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 136 for “"Craton"”.
-
The petrogenesis of Liberian diamondiferous rocks, Man Craton, West Africa
… it has been shown (e.g., in the Dharwar Craton, India) that both kimberlites and lamproites may be derived from the same asthenospheric mantle source. During their ascent to the surface, they assimilate differently metasomatized SCLM material. However, it is not clear if this process …
-
Seismicity and structure of the eastern Gawler Craton and Lake Eyre region
… in Australia. Located northeast of the Gawler Craton, the region is associated with pronounced intraplate seismic activity and thick sedimentary cover that potentially obscures the elusive boundary between older Proterozoic and younger Phanerozoic eastern Australia. Despite this, the area had …
-
Seismicity and structure of the eastern Gawler Craton and Lake Eyre region
… in Australia. Located northeast of the Gawler Craton, the region is associated with pronounced intraplate seismic activity and thick sedimentary cover that potentially obscures the elusive boundary between older Proterozoic and younger Phanerozoic eastern Australia. Despite this, the area had …
-
Seismic Imaging of a Granitoid-Greenstone Boundary in the Paleoarchean Pilbara Craton
… were deformed was investigated in the Pilbara Craton in Western Australia, which has not been substantially tectonically deformed since ~3.2 Ga. The craton consists of a unique dome and keel structure where vertical, low-grade metamorphism basaltic greenstone keels surround large granitic (TTG) …
-
Mesozoic alkaline volcanism and mantle evolution of the southwestern São Francisco craton, Brazil
… the southwestern margin of the São Francisco craton and the relation of variations in the petrochemistry of kimberlites and related alkali igneous rocks to variations in age, thickness and thermodynamic history of their continental lithospheric hosts. The São Francisco craton is a mid- to …
-
Petrology of the micaceous Koidu and Tongo - Tonguma kimberlites, Man Craton, Sierra Leone
Sierra Leone contains two Jurassic-aged diamondiferous volcanic clusters, namely Koidu and Tongo-Tonguma (hereafter referred to as Tongo), consisting of eruptive pipes at Koidu and NESW trending dikes at both Koidu and Tongo. Petrographically, the diamondiferous rocks from both clusters have …
-
Teleseismic imaging of the Slave craton and implications for the assembly of cratonic lithosphere
… the assembly and evolution of the Archean cratonic lithosphere by using two complementary seismological methods to image the lithospheric structure of the Slave craton in Canada. First, I perform surface wave tomographic inversions to constrain the depth dependence of Rayleigh wave phase …
-
Nominally volatile-free mantle minerals: a reservoir for water and fluorine in the Kaapvaal Craton
The extent to which Earth’s sub-cratonic lithospheric mantle acts as a major repository for volatile elements is poorly constrained. This study presents the first systematic investigation into water, fluorine and chlorine storage in nominally volatile-free mantle minerals from sub-cratonic mantle. …
-
Stratigraphic and structural interpretation of seismic reflection data across selected sections of the Kaapvaal Craton
The Kaapvaal Craton is one of the best preserved of all Archean cratons. It is partially covered by the supracrustal sequences of the Witwatersrand, Ventersdorp and Transvaal Basin (and correlated Griqualand West Basin), which span almost a billion years (~3.1 to 2.2 Ga). This thesis describes and …
-
A thermotectonic framework for the growth and stabilization of the eastern Kaapvaal craton, southern Africa
… subsequent stabilization of the eastern Kaapvaal craton. This thesis uses structural, geochronological, thermochronological and isotopic constraints to examine the tectonothermal processes responsible for the growth and stabilization of this portion of Mesoarchean lithosphere. Field mapping was …
-
Thermobarometry and geochemistry of peridotite xenoliths from the southwestern margin of the Kaapvaal craton, South Africa
… data, suggest that thermal gradients beneath cratonic regions (Archean blocks which stabilized > 2.5 Ga) are lower than those in off-craton regions, commonly attributed to thinner lithosphere in Proterozoic domains. Although this is true to an extent for southern Africa, the contrasts appear …
-
Aeromagnetic interpretation of a section of the Willyama Inliers in the Curnamona Craton, South Australia / Mohammad Reza Haidarian.
Figure 5.13 is folded and in plastic pocket inside back cover.
-
S-wave velocity structure beneath the Kaapvaal Craton from surface-wave inversions compared with estimates from mantle xenoliths
… inversions across the Archean Kaapvaal craton of southern Africa are compared with seismic velocities estimated from approximately 100 mantle xenoliths brought to the surface in kimberlite pipes. As the xenoliths represent a snapshot of the mantle at the time of their eruption, …
-
Petrogenesis of Mesoarchean high-K rocks in the Kaapvaal Craton: Investigating the Boesmanskop Alkaline Complex and Salisbury Kop batholith
… situated on the eastern margin of the Kaapvaal Craton. The BAC consists of small intrusions at the southern end of the Barberton greenstone belt, recording shear deformation and containing the most potassic and REE-rich rocks of the GMS suite. In contrast, the SB is a homogeneous batholith at …
-
Geochemistry of selected South African group I, group II and transitional kimberlites located on and off the Kaapvaal craton
… been emplaced through both the Archean Kaapvall craton (on-craton) and Proterozoic Namaqua-Natal belt (off-craton), have been selected for a comparative study aimed at characterising their geochemistry and source region compositions, as well as understanding the petrogenetic processes that have …
-
Geodynamic evolution and petrogenesis of the neoarchaean Francistown granite-greenstone complex in NE Botswana, SW margin of the Zimbabwe craton
… part of the southwestern margin of the Zimbabwe Craton. It includes a suite of geochemically diverse Neoarchaean granitoids and mafic dominated-supracrustal assemblages. All the supracrustal rocks and mafic intrusions have undergone greenschist to lower amphibolite facies metamorphism, but most …
-
Mantle flow and lithosphere-asthenosphere coupling beneath the southwestern edge of the North American craton: constraints from shear-wave splitting measurements
… mechanisms in the vicinity of a cratonic edge. Systematic spatial variations of anisotropic characteristics are revealed by 3027 pairs of splitting parameters measured at 547 broadband seismic stations. The western and southern edges of the North American craton show edge-parallel …
-
Paleomagnetic Constraints on Assembly of the Superior Craton: Results from the 2.72-2.69 Ga Vermilion District of the Wawa Subprovince, MN
… in the 2.72-2.69 Ga Vermillion Belt, Superior Craton, Minnesota. The Vermillion Belt has experienced lower greenschist facies alteration associated with volcanic-hosted massive sulfide (VHMS) deposits on the Archean paleoseafloor, as well as weak metamorphism from later reworking events. We …
-
The geochemistry of a suite of eclogite xenoliths from the Rietfontein Kimberlite, South Africa
The Rietfontein kimberlite is an off-craton kimberlite pipe, located west of the Kaapvaal Craton at 26.75°, 20.04°E and hosts a range of xenocryst lithologies, including peridotite, eclogite and a suite of megacryst minerals. This study focuses on a suite of eclogite xenoliths, which were subject …
-
Two phases of extension in North China since Mesozoic :
The North China Craton was formed around 1.8 Ga by collision and amalgamation of the Eastern and Western blocks. It remained tectonically stable since then until the Mesozoic, when its eastern part experienced widely distributed extension and volcanism. This distributed extension waned during the …
Page 1 of 7