The deformed Permian Dun Mountain Ophiolite Belt (DMOB) forms the basement of the
Dun Mountain-Maitai terrane and is traceable through the entire length of New Zealand.
The DMOB contains a variably serpentinised mantle portion and a crustal portion
containing gabbros, dolerites, cross cutting dikes and extrusives, together they are similar
to oceanic crust. The initial crustal portion, however, is atypical when compared to other
ophiolites, being thin and lacking a sheeted dike complex, but has well spaced inclined
intrusive sheets and sills. At least four post-Permian deformation periods affect the DMOB;
collision and rotation during emplacement of the DMOB on the Gondwana margin,
compression during Mesozoic orogenies, extensional deformation during the Gondwana
break-up and transpressive deformation related to the modern plate boundary through
New Zealand.
Structural work in the Northern Bryneira Range focused on well preserved outcrops to
investigate crustal growth and contemporaneous deformation during the Permian.
Structural evidence of Permian deformation was determined by examination of
pseudostratigraphy, structures constrainable to the Permian, and the geometric
relationships with the overlying Maitai sedimentary sequence. Crosscutting by intrusive
phases was used to determine a chronological order of crustal growth and deformation
episodes. It was concluded that all deformation was extensional and that two major
phases of magmatism were separated by a period of deformation and were followed by
ongoing syn-sedimentary deformation during the deposition of the Maitai Group. After
removal of Mesozoic rotation, the resulting orientations of paleo-horizontal markers and
diverse orientations of intrusive sheets were analysed. Two hypothesises were tested to
assess the origin of inclined intrusive sheets: a) that the diverse orientations were the
result of tectonic rotation coeval with the intrusion of dikes. b) that primary orientations of
the sheets had been diverse. Results show that the sheets were intruded with diverse
orientations, probably related to variation in the principle horizontal stress over time.
Further rotation of the assemblage of sheets occurred during the last stages of
magmatism and during the subsequent period of sedimentation. The last stage probably
relates to large scale normal faulting during the development of the sedimentary basin.
iii
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/1587 |
| Date | January 2008 |
| Creators | Adamson, Thomas Keeley |
| Publisher | University of Canterbury. Geological Sciences |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Thomas Keeley Adamson, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
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