Proefschrift Leyden. / Summaries in English, Spanish and Dutch. "Will be published with the same paging in Leidse geologische mededelingen, vol. 96." Vita. "Stellingen": leaf inserted. Bibliography: p. [195]-201.

Proefschrift--Utrecht, 1958. / Summary in French and Dutch. Bibliography: p. 116-118.

The Central Asian Orogenic Belt (CAOB), the largest accretionary collage on the Earth, has a complicated and prolonged accretionary history which remains being highly debated. High-grade terranes were previously interpreted as Precambrian micro-continents which played a very important role during the evolution of the CAOB. However, some of their presumed old ages are challenged by recent high-resolution dating results which raise questions on their Precambrian origins. The Chinese Altai and Tseel Terrane in the SW CAOB, two typical high-grade terranes occupy vital structural positions, feature various lithological elements and exhibit complicated deformation-metamorphism patterns, making them key areas in the reconstructing of the evolution of central Asia. However, their origins are not firmly constrained. Paragneisses were considered as Precambrian basements, but yielded detrital zircon ages predominantly between 440 and 580 Ma. The associated granitic gneisses and amphibolite gave crystallization ages at 420-463 Ma. Geochemical and zircon Hf isotopic data of paragneisses support that their protoliths may represent significant erosion products of arc rocks that were developed in a subduction environment. This feature is similar with that of the associated low-grade volcanogenic schists which probably represent immature sediments in an active margin. Detrital zircons from the paragneisses and schists show similar age patterns, supporting derivation from similar provenance. Accordingly, our data reveal that these high-grade terranes do not represent Precambrian microcontinents. Moreover, the U-Pb age pattern for the detrital zircons, and some xenocrystic zircons from the associated granitoids, is comparable with the age patterns of the micro-continents and arc terranes in western Mongolia. The predominant zircon population of 440-580 Ma matches the widely distributed granitoids within the Neoproterozoic-early Paleozoic terranes in western Mongolia, while the minor Precambrian ages (>540 Ma) resemble those old rocks preserved in the Tuva-Mongolian (TM) block and its adjacent Neoproterozoic arc terranes. These features suggest that detrital and xenocrystic zircons more likely represent the detritus recycled from western Mongolia. Accordingly, the crustal growth of the SW CAOB in the early Paleozoic could be outlined by secular amalgamation of magmatic arcs around a Precambrian micro-continent. In addition, the TM-derived Precambrian zircons are further used to trace the origin of the TM block, which favors that the TM block was possibly rifted from the Indian block in the Neoproterozoic. Further efforts have been made to decipher the controversial tectono-metamorphic history. In the Chinese Altai, U-Pb dating on the metamorphic zircon portions yielded consistent ages of ~390 Ma. Temperature estimations using mineral-pair as well as Ti-in-zircon thermometers revealed high-temperature conditions up to ~720℃. Detailed investigations on the metamorphic rocks in the Tseel area revealed that middle-pressure metamorphic fabrics developed under progressive NNE-SSW convergent setting, possibly at 385-374 Ma. A later low-pressure/high-temperature metamorphic sequence developed during decompression, associated with high-level anatexis at 374-363 Ma. Collectively, our data support that the final amalgamation of North Mongolian Domain on its southern margin occurred at Middle-Late Devonian, and might be immediately followed by the subduction of an active oceanic ridge. / published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

No description available.

No description available.

