Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

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Abstract Three dimensional finite strain and kinematic data from the Resolution Island Shear Zone, Fiordland, New Zealand record the progressive evolution of a lower crustal metamorphic core complex. The Resolution Island Shear Zone is a mid-Cretaceous (~114-90 Ma) extensional shear zone that juxtaposes high-pressure (P~17-19 kbar) garnet-granulite and eclogite facies orthogneiss from the lower crust against mid-crustal (P~6-8 kbar) orthogneiss and paragneiss along a low-angle upper amphibolite facies ductile normal fault. In the lower plate of the Resolution Island Shear Zone the high-pressure garnetgranulite and eclogite facies gneissic foliations (S1) are attenuated by granulite facies extensional shear zone foliations (S2). Retrograde metamorphism marked by the breakdown of omphacite and garnet to amphibole and feldspar in S2 foliation records the unloading of the lower plate during extension. Continued extension localized strain into weaker amphibole and feldspar-bearing lithologies. Upper amphibolite facies shear zones anastomose around rigid lenses that preserve the S1 and S2 fabric. Upper amphibolite facies shear zone fabrics (S3/L3) that envelop these pods display a regional-scale domeand- basin pattern. These shear zones coalesce and form the Resolution Island Shear Zone. Coeval with the formation of the Resolution Island Shear Zone, a conjugate, southwest dipping, and lesser magnitude shear zone termed the Wet Jacket Shear Zone developed in the upper plate of the Resolution Island Shear Zone. Three-dimensional strain analyses from S3/L3 fabric in the Resolution Island Shear Zone show prolate-shaped strain ellipsoids. Stretching axes (X) from measured finite strain ellipsoids trend northeast and southwest and are subparallel to L3 mineral stretching lineations. Shortening axes (Y, Z) are subhorizontal and subvertical, respectively, and rotate through the YZ plane of the finite strain ellipsoid. This pattern reflects the dome-and-basin geometry displayed by anastomosing S3 foliations and indicates the Resolution Island Shear Zone developed in the field of constriction. Threedimensional kinematic results indicate a coaxial-dominated rotation of stretching lineations toward the X-axis in both the XZ and XY planes of the finite strain ellipsoid. Results suggest that a lower crustal metamorphic core complex developed in a constrictional strain field with components of coaxial-dominated subvertical and subhorizontal shortening. Mid-Cretaceous (~114-90 Ma) extensional structures exposed in Fiordland, including the Resolution Island, Wet Jacket, Mount Irene and Doubtful Sound shear zones and the Paparoa metamorphic core complex allows the reconstruction of a crustal column that describes the geometry of mid-Cretaceous continental rifting of Gondwana. The overall symmetry of crustal-scale structures during continental extension suggests kinematic links between flow in the lower crust and the geometry and mode of continental extension. This result is consistent with numerical models of lithospheric rifting that predict the lower crust has a primary control on the style of continental extension.

