1
10
3
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http://theses.otagogeology.org.nz/files/original/d9b750ebe884a6d1f77a3623dedcba3d.pdf
14833ea6574c9fa483ddfc9da3105cb4
Dublin Core
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Title
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Geology theses
OU Geology thesis
Thesis or dissertation completed by University of Otago Geology students
Author last name
Last name of the Author
Verolino
Project type
Is it an MSc, PhD, BSc(Hons) or PGDipSci?
PhD
Advisers
Who supervised/advised this student
White, James D. L.
Schipper, C. Ian
Abstract
The Abstract for this thesis
Shallow to emergent basaltic subaqueous explosive eruptions, here referred as Surtseyan, are a source of pyroclastic material expelled from subaqueous vents and transferred to the water column and atmosphere. They can threaten coastal communities in different ways. One of these is through the generation of pyroclastic density currents travelling over water once the eruption becomes subaerial, and which may be preceded or accompanied by eruption-fed currents moving along the sea/lake floor; another potential danger offered by these eruptions is from the subaerial eruption, which can deliver hot fragments locally and abrasive ash over hundreds or thousands of km2. Both for their potential hazard, and to better understand the mechanics of such eruptions as one class of volcanic thermodynamics, these volcanos have been the subject of significant investigations for more than 50 years, particularly since the start of the Surtsey eruption in 1963. One approach for studying the early stages of these eruptions is through analysis of their proximal, edificebuilding deposits, but these are commonly either inaccessible (under water) or poorly preserved by the time they are exposed subaerially. The sites selected for this work, Pahvant Butte, Utah, and Black Point, California, USA, overcome these limitations. These volcanos were formed in the late Pleistocene by eruptions at hundred meter depths in the giant former Lake Bonneville and Lake Russell respectively. The water is now drained and all the deposits (both edifice-forming and at medial distances on the old lake floors) are easily accessible and maintain a good level of preservation. This allowed me to investigate the eruption dynamics and conduit conditions of these volcanoes, potentially extendable to other Surtseyan volcanoes.
The combination of field-based work, granulometry, geochemical analysis of majorelements (glass, minerals and melt inclusions) and dissolved-water content of tephra glass, and particle tomography allow me to reconstruct the pre-eruptive and syn-eruptive dynamics for Pahvant Butte and Black Point. Overall, the results suggest that the explosivity of these two monogenetic volcanoes was mainly driven by hydromagmatic explosions, with gas expansion only playing a secondary role. Inferred eruption dynamics are consistent with those inferred by previous authors, and the eruptions yielded ash dispersed both by eruption-fed density currents subaqueously, and subaerially by wind. This study demonstrates that eruption-fed density currents generated prior to eruptive emergence can travel up to > 20 km on a nearly horizontal lake floor (i.e., Pahvant Butte), even in early stages of the subaqueous eruption. In this work, it is shown that geochemistry can be a powerful tool for correlating edifice-building tephra with ash deposited in proximal/medial locations, based on the magma evolution recorded in the glass.
Another way to study shallow subaqueous explosive eruptions is through experimental investigation. I carried out underwater experiments at bench scale to investigate the behaviour of particles transferred to the water column from underwater explosive bursts. In the natural counterpart, there are two different types of particles involved in the explosions, juvenile particles, directly produced by the magma fragmentation, and non-juvenile particles (sea/lake floor sediments or country rock sediments). The former ones are initially dry, while the latter are wet, and these conditions were investigated independently during the experiments. The results show that these two conditions impart different particle behaviours. Wet particles are better coupled with tank water than are dry particles, and this behaviour can be associated with a more efficient transfer in nature from eruption bursts into eruption-fed subaqueous currents.
Keywords
western USA, Surtseyan eruptions, Lake Bonneville, Lake Russell, Mono Lake, Pahvant Butte, Black Point
OURArchive handle
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http://hdl.handle.net/10523/8772
OURArchvive access level
Open Access
Department
The department where the student is studying primarily.
Geology
Thesis description
Number of pages, maps, CDs, etc.
270 pages A4
Named locality
Named locality describing the field area location.