Investigations in the northwestern part of the Willyama Complex centred on the Mt Franks - Mundi Mundi area have established a 4 km thick stratigraphic section of conformable metasediments containing thin horizons of basic volcanics in the lower two - thirds of the sequence. Establishment of this sequence was only possible once it was shown that the dominant lithological layering in metasediments is bedding, and that there has been no mesoscopic transposition during deformation. The metasediments represent a sequence of clay sands deposited in a distal shelf-slope or basin type of environment. A sequence of deformational and metamorphic events established in these rocks is regarded as an expression of the Middle Proterozoic Olarian Orogeny ( c.1695 - 1520 Ma. ) and except for some reactivation of shear zones, predate deposition and deformation of the unconformably overlying Adelaidean sediments. The important D₁ deformation is a complex, progressive event with pre-S₁ static mineral growth (biotite, andalusite, sillimanite, white mica) and early minor micro-folding recognized before syn-S₁ growth and F₁ folding. An even earlier period of pre-S₁ fabric formation mainly defined by white mica, biotite and ilmenite, is not related to any visible folding and may either represent an earlier discrete event or an early phase of the D₁ event, However, as now defined, minerals outlining this pre-S₁ fabric are related to the D₁ event. The low, medium and high grade metamorphic zones defined in the field by biotite, andalusite and sillimanite respectively are pre-S₁ in age and predate F₁ folding. The intensity of metamorphism increases with depth so that there is a broad depth control on metamorphism. Relations at the andalusite/sillimanite isograd conform to a Carmichael (1969) type model and reactions took place via an intermediate sericite phase. The main effect of F₁ folding is the formation of the variably plunging variably oriented Kantappa - Lakes Nob Syncline of regional extent. Only the western limb of this fold is now visible over much of its length. This fold deforms existing metamorphic zones and thus controls the relationship of low, medium and high grade rocks in this part of the Willyama Complex. The orientation of this syncline changes from vertical in the low grade rock to inclined at depth. The western limb becomes overturned at depth so that subsequent folds are downward facing. There is also a change in fold tightness with depth - from open-tight in the low grades to tight-isoclinal in the high grades, and this is accompanied by a change in S₀/S₁ relations (from core to limb area) from non parallel to parallel. These changes are coupled with a rotation of extension direction (mass transfer direction) from subvertical to inclined and may be explained by original formation and subsequent modification of upright F₁ folds. Later modifications are recorded by open folding and overturning of S₁ - this is ascribed to a final phase of the D₁ event. Mineral growth in D₁ time resulted in the formation of S₁ varying in grade from muscovite + quartz to sillimanite. S₁ varies from homogeneous to layered, and in the latter case, consists of M + QM layers,the spacing of which is controlled by F₁ microfolding. S₁ formation involved rotation, mass transfer, and volume decrease in M layers and (re) crystallisation. The D₂ event in this area was of only minor significance. The D₃ event developed in response to NW-SE shortening and resulted in the formation of variably plunging, vertical northeast trending folds. Where SW plunging, these folds lie subparallel to L₁. The nature of the D₃ event is controlled to a large extent by S₀ / S₁ relations and folding of S₁ across unfolded S₀ occurs where S₀ lies parallel to the XY plane of the D₃ event. S₃ formed as a muscovite + quartz schistosity by rotation, re crystallisation, mass transferand mimetic growth. During the final stages of the D₃ event, north-east trending retrograde schist zones were formed. These were later reactivated during the folding of the Adelaidean. The final phase of the Olarian Orogeny consists of minor D₄ folding and crenulation. / Thesis (Ph.D.) -- University of Adelaide, Department of Geology and Mineralogy, 1978.

