Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 15 of 15 for “"crustal evolution"”.
-
Metamorphic and crustal evolution of Australian-Antarctic Proterozoic margins
… details of the Mesoproterozoic metamorphic evolution of some constituent terranes of the MAFWO are unclear. A metamorphic framework for the orogen in its entirety is also non-existent. To address this deficiency, this thesis firstly presents an integrated metamorphic, geochronological and …
-
Sedimentological constraints on Precambrian crustal evolution in northern New Mexico
… arc complex and represents an early period of crustal instability. Between 1,755 and 1,700 m.y., the volcanogenic sequence was intruded by voluminous, coeval granodiorites and tonalites which stabilized the early crust. Unconformably overlying the volcano-plutonic terrane is a thick sequence of …
-
Granite petrogenesis and crustal evolution studies in the Damara Pan-African orogenic belt, Namibia
… three geochemically distinct granitoid groups, - crustal-melt granitoids, calc-alkaline granitoids and within-plate granitoids. The overwhelming majority of the Oamara granitoids are peraluminous crustal-melt leucogranites which have elevated <sup>87</sup>Sr/<sup>86</sup>Sr ratios (> 0.710) and …
-
Crustal evolution of Grenville terranes in the central and southern Appalachians: the Pb isotope perspective for Grenville tectonics
Nine basement blocks were sampled from locations spanning from Pennsylvania to Georgia in the eastern United States. These basement blocks are similar in that they have radiometric ages of approximately 1.0 billion years (with one exception), they are all at upper amphibolite to granulite grades, …
-
Proterozoic crustal evolution of the Awasib Mountain terrain, southern Namibia, with speical reference to the volcanic Haiber flats formation
… Namibia. The AMT is made up of two major crustal components, the older of which is correlated with the Namaqualand Metamorphic Complex (NMC), and the younger with the Sinclair Sequence.
-
Geodynamic evolution and petrogenesis of the neoarchaean Francistown granite-greenstone complex in NE Botswana, SW margin of the Zimbabwe craton
… Neoarchaean granitoids and mafic dominated-supracrustal assemblages. All the supracrustal rocks and mafic intrusions have undergone greenschist to lower amphibolite facies metamorphism, but most mafic intrusions have preserved original igneous textures. The Francistown Granite Greenstone Complex …
-
Modeling target rock composition of two impact events
… a rare opportunity to investigate early Earth's crustal evolution. Spherule layers, formed through condensation of vaporized target rock and bolide material during meteorite impacts, represent a unique window into this time. This study models target rock compositions of two …
-
The geology of kimberlites from the Fort a la Corne area, Saskatchewan, Canada
… A new term, pateran crater, and process of evolution is proposed for these and other kimberlites of similar morphology. The survival of these volcanic edifices in the sedimentary environment is also considered. The geochemistry of the kimberlites is presented, both bulk rock, and over 450 …
-
Paleogeography of Western North America: Insights from Detrital Zircon U-Pb Geochronology and Hf Isotope Geochemistry
Reconstructing the geologic and tectonic evolution of western North America from Paleozoic through Eocene time is the goal of this dissertation. Three geographical regions were selected for analysis using modern analytical techniques including U-Pb geochronology and Hf isotope geochemistry of …
-
Structural studies in a Proterozoic gneiss complex and adjacent cover rocks, west Needle Mountains, Colorado
… resulted from regional north-northwest crustal shortening induced by tectonic interactions along the southern margin of the Colorado Province. These results support the hypothesis that terrane accretion was important in the Proterozoic crustal evolution of southwestern North America.
-
Tracing past and present Arctic geochemical cycling and its link to climate change using neodymium isotopes
… been used extensively as a tracer of continental crustal evolution and in sediment and seawater provenance studies. In this thesis εNd is measured on a suite of marine and terrestrial sediment and waters, broadly focused on the circum-Arctic region, providing insights into both past and current …
-
Petrology and geochemistry of the granitoids of the Halfway House Dome
… terrane is well suited for studies of Archaean crustal evolution and the study area is therefore delineated as the window of Archaean granitoids occurring between Johannesburg and Pretoria, South Africa. The main objectives of the present work is to present an integrated field, geochemical and …
-
Triassic to Neogene Evolution of the Andean Retroarc: Neuquén Basin, Argentina
… to analyze the relationship between the tectonic evolution of a subduction margin, retroarc shortening, basin morphology, and volcanic activity. Timing of initial shortening and foreland basin development in Argentina is diachronous along strike, with ages varying by 20-30 million years. The …
-
Zircon U-PB and LU-HF isotopic data from some peri-gondwana variscan terranes (Sardinia-Corsica block and calabropeloritan arc): new insights on the cenozoic geodynamic evolution of the central mediterranean basin
… in unraveling the peri-Tyrrhenian area evolution of the peri-Gondwana terranes, amalgamated during Variscan and widespread during Cainozoic opening (and closing) of Tethys, both Variscan and Tertiary rocks cropping out in the two Blocks have been investigated, either magmatic or …
-
Tektonometamorphe Entwicklung von Scherzonen im präkambrischen Basement Südindiens
In the South Indian basement, several crustal-scale amphibolite facies shear zones occur between high-grade metamorphic units with a different geological history: the EW-trending Moyar Shear Zone (MSZ) is a zone of predominantly dip-slip transport separating the Archaean Dharwar Craton in the north …