Pahvant Butte and Black Point, Western USA
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Surtseyan volcanism: case studies from Pahvant Butte and Black Point, Western USA
Subject
The topic of the resource
volcanism
Creator
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Verolino, Andrea
Date
A point or period of time associated with an event in the lifecycle of the resource
2019
Identifier
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2019Verolino
Black Point
garnet zone
Lake Bonneville
Lake Russell
Mono Lake
Pahvant Butte
Pounamu Ultramafics
Surtseyan eruptions
western USA
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http://theses.otagogeology.org.nz/files/original/dd814af7c1072dde523d4df1f6e9ed9e.pdf
534f757d9a3974965a0872208bec9602
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
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Geology theses
OU Geology thesis
Thesis or dissertation completed by University of Otago Geology students
Location WKT (WGS84)
The location stored in WKT (WGS84) format
POLYGON ((170.804792259000124 -43.093752638999945,170.812693708000097 -43.098637666999934,170.815295270000092 -43.100245790999963,170.787713868000083 -43.12539808799994,170.736502671000039 -43.16979622599996,170.704350083000122 -43.150371917999962,170.672709750000081 -43.131236563999948,170.649603402000025 -43.117249322999953,170.650862966000091 -43.116169698999954,170.691039041000067 -43.081705470999964,170.693068851000021 -43.079945320999968,170.697415656000089 -43.07621123399997,170.698295432000123 -43.076786109999944,170.712912034000055 -43.086334669999985,170.715806329000088 -43.08822485,170.725774328000057 -43.080142251999973,170.733859108000047 -43.073584414999971,170.736275657000078 -43.075084451999942,170.750541983000062 -43.083937532999983,170.767349142000057 -43.069806951999965,170.776707274000046 -43.075937108999938,170.786540286000104 -43.082376199999942,170.788961436000022 -43.083961338999984,170.804792259000124 -43.093752638999945))
Author last name
Last name of the Author
Green
Project type
Is it an MSc, PhD, BSc(Hons) or PGDipSci?
BSc(Hons)
Advisers
Who supervised/advised this student
Cooper, A.F.
Reay, A.
Abstract
The Abstract for this thesis
The geology of an area about the Waitaha River, Westland is studied. The A1 pine-Fraser Fault zone separates Greenland Group and Mt Bonar Granite to the west from Haast Schist to the east.
Greenland Group west of the Fraser Fault is interlayered hornfels and schist reflecting original compositional bedding. It is intruded by granite and granodiorite of the Mt Bonar Granite.
Haast Schist is dominated by quartzofeldspathic schist, but amphibolite, quartz schist and marble do occur. Three localities of Pounamu Ultramafics with poorly developed metasomatic zonation are described. Metamorphic grade increases monotonically from albite (biotite) zone to the east, to a K-feldspar bearing zone to the west. Zonation in quartzofeldspathic schist is consistently retarded with respect to interlayered amphibolite; the areal offset of equivalent mineral isograds is about lkm. Three Rangitatan episodes of folding and of recrystallisation of the schist are recognised, the ultimate metamorphic grade occurring during the latest episode.
A progressive increase in the metamorphic grade, of incipiently developed retrogressive mineral assemblages toward the west is interpreted to result from thermal metamorphism associated with activity on the Alpine Fault. Structural deformation associated with fault activity has resulted in a lkm wide belt of fault rocks to the western margin of the Haast Schist zone. Strike slip motion on the Alpine Fault has produced conjugate kinks, joints and faults; uplift of the schist produces joints, faults, schist overthrusting westward, hydrothermal veining, and tilting of Quaternary gravels.
Sandwiched between Haast Schist and lower Paleozoic rocks, the Fraser Group is a collage of fault bounded blocks: chiefly of fault rocks derived from various original litho1ogies to the east and west of the group, inc1uding pre-Tuhuan paragneiss and orthogneiss. The latest fault rock textures were impressed in the Plio-Pleistocene to the east, and earlier to the west, and are thought to have formed during relative movement of the blocks.
Study of the microstructures of minerals and textures in the fault rocks indicates that (i) strain rate has consistently been greater to the east of fault planes than to the west, (ii) typical distributed shear stress during faulting was 60 MPa, (iii) shear deformation of individual minerals is complex, with several deformation mechanisms active in each phase simultaneously.
Department
The department where the student is studying primarily.
Geology
Named locality
Named locality describing the field area location.
Waitaha Valley
Thesis description
Number of pages, maps, CDs, etc.
vii, 164 p, photos, map (folded in pocket), 30 cm.
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Identifier
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1982Green
Creator
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Green, DC
Date
A point or period of time associated with an event in the lifecycle of the resource
1982
Title
A name given to the resource
The Alpine Fault Zone of the Waitaha Valley Area.
