Dissertations / Theses: 'Metamorphism'

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Goswami, Sudipta. "Inverted metamorphism in the Sikkim-Darjeeling Himalaya : structural, metamorphic and numerical studies." Thesis, University of Cambridge, 2005. https://www.repository.cam.ac.uk/handle/1810/284048.

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The structural and metamorphic evolution of the Darjeeling-Sikkim Himalaya, a “classical” region of inverted metamorphism in the Himalaya, has been investigated by field studies combined with 2-D numerical modelling of the thermal evolution. In the Himalaya, an orogen-wide zone of inverted isograds is spatially associated with the Main Central Thrust (MCT). In the Sikkim-Darjeeling region, an inverted metamorphic field gradient is indicated by garnet-grade rocks in the upper Lesser Himalaya (LH), which increase in grade to sillimanite + K-feldspar assemblages in the middle to upper structural levels of the Higher Himalayan Crystallines (HHC). Metamorphic breaks in the “Barrovian sequence” have been established between the garnet- and sillimanite-bearing rocks in the Darjeeling region and between the kyanite-staurolite schists and biotite-sillimanite schists in Sikkim. Since the accurate location of the MCT is critical to constraining the metamorphic evolution of the Higher and Lesser Himalaya, a number of criteria are used in defining the MCT zone in this region. These include lithologic contrasts, increase in non-coaxial deformation features towards the MCT zone and geomorphology. The MCT forms a zone of distributed ductile deformation that has propagated southwards with time, resulting in a 3-10 km wide zone, containing rocks from both the Higher and Lesser Himalaya. Four episodes of deformation and two metamorphic events have been identified in the HHC. Textural evidence and garnet zoning profiles indicate a single episode of prograde metamorphism, but four deformation events in the MCT zone and the LH. Garnet zoning profiles from the HHC indicate retrograde equilibrium. M₁ resulted in a peak assemblage of prismatic sillimanite + K-feldspar as well as muscovite dehydration melting resulting in millimetre to centimetre scale leucosomes, while M₂ is associated with rapid exhumation of the HHC during simultaneous movement along the MCT and the South Tibetan Detachment System (STDS) forming decompression textures in metabasic boudins and pelites.

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Rougvie, James Russell. "Metamorphism in the northern Park Range of Colorado : fluid-rock interactions and thermobarometry /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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Baker, Judith Mary. "Petrological and isotopic constraints on metamorphism and metamorphic fluid flow on Naxos, Greece." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358416.

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4

Johnson, Amy Mechel. "Textural and Chemical Relations Among Spinel-Sapphirine-Garnet-Orthopyroxene, Salt Hill Emery Mine, Cortlandt Complex, N.Y." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36988.

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Very high temperature (>900 Â°C) contact metamorphism and metasomatism of aluminous schist xenoliths in the mafic to ultramafic Cortlandt Complex, New York, resulted in formation of bodies of unusual Fe- and Al-oxide-rich rock called emery. During contact heating, disequilibrium thermal decomposition of the protolith schists in one closely examined xenolith produced two end-member materials: a quartzo-feldspathic water-undersaturated melt which partitioned much of the silica and calcium and all of the alkalis of the original schist; and a highly aluminous fine-grained emery residuum which contained spinel, magnetite, ilmenohematite, sillimanite, and sporadically corundum. During cooling, melt within the xenoliths was injected as cm-scale veinlets into the silica-poor solid residuum. Local increase in silica activity resulted in progressive silication reactions of spinel-rich residuum to several silicates. A simple model of progressive silication would require that reactions should occur from lower to higher silica content of product silicates in stages, e.g., spinel â sapphirine (Si/O=0.10), sapphirine â garnet (0.25), garnet â orthopyroxene (0.28), rather than directly from spinel to higher-silica minerals which would overstep intermediate reaction steps. However, observed reaction textures indicate the latter more complex behavior in which spinel may have reaction rims of, or occur as inclusions within, any of the three silicate minerals.

Statistical analysis of several samples has shown the mode to be the spinel-orthopyroxene reaction rim boundary although orthopyroxene is the highest-silica product mineral, based on Si/O ratio. Chi-square test results are significant and show that the textural relations observed among spinel, sapphirine, garnet, and orthopyroxene are dependent. Increased silica activity therefore cannot be the only factor controlling the reaction sequence.

Microprobe data has been collected in an attempt to correlate mineral compositions with the different textural occurrences. The effects of local equilibria appear to be the dominant factors in the overstepping of sequential reactions. Qualitative activity-activity diagrams proved useful for examining the effects of bulk composition on the relative stabilities of spinel and the three silicates, including variations in Fe/(Fe+Mg), bulk Mn and Zn contents, and minor local variation in oxygen fugacity. Matrix spinel compositions (i.e., those not modified by reaction to silicates) fall into two groups: a more magnesian one containing spinels with average Fe/(Fe+Mg) (Fe#) of 0.49 and a less magnesian one, average Fe# of 0.67. With regard to this bulk compositional effect, the more magnesian composition should reduce garnet stability due to the strong fractionation of Fe into garnet, thus favoring the reaction of spinel to orthopyroxene within silica-rich areas. In more aluminous areas, spinel will react to form sapphirine, then garnet, then possibly orthopyroxene. A less magnesian composition would expand the stability of garnet at the expense of sapphirine and, to a lesser extent, orthopyroxene.