Ph.D. / Preserved Archean crust dominantly recording lower temperature conditions (greenschist to amphibolites facies), the earliest widespread record of ultrahigh- temperature metamorphism occur in the Neoarchean. Considering that, collisional tectonic setting has been postulated as a possible tectonic scenario for the generation of ultrahigh-temperature metamorphism, sites where Archean cratons underwent collision can be potential sites for preservation of ultrahigh-temperature metamorphic granulites. The Limpopo Complex is a high-grade metamorphic terrain considered to have formed by collision in Neoarchean time between the Archean Kaapvaal and Zimbabwe cratons.Detailed petrographic and mineral chemical characterization of representative high Mg-Al granulites from the Southern Marginal Zone, Central Zone and the Northern Marginal Zone – forming the three subzones of the Limpopo Complex – was carried out. Evidence for the preservation of mineral assemblages considered diagnostic of ultrahigh- temperature metamorphic conditions, such as orthopyroxene+sillimanite±quartz, high-Al/(MgTs) orthopyroxene, sapphirine+quartz, spinel+quartz, corundum+quartz and antiperthite, are shown from these high Mg-Al granulites. Most of these mineral assemblages are reported for the first time from the Limpopo Complex. In addition, two unique textures are also reported – one, the discovery of corundum lamellar intergrowth with orthopyroxene from a high Mg-Al granulite from the Southern Marginal Zone, and second, the rare occurrence of sapphirine+quartz post dating orthopyroxene+sillimanite±quartz from two Mg-Al granulites from the Central Zone. Pressure-temperature calculations including representative P-T phase diagrams computed for the bulk compositions of the granulites studied clearly indicate ultrahigh- temperature conditions for all the three subzones. In contrast to two previous studies, one each for the Southern Marginal Zone (~950°C) and the Central Zone (~930°C), this study presents higher temperature estimates of ~1050 to ~1100°C for the three subzones. Together with examples of ultrahigh-temperature metamorphic conditions reported by the two previous studies, this study shows that the ultrahigh-temperature event reported here has affected the length and breadth of the three subzones of the Limpopo Complex. Further, the high-pressure conditions inferred from the early composition of orthopyroxene from the unique orthopyroxene-corundum intergrowth and the P-T phase diagrams computed for representative granulites from the three zones suggest a common high pressure event in all the three sub zones of the Limpopo Complex.

Strain within the crust is accommodated along vertical gradients, but a general characterization is difficult given the heterogeneity of the earth's outermost layer. The western termination of the Chugach metamorphic complex in southern Alaska includes a uniquely well exposed crustal section ideal for obtaining the vertical profile of a crustal section. Field studies in this area resulted in the characterization of deformational fabric and analysis of finite strain magnitude and orientation. These observational data provide constraints for kinematic modeling following results presented in Teyssier and Cruz (2004). By optimizing the fit between field data, finite strain analysis, and modeling, a complex ductile stratification of the crust is inferred. I conclude that strain was concentrated within the lower crust, becoming more diffuse in upper ductile levels. This unconventional crustal stratification and vertical strain gradient was consistent with an anomalously high thermal gradient created by the adjacent subducting spreading ridge.

La lithosphère continentale peut s’étirer selon trois modes (rift large, rift étroit et Core Complex). En Asie de l’Est, une extension continentale a eu lieu de la fin du Mésozoïque au Cénozoïque et ne semble correspondre à aucun des trois modes actuellement définis. Cette période est caractérisée par un amincissement lithosphérique exceptionnel (>100 km), la présence de MCC, de bassins sédimentaires et une importante activité magmatique. Basé sur une approche multi-échelles, ce travail vise à mieux comprendre les mécanismes à l’origine de cette déformation lithosphérique (jamais abordés) ainsi que du moteur de l’extension (encore vivement discuté). Pluridisciplinaire, cette étude apporte de nouvelles contraintes à partir de l’analyse de la déformation finie (ductile ou fragile), du magnétisme des roches (ASM, paléomagnétisme), de la géochronologie (U/Pb sur zircon et 40Ar/39Ar sur monograins) et de la gravimétrie. Différents objets reconnus, révélant des quantités d’extension différentes (MCC vs. pluton cisaillé), montrent que la croûte continentale se déforme de manière très localisée, par la mise en place de larges dômes extensifs séparant des domaines de « radeaux » ou « boudins » présentant une déformation faible à nulle. Par comparaison des données crustales et mantelliques (tomographie sismique, géochimie) disponibles, cette étude met en évidence que l’amincissement lithosphérique reconnu pour le Mésozoïque est principalement lié à un important flux thermique du manteau, l’extension n’ayant qu’un rôle limité dans cet amincissement (<20%). En outre, eu égard au gradient géothermique exceptionnellement élevé de la région, à la fin du Mésozoïque, il semble très probable que des MCC puissent s’être développés sans épaississement préalable de la croûte. L’analyse comparée des directions d’étirement dans la croûte et dans le manteau met en évidence le rôle majeur de la subduction des panneaux plongeants le long de la marge est-asiatique. Un modèle géodynamique a été proposé montrant le rôle du retrait successif des panneaux plongeants couplé à un phénomène d’érosion thermique de la lithosphère. / Continental lithosphere can be stretched according to three modes (wide rift, narrow rift, Core Complex). In East Asia, a continental extension occurred during the Late Mesozoic to Cenozoic times and seems to do not correspond to any of three modes currently defined. This period is characterised by an exceptional lithospheric thinning (> 100 km) with the presence of MCC, sedimentary basins and a huge magmatic activity. Based on a multi-scale approach, this work aims to better understand the mechanisms of this lithospheric deformation (never addressed) and the engine of the extension (yet highly debated). This study provides new multidisciplinary constraints from the analysis of finite strain (ductile or brittle), rock magnetism (AMS, palaeomagnetism), geochronology (U/Pb on zircon and 40Ar/39Ar on single crystals) and gravity. Different objects have been recognised, revealing different amounts of extension (MCC vs. sheared pluton), and show that the continental crust is locally highly deformed, with emplacements of large MCCs between "rafts" or "boudins" domains which are weakly strained to unstrained. By comparison of available crustal and mantle data (seismic tomography, geochemistry), this study shows that the lithospheric thinning recognised for the Mesozoic is mainly related to a major mantle heat flux, the extension plays a limited role in this thinning (<20%). In addition, given the exceptional high geothermal gradient in the region at the end of the Mesozoic, it seems very likely that MCC may have developed without pre-thickened crust. Comparative analysis of stretching directions within the crust and mantle highlights that the subduction of the (palaeo) Pacific plate along the East Asian margin may play an initial and major role during Late Mesozoic extensional event. A geodynamic model has been proposed to show the role of the successive retreat of subducting slabs coupled to a thermal erosion of the lithosphere.