Subject
The topic of the resource
Map
Metamorphic geology
Structural geology
Tectonics
microstructures
Pounamu Ultramafics
retrograde metamorphism
-
http://theses.otagogeology.org.nz/files/original/6886ae323ffbec20cb1390a039480036.pdf
f72b34e0fb3251b16fe40bcb10830194
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Title
A name given to the resource
Geology theses
OU Geology thesis
Thesis or dissertation completed by University of Otago Geology students
Location WKT (WGS84)
The location stored in WKT (WGS84) format
POLYGON ((171.27837442800012 -42.822688826999979,171.287667658000032 -42.815638641999954,171.299959543000114 -42.806410491999941,171.325432459000012 -42.787273537999965,171.330109419000109 -42.783757968999964,171.331461015000059 -42.783776614999965,171.349934961000031 -42.78402985799994,171.352525769000067 -42.784065132999956,171.354834818000086 -42.78409652199997,171.363532427000109 -42.784214332999966,171.36548876300003 -42.784240740999962,171.365482823000093 -42.807388793999962,171.354133185000023 -42.816132531999983,171.286292826000022 -42.868320888999961,171.262924991000091 -42.886144818999981,171.243079960000046 -42.885758993999957,171.244227560000013 -42.848573391999935,171.26195017100008 -42.835143030999973,171.27837442800012 -42.822688826999979))
Author last name
Last name of the Author
Koons
Project type
Is it an MSc, PhD, BSc(Hons) or PGDipSci?
MSc
Advisers
Who supervised/advised this student
Cooper, A.F.
Abstract
The Abstract for this thesis
This thesis is an investigation of metasomatism developed at the contacts of the Pounamu Ultramafics in the Turiwhate Survey District.
The lithologies in the Turiwhate Survey District are characterized by a regional schistosity, sub-parallel in most cases, to the original lithological layering. In the quartzofeldspathic schists the earliest recognised schistosity, s1, is a result of the F1 deformation period of tight isoclinal folding. Departure from true parallelism of s0 and s1 planes produces an L1 lineation as the line of intersection. L1 trends north-east and plunges steeply to the east, and is colinear with observed axes of F1 mesoscopic folds. Although original sedimentary structures are commonly preserved, s0 structures are obliterated in hinge zones of F1 mesoscopic folds.
F1 structural elements are clearly represented in the ultramafic bodies indicating that emplacement of the ultramafite occurred prior to F1 deformation. The contacts between the ultramafic bodies and the surrounding schists are parallel to s0 surfaces. The McArthur CragsGriffin Range ultramafic pods outline a steeply plunging F 1 macroscopic fold with the fold hinge exposed on the southern extremity of McArthur Crags.
Broad, open F2 post-metamorphic folds occur along slightly plunging axes. Mesoscopic and microscopic expression of F deformation is given 2 by the growth of late-stage chlorite plates on s 2 surfaces across the s 1 foliation.
F3 deformation occurred in response to high-angle east striking faults 3 which are associated with movement along the Alpine Fault. On a mesoscopic and microscopic scale F 3 structures are typically kink-folds and are restricted to the rocks adjacent to the east striking fault planes. The formation of gem quality nephrite through the production of a highly tectonized, non-oriented fabric is due to F3 deformation of metasomatic tremolite.
The Pounamu bodies are comprised of a core of generally low alumina antigorite with metamorphic olivine (Fo94-Fo98) developed only in the larger bodies. The antigorite-olivine core is surrounded concentrically by one of three metasomatic zonation sequences, the normal zonation sequence, the schist-poor zonation sequence or the metasomatic marble sequence. Each of the sequences exhibits a marked trend towards monomineralism or bimineralism.
The normal zonation sequence consists of an inner zone of antigorite: magnesite, surrounded successively by a talc:magnesite zone, monomineralic talc zone, and a monomineralic zone of interwoven tremolite. A zone of massive magnesian chlorite with accessory prismatic sphene represents the innermost, schist-derived metasomatic zone. The original schist:ultramafite border is placed at the tremolite and chlorite zone contact on the basis of a_pronounced trace element discontinuity. On the schist side of the chlorite zone, the metasomatic m~scovite zone consists of non-oriented phengitic muscovite and phlogopitic biotite overprinting an earlier s 1 sch.istosity preserved by the aligned metamorphic epidote grains. Podiform albitites occur discontinuously between the chlorite and muscovite zones.
The schist-poor zonation sequence is formed in regions of low schist to ultramafite ratio, and con.sists of an antigorite:tremolite zone; an antigorite:tremolite:chlorite zone; a tremolite:chlorite zone and a chlorite zone.
The metasomatic marble sequence is formed in the ultramafite near the schist contact by replacement of antigorite by idioblastic tremolite followed by the pseudomorphic replacement of antigorite and tremolite by dolomite. The replacement sequence gives rise to bands of calcite and dolomite surrounded by a shell of tremolite crystals within an antigorite matrix.