Zinc has a subtle effect on mineral stabilities. Because Zn is strongly partitioned into spinel, higher zinc contents (concentrations in some spinels are as high as 14.9 mol% gahnite) may expand the stability of that mineral considerably. Consequently, spinel stability may increase relative to the three silicates, but this may be quite variable due to variable reaction stoichiometry and different reaction-boundary slopes in the activity-activity diagram. In general, spinels with the highest Zn content occur next to orthopyroxene (ave. 4.9 mol% gahnite in spinels) for which the stability appears to be only slightly affected by this increase in Zn. The greatest decrease in silicate stability is observed in sapphirine. Spinels adjacent to sapphirine contain no more than 1.3 mol% gahnite.

The effects of manganese and oxygen fugacity were also examined. Mn increases the stability of garnet due to strong partitioning of Mn into this mineral. It can be inferred using statistical and chemical data that this has some bearing on textural relations in garnet-bearing samples, but the lack of obvious Mn fractionation by other minerals examined makes it impossible to interpret the effects of Mn in the garnet-free samples. Calculated ferric-ferrous ratios in analyzed minerals were examined in an attempt to study the effect of oxygen fugacity on the stabilities of minerals. In the more magnesian compositions, which may correlate with slightly higher fO2 during reactions, spinels should react to form sapphirine, then possibly garnet or orthopyroxene with further silica activity increase. In lower-fO2 environments (perhaps those with higher bulk Fe#), spinel should react directly to form orthopyroxene. The coexistence of magnetite and ilmenohematite dictates T-fO2 conditions very nearly at those of the Hematite-Magnetite buffer. Minor fO2 variations that might have had an effect on silicate-forming reactions would only be recorded by small variations in magnetite and ilmenohematite solid solutions (ulvospinel and ilmenite contents, respectively). These data were not acquired in this study, however, so no definite conclusions could be made.
Master of Science

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Cui, Xiaojun. "Numerical modeling of reactive fluid flow in the Notch Peak contact metamorphic aureole, Utah /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3060092.

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6

McFarlane, Christopher R. M. "Metamorphism, structure and tectonic evolution of the Matthew Creek Metamorphic Zone, Kimberley, British Columbia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0024/MQ31363.pdf.

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7

Ambrose, Tyler. "Structure, metamorphism, and tectonics of the northern Oman-UAE ophiolite and underlying metamorphic sole." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:e9520624-0f91-4c9d-a9b9-e9e2fc5d5517.

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Ophiolites - thrust sheets of oceanic lithosphere that have been emplaced onto the continental margin - provide the opportunity to explore the structure and genesis of oceanic crust. As many ophiolites formed above subduction zones, they also allow for the investigation of mantle wedge and subduction interface processes. This the- sis examines the Oman-United Arab Emirates (UAE) ophiolite, which is the largest and most intensely studied ophiolite on Earth. Three distinct problems are addressed. (1) Recent research has proposed that the architecture and tectonic evolution of the ophiolite in the UAE differs from in Oman. In Chapter 2, I test this hypothesis by integrating new geological mapping and field observations with previously published maps of the ophiolite in the UAE. My results indicate that the ophiolite is gently folded, but otherwise largely intact. I demonstrate that the architecture of the ophi- olite in the UAE is not significantly different from in Oman. Thus, there is no basis for a different tectonic evolution as recently proposed. (2) Observations from exper- iments and small-scale natural shear zones indicate that volumetrically-minor phases can control strain localization. In Chapter 3, I test the hypothesis that minor phases control strain-localisation at plate boundaries. To do so, I analyzed peridotites from the base of the ophiolite, a palaeosubduction interface. My results demonstrate that minor phases limited olivine grain growth, which led to rheological weakening. (3) The mechanisms by which metamorphic soles detached from the downgoing slab and accreted to the hanging-wall mantle is unclear. In Chapter 4, I examine a transect across the metamorphic sole in the UAE. My results reveal that granulite formation was more extensive than is typically considered. I propose that granulite formation resulted in rheological strengthening, which caused the subduction interface to migrate into the downgoing slab and accrete the metamorphic sole.

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McLaren, Sandra. "The role of internal heat production during metamorphism of the Eastern Arunta Complex, central Australia, and the Mount Isa Inlier, Queensland /." Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09SB/09sbm161.pdf.

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Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1997?
National Grid reference SF53-14 (Alice Springs), SF54-1 (Mount Isa) (1:250 000). Includes bibliographical references (leaves [32-36]).

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9

Strowbridge, Susan Leah. "Metamorphic evolution of anatectic metapelites from the Gabriel high strain zone, Grenville Province /." Internet access available to MUN users only, 2005. http://collections.mun.ca/u?/theses,62592.

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Nagurney, Alexandra Bobiak. "Microstructural Controls on the Crystallization and Exhumation of Metamorphic Rocks." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103773.

