1 10 2 https://theses.otagogeology.org.nz/files/original/520a10c50daf7848bc3e4d0a9615e8cc.pdf 1ff679ebe8ee0ee8ce1aad545afb9788 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 Gurney Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? BSc(Hons) Advisers Who supervised/advised this student Reay, A. Abstract The Abstract for this thesis The Kaiwekite is an inclusion-rich lava flow outcropping in cliffs on either side of the mouth of the Otago Harbour, and was erupted during the First Main Eruptive Phase (Benson, 1941) of the Dunedin Volcano. It contains a large variety of lithic inclusions and kaersutite megacrysts, many of which are associated with calcite. The Kaiwekite contains phenocrysts of clinopyroxene, kaersutite, olivine, feldspar, and titanomagnetite, within a microcrystalline groundmass of feldspar, clinopyroxene and titanomagnetite. The phenocrysts commonly display zoning, rimming, and resorption textures. At least two chemically distinct groups can be recognised for each of the main phenocryst phases. These do not correlate- simply with .observable petrographical groups. The presence of features indicating strong resorption in clinopyroxene and feldspar phenocrysts within the Kaiwekite are thought to have arisen through decompression on rapid transport to the surface, or magma mixing. Disequilibrium textures suggest changing physical conditions in the magma chamber, and a possible high pressure origin for some of the clinopyroxene phenocrysts is suggested by their high Al203 contents, feldspars by their high Ca contents, and for some of the olivine phenocrysts by their high Mg contents. The major element chemistry does not reflect the homogeneous appearance of the rock. It has a highly variable Mg-number (reflecting variations in the MgO and Fe203 contents of the rocks) which is suggestive of quite evolved rocks (benmoreite, mugearite, hawaiite, trachyandesite) as does its alkali content. The similarity of the Kaiwekite's trace element pattern to that of crustally fractionated rocks from the Dunedin Volcano, and modelling done in this stud}) suggest that low-pressure crystal fractionation may have influenced the composition of the rock. Additional evidence from the petrography and trace element data suggests that magma mixing, or simply phenocryst resorption (and/or decompression through rapid transport to the surface) may also have had an influence on the composition of the Kaiwekite. The lithic suite is composed of lower crustal-derived cognate xenoliths (cumulates crys~(sed at depth early in the history of the host rock) and accidentally incorporated fragments of sedimentary rocks of the Dunedin Tertiary Sequence and Haast Schist. The kaersutite megacrysts are also believed to be cognate to their host, having a crustal origin. They exhibit major element chemistries similar to kaersutite megacrysts occurring associated with alkali basaltic rocks from around the world, but exhibit significantly higher Ti contents than the other analysed megacrysts. Major and trace element modelling carried out in this study suggests that crystal fractionation, in association with magma mixing and (possibly) ponding in several magma chambers at different levels in the crust, are the major processes influencing the composition of !he Kaiwekite. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. East Otago Thesis description Number of pages, maps, CDs, etc. 144 p. : col. ill., maps ; 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 1993Gurney Creator An entity primarily responsible for making the resource Gurney, Patricia. Date A point or period of time associated with an event in the lifecycle of the resource 1993 Title A name given to the resource Geochemistry of the Kaiwekite flow, East Otago, New Zealand Subject The topic of the resource Geochemistry basement extrusives geochemistry Moeraki Peninsula https://theses.otagogeology.org.nz/files/original/7c74b5668de132bb6b988976e5ff58c3.pdf 8e6f997894c7f3f8906d1d0553acba74 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 ((170.87805011965915 -45.352666839861563,170.877434875500171 -45.40296724934916,170.850795918331045 -45.403361996964378,170.824853421067445 -45.38560393584121,170.827818367106602 -45.35231756677905,170.87805011965915 -45.352666839861563)) Author last name Last name of the Author Brown Project type Is it an MSc, PhD, BSc(Hons) or PGDipSci? BSc(Hons) Advisers Who supervised/advised this student Reay, A. Abstract The Abstract for this thesis The Moeraki Peninsula is