Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/110563
Type: Thesis
Title: Magnetotelluric imaging of a Palaeozoic Andean margin subduction zone in western Victoria
Author: Stepan, M.
Issue Date: 2014
School/Discipline: School of Physical Sciences
Abstract: The geological setting for the accretion of the Lachlan and Delamerian Orogens in south-eastern Australia is controversial, with two different models proposed. The Lachlan Orogen resulted from either subducting oceanic crust and wedge accretion, or shortening and compression between two continental blocks. Broadband magnetotelluric (MT) data recorded over the transition between the Delamerian and Lachlan Orogens impose new constraints on the formation of southeastern Australia. The east-west MT survey extended for approximately 120 km, recording at 44 stations. A 2D inversion of the data in the bandwidth of 0.05-2000 s yielded a resistivity model to a depth of 150 km, with resistivity ranging from 1-10 000 Ωm. The upper crust was most resistive (>10 000 Ωm), and transitioned to a relatively flat conductor of 50-100 Ωm at ∼20 km. The upper mantle is resistive (>1 000 Ωm) and uniform below this layer. The Escondida, Moyston and Avoca Faults are imaged as low resistivity pathways (100-200 Ωm) extending to the surface. Faults may be anomalously conductive from alteration to serpentinite, and other trace mineralisation such as graphite. The Lachlan Orogen likely formed from west dipping subduction of mafic to ultramafic oceanic crust. This crust was altered to serpentinite, with magnetite coating grain boundaries. Imaged conductive bodies show where shearing caused interconnectivity of the magnetite.
Dissertation Note: Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2014
Where: Lachlan, Delamerian Orogens, southeastern Australia
Keywords: Honours; Geology; Tasmanides; magnetotellurics; western Victoria; subduction
Description: This item is only available electronically.
Provenance: This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the author of this thesis and do not wish it to be made publicly available, or you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals
Appears in Collections:School of Physical Sciences

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