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Microstructural data on the orientation and distribution of minerals can be utilized to better understand the processes controlling mineral crystallization during metamorphism and the extent to which equilibrium versus kinetic factors control the evolution of metamorphic rocks. Four studies in this dissertation address this, finding that: i) garnet crystals crystallize via epitaxial nucleation in which garnet crystallizes by templating on the crystal structure of muscovite; ii) the distribution of grain boundary void space at quartz-quartz and garnet-quartz grain boundaries is a function of the orientation of quartz crystals on either side of the grain boundary. There are more voids, and in some cases larger voids, at grain boundaries in which the a-axis of a neighboring quartz grain is perpendicular to the grain boundary than any other orientation; iii) the chemical potentials of garnet-forming components evolve differently in samples in which garnet growth either significantly or minimally overstepped equilibrium garnet-forming reactions; iv) the southwestern Meguma Terrane, Nova Scotia, experienced peak metamorphic conditions of ~630ºC and 4.0 kbar, likely resulting from regional metamorphism during the Neoacadian orogeny. A case study on the mechanisms controlling garnet crystallization in one Nova Scotian sample reveals that the rate limiting step of garnet crystallization was probably the diffusional transport of Al through the intergranular matrix. Taken together, this work has implications for understanding: i) the properties of grain boundaries in metamorphic rocks and ii) the extent to which equilibrium versus kinetic factors impact metamorphic petrogenesis.
Doctor of Philosophy
A fundamental question in the development of metamorphic rocks, or rocks that form due to changes in pressure and temperature conditions deep in the Earth's mountain belts, is: what controls the crystallization of new minerals? While pressure, temperature, and bulk composition likely play a major role in this, it is also possible that the distribution of reactant minerals and the transport of elements through the rock may also play a role in mineral crystallization. This dissertation explores several projects related to this broad topic. In one example, garnet, an important metamorphic mineral, was found to crystallize by utilizing the atomic structure of another mineral in the rock. This creates a favorable pathway for the crystallization of garnet, which preferentially grows on this 'parent' mineral. Further, the distribution of porosity, or void space, at the interfaces between mineral grains in metamorphic rocks is found to be controlled by the orientation of those minerals. This porosity likely formed when the rocks were exhumed from deep in the Earth towards its surface. Metamorphic rocks can also tell the story of continental plates colliding millions of years ago. In an example from the formation of the Appalachian Mountains ~400 million years ago, a combination of collisional tectonic forces and the heat from magmas in the shallow crust resulted in metamorphic rock, which make up much of southern Nova Scotia today. This work has important implications for understanding: i) porosity in metamorphic rocks and ii) how minerals crystallize during metamorphism.

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Standley, Carl E. "Banda forearc metamorphic rocks accreted to the Australian continental margin : detailed analysis of the Lolotoi Complex of East Timor /." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1696.pdf.

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Lisowiec, Nicolas John. "The Metamorphic framework for the Moine series : evidence for wide-spread Neoproterozoic metamorphism in Scotland /." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09SB/09sbl771.pdf.

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Eser, Mehmet. "Shape metamorphism using p -Laplacian equation." abstract and full text PDF (free order & download UNR users only), 2005. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1433292.

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Goto, Atsushi. "Material migration during high pressure metamorphism." 京都大学 (Kyoto University), 1993. http://hdl.handle.net/2433/168941.

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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第5292号
理博第1466号
新制||理||813(附属図書館)
UT51-93-F49
京都大学大学院理学研究科地質学鉱物学専攻
(主査)教授坂野昇平, 教授鎮西清高, 教授西村進
学位規則第4条第1項該当

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Walker, James David. "The structure and metamorphic evolution of the High Himalayan Slab in SE Zanskar and NW Lahaul." Thesis, University of Oxford, 1998. http://ora.ox.ac.uk/objects/uuid:fc8b8fd3-e155-4f2f-9256-3667c2b31f4f.

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This thesis attempts to unravel the complex thermal and structural history of part of the High Himalayan Slab in NW India and combines reconnaissance-style field structural mapping of an area covering ~10,000 km² with petrography, microstructural analysis, thermobarometry and geochronology techniques. The results of this work show that the oldest protoliths of the High Himalayan Slab are at least Cambrian in age and that they may have experienced a major pre-Himalayan metamorphism at c.500 Ma. The youngest protoliths are Mesozoic in age (the Tandi Group) and demonstrate that the High Himalayan Slab represents the metamorphosed equivalents of the Tibetan Sedimentary Series. Metamorphism was achieved via substantial crustal shortening and thickening following the India-Asia collision at 50-54 Ma ago. Phase relationships demonstrate that metamorphism was a regional Barrovian-type event associated with the growth of biotite-, garnet-, staurolite-, kyanite- and sillimanite-bearing assemblages in metapelites. Quantitative thermobarometry demonstrates that near-peak conditions of c.6-8 kbar and 550-650°C were attained in the deepest exposed levels. Growth of metamorphic assemblages was underway by at least 30 Ma, as indicated by U-Pb ages of metamorphic monazites. Exhumation of the High Himalayan Slab was achieved through a combination of extensional unroofing along major detachments (namely the Zanskar Shear Zone), thermal doming, thrusting along the Main Central Thrust and surface erosion. Exhumation is closely associated with the growth of sillimanite- and cordierite-bearing assemblages in pelites and the generation and emplacement of crustal melt leucogranites in the upper parts of the slab. U-Pb dating of accessory phases from one of the crustal melt leucogranites (the Gumburanjon leucogranite) constrains its crystallisation and emplacement age at c.21-22 Ma. This is only slightly older than its ⁴⁰Ar/³⁹Ar muscovite and biotite cooling ages of c.20-21 Ma, which is attributed to the emplacement of the Gumburanjon leucogranite into the immediate footwall of the ZSZ. Field and geochronological data therefore support a strong temporal and spatial relationship between upper crustal melting and extension in a convergent orogen.

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Huff, Timothy A. "Fluid inclusion evidence for metamorphic fluid evolution in the Black Hills, South Dakota /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1421144.

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Hicks, Judith Anne. "Gahnite and its formation in the context of regional metamorphism and mineralization in the Namaqualand metamorphic complex." Master's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/22024.

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Bibliography: pages 150-158.
Gahnite (ZnAl₂O₄) is commonly associated with sulphide mineralization in metamorphosed massive sulphide deposits, and also occurs in marbles, pegmatites and quartz veins. Its formation has been attributed to the breakdown of Zn-staurolite or desulphidation of sphalerite during metamorphism. The stability of zinc-rich spinels under a wide range of metamorphic conditions in a variety of lithologies results in its persistence in rocks where many other prograde, high temperature minerals and sulphides have been altered. Thfs has resulted in various investigations into its use in exploration and potential for determining metamorphic parameters. With the interest in finding new ore bodies and in determining the metamorphic history and mineralogy in Namaqualand, some gahnite-bearing localities have been investigated in this study.

