Search results for "TECTONICS"
showing 10 items of 385 documents
Porphyroblasts and Reaction Rims
1998
A volume of rock involved in deformation and metamorphism will continuously undergo changes in structure and mineral content. This chapter treats mineral growth and replacement structures and the way in which their geometry can be used to reconstruct tectonic history. Two types of informative structures are treated: porphyroblasts and reaction rims.
Mechanisms of fluid flow and fluid-rock interaction in fossil metamorphic hydrothermal systems inferred from vein-wallrock patterns, geometry and mic…
2001
Comparison of mass transfer patterns, geometry and microstructures developed within and around veins allows the interpretation of processes of fluid flow during deformation, metamorphism and mineralization. A classification of vein types based on the degree of interaction with wallrock (using petrological, geochemical or isotopic indicators) can be used to identify a range of processes, from closed system behaviour in which the vein mass is derived from local wallrock, through to open system behaviour in which the vein mass is derived externally. Microstructural characteristics, such as wallrock selvages, multiple growth events recorded by vein seams and vein crystal morphology, also help t…
3D visualization of sheath folds in Ancient Roman marble wall coverings from Ephesos, Turkey
2014
Abstract Archaeological excavations and restoration of a palatial Roman housing complex in Ephesos, Turkey yielded 40 wall-decorating plates of folded mylonitic marble (Cipollino verde), derived from the internal Hellenides near Karystos, Greece. Cipollino verde was commonly used for decoration purposes in Roman buildings. The plates were serial-sectioned from a single quarried block of 1,25 m3 and provided a research opportunity for detailed reconstruction of the 3D geometry of meterscale folds in mylonitized marble. A GOCAD model is used to visualize the internal fold structures of the marble, comprising curtain folds and multilayered sheath folds. The sheath folds are unusual in that the…
PAN-AFRICAN MOBILE BELTS AS EVIDENCE FOR A TRANSITIONAL TECTONIC REGIME FROM INTRAPLATE OROGENY TO PLATE MARGIN OROGENY
1979
Pan-African belts of the African mainland and the Arabian-Nubian Shield exhibit evolutionary features which are either compatible with intracontinental ensialic development or with plate margin and Wilson cycle tectonics. Some of these belts are discussed and, considered together, they appear to reflect variations in crustal mobility during a transitional tectonic regime from intraplate to plate margin orogeny which lasted some 50. Ma from ca. 1000 Ma to ca. 500 Ma ago.
Geochemistry, PbPb single zircon ages and NdSr isotope composition of Precambrian rocks from southern and eastern Ethiopia: implications for crusta…
1998
Abstract Geochemical and isotope data for granitoid rocks from southern and eastern Ethiopia delineate the presumed margin of the Pan-African juvenile terrain of the Arabian-Nubian Shield against an older crustal segment of unknown origin extending from eastern Ethiopia to northern Somalia. Granitoids from southern Ethiopia have higher Na2O and Na 2 0 K 2 O and lower Cr and Ni than granitoids with comparable SiO2 values from eastern Ethiopia. In southern Ethiopia three periods of magmatism are identified on the basis on single zircon 207 Pb 206 Pb evaporation ages, namely at ∼850, ∼750-700 and ∼650-550 Ma, and these correlate well with events documented from other parts of Ethiopia and the …
Fabric Development in Gneiss Terrains
1990
This chapter describes some aspects of the development of fabrics in gneiss terrains. It provides essential background information that should be read before attempting to map a gneiss terrain. Inevitably, the interpretations are ‘state of the art’ and not necessarily the absolute answer. Additional information can be found in the cited literature and various specialised journals such as the Journal of Structural Geology, the Journal of Metamorphic Geology, Tectonophysics, Tectonics and Precambrian Research.
Layered lower crust and mantle reflectivity as imaged by a re-processed crustal seismic profile from Sicily in the central Mediterranean
2015
Abstract Though Sicily is a key area for understanding the central Mediterranean tectonics, a number of questions on its dynamics remains open due to the lack of detailed data on the lithospheric structure. Deep reflectivity images of the African lithosphere, beneath Sicily, have been derived from the re-processing of the crustal seismic reflection stack (SI.RI.PRO. Project). Of specific interest was the imaging, beneath central-southern Sicily, of a thinned crust with a reflective, “layered” pattern for the lower crust that differs from the one, thicker and sub-transparent, of the northern-central sector. Brittle deformation in the upper crystalline crust along a low-angle normal fault and…
Three-dimensional evolution of the Keuper of the Paris basin based on detailed isopach maps of the stratigraphic cycles: tectonic influences
1997
Detailed isopach maps of the stratigraphic cycles of the Keuper of the Paris basin are used to reconstruct the 3D evolution of the basin cycle by cycle and to investigate the influence of tectonic movements. The major base-level cycles record variations in the rate of subsidence in time and space. The area of greatest subsidence, which was confined to the east of the basin during the Scythian–Carnian cycle, shifted northwestwards during the Carnian–Liassic cycle. Within the “Marnes irisees inferieures”, the E–W faults abruptly limited the extent of salt deposits to the north and south by forming a “corridor” where subsidence was greater. The westward shift of areas of subsidence induced by …
Tectonic Sustainable Building Design for the Development of Renovation Scenarios – Analysis of ten European renovation research projects
2018
The investigation of 10 European building renovation research projects presented in this paper demonstrates that recent research in this field is currently centralized around quantifiable objectives i.e. development of energy efficient renovation scenarios, whereas the more qualitative objectives in renovation projects such as aesthetics, identity and/or social dimensions are rarely addressed. Furthermore, the result of this investigation together with the recent researches about the current practice of building renovation indicates that many of renovated buildings, which now are claimed to be sustainable are not addressing all aspects of a conventional definition of sustainability. Lastly,…
Sedimentary dynamics and extensional structuring related to early Cretaceous rifting of Neocomian and Barremian deposits of the interior basin of Gab…
2008
18 pages; International audience; Recent field and subsurface data about the early Neocomian N'dombo series and the Neocomian to mid-Barremian Schistes series of the interior basin of Gabon further our understanding of the initial stages of early Cretaceous N40–60E extensional rifting. The syn-rift series comprise fluvial–lacustrine claystones–sandstones, rare conglomerates, and carbonates. The syn-rift fill begins with braided-stream feldspathic sandstones. These are overlain first by fluvial–lacustrine deposits and then by predominantly lacustrine–palustrine claystones, which are potential petroleum source rocks. The claystones are eroded in part and are capped by the pre-Aptian angular u…