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 20 of 30 for “"ophiolites"”.
-
Granitic Rocks of Ophiolites
… and associated formations in five ophiolites are described. In addition, the occurrence of similar rocks in other ophiolites, some island arcs and in the ocean crust is reviewed. Plagiogranites in ophiolites can be distinguished from all other granitic rocks by their almost complete …
-
Mantle melting processes: evidences from ophiolites, large igneous provinces, and intraplate seamounts
… and petrological evidence preserved in ophiolites, large igneous provinces, and intraplate seamounts to understand causes, timing and implications of melting in these different tectonic environments. We studied melting at extensional environments, in mid-ocean ridges and back-arc basins, …
-
Formation of mineralogical zonations in ophiolites through reactive porous flow : a modeling study
In the mantle section of many ophiolite sequences, dunite dikes are present. Around dunite dikes at the Josephine and Trinity ophiolite, a sequence of lithologies consisting of plagioclase lherzolite, lherzolite, and harzburgite is present. This sequence of rocks has been interpreted to be the …
-
Novel Insights into the Palaeomagnetism of Serpentinized Peridotites from the Troodos and Oman Ophiolites
… peridotite are exposed at the Earth’s surface in ophiolites, becoming vulnerable to the concurrent chemical alteration processes of serpentinization and carbonation. Serpentinization frequently results in the production of secondary magnetite that can record the direction of the Earth’s magnetic …
-
THE TECTONIC EVOLUTION OF THE HATAY OPHIOLITE OF SOUTHEAST TURKEY
… part of a prominent chain of southern Neotethyan ophiolites that stretches from the Troodos ophiolite of Cyprus eastwards to the Semail ophiolite of Oman. The Hatay ophiolite and the related Baer-Bassit ophiolite of Syria comprise the most westerly ophiolites emplaced onto the Arabian platform in …
-
Geochemistry, structure, and tectonic evolution of the Eldivan ophiolite, Ankara Melange, central Turkey
… the overlying Karadağ Formation suggest the ophiolites maximum age is 143.2 (±2) Ma, and the overlying Karadağ Formation is 105.2 (±5) Ma. The angular unconformity between the ophiolite and Karadağ formation reveal that the Eldivan ophiolite was imbricated between 105.2 (±5) Ma and 143.2 (±2) …
-
ΓΕΩΛΟΓΙΚΗ ΔΟΜΗ ΚΑΙ ΓΕΩΔΥΝΑΜΙΚΗ ΕΞΕΛΙΞΗ ΤΗΣ ΟΡΟΣΕΙΡΑΣ ΤΟΥ ΚΟΖΙΑΚΑ (ΔΥΤΙΚΗ ΘΕΣΣΑΛΙΑ)
… THE PLATFORM WITH PELAGIC- ABYSIAL SEDIMENTS AND OPHIOLITES. THE REPRESENTATION OF THE PALAEOGEOGRAPHY OF THE UNIT'S REGION LED TO ITS POSITIONING IN THE TETHYS SYSTEM.
-
Paleocene Turbidite Deposition in the Central American Seaway (NW Costa Rica): Geochemical Analysis and Provenance of Detrital Spinel and Clinopyroxene
… clinopyroxene are possibly sourced from: mantle ophiolites, mid-ocean ridge gabbros, or volcanic arc tholeiitic basalts or calc-alkaline andesites. Spinel and clinopyroxne geochemistry suggests a possible peridotitic source, linked to mantle rocks that are now covered by Tertiary volcanic rocks …
-
Petrologic and microstructural constraints on focused melt transport in dunites and the rheology of the shallow mantle
… from observations at mid-ocean ridges and ophiolites. Chapter 2 uses the size distribution and abundance of dunites measured in the Oman ophiolite to place limits on the potential mechanisms by which dunites form and subsequently estimate the flux of chemically unequilbrated melt which a …
-
Petrologic and microstructural constraints on focused melt transport in dunites and the rheology of the shallow mantle
… from observations at mid-ocean ridges and ophiolites. Chapter 2 uses the size distribution and abundance of dunites measured in the Oman ophiolite to place limits on the potential mechanisms by which dunites form and subsequently estimate the flux of chemically unequilibrated melt which a …
-
The origin and tectonic significance of the mafic-ultramafic association in the central Virginia Blue Ridge post-Grenville cover sequence
… bodies do not show characteristics that resemble ophiolites. The three complexes are broadly conformable with stratigraphic layering, and the Lynchburg Group host strata form a continuous and conformable stratigraphic sequence unbroken by faults and without evidence of mélange. Contacts between …
-
The evolution of oceanic gabbros : in-situ and ancient examples
… a remnant of an incipient ocean-arc. Such ophiolites are better models for the structural evolution than the geochemical evolution of the lower oceanic crust at mid-ocean ridges. Minerals in gabbros from Atlantis Bank, Southwest Indian Ridge, a modern, in-situ example of lower ocean-crust, …
-
Platinum-group element mineralisation in the Shetland ophiolite complex
… contain levels of Pt and Pd which are unusual in ophiolites. Aspects of this mineralisation suggest both magmatic and hydrothermal concentration processes, although neither individually explain the observed paragenesis. This study examines the distribution of PGE within a representative fresh …
-
Application of the 190Pt-186Os isotope decay system to dating platinum-group minerals
… of the Pt-Os geochronometer as a tool for dating ophiolites, layered intrusions and placer platinum mineralisation despite potential derivation of PGM from various isolated chromitites. Analysis of large PGM populations has allowed improvement on published constraints for Pt/Os inter-element …
-
Geology and Tectonic Significance of the Late Precambrian Eastern Blue Ridge Cover Sequence in Central Virginia
… one of the most important arguments for ophiolites. These diagrams were tested by plotting samples from Jurassic rift basalts-diabases of eastern North America (ENA). The ENA samples, as well as the post Grenville mafic rocks in the Blue Ridge, tend to plot outside the within-plate field. …
-
Proterozoic Farwell Mountain-Lester Mountain suture zone, northern Colorado : subduction flip and progressive assembly of arcs
… along the zone and may represent dismembered ophiolites. One of the major contributions of this study is the correlation of metamorphic and deformational fabrics among four field subareas (Farwell Mountain, Lester Mountain, Mica Basin, and the Soda Creek–Fish Creek shear zone), in an attempt …
-
A search for layering in the oceanic crust
… comprise the inferred crust/mantle transition in ophiolites might also be characteristic of the oceanic crust. Although ophiolites provide a useful model of the lithological structure of the oceanic crust, the unambiguous correlation of geologic and seismic structures can only be achieved by …
-
Evolution of oceanic gabbros : in-situ and ancient examples
… a remnant of an incipient ocean-arc. Such ophiolites are better models for the structural evolution than the geochemical evolution of the lower oceanic crust at mid-ocean ridges. Minerals in gabbros from Atlantis Bank, Southwest Indian Ridge, a modern, insitu example of lower ocean-crust, …
-
Making oceanic plagiogranite bodies by thermal migration: evidence from the Agros transect, Troodos ophiolite, Cyprus
… at the sheeted dike-gabbro boundary of most ophiolites, represent highly differentiated compositions produced in a steady state temperature gradient of a spreading center melt lens via thermal migration. For this study, twelve samples were collected along a spatial transect from the uppermost …
-
Oroclines of the Iberian Variscan belt: Tectonic and paleogeographic implications
… data and the distribution of Variscan ophiolites support a model of mid-Paleozoic separation of the Variscan autochthon (Armorican continental ribbon) from north Gondwana preceding or in conjunction with a 90º rotation required to reorient the ribbon to a Late Carboniferous north-south …
Page 1 of 2