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18

Gupta, Saibal. "Structure and metamorphism of Sikinos, Cyclades, Greece." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363344.

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Munn, Barbara J. "Metamorphism in the Northern Front Range, Colorado." Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/29154.

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Thermobarometry, detailed petrography, electron microprobe analysis, and fluid inclusion microthermometry were used to quantify the history of a high grade Proterozoic terrane exposed within the northeastern Colorado Front Range. Pressure-temperature calculations identified two blocks from different crustal levels exposed adjacent to one another within the Poudre Canyon west of Fort Collins. They are the eastern, higher pressure, block (HPB; 734 degree C, 7.1 kbar) and the western, lower pressure, block (LPB; 655 degree C, 5.2 kbar). The blocks followed a clockwise uplift path and were juxtaposed by ductile shear near the end of the decompressive stage of uplift. Final assembly of the separate blocks to the same crustal level was constrained by mineralogic and textural considerations and by the isochores of identical low density carbon dioxide inclusions trapped by both blocks. Both blocks experienced peak metamorphism within the sillimanite-K-feldspar zone accompanied by partial melting, are characterized by stromatic migmatites, and show textural evidence for localized reactions related to decompression and cooling. Differences between the blocks include the type of melt-generating reactions and the pronounced late muscovite in the LPB. Gibbs' Method calculations indicate that local (outcrop scale) textural and mineralogical differences between HPB Mg-enriched pelites are caused by small differences in bulk composition and locally variable H2O content. The quartzo-feldspathic biotite gneisses in the LPB generated migmatites by wet melting, whereas the pelitic schists and gneisses in the HPB generated migmatites by dehydration melting of muscovite and biotite. Biotite dehydration melting enriched the leucosomes in HPB pelitic migmatites in K-feldspar and garnet. The minor presence of late muscovite in the HPB relative to the LPB was controlled by the different positions of their uplift paths relative to the muscovite breakdown reaction.
Ph. D.

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Songul, Gunes. "Archaeometrical Study On Marble Forgery." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614566/index.pdf.

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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

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Cox, Richard Alexander. "Eclogite facies metamorphism of mafic and ultramafic rocks in the Tshenukutish terrane, Manicouagan Imbricate Zone, eastern Grenville Province." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ54832.pdf.

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Schorn, Simon. "High-temperature metamorphism in the western Namaqua-Natal Metamorphic Province (South Africa): implications for low-pressure granulite terranes." Doctoral thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/30546.

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The interpretation of pressure (P)-temperature (T)-time (t) data is key to reconstruct the geologic evolution of ancient exhumed orogens. Of these, temperature is regarded as proxy for the heat energy available during orogenic metamorphism. Heat - the ultimate driving force of metamorphism - is consumed by a number of processes occurring during orogeny. Metamorphic rocks evolve through chemical reactions that consume energy in order to advance. As long as strongly energy-intensive processes advance in the crust, the temperature that is effectively attained is controlled by the interplay between the rate of heat energy supplied to the site of reaction and the rate of heat consumed by the process(es). Melting reactions in particular are strongly endothermic and consume a substantial proportion of the orogenic heat budget. Fertile metapelites are volumetrically minor but petrologically significant, as P-T-t-deformation constraints and burial-exhumation paths are preferentially derived from this lithology, whereas refractory granites sensu lato compose the bulk of orogenic crust. Metapelites are affected by a number of heat-consuming reactions that cause a near-isothermal state as long as they advance, however granites intersect few endothermic meltproducing reactions during orogenic metamorphism. Granitoids therefore may effectively reach a higher temperature compared to metapelites exposed to the same heat input. Temperature determined from metapelites may therefore not represent the true thermal maximum experienced by a portion of metamorphic crust - especially in granulite terranes where partial melting is widespread. Because temperature is an effect rather than the cause of heat energy transferred into the crust, it may not represent the most geodynamically relevant parameter to describe metamorphism. In this study a suite of supracrustal litholgies from the Bushmanland Subprovince (BSP) of the Namaqua-Natal Metamorphic Province (NNMP) of southern Africa are investigated via thermodynamic modelling and zircon-monazite U-Pb in-situ geochonology. Regional P-T-t distribution reveals a complex polyphasic evolution with two major tectonometamorphic episodes at ∼1.2-1.1 and 1.04-1.0 Ga, respectively. The older event is temporally linked to the emplacement of the felsic pre- to syn-tectonic Little Namaqualand Suite that caused widespread greenschist- to amphibolite facies contact metamorphism. This is recorded in garnet-cordierite-sillimanite gneisses exposed at the northernmost locality investigated here and as cm-sized porphyroblasts (e.g. andalusite) hosted in rare Mg-Al-rich gneisses. The younger event is characterised by granulite facies metamorphism peaking at 1040-1000 Ma in the entire BSP, with pelitic granulites recording variable apparent temperatures of between ∼760 and <900 ◦C at 5-6 kbar. Coarse-grained porphyroblasts of andalusite in an example of Mg-Al-rich gneiss were replaced by symplectites of high-grade phases during heating at the granulite event. At upper-greenschist facies conditions the immobility of Al caused the formation of monomineralic coronae at the expense of andalusite, effectively isolating the porphyroblasts from the matrix. Diffusion of Fe + Mg along respective gradients of µFe and µMg with simultaneous immobility of Al + Si led to the breakdown of andalusite to symplectites of cordierite + spinel during near-isobaric heating to peak conditions. Monomineralic coronae of sapphirine developed during near-isobaric cooling at the expense of previously-formed symplectites. Detailed investigation of a conformable sequence of sedimentary and mafic granulites from the locality Hytkoras in central Bushmanland reveal a disparity of some 60-70 ◦C in estimated peak metamorphic temperature. Aluminous metapelites equilibrated at ∼770-790 ◦C whereas two-pyroxene granulite and garnet-orthopyroxene-biotite gneiss record distinctly higher conditions of ∼830-850 ◦C. Semipelite and Mg-Al-rich gneisses yield poorly-constrained estimates that span the range derived from other lithologies. All samples record peak pressure of ∼5-6 kbar, and followed a roughly isobaric heating path from andalusite-greenschist / lower-amphibolite facies conditions through a tight clockwise loop at near-peak conditions, followed by near-isobaric cooling. The disparity in peak temperatures appears to be robust, as the low-variance assemblages in all samples reflect well-known melting reactions that only occur over narrow temperature intervals. The stable coexistence of both products and reactants of these melting reactions indicates that they did not go to completion before metamorphism waned. vi Calculated pressure-enthalpy diagrams show that the melting reactions are strongly endothermic and therefore buffer temperature while heat is consumed by melting. Because the respective reactions occur at distinct P-T conditions and have different reactant assemblages, individual lithologies are thermally buffered at different temperatures and to different degrees, depending on the occurrence and abundance of reactant minerals. If little to no thermal communication is assumed, this implies that lithology exerts a first-order control over the heating path and the peak temperature that can be attained for a specific heat budget. Calculations show that all lithologies received essentially the same suprasolidus heat budget of 19 ± 1 kJ.mol−1 , which led to manifestation of lower peak temperatures in the more fertile and strongly buffered aluminous metapelites compared to more refractory rock types. The heat source responsible for near-isochronous high-grade metamorphism at a regional scale most likely was a mixture of mafic mantle underplating combined with radiogenic heating in a slowly buried juvenile crust. Heat transfer to higher levels of the crust was aided by advective heating via the syn-metamorphic emplacement of the post-tectonic Spektakel Suite that locally led to near-ultrahigh temperature (UHT) conditions recorded by proximal pelitic granulites. The overall characteristics of the BSP, namely (i) heating from shallow low-grade conditions to granulite facies temperatures at a maximum depth of ∼20 km along a roughly isobaric heating path with minor concomitant burial, (ii) seemingly coeval peak metamorphism recorded at a regional scale that was accompanied/preceded by voluminous felsic magmatism (iii) that was followed by (iv) slow, largely isobaric cooling to an ambient geotherm with no significant attending exhumation, are consistent with a long-lived evolution in a continental back-arc mobile belt setting.