This study aims to develop a robust research methodology to examine the evolution of magmatic volatile phases during the cooling of felsic magmas via detailed melt- and fluid-inclusion studies, in particular the investigation of inclusions originally containing both melt and aqueous fluid. Then, using these techniques I will examine fluid immiscibility processes in two felsic magmatic systems, one mineralised, the other barren. In particular, I address the constraints on the exsolution of magmatic vapour and aqueous liquids, and how it is manifested in quartz-hosted inclusions, as well as the nature and composition of the exsolved phases. In developing a research philosophy two factors need to be paramount, it needs to be as widely applicable as possible, and the limitations need to be recognised and explored. Thus, the results deriving from these techniques may provide a test of the methodology. The thesis is based on two case studies, Rio Blanco (Chile) and Okataina (New Zealand). The first case study involves sub-volcanic intrusives and associated extrusives from the La Copa Rhyolite, and intrusives from the Don Luis Porphyry, two post-ore rhyolitic suites from the Los Bronces-Rio Blanco Porphyry Cu-Mo deposit. The second case study involves rhyolitic lavas (< 65 Ka) from the Okataina Volcanic Centre in the Taupo Volcanic Zone in New Zealand. This study is not intended to examine the geology of these systems, but rather to use them as examples of felsic systems, in diverse tectonic settings. Both as test cases for developing robust research techniques and for any information that they can provide regarding late-stage magmatic processes, particularly volatile phase exsolution, and the role of melt/fluid and liquid/vapour immiscibility. At Rio Blanco, the melt inclusion populations consist predominantly of glass inclusions and coexisting dark, inhomogeneous crystalline silicate melt inclusions (CSMI's). An important discovery from this study is the recognition that CSMI's trap volatile-rich melt, probably identical to the melt trapped as glass inclusions, and are crystallised, not "devitrified" or the product of post-magmatic alteration. Heating experiments demonstrate that both the glass and CSMI's from Rio Blanco have decrepitated and degassed post-trapping, notwithstanding the apparent lack of petrographic indicators of degassing in the glass inclusions. This coexistence appears to be a common occurrence; however, its significance seems to have been overlooked in a number of previous studies. From an initial volatile-rich melt, aqueous volatile phases (dominantly vapour) exsolved, forming bubbly magmatic emulsions. Inherently, magmatic emulsions are metastable, and disrupt into discrete melt and vapour phases. The vapour-rich phases separated from the melt and escaped, cooling, condensing, and mixing as they did so. Rio Blanco melt inclusions and fluid inclusions trapped all of these phases, in various combinations, both demonstrating the process in fine detail, and sampling the phase compositions. Analysis of the phases demonstrates partitioning of metals (Cu, Zn, and possibly Pb) into the vapour phase, its transport out of some of the magma bodies, and implies concentration by mixing and condensing to form metal-rich hypersaline fluid inclusions in the carapace of the Don Luis Porphyry. The Okataina case study provided an invaluable counterpoint to Rio Blanco. Phenocryst crystallisation pressures were supercritical, although the evidence suggests that volatile phase exsolution (VPE) occurred post- rather than pre-trapping, so that trapped magmatic emulsions are not observed. Okataina also contains coexisting CSMI's and glass inclusions, although many of the samples contains a complex array of partly crystalline silicate melt inclusions. Importantly for this study, many of the inclusions do homogenise during experimental heating, indicating that decrepitation and degassing were not as pronounced as at Rio Blanco. Heating experiments showed that despite coexisting CSMI's and glass inclusions, there was only a single melt trapped. This provides evidence of the post-trapping behaviour of melt inclusions, lacking at Rio Blanco. Although pre-trapping VPE did not occur to a large degree, post-trapping VPE did. Inclusions in which exsolution of an aqueous volatile phase has occurred provide a measure and sample of the amounts of fluids that were exsolved from a known quantity of melt, and may provide a method of determining the actual amounts of hydrothermal fluids that a magma body may exsolve. In evaluating these results some inevitable limitations of the techniques have been uncovered, particularly those relating to the vagaries of melt inclusion formation and preservation, and these have been evaluated. However, qualitative, and to some extent quantitative results have been produced, some of which have been published in research journals. Together, the case studies demonstrate and sample the fine detail of the exsolution of volatile-rich phases from silicate melts, their escape from those melts, and eventual cooling and condensing to form the kinds of hypersaline hydrothermal fluids found as fluid inclusions in ore-bodies. Further, they provide insights into common post-trapping behaviours of melt inclusions, some aspects of which appear to have been misinterpreted in some published melt inclusion studies.

