The structure of epithermal deposits of the Coromandel Peninsula : dynamic processes and three-dimensional strain

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dc.contributor.advisor Assoc. Prof Bernhard Spörli en
dc.contributor.advisor Mr Don Clarke en
dc.contributor.advisor Assoc. Prof Pat Browne en
dc.contributor.advisor Prof. Philippa Black en Irwin, Marion Ruth en 2010-11-03T02:12:52Z en 2010-11-03T02:12:52Z en 2004 en
dc.identifier.citation Thesis (PhD--Geology)--University of Auckland, 2004 en
dc.identifier.uri en
dc.description.abstract The many epithermal deposits of the Coromandel Peninsula, ('Hauraki volcanic zone') display a range of structural characteristics at a number of scales that illustrate the varied processes involved in their formation. Structural information synthesised from existing literature, including the theses on different parts of the Coromandel Peninsula suggests that there is widespread tilting towards the east and south throughout the region. Blockfaulting in the basement influences trends within the overlying volcanics. On a large scale, deposits may exhibit plane strain (e.g. Karangahake) or three dimensional strain in an orthorhombic fashion (e.g. Kapanga) or in a fashion akin to the model proposed by Harding for strike slip systems (e.g. Golden Cross underground). Other deposits have a more complex three-dimensional structure (e.g. Hauraki). Linked deposits, such as those seen underground and in the open pit at Golden Cross, may have quite different characteristics (Harding 3-D and plane-strain respectively). At an outcrop scale, vein opening processes are reflected in the patterns of veining and shape of individual veins. There are several very common vein shapes in Coromandel epithermal deposits. The influence of pre-existing planar features, including columnar jointing, is important, with veins often following their precursors. The main processes which influence vein patterns and shapes are shearing (pre, syn, alternating with and post vein opening), oblique opening ('shear opening') and perpendicular opening ('dilational opening') of veins. Rotation between adjacent blocks causes tapering veins. Other, non-dilational, processes resulting in vein opening or widening include erosion, dissolution and desiccation. The influence of folding on individual patterns is not clear. Jigsaw breccias are gradational with vein networks. Vein fill material gives information about some opening processes -such as cyclic opening and sealing- as well as filling processes that are influenced by such factors as fluid composition, hydrology, kinetics (which may in tum be influenced by factors such as seismic activity) and sedimentology within the veins. There are a variety of breccia types, probably reflecting a number of brecciation processes. A mathematical model is developed for ascertaining opening vectors for systems of three intersecting veins. Careful study of one level of a deposit can reveal a great deal of information about the whole deposit (e.g. Golden Cross underground workings. Golden Cross open pit). Old mine plans, used in conjunction with modern field studies, are a valid and valuable additional source of information (Kapanga). en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA1229816 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri en
dc.title The structure of epithermal deposits of the Coromandel Peninsula : dynamic processes and three-dimensional strain en
dc.type Thesis en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en

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