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Bendersky, Claire. "The onset of thermal metamorphism in enstatite chondrites /." Connect to online version, 2006. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2006/189.pdf.

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Staron, Patrick Joseph. "Nonequilibrium thermodynamics of temperature gradient metamorphism in snow." Thesis, Montana State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3560693.

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In the presence of a sufficient temperature gradient, snow evolves from an isotropic network of ice crystals to a transversely isotropic system of depth hoar chains. This morphology is often the weak layer responsible for full depth avalanches. Previous research primarily focused on quantifying the conditions necessary to produce depth hoar. Limited work has been performed to determine the underlying reason for the microstructural changes. Using entropy production rates derived from nonequilibrium thermodynamics, this research shows that depth hoar forms as a result of the snow progressing naturally toward thermal equilibrium.

Laboratory experiments were undertaken to examine the evolution of snow microstructure at the macro scale under nonequilibrium thermal conditions. Snow samples with similar initial microstructure were subjected to either a fixed temperature gradient or fixed heat input. The metamorphism for both sets of boundary conditions produced similar depth hoar chains with comparable increases in effective thermal conductivity. Examination of the Gibbs free energy and entropy production rates showed that all metamorphic changes were driven by the system evolving to facilitate equilibrium in the snow or the surroundings. This behavior was dictated by the second law of thermodynamics.

An existing numerical model was modified to examine depth hoar formation at the grain scale. Entropy production rate relations were developed for an open system of ice and water vapor. This analysis showed that heat conduction in the bonds had the highest specific entropy production rate, indicating they were the most inefficient part of the snow system. As the metamorphism advanced, the increase in bond size enhanced the conduction pathways through the snow, making the system more efficient at transferring heat. This spontaneous microstructural evolution moved the system and the surroundings toward equilibrium by reducing the local temperature gradients over the bonds and increasing the entropy production rate density.

The employment of nonequilibrium thermodynamics determined that the need to reach equilibrium was the underlying force that drives the evolution of snow microstructure. This research also expanded the relevance of nonequilibrium thermodynamics by applying it to a complicated, but well bounded, natural problem.

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25

Bishop, Andrew Nicholas. "Contact metamorphism as a model for burial maturation." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386748.

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26

Horsfall, Christopher J. "⁴⁰AR/³⁹AR laser probe dating of prograde metamorphism." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497440.

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Dating by 40Ar/39 At laser probe mass spectrometry can provide high spatial resolution data on in-situ K-bearing minerals, such as micas and amphiboles. When used in conjunction with careful petrographic investigations, separate generations of minerals related to different metamorphic conditions may be accurately dated. This can provide a detailed history of metamorphism and deformation, and ultimately provide data as to the dynamics of erogenic processes. This project has determined that 40Ar/39Ar laser probe mass spectrometry can be successfully utilized to determine prograde histories of metamorphic rocks.

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27

Guilmette, Carl. "High-P Granulite facies metamorphism from the tibetan plateau and the Himalaya: Metamorphic history and geochemistry of lower crustal and early subduction metamorphic rocks." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27631/27631.pdf.

