• Admin
    UC Research Repository
    View Item 
       
    • UC Home
    • Library
    • UC Research Repository
    • College of Science
    • Science: Theses and Dissertations
    • View Item
       
    • UC Home
    • Library
    • UC Research Repository
    • College of Science
    • Science: Theses and Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of the RepositoryCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects

    Statistics

    View Usage Statistics

    The petrology and geochemistry of the Acheron intrusion

    Thumbnail
    View/Open
    eady_thesis.pdf (17.71Mb)
    Author
    Eady, Angela Elizabeth
    Date
    1995
    Permanent Link
    http://hdl.handle.net/10092/6783
    Degree Grantor
    University of Canterbury
    Degree Level
    Masters
    Degree Name
    Master of Science

    Subalkaline transitional gabbros have intruded the Cretaceous - Paleocene sediments of the Acheron Outlier. The gabbroic magma has differentiated in situ to form a laccolith and sill-like apophysis, as well as having a strong thermal effect on the sediments and especially the coals of the Broken River Formation. This research concentrates on the geochemical characteristics and differentiation processes. Additional research on the thermal alteration of the coals at Acheron has provided data for heating models of the sediments. Thermal alteration of the sediments is extensive with the thermal aureole of the intrusion affecting the entire thickness of Tertiary sediments exposed at Acheron, increasing coal ranks from regional lignite A to anthracite. Vitrinite reflectance data indicate circulating hydrothermal fluids had a strong control on the degree of heating sediments underwent. It is suggested that the Acheron magma was modified by flowage differentiation within the conduit prior to emplacement. This created an olivine phenocryst-rich magma and an olivine phenocryst-poor melt. The latter was emplaced into the Tertiary sediments as a thin proto-laccolith which inflated to form the bulk of the Acheron Intrusion prior to the emplacement of the denser and more viscous olivine-rich magma which formed a basal layer within the intrusion and also breached the laccolith margin to form the apophysis. Crystallisation proceeded from the walls, roof and floor by sidewall crystallisation. This produced the five lithotypes recognised within contact gabbro, olivine mela-gabbro, gabbro, monzogabbro and differentiates. Geochemical analyses of these rocks show differentiation trends consistent with crystal fractionation of a relatively basic melt. Geochemical trends are complicated by the extensive deuteric alteration of the intrusion. Alteration of feldspar by late stagedeuteric fluids has produced secondary analcime and other zeolites, as well as quartz, giving the false impression that the intrusion was originally undersaturated.

    Collections
    • Science: Theses and Dissertations [3296]
    Rights
    http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml

    UC Research Repository
    University Library
    University of Canterbury
    Private Bag 4800
    Christchurch 8140

    Phone
    364 2987 ext 8718

    Email
    ucresearchrepository@canterbury.ac.nz

    Follow us
    FacebookTwitterYoutube

    © University of Canterbury Library
    Send Feedback | Contact Us