1 10 2 https://theses.otagogeology.org.nz/files/original/a6239291413cd325f45e070418bc9f38.pdf 630f1f7cbe0741e86ad51b9ccecd8472 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 ((168.754416137838149 -44.500151899889865,168.750598124707892 -44.545741231960108,168.688426798921029 -44.541977734441211,168.69614379829369 -44.498324191733104,168.754416137838149 -44.500151899889865)) Author last name Last name of the Author Alder Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? BSc(Hons) Advisers Who supervised/advised this student Smith, S.A.F. Scott, J.M. Abstract The Abstract for this thesis The Moonlight Fault Zone (MFZ) is a regionally significant structure in Otago that was reactivated as a high angle reverse fault in the Miocene. This movement exhumed fault rocks from the mid to upper crust which has provided the opportunity to study the structure of the fault zone from this depth, the dominant deformation processes that occurred during faulting and, significantly, the weakening mechanisms that may have facilitated high angle reverse movements. Field and microstructural examination of the Moonlight Fault Zone in the Matukituki Valley revealed that solidified frictional melts (pseudotachylytes) are present within the hanging wall greenschist at least 500 m from the main fault trace. The pseudotachylytes lie parallel or sub-parallel to the steeply-dipping host rock foliation. The presence of pseudotachylytes indicates that the hanging wall was exhumed from at least 5 km depth and that brittle failure within the MFZ occurred, at least in part, by localised seismic slip. Along the main trace of the Moonlight Fault there is a c. 15 m wide zone of deformation that contains a progressive transition from random fabric breccias to well foliated cataclasites ≤1 m from the fault trace. The foliated cataclasites contain microstructural evidence (e.g. dissolution seams enriched in titanite, overgrowths of chlorite in strain-shadows) of fluid-induced dissolution – precipitation reactions associated with diffusive mass transfer. Alteration of load bearing phases such as quartz and feldspar led to the widespread formation of chlorite and muscovite in the main fault. This produced well foliated, interconnected networks of weak phyllosilicate-rich fault rocks. The presence of interconnected phyllosilicates may have lowered the frictional strength of the Moonlight Fault and thus likely contributed towards reactivation of this poorly oriented, high angle reverse fault. The network of foliated phyllosilicates may also have acted as a fluid seal, allowing for build-up in fluid pressure in the footwall and leading to further weakening. The close association between pseudotachylytes and phyllosilicates (containing evidence for dissolution – precipitation) suggests that the MFZ preserves fault rock evidence for both seismic slip and slower aseismic creep. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Moonlight Fault zone Matukituki Valley Wanaka Otago Thesis description Number of pages, maps, CDs, etc. x, 99 pages A4 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 An unambiguous reference to the resource within a given context 2014Alder Creator An entity primarily responsible for making the resource Alder, Simon Date A point or period of time associated with an event in the lifecycle of the resource 2014 Title A name given to the resource Structure and ancient seismicity in the Moonlight Fault Zone, Matukituki Valley, Wanaka. Subject The topic of the resource Structural Geology aseismic creep greenschist Pseudotachylytes shear zone slip https://theses.otagogeology.org.nz/files/original/a832c6fa12df379eb506c2cd03dc544c.pdf edae67be149a258fadfd05e6fad8b8c9 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 Author last name Last name of the Author Ritchie Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? BSc(Hons) Advisers Who supervised/advised this student Toy, V.G. Abstract The Abstract for this thesis Pseudotachylytes produced during coseismic slip are ubiquitous within the rocks of the Alpine Fault zone, New Zealand. Pseudotachylytes from three principal host rocks are described and characterised from field and petrographic observations. The pseudotachylytes range from ~ 1 mm thick in Alpine Schist-derived mylonites to ~1 cm thick in Western Province-derived augen mylonites and cataclasites. Depth estimates based on field and petrographic relationships divide the differently hosted pseudotachylytes into two broad groups that formed during seismic rupture in the upper crust of the Alpine Fault zone: 1) relatively low volume pseudotachylytes forn1ed in Alpine Schist-derived mylonites at- 8 km depth, where shear stress was relatively low, during low magnitude events just below the brittle-ductile transition; and 2) voluminous pseudotachylytes formed at shallower levels of- 2-5 km, where shear stresses were high, in Western Province granitoid-derived augen mylonites and cataclasites during higher magnitude events. Bulk-rock powder X-ray Fluorescence (XRF) of host rocks and Electron Microprobe Energy Dispersive Spectroscopy (EMP-EDS) spot analysis on pseudotachylyte matrices reveal that relative to their host rocks, the Alpine Fault pseudotachylytes are depleted in SiO? and enriched in Al?O?, alkalis and metallic oxides. This is interpreted to be the result of preferential inclusion of hydrous, ferromagnesian mineral phases and to a lesser extent feldspar into the melt, and the exclusion of quartz from the melt. The preferential selection relationship in part controls the voluminous nature of pseudotachylytes within retrogressed host rocks containing high proportions of hydrous, ferromagnesian minerals. Size analysis of the clasts within the pseudotachylytes reveals power law size-frequency distributions that are modified in the finer fraction of the clasts, suggesting pervasion of friction melt depleted the fine fraction of precursor ultracataclasites by incorporation into the melt phase by uniform rim melting. OURArchive handle The handle from the Otago University Research Archive (OURArchive) <a href="http://hdl.handle.net/10523/2709">http://hdl.handle.net/10523/2709</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. Alpine Fault Thesis description Number of pages, maps, CDs, etc. 82 leaves. Ill. Photos. Diagms. 30 cm.CD-ROM (4 3/4in.) 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 An unambiguous reference to the resource within a given context 2009Ritchie Creator An entity primarily responsible for making the resource Ritchie, Samuel D. (Samuel David) Date A point or period of time associated with an event in the lifecycle of the resource 2009 Title A name given to the resource Alpine fault pseudotachylytes Subject The topic of the resource Structural geology Alpine Fault Alpine Schist Pseudotachylytes