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28

Bailey, David Elliott. "Metamorphic evolution of the crust of south-western Norway : an example from Sognefjord." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:9c297189-fe46-4d4d-8821-4fce08d5f5cd.

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It is suggested that the Mafic Units and HS are allochthonous and were emplaced onto the WGR during an early stage of the Caledonian Orogeny. All units, including the Basement Gneisses, have suffered retrogression during a late extensional phase which continued into at least the Middle Devonian.

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29

Miller, Martin Gregg. "Structural and kinematic evolution of the Badwater Turtleback, Death Valley, California /." Thesis, Connect to this title online; UW restricted, 1992. http://hdl.handle.net/1773/6716.

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30

Mildren, Scott. "Heat refraction and the metamorphic process : calculations with applications to unconformity -related contact metamorphism in the northern Flinders Ranges /." Title page, contents and abstract only, 1992. http://web4.library.adelaide.edu.au/theses/09SB/09sbm641.pdf.

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Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1993.
On title page : "National Grid reference SH54 6737." One col. folded map in pocket inside back cover. Includes bibliographical references (leaves 39-41).

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31

Rose, Shellie R. "Timing constraints and significance of Paleoproterozoic metamorphism within the Penokean orogen, northern Wisconsin and Michigan (USA)." Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1090940526.

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32

Scudder, Susan Marie. "A Multi-Method Study of Metamorphism and Fluid Flow During Contact Metamorphism of the May Lake Interpluton Screen, Yosemite National Park, California." Thesis, San Jose State University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10624355.

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The May Lake interpluton screen is a 4 km long, ∼0.5 km wide swath of metamorphic rock cropping out between plutons of the ∼103 Ma Yosemite Valley Intrusive Suite and the ∼93-85 Ma Tuolumne Intrusive Suite in Yosemite National Park, California. Metasomatic alteration and recrystallization due to contact metamorphism and fluid infiltration resulted from the emplacement of the Cretaceous plutons. Mineral assemblages are consistent with metamorphism to hornblende-hornfels and amphibolite facies. The presence of sillimanite-bearing metapelite and more Mg-rich clinopyroxene in calc-silicate assemblages of the northeast section of the screen than the southwest suggest higher grade metamorphism was experienced to the northeast. Pseudosection diagrams created from whole rock chemical analyses of three metapelite rocks also indicate higher temperatures in the northeastern section of the screen with minimum temperatures estimated from ∼540-617°C. Based on petrographic analysis of andalusite- and sillimanite-bearing metapelite, it is likely that the screen experienced two stages of contact metamorphism: relatively lower temperature metamorphism during intrusion of the Yosemite Valley Intrusive Suite followed by relatively higher temperature contact metamorphism during intrusion of the more mafic Tuolumne Intrusive Suite. Stable isotope data suggest that rock permeability and preexisting structures were the strongest factors controlling fluid infiltration through the contact aureole.

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33

Roberts, Hazel Jane. "An investigation of a polymetamorphic terrain using ⁴⁰Ar-³⁹Ar geochronology." Thesis, Open University, 1999. http://oro.open.ac.uk/54421/.

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This research is an exploration both of the Precambrian metamorphic geology of south-western Montana and the Wlaser ablation microprobe ^4OAt-³⁹At geochronological technique. Using the high spatial resolution of the UV laser microprobe it has been possible to produce systematic ^4OAt-³⁹Ar ages within individual mica grains. Further, the UV laser has been used to drill into biotite inclusions within garnet to look at the shielding effect of the garnet lattice, and to drill depth profiles into garnet to measure helium diffusion in laboratory experiments. The south-western Montana region of the Precambrian Wyoming Province was believed to have undergone at least three separate periods of metamorphism: M1- granulite facies in the Archaean, M2 - amphibolite facies in the Early Proterozoic, and M3 - greenschist to epidote-amphibolite facies in the Mid-Proterozoic. Because of the relatively low blocking temperature of the 40Ar- 39Ar geochronological system in mica (c.300-350 °C), it is readily reset by regional metamorphic events and previous K-Ar and 4OAr_38 Atgeochronology had found that the Early Proterozoic event dominated the ages obtained. UV laser 40Ar-39At dating of the matrix mica constrained the timing of cooling from the Early Proterozoic metamorphic event to between 1780 to 1740 Ma with a cooling rate between 1 and 8 °C/m.y. 4OAr_39Ar analyses of individual biotite inclusions in garnet also produced similar ages. However, Pb-Pb step leach dating of a small subset of garnet yielded ages between 1808 and 1765 Ma, demonstrating that the garnet did not grow during an Archaean event but, rather, during the Early Proterozoic metamorphic event. Thus, the shielding properties of garnet on biotite inclusions could not be easily assessed in these samples. However, where matrix biotite had been partially reset by the Cretaceous plutons, there was some evidence to suggest that a minority of the biotite inclusions in the same sample had been shielded from resetting. The influence of fractures, defects and other fast diffusion paths is believed to have prevented most of the inclusions from being shielded. No evidence was found to show that the rocks in south-western Montana were metamorphosed during the Archaean and it seems likely that the M1 and M2 events were not greatly separated in time and were both Early ProterozoiC in age. The high spatial resolution of the UV laser microprobe was used in order to date highly altered biotite within rocks that had undergone later (M3) greenschist metamorphism. Biotite was interlayered with chlorite, clinozoisite and prehnite but using the UV laser it was possible to separately analyse areas of unaltered biotite and areas of alteration within a single mineral and produce ages from both. It was thus possible to measure two ages from one sample: an unaltered age consistent with the timing of the Early Proterozoic metamorphism, and a younger age that could be linked to the c.1500-1360 Ma timing of Belt basin formation to the north and west of the region. This technique therefore was able to overcome the difficulties associated with producing meaningful ages from altered samples whilst constraining the timing of the M3 metamorphic event.

