1 10 1 https://theses.otagogeology.org.nz/files/original/ce6c199a5627b474262d6ccc113b6c46.pdf 5f32cc3a2ea7ae8738fd4f272c9c8605 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 ((169.012198067740655 -43.916285715078487,171.364720758842765 -42.718400780294587,171.450873179248049 -42.788218571237849,169.121663034268721 -43.996283201430948,169.012198067740655 -43.916285715078487)) Author last name Last name of the Author Campbell Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? MSc Advisers Who supervised/advised this student Craw. D Abstract The Abstract for this thesis Hydrothermal alteration, hosted in brittle structures, has been documented along the length of the Alpine Fault Zone. The along-strike profile has been divided into two geographical groups based on differing fault zone character. The central section, Havelock Creek to the Whataroa River, and the northern section, Whataroa River to the Taramakau River, host different late-stage hydrothermal assemblages. Alteration occurs as veins, cemented breccias, and partially or wholly recrystallised fault rocks throughout the -1 km wide fault zone. Geochemical investigations suggest that gouges, cataclasites, and mylonites within the hangingwall of the Alpine Fault Zone have been derived from a metabasite-poor, intermediate greywacke protolith of Torlesse affinity. Western Province derived fault rocks are not confirmed in the hangingwall. Cataclasites and gouges are retrogressed, hydrated equivalents of adjacent schist-derived amphibolite (upper greenschist) facies mylonite. CaO, MgO, Fe20 3\ and SrO are mobile while Ti02, Al20 3, and K20 are immobile within the Alpine Fault Zone. Most base metals show no distinctive enrichment or depletion trends. Cu and As occur in anomalously high concentrations at Dickson River and tributaries of Wainihinihi River, respectively. o13C and o180 results for vein and fault gouge calcites indicate a derivation from a meteoric fluid with a minor rock exchanged component (o13C -7.0 to 1.6%o; 0180 10.4 to 27.4%o; n=lO). The analysed ankerite veins and breccias were derived from a mixed, meteoric rock-exchanged fluid (o 13C -7.6 to 3.4%o; o180 12.1 to 25.2%o; n=21). Along-strike variation in isotope signatures is negligible. Retrogression within cataclasites and fault gouges is pervasive. Green mylonites have been thoroughly retrogressed under semi-ductile conditions while localised retrogression has occurred proximal to fault/ fracture systems within the Alpine Fault Zone. Ankerite is the dominant alteration phase in the northern section while calcite is the major alteration phase in the central section. Alteration volume is greater in the northern section where three hydrothermal breccias and numerous vein networks have been reported. No hydrothermal breccias and minimal vein networks are reported from the central section of the Alpine Fault Zone. Throughout the entire strike length of the fault zone, increases in metallic mineralisation correspond to increases in dilatancy and fluid-rock ratios (i.e. cemented breccias contain highest amounts of metals). Upper greenschist facies rocks, particularly chlorite-bearing, argillaceous-type mylonites, appear to be the best sources of ankeritic carbonate. Lowered geothermal gradients may also enhance ankerite stability and promote ferromagnesian mineralisation to the north. Strain and seismicity are closely linked to hydrothermal mineralisation. Local fault-fracture networks, especially high-angle minor faults, have acted as permeable flow networks channelising fluids and providing favourable mineralising sites. Gouges and cataclasites have acted as fluid distributors and poor mineralising sites. Active and passive porosity and permeability have been assessed for the Alpine Fault Zone. Passive estimates of porosity from several outcrops and specimens have permitted the extrapolation of passive and active porosity and permeability at depth during and shortly after seismic events. Using this approach, brecciated and fractured mylonite are found to be the most permeable mediums during passive (interseismic) periods. During active (eo- and post-seismic) intervals, fluids are believed to be discharged from fluid sinks (cataclasites, gouges) and focused onto backbone networks (i.e. minor faults, large fractures) within fractured mylonites. Brittle strain distribution is highest to the north, possibly associated with the crustal-scale Alpine-Hope Fault junction. This increased fault/fracture distribution correlates with frequent shallow earthquakes and elevated levels of hydrothermal alteration. The Wainihinihi River area, lying near the fault junction, contains anomalously high arsenic which is thought to represent a deeper fluid source. It is suggested that enhanced shallow seismicity has created a crustal plumbing network which taps deeper, metal-rich metamorphically-derived fluids. The nearby Wilberforce Valley (Main Divide) is characterised by similar arsenic, isotope and seismicity signatures suggesting that the hydrothermal systems may be regionally related. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Southern Alps Thesis description Number of pages, maps, CDs, etc. ix, 138, A27 leaves : col. ill., maps (some col.) ; 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 An unambiguous reference to the resource within a given context 2002Campbell Creator An entity primarily responsible for making the resource Campbell, Ryan (Johnathan Ryan) Date A point or period of time associated with an event in the lifecycle of the resource 2002 Title A name given to the resource Hydrothermal alteration within the Alpine Fault Zone Subject The topic of the resource Structural geology Geochemistry Mineralogy Tectonics Alpine Fault faults fluid distribution Hydrothermal alteration