Massif forms a tonalite pluton in the W’ Bergstrasser Odenwald, which is interpreted as part of a magmatic arc of Devonian to Carboniferous age. Dikes of various compositions intrude frequently this tonalite. Different dike-lithologies are associated with different strike directions. Most dikes show evidence of high-temperature shearing. A probable maximum paleostress direction of ca. 060° can be estimated, i.e. nearly parallel to the known Variscan subduction zone in the Northwest. Due to their ductile deformation under conditions around the Ar-closing temperature of amphibole, intrusion likely occurred during the Carboniferous (Mississippian). The gabbroic to dioritic dikes …
Tectonic transport directions of the Lycian nappes in southwest Turkey constrained by kinematic indicators
2013
The orientation, asymmetry and cross-cutting relationships of the structures along the contact zone between the Lycian nappes and the Menderes Massif suggest the presence of three deformation phases in the Milas region of southwest Turkey. The first deformation phase (D1) is characterized by a ductile deformation with top-to-the-NE sense of shear. Structural data of the first deformation measured along the uppermost part of the Menderes Massif and the base of the Lycian nappes suggest that the lowermost unit of the Lycian nappes was emplaced initially from southwest to northeast onto the Menderes Massif during the Early Eocene. The second deformation phase (D2) is also ductile in nature and…
Causes of the genetic architecture of south-west European high mountain disjuncts
2008
Background: Postglacial climatic warming in south-western Europe and the retreat of cold-adapted species into higher elevations, starting in the Sierra Nevada and proceeding northwards to the Pyrenees and Alps, should have resulted in a pattern of ‘successive vicariance’. Alternatively, long-distance dispersal might explain the extant distribution pattern of mountain species in this region. Aims: Here, we report an investigation of two alpine plants, Saxifraga oppositifolia and S. stellaris, which co-occur in the Sierra Nevada, the Pyrenees, and the south-western Alps/Massif Central. Our aim was to distinguish between (successive) vicariance and long-distance dispersal as alternative explan…
Pan-African granulite formation in the Kabye Massif of northern Togo (West Africa): Pb−Pb zircon ages
2000
Metamorphic zircons from seven granulite facies orthogneisses of tonalitic composition (ender- bites), collected from four different nappes of the Kabye Massif in the Dahomeyide belt of northern Togo, were dated by the Pb-Pb evaporation method. They yielded consistent Neoproterozoic ages with a mean of 612.5 0.8 Ma, interpreted to reflect the peak of regional granulite facies metamorphism following Pan-African continental collision between the West African and Benin-Nigerian plates. These results sup- port previous ages obtained by various chronometers on high-grade rocks from the same suture zone and from surrounding units in Togo, Benin and Ghana. They are also similar to zircon ages fr…
Pierwsze stanowisko Aneurus avenius (DUFOUR, 1833) (Heteroptera: Aradidae) w Sudetach
2013
The evolution of the southern Menderes Massif in SW Turkey as revealed by zircon dating
1999
This geochronological study concentrates on the evolution of the southern part of the Menderes Massif, a metamorphic core complex in W Turkey, by dating single zircons with the Pb–Pb evaporation and the U–Pb methods. We have analysed zircons from granitic augen gneisses of the core as well as from quartzites of the metasedimentary envelope. Zircons from the granitic core gneisses are euhedral with typical igneous morphologies. The single zircon ages of these gneisses indicate a time span for magmatic activity from 520 to 570 Ma with a major event at about 550 Ma. Some gneisses contain older zircons of c. 660 Ma which are interpreted as inherited grains. Zircons from the quartzites are detri…
Différentes approches pour la datation U/Pb des tonsteins intercalés dans les séries continentales d’âge fini-carbonifère à permien de Lucenay-lès-Ai…
2018
International audience; D’une manière générale, la présence de niveaux volcaniques (cendres ou laves) intercalés dans les séries sédimentaires présente un avantage non négligeable pour dater la sédimentation de ces séries. Des datations précises peuvent même permettre d’estimer des taux de sédimentation, ou encore de proposer des corrélations à l’échelle de différents bassins.Les séries sédimentaires du Carbonifère-Permien de Lucenay-lès-Aix, étudiées par forage, sont géographiquement situées entre des séries de même âge connues à l’affleurement : Decize-La Machine (au nord), Aumance (à l’ouest) et Autun (à l’est). Ce (ou ces) bassin(s) sont consti- tués de dépôts continentaux dans lesquels…
Caractérisation pétro-géochimique et datation U/Pb du volcanisme contemporain des bassins d’âge fini-Carbonifère à Permien du Nord du Massif Central
2018
International audience; La formation de la chaîne hercynienne, dont l’apogée a lieu au Carbonifère, participe à l’assemblage de la Pangée, qui se démantèlera par la suite à partir du Trias. La limite Carbonifère- Permien correspond donc à une période clé dans l’évolution géodynamique globale, à la transition entre une période orogénique et une période de rifting. Cependant, les reconstitutions paléogéographiques et paléoclimatiques pour cette époque sont assez peu contraintes, notamment du fait du manque de datations radiométriques et de corrélations stratigraphiques fiables entre les différents domaines sédimentaires. Plusieurs bassins sédimentaires fini-carbonifères à permiens sont préser…
Floristic traits and biogeographic characterization of the Gennargentu massif (Sardinia)
2013
A study on the vascular flora of the Gennargentu Massif (Central-Eastern Sardinia) is presented. According to our results, the flora consists of 948 taxa: 686 species, 249 sub- species, 10 varieties and 3 hybrids, belonging to 97 families and 427 genera. Three taxa are new findings for the flora of Italy and eight for that of Sardinia. Life form analysis revealed, in particular, dominance of 35.65 % hemicryptophytes, 34.6 % therophytes, 12.13 % geophytes and 11.6 % (nano)-phanero- phytes. As concerns chorology, the Mediterranean element is largely prevailing (68.14%), mainly represented by circum- Medit. (29.1 %) and Euro-Medit. (23.07 %). Endemics are 14.87% of the whole flora (141 taxa), …
?Short Distance?-Variabilit�t der Na-Gehalte niedrigmetamorpher mit Albit ber�hrungsparagenetisch koexistierender Hellglimmer
1973
White micas coexisting with albite, quartz, chlorite, and clinozoisite in low-grade schists of the Beaume Valley (Massif Central, France) have been analyzed by standard microprobe techniques. As the micas of an albite-rich thin section show significantly higher Na-contents than those of an albite-poor one of the same rock sample, the application of the muscovite-albite-geothermometer results in inconsistent temperature values. Thus the analyses may indicate that the distribution of sodium between coexisting white micas and albite not only depends on temperature and pressure but also on the chemical potentials of the alkalies in the metamorphic fluid phase.