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34

Cooley, Michael Ames. "Closely spaced metamorphic isograds along the Matthew Fault, Cariboo Mountains, British Columbia, relationships between metamorphism and dextral strike-slip faulting." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq20618.pdf.

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35

McStay, Jonathan Hugh. "Granulite-facies metamorphism, fluid buffering and partial melting in the Buffels River area of the Namaqualand metamorphic complex, South Africa." Doctoral thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/18280.

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The Buffels River area of central Namaqualand comprises a sequence of Proterozoic volcano-sedimentary gneisses intruded by granitoid orthogneisses. This study concentrates on the mechanisms of granrilite-facies metamorphism in a small area of isofacial rocks. Particular emphasis is placed on the role of partial melting and the infiltration and buffering of metamorphic fluid is examined.

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36

Heiligmann, Martin. "Genesis and metamorphism of the Hemlo gold deposit, Ontario." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100622.

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The worldclass Hemlo deposit is one of Canada's largest gold producers, containing 95 million tons of ore grading ~8 g/t Au; the mineralization is hosted mainly by two sub-parallel shear zones. However, unlike most Archean lode gold deposits, the ore occurs as finely disseminated Hg- and Ag-bearing native gold in potassically altered rocks, and is associated with molybdenite, stibnite and realgar.
Mineralization occurred at greenschist conditions (400 to 500°C), and was subsequently overprinted by a single metamorphic event that peaked at ~630°C and 5 to 7 kb, which recrystallized the ore and alteration assemblages. Retrograde cooling lasted for ~80 m.y., with temperature decreasing on average ~5°C per m.y. Ore formation involved three reactions that affected ∫S2,∫O2, and pH: the dissolution of sedimentary barite, the precipitation of pyrite, and the replacement of muscovite by K-feldspar. During sulfidation, caused by the dissolution of barite, iron partitioned preferentially into pyrite, which prevented the formation of Fe-bearing metamorphic index minerals (such as garnet and staurolite), oxides (e.g., magnetite, hematite, ilmenite), and low- ∫S2 sulfides (e.g., pyrrhotite). In addition, K-alteration strongly enriched the ore zones in K-feldspar (microcline) and muscovite, which buffered pH, and prevented formation of aluminosilicates. Hemlo is an example of a mesothermal deposit which formed from metamorphic fluids with a significant magmatic component. Deposition of native gold and molybdenite occurred due to decreases in pH and ∫O2 that accompanied potassic alteration and pyrite precipitation. Other elements, such as Sb and As were adsorbed initially onto pyrite growth surfaces. Near peak metamorphism, the deposit evolved a sulfide melt that formed through release of As and Sb from pyrite during metamorphic recrystallization, partial decomposition of primary minerals (such as native gold), and interaction of the melt with sulfur-bearing aqueous metamorphic fluids. The mineral assemblages that crystallized from this melt are similar to those predicted by experimental data for the As-Sb-S and related systems, and are interpreted to have formed by fractional crystallization.

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37

Primmer, T. J. "Low-grade Variscan regional metamorphism in south west England." Thesis, University of Bristol, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370706.

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38

Hollis, Julie Alison. "Natural and experimental constraints on ultra-high temperature metamorphism." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/15035.

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Independent determination of the heat capacity of the sapphirine used in this study is currently underway. It is expected that extrapolation of this data to the results of this study will result in the derivation of a heat capacity function for natural sapphirine from 0-1573K. Incorporation of this into existing thermodynamic datasets should allow the quantitative determination of the position of sapphirine-bearing reactions in petrogenetic grids relevant to ultra-high temperature metamorphism in natural systems. The Archean Napier Complex of Antarctica is one of the best documented UHT terrains, long recognised as having experienced temperatures in excess of 1000°C followed by a long period of near-isobaric cooling at deep crustal levels. However, the early history of the terrain, the timing of deformation and metamorphism, and the tectonic processes responsible for the generation of the extreme temperatures of metamorphism, have not been resolved (e.g. Ellis, 1987; Harley, 1989; Sandiford, 1989; Hensen and Motoyoshi, 1992). Mineral textural relationships linked to deformation features from a range of localities in and around Amundsen Bay are consistent with peak metamorphic conditions of 900-1100°C at 0.8-1.1 GPa during intense lower crustal extension. Rare decompression textures from widely spaced localities attest to decompression of the whole terrain to depths equivalent to the base of a normal thickness crust after peak metamorphism, while still under UHT conditions, and indicate that intense lower crustal extension and UHT metamorphism occurred synchronously with crustal thickening. Retrograde reactions textures may have been produced either by isobaric cooling, or by later granulite facies metamorphic event/s, or both. Mineral reaction textures and structural features support a tectonic model of lithosphere delamination for the development of UHT metamorphism, in the Napier Complex. This model involves the detachment of the lower part of the mantle lithosphere during continental collision, allowing upwelling of hot asthenosphere material directly beneath the crust, which in turn results in intense extensional deformation of the lower crust and lateral expulsion of melts.

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39

Daczko, Nathan Robert. "The Structural and Metamorphic evolution of cretaceous high-P granulites, Fiordland, New Zealand." University of Sydney. Geosciences, 2002. http://hdl.handle.net/2123/822.

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Fiordland is located southwest of South Island of New Zealand. The field area of this thesis is in northern Fiordland, at the boundary of pristine arc rocks (Median Tectonic Zone) and a belt of Paleozoic paragneisses and orthogneisses of variable age that represent the metamorphosed paleo-Pacific Gondwana margin.