16 samples of increasing metamorphic grade from the Ballachulish Igneous Complex and Aureole, located in the west of Scotland, were studied in order to analyze the sulfide mineralogy and to what extent they were affected by contact metamorphism. The samples were collected from two lithologies, the Creran Succession and the Ballachulish Slate lithology, as well as from the igneous complex. The sulfides of main interest in the samples are pyrite and pyrrhotite. At the onset of contact metamorphism, pyrite disappears while pyrrhotite gets more abundant as metamorphic grade increases. Pyrrhotite also undergoes multiple changes such as 1) elongation and thinning of the grains, 2) development of 120° grain-boundaries, 3) development of pyrite-zones within the pyrrhotite and 4) the decomposition of pyrrhotite and alignment of pyrite along its grain-boundaries at high temperature. The elongation of the grains occurs in both the Creran Succession and the Ballachulish Slate. The rest of the textures, however, can only be found in the Creran Succession. The two lithologies differ by the high graphite content in the Ballachulish Slate. The elongated grains as well as the pyrite inclusions in the pyrrhotite both are strong evidence of recrystallization. The absence of pyrite in the Ballachulish Slate was most probably caused by the buffering properties of the graphite-rich fluid in these rocks, causing more reducing conditions. There is evidence against a heavy, pervasive fluid flow through the aureole. However, the inner contact zone seems to have been affected by a more pronounced fluid flow. This could have been caused by the metamorphic fluid working in conjunction with fluids released from the intrusion. Regarding the mobility of S in the aureole, no strong evidence could be found, other than the decomposition of pyrrhotite grain-boundaries in the high-grade metamorphic samples.

This thesis focuses on the detection of marble sculpture forgery made of cultured marble. Cultured marble is a mixture of marble dust, polyester and accelerators. Thus chemical analysis of cultured marble would give declined levels of calcium when compared to authentic sculptures. Since sample removal is a problem when dealing with archaeological heritage, the instrument used was portable X-Ray Fluorescence device which provides in situ analysis of the samples. Device has been used to analyze six authentic and four forgery sculptures. Seven of the sculptures were provided by Anatolian Civilizations Museum and three of them were provided by a sculpture workshop, Ak

Thesis (M.S.)--Ohio University, August, 2009. / Title from PDF t.p. Includes bibliographical references.