Un-metasomatized quartzofeldspauhic schists surrounding the ultramafite maintain mineral assemblages diagnostic of the garnet zone of epidote-amphibolite metamorphic terrains, i.e. quartz, peristerite plagioclases, biotite, phengitic muscovite; epidote, almandine garnet, and chlorite with apatite, sphene, rutile, and sulfides in accessory proportions. Almandine garnet with a high grossular component and clinozoistic epidote are concentrated adjacent to the metasomatic zones.
Greenschists contain the assemblage; peristerite plagioclases, biotite, chlorite, epidote, hornblende, and almandine garnet with accessory proportions of magnetite, sphene and sulfides. Metacherts and marbles occur as thin lenses within greenschist lithologies.
An experimental investigation of metasomatism was carried out in cold 0 seal apparatus over periods extending to 40 days at 450 c and 2Kb. In several runs, oxalic acid was used to provide an internal buffer and as a source for the production of co 2 • The gas phase was analysed by mass spectrometry. The absence of CH 4 indicates that the experimental metasomatic event occurred under conditions of relatively high P 0 enabling the 2 gas phase to be defined in terms of an ideal binary XH 0 - XCO system.
Petrographic and electron microprobe analyses of the experimental runs indicate component migration trends in order as follows; co 2 , Sio 2 and cao migrate from the schist into the ultramafite; MgO migrates from the ultramafite into the schist; Na o and K2o migrate from the schist . 2 adjacent to the ultramafite to the ultramafite further i~to the schist; Al 2 o 3 and Ti0 2 remain in their original configurations. The component migration scheme leads to the formation of reaction zones within both the schist and the ultramafite. In the schist the reaction zone consists of fine grained chlorite replacing the other schist specie by the dissolution of quartz, albite, epidote, muscovite, biotite, and garnet. Magnesite and talc are the reaction products within the ultramofite formed by the breakdown of antigorite upon the introduction of co2 and Sio2.
In conjunction with the experimental and petrographic data, a thermodynamic approach is utilized to produce a comprehensive scheme of component behaviour during the metasomatic event. The metasomatic zones formed by diffusion of components in a direction such that energy differences caused by the juxtaposition of the schist and ultramafic bodies were minimized. The reaction zones; are assemblages in local equilibrium with each adjacent assemblage. Diffusion occurs down chemical potential gradients for each diffusing component. The incompatibility of chemical potential gradients defined solely by compositional gradients is illustrated, and a method for -delineating and demonstrating the behaviour of the chemical potentials of diffusing components in complex systems is formulated. The method utilizes molar free energy:composition plots to define behavioural trends of perfectly mobile and inert components. As an illustration, the properties of molar free energy:composition plots are applied to the case of Si02 diffusion in the normal metasomatic zonation sequence. The theories derived from the examination of sio 2 diffusion are then utilized in a qualitative manner to define diffusion phenomena in the normal metasomatic sequence, the schist-poor sequence and the metasomatic marble sequence.
Relative component mobilities are examined and an order of increasing mobility among.~:-the ·system components is developed. The rate of diffusion is shown to be time and distance dependent and the existence of a theoretical point beyond which the rate of diffusion is infinitesimal is shown.
Simple mass-balance calculations combined with garnet and epidote analyses indicate the existence of high concentrations of CaO and Al 2o3 prior to the latest metasomatic event. The high concentrations of these components are postulated to be due to the development of rodingite assemblages during serpentinization of the ultramafite in its present quasi-stratigraphic position. Diffusion during the later metamorphic event redistributed the rodingite components.
With the above data, an approximate tanporal sequence of serpentinization, deformation. metamorphism and metasomation, and post metamorphic deformation is delineated.
OURArchive handle
The handle from the Otago University Research Archive (OURArchive)
<a href="http://hdl.handle.net/10523/3051">http://hdl.handle.net/10523/3051</a>
OURArchvive access level
Open Access
Department
The department where the student is studying primarily.
Geology
Named locality
Named locality describing the field area location.
Turiwhate
Westland
Thesis description
Number of pages, maps, CDs, etc.
161 leaves : illus., map and chart in pocket ; 30 cm.
Dublin Core
The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/.
Identifier
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1978Koons
Creator
An entity primarily responsible for making the resource
Koons, Peter O., 1952-
Date
A point or period of time associated with an event in the lifecycle of the resource
1978
Title
A name given to the resource
The Pounamu ultramafics : a study of metasomatism.
Subject
The topic of the resource
Map
Geochemistry
Structural geology
diffusion
mineral reaction zones
Pounamu Ultramafics
thermodynamics