1 10 1 https://theses.otagogeology.org.nz/files/original/0d83cf9cbbf3d0c84fc2ed953f06cf99.pdf c513051d6cd55ff4c376eae193058661 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 ((167.684560242620393 -46.314211846419092,167.699273705839744 -46.314896841453731,167.699404822204968 -46.324191522481442,167.741023257258831 -46.32754768104369,167.739450449649496 -46.347481240721294,167.682272788767506 -46.344828997526719,167.684560242620393 -46.314211846419092)) Author last name Last name of the Author Wadsworth Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? MSc Advisers Who supervised/advised this student Reay, A. Abstract The Abstract for this thesis A suite of calc-alkaline to tholeiitic plutonic rocks exposed along a five kilometre stretch of coastline on the south .coast of the South Island, New Zealand, form the coastal section of the Longwood Complex. On the basis of field relations, geochemistry and mineralogy, the Pahia Inirusives can be differentiated into two gabbroic suites, here termed the Hill H Gabbro (HHG) and the Pahia Point Gabbro (PPG). In between the gabbroic units is a quartz-diorite unit termed the Boat Harbour Diorite (BHD). Two phases of hornblende microdiorite mafic dikes intrude the main rock units, with the first phase defined as comprising< 68 ppm Zr, and the second phase> 82 ppm Zr. At Pahia Point a zone approximately 250 metres wide is recognised as the result of coexisting, yet contrasting magmas, in the form of the PPG and the BHD, interacting to produce a mingled (and possible mixed) zone. Field relationships and geochronology indicates near-coeval magmatism for these two rock-types. The contact zone between the gabbro and the diorite (termed the MZG) is characterised by an abundance of acid-net veining, and multiple dike intrusions in the form of hornblende microdiorite and mingled composite dikes. Plagioclase is often the only primary mineral remaining, and records a complex evolution of remelting, and re-crystallisation in disequilibrium conditions. Previously the MZG has been interpreted as a hybrid zone (Price and Sinton, 1978) comprising rocks with gradational textures and mineralogy between the gabbro and diorite (Bignall, 1987). However field relationships, petrography, mineralogy, and geochemistry interpretations made during this study suggest that significant mixing has not taken place. The contact proper can be defined as a two to three metre wide zone coarsely feldspathic in nature, and characterised by ragged plagioclase cores, overprinted by secondary plagioclase crystallisation, and an abundance of amphibole. Composite dikes are composed of mafic enclaves enclosed within a relatively more felsic host. Enclaves are elongate and boudinaged parallel to the margins of the dike, indicating the mafic 'globules' were mobile within the felsic host. Two phases of composite dikes can be interpreted on the basis of colour and orientations observed in the field, and geochemistry. Typically more evolved composite dikes with lighter coloured hosts intrude the BHD, whilst relatively more primitive composite dikes intrude the MZG with hosts less discernible from the gabbroic rocks. Analyses of the composite dikes and the MZG reveal a complicated evolution involving magma mingling (and possible mixing), perhaps associated with fractional crystallisation. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Pahia Point (Southland) Thesis description Number of pages, maps, CDs, etc. viii, 186 leaves : ill. (some col.), maps (1 col., folded) ; 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 2000Wadsworth Creator An entity primarily responsible for making the resource Wadsworth, Craig Allan, 1975- Date A point or period of time associated with an event in the lifecycle of the resource 2000 Title A name given to the resource Petrochemistry of a gabbro-diorite contact, Pahia Point, Southland Subject The topic of the resource Geochemistry Igneous petrology contact zone diorite gabbro petrochemistry