1 10 2 https://theses.otagogeology.org.nz/files/original/cd307064e2865dbd5ab1f004001f4a61.pdf 533ac794f9c43f263f1eaad17704eb87 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 Webster 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 Greenhills Ultramafic Complex lies about 12km to the south-west of Invercargill and occupies approximately 15km2 of the n~rthernmost corner of the Bluff Peninsula. It is part of the Brook St terrane" and is believed to represent the roots of a Late Permian island arc volcanic chain that has had its upper portion subsequently removed by erosion. Mossman(1970) undertook a comprehensive study of the area as the basis of a PhD thesis and concluded that the Greenhills Ultramafic Complex represents the remains of a shallow level magma chamber that was open to the atmosphere and of a hydrous nature. The Greenhills Ultramafic Complex consists of a layered structure consisting of ultramafic rocks at the base and a gabbroic portion at the top. The sequence of minerals observed is consistent with fractionation of a basaltic magma with olivine predominating and being accompanied by residual chromite in the first rock type to occur: dunite. Later in the sequence clinopyroxene begins to crystallise and the rock type becomes a wehrlite. Next in the sequence of minerals is orthopyroxene, however its modal proportion is far lower than most other layered ultramafic complexes. Skaergaard (Wager and Deer 1939)contained websterite rather than wehrlite the difference being the predominance of orthopyroxenes in the rock rather than the clinopyroxenes as occurs at Greenhills. Repeated intrusions of more felsic magma as dikes up through the base and into the intrusion pre-empted the fractional crystallisation that was occurring so that an upper gabbroic layer was deposited at the top of the sequence. Mossman concluded that the composition of the magma was basaltic and that it had affinities between calc-alkaline and tholeiitic, which at the time of his investigation was quite an innovative idea. ~] _]! _] -] -] J J J J J J J ] J l l This suggestion is investigated to try to determine whether this is a viable source magma for the observed fractionation sequence and the conclusion is that it is a viable mechanism for forming the minerals that comprise the complex. The difference between this study and that of Mossman is that it is suggested here that the corrugated contact between the wehrlite and dunite was caused by small scale convection cells eroding the base of the magma chamber and depositing the debris by gravitational settling elsewhere in the magma chamber and this process results in the rhythmic layering observed here . This is a similar, process to that which occurred in the Skaergaard intrusion (Irvine 1987) except that the small convection cells do not occur as a consequence of double diffusive convection but simply that the magma chamber has too low a roof to allow the development of a convection cell that is the full width of the magma chamber. A time constraint has been put on the age of the intrusion by some recent work and the collection of ages for surrounding metasediments allows a clearer picture top be obtained on how and when the complex developed. The geochemical bias of this project has meant that confirmation could be obtained for multiple intrusions of magma throughout the complex because in the past the evidence had been entirely petrographical. A clearer understanding of how the Greenhills Ultramafic Complex developed and of the processes that occurred inside it while it was still crystallising. Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Greenhills Thesis description Number of pages, maps, CDs, etc. 98 leaves, [1] folded leaf of plates : ill. (some col.), col. map ; 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 1994Webster Creator An entity primarily responsible for making the resource Webster, Glen Robert. Date A point or period of time associated with an event in the lifecycle of the resource 1994 Title A name given to the resource Greenhills revisited : an investigation into the geochemistry of the Greenhills Ultramafic Complex Subject The topic of the resource Geochemistry Bluff Peninsula Brook Street Greenhills Ultramafic Complex https://theses.otagogeology.org.nz/files/original/0ff4e90adc2f6fcd3c9c773fc6263da4.pdf 5ffa0e46f9e022501daa032e99f34429 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 ((168.324185158000091 -46.590544009999974,168.324049425000112 -46.592147125999986,168.323314835000019 -46.600719178999952,168.318124152000109 -46.600528732999976,168.315823832000092 -46.600442774999976,168.311861722000117 -46.60029586,168.270814986000119 -46.598762532999956,168.272078617000034 -46.584858797999971,168.273326607000058 -46.571134626999935,168.273585456000092 -46.568270304999942,168.273651605000055 -46.567556534999937,168.274153460000093 -46.562016493999977,168.274390102000098 -46.559417117999942,168.276695517000121 -46.559499676999963,168.29353061200004 -46.560099362999949,168.300554472000044 -46.560349990999953,168.304371169000092 -46.560482666999974,168.326681021000013 -46.561270885999932,168.324483232000034 -46.58705497699998,168.324475441000118 -46.587149285999942,168.324395751000111 -46.588074279999944,168.324389444000076 -46.588150624999969,168.32437311800004 -46.588348223999958,168.324185158000091 -46.590544009999974)) Author last name Last name of the Author Elder 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 In the Bluff area lower green schist facies Greenhills Group rocks of the Brook Street terrane derived from a Permian volcanic arc have been intruded ~ by igneous bodies inducing contact metamorphism. Facies of contact metamorphism are observed as pyroxene hornfels facies in assimilated xenoliths in a hybrid rock zone, further out from the intrusions hornblende hornfels are observed. At a distance of 800 m from the intrusive contacts albite-epidote facies of contact metamorphism are observed in metabasaltic dykes. Evidence for this facies comes from the mineral assemblages in the metabasalt dykes which have cut vertically through Greenhills Group metasediments very soon after the tilting of the Greenhills Group bedding associated with the intrusion of the large igneous bodies. The intrusive bodies are the Flat Hill gabbronorite and the Ocean Beach diorite which show a distinct difference in the bulk rock chemistry with the diorite appearing as a· more evolved rock. Dyke intrusion of microgabbro, quartz diorite and hornblende pegmatite is part of late stage activity associated with the cooling of the large igneous~ bodies. Granitic dykes present post date the intrusion of the large igneous bodies and the late stage dyke activity. The age of the Flat Hill gabbronorite is given as 265 M a, the oldest recorded rocks of the Brook Street terrane. - --l J Department The department where the student is studying primarily. Geology Named locality Named locality describing the field area location. Flat Hill Bluff Peninsula Thesis description Number of pages, maps, CDs, etc. 71 p. : ill. (some col.), 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 1994Elder Creator An entity primarily responsible for making the resource Elder, Damon Jon. Date A point or period of time associated with an event in the lifecycle of the resource 1994 Title A name given to the resource Geology of Flat Hill-Ocean Beach, Bluff Peninsula Subject The topic of the resource Areal geology Bluff Peninsula Brook Street plutonics Southland Region