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40

Baker, Andrew James. "Metamorphic studies in the Scottish Highlands." Thesis, University of Oxford, 1985. http://ora.ox.ac.uk/objects/uuid:0000df07-a390-4b43-af48-31f04ba628ec.

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Conditions of 8kb and 800°C are estimated for sillimanite K feldspar bearing metapelites and garnet-clinopyroxene bearing amnphibolites in Glen Muick. These conditions are inconsistent with the simultaneous nearby presence of equilibrium between andalusite and kyanite. Andalusite in the Glen Muick area is late. The sillimanite zone may have been in part primary. There is a transition without major structural break between Tay Nappe flat belt and the "Banff Nappe". A dataset has been derived for phases in the system KCMASHCO₂. The MHSRK equation of Kerrick and Jacobs (1981) has been used to extract data from mixed devolatilisation equilibria. Heats of formation are in agreement with calorimetrically determined values. Phlogopite equilibria calculated using disordered phlogopite data seem most appropriate to natural metapelite assemblages. Variations in pressure and temperature have been constrained across the Dalradian using various calibrated reactions. Temperatures vary from about 500°C in the low kyanite zone to 800°C in the sillimanite-K feldspar zone and pressures vary from 4kb to 10kb. Pressure estimates are justified on the basis that they are consistent with the aluminosilicate phase diagram. Rocks from the Central Highlands to Glen Clova underwent a decrease in pressure during evolution through peak metamorphic conditions. Amphibolites from the southern Moines show evidence of a former eclogitic assemblage of early Grampian age or earlier. High temperature regional metamorphic rocks lie at high structural levels and are are suggested to be an allochthonous unit, the Banff Nappe of Grampian age. The western margin of the Banff Nappe is marked by a temperature maximum to the immediate east, sharp thermal transitions, a train of metabasites and a high strain zone. It is suggested that emplacement of a Banff Nappe resulted in the deformation and metamorphism of structurally lower rocks.

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41

Mawby, Joanna. "Metamorphic and geochronologic constraints on Palaeozoic tectonism in the eastern Arunta Inlier." Title page, table of contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phm462.pdf.

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Appendix 4 and 5 in pocket on back cover. Bibliography: p. 123-130. The isotopic data indicates the Harts Range Metamorphic Complex formed within a previously unrecognized intracratonic tectonic province in Central Australia

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42

Hurdle, E. J. "Stratigraphy, structure and metamorphism of Archean rocks, Clan Lake, N.W.T." Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/4875.

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43

Hicks, Roberta Jean. "Low-grade metamorphism in the Meguma Group, southern Nova Scotia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24971.pdf.

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44

Magyarosi, Zsuzsanna. "Metamorphism of the Proterozoic rocks associated with the Sudbury Structure." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0007/MQ32431.pdf.

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45

Hozjan, David J. "Blueschist metamorphism within the Bridge River Complex, Goldbridge, British Columbia." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0015/MQ48015.pdf.

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46

Slaughter, Andrew Edward. "Numerical analysis of conditions necessary for near-surface snow metamorphism." Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/slaughter/SlaughterA0510.pdf.

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Faceted snow crystals develop at or near the snow surface due to temperature gradients. After burial, snow avalanches regularly fail on these layers. Generally, surface hoar deposits when the snow surface is cooler than the surrounding environment; near-surface facets form when the subsurface is warmed by solar radiation and the surface is cooled by radiative, convective, and latent heat exchange. Field research stations were established that included daily observations and meteorological data. In two seasons, 14 surface hoar and 26 near-surface facet events were recorded. Statistical analysis of the surface hoar events indicated three factors that were related to surface hoar growth: incoming long-wave radiation, snow surface temperature, and relative humidity. The ideal conditions for each of these parameters were 190-270 W/mÂ², -22 to -11 Â°C, and 45-80%, respectively. For near-surface facet formation, long- and short-wave radiation and relative humidity were statistically linked to the events. The ideal conditions for these parameters ranged from 380-710 W/mÂ², 210-240 W/mÂ², and 23-67%, respectively. Using a thermal model, sensitivity analysis, and Monte Carlo simulations the conditions that lead to facet formation were explored. Based on computed mass-flux, the formation of surface hoar was mainly driven by changes in long-wave radiation, air temperature, wind velocity, and relative humidity. From these terms graphical tools were developed to predict surface hoar; the numerical results matched reasonably well with the field observations. Based on the presence of a specific temperature gradient understood to lead to near-surface facets, three terms were determined to be the most influential: density, thermal conductivity, and incoming long-wave radiation. Using these terms, albedo, and incoming short-wave radiation--a requirement for radiation-recrystallization--a means for predicting the presence of near-surface facets was presented. The physical and analytical data presented indicates that incoming long-wave radiation is the most influential parameter governing the conditions that lead to surface hoar and near-surface facet growth. The analysis suggests that snow with low density and high thermal conductivity may be conducive to the formation of near-surface facets.

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47

Scrimgeour, Ian. "Early Proterozoic metamorphism at the Granites gold mine, Northern Territory /." Adelaide, 1989. http://web4.library.adelaide.edu.au/theses/09SB/09sbs434.pdf.

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48

Miller, Stephen John. "High pressure acadian metamorphism of the Straits Schist, Western Connecticut." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03242009-040839/.

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49

Forest, Richard C. "Structures and metamorphism of Ptarmigan Creek area, Selwyn Range, B.C." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63337.

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50

Wain, Alice Louise. "Ultrahigh-pressure metamorphism in the Western Gneiss region of Norway." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300050.

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Dissertations / Theses on the topic 'Metamorphism'

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