Investigations in the northwestern part of the Willyama Complex centred on the Mt Franks - Mundi Mundi area have established a 4 km thick stratigraphic section of conformable metasediments containing thin horizons of basic volcanics in the lower two - thirds of the sequence. Establishment of this sequence was only possible once it was shown that the dominant lithological layering in metasediments is bedding, and that there has been no mesoscopic transposition during deformation. The metasediments represent a sequence of clay sands deposited in a distal shelf-slope or basin type of environment. A sequence of deformational and metamorphic events established in these rocks is regarded as an expression of the Middle Proterozoic Olarian Orogeny ( c.1695 - 1520 Ma. ) and except for some reactivation of shear zones, predate deposition and deformation of the unconformably overlying Adelaidean sediments. The important D₁ deformation is a complex, progressive event with pre-S₁ static mineral growth (biotite, andalusite, sillimanite, white mica) and early minor micro-folding recognized before syn-S₁ growth and F₁ folding. An even earlier period of pre-S₁ fabric formation mainly defined by white mica, biotite and ilmenite, is not related to any visible folding and may either represent an earlier discrete event or an early phase of the D₁ event, However, as now defined, minerals outlining this pre-S₁ fabric are related to the D₁ event. The low, medium and high grade metamorphic zones defined in the field by biotite, andalusite and sillimanite respectively are pre-S₁ in age and predate F₁ folding. The intensity of metamorphism increases with depth so that there is a broad depth control on metamorphism. Relations at the andalusite/sillimanite isograd conform to a Carmichael (1969) type model and reactions took place via an intermediate sericite phase. The main effect of F₁ folding is the formation of the variably plunging variably oriented Kantappa - Lakes Nob Syncline of regional extent. Only the western limb of this fold is now visible over much of its length. This fold deforms existing metamorphic zones and thus controls the relationship of low, medium and high grade rocks in this part of the Willyama Complex. The orientation of this syncline changes from vertical in the low grade rock to inclined at depth. The western limb becomes overturned at depth so that subsequent folds are downward facing. There is also a change in fold tightness with depth - from open-tight in the low grades to tight-isoclinal in the high grades, and this is accompanied by a change in S₀/S₁ relations (from core to limb area) from non parallel to parallel. These changes are coupled with a rotation of extension direction (mass transfer direction) from subvertical to inclined and may be explained by original formation and subsequent modification of upright F₁ folds. Later modifications are recorded by open folding and overturning of S₁ - this is ascribed to a final phase of the D₁ event. Mineral growth in D₁ time resulted in the formation of S₁ varying in grade from muscovite + quartz to sillimanite. S₁ varies from homogeneous to layered, and in the latter case, consists of M + QM layers,the spacing of which is controlled by F₁ microfolding. S₁ formation involved rotation, mass transfer, and volume decrease in M layers and (re) crystallisation. The D₂ event in this area was of only minor significance. The D₃ event developed in response to NW-SE shortening and resulted in the formation of variably plunging, vertical northeast trending folds. Where SW plunging, these folds lie subparallel to L₁. The nature of the D₃ event is controlled to a large extent by S₀ / S₁ relations and folding of S₁ across unfolded S₀ occurs where S₀ lies parallel to the XY plane of the D₃ event. S₃ formed as a muscovite + quartz schistosity by rotation, re crystallisation, mass transferand mimetic growth. During the final stages of the D₃ event, north-east trending retrograde schist zones were formed. These were later reactivated during the folding of the Adelaidean. The final phase of the Olarian Orogeny consists of minor D₄ folding and crenulation. / Thesis (Ph.D.) -- University of Adelaide, Department of Geology and Mineralogy, 1978.

Thesis (B.Sc. Hons.) - Dept. of Geology, University of Adelaide, 1976. / Typescript (photocopy).

Thesis (B.Sc. Hons.) - Dept. of Geology, University of Adelaide, 1971. / Typescript (carbon copy).