located on· the east coast of the South Island of New Zealand, approximately 70 kilometres north of Dunedin. The regional schist basement, and the overlying fault derived breccias of the Shag Point Group both outcrop to the west (Mutch, 1963), and are not exposed on t~e Peninsula. These units are overlain by the marine sediments of the Moeraki, Kurinui, Hampden, and Iviokihi Formations, which collectively represent a marine transgressive sequence formed during a period of regional subsidence in the Eocene. The latter formations comprise fossiliferous mudstones and greensands, and are overlain by late Eocene or younger hyaloclastic volcanic agglomerates, breccias and tuffs, erupted in a submarine environment. Voluminous basaltic magmas, similar in age to the volcanics, have intruded the Tertiary sedimentary sequence to form numerous dykes and sills. The largest of these structtires is the Moeraki Dolerite, an elongated sill-like body which outcrops along the southeast coast of the peninsula, and has an estimated minimum volume of 0.06 cubic kilometres. The mineralogy of the Moeraki Dolerite is plagioclase feldspar (Anoo-An2o), diopside, augite, ilmenite, magnetite, and an unidentified amphibole. The minerals occur as both phenocrysts displaying a doleritic texture, and groundmass, where the feldspars display prominent chill textures, indicating quenching of the body after emplacement. The main body of the sill is basaltic in composition, ranging from ~48-53% silica, and has been intruded subsequent to emplacement and solidification, by a more differentiated liquid (Si02 ~52-62%) which has formed thin, laterally continuous veins, occurring throughout the main sill, spaced approximately lm apart, and running parallel to the upper and lower contacts of the latter. The major and trace element chemistry of these two rock-types suggest that the se~ond, more differentiated liquid was derived from the same source as the more basic main sill rocks, chemically differentiated by the fractional crystallization of olivine, clinopyroxene and plagioclase. Some crusta! assimilation of the regional schist basement is indicated by the dramatic silica enrichment seen in the differentiated veins, which can not be accounted for by fractional crystallization alone. The textures along the contact between the main sill rocks and the differentiated veins indicate that the latter were injected after the solidification of the former, but while it was still hot enough to prevent quenching of the second liquid. This short time frame suggests that the source magma chamber was probably already differentiated and zoned prior to the emplacement of the Moeraki Dolerite. Spatial chemical variation within the main sill rocks indicate that the outer margins of the sill are more differentiated than the central portions. Two petrogenetic models have been proposed, both involving multiple pulses of injection from a parent magma chamber at depth. One proposes that in-situ fractionation is responsible for the variation within the main sill rocks, while the second s~ggests that the variation is entirely the result of the tapping of a zoned magma chamber at depth. Schist xenoliths occur in the main sill rocks, and within a vein-like structure which is parallel to the upper contact of the Moeraki Dolerite, consisting of -90% xenoliths in a fine grained igneous groundmass. The layer may represent the injection of a liquid tapped from near the top of the parent magma chamber, where quartz xenoliths had been concentrated through floatation. Recent lithologies in the study area include extensive loess cover, raised beach deposits which represent sea-level fluctuations, and a mafic heavy mineral beach sand which occurs on the south coast of the peninsula, and is derived predominantly from the local dolerites through erosional processes. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Moeraki Thesis description Number of pages, maps, CDs, etc. 149 p. : col. ill., maps ; 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 1993Brown Creator An entity primarily responsible for making the resource Brown, Justin. Date A point or period of time associated with an event in the lifecycle of the resource 1993 Title A name given to the resource Aspects of the geology of Moeraki Peninsula and the geochemistry of the Moeraki dolerite Subject The topic of the resource Geochemistry Hampden Formation Kurinui Formation loess marine terraces Moeraki Formation Moeraki Peninsula Mokihi Formation Otago Region