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https://hdl.handle.net/2440/129334
Type: | Thesis |
Title: | A structural, geochronological & geochemical investigation of the Abt Schist; Ad Dawadimi Terrane; central Saudi Arabia |
Author: | Lewis, C. J. |
Issue Date: | 2009 |
School/Discipline: | School of Physical Sciences |
Abstract: | The Ad Dawadimi Terrane lies on the eastern margin of the Arabian-Nubian Shield between the ~800-600 Ma Ar Rayn Terrane to the east and the Palaeo-Neoproterozoic (1800-630 Ma) Afif Terrane to the west. The Ad Dawadimi Terrane is considered to be one of the most homogeneous terranes of the Arabian Shield and is dominated by the Abt Schist, a greenschist facies metamorphic unit of fine-grained sandstones and siltstones. Structural data shows variations in the foliations between the Ad Dawadimi Terrane’s eastern and western margins. The east is dominated by westsouth-west verging sub-horizontal, moderately inclined, open, asymmetrical folds with a subhorizontal to gentle south-south-east plunge. The western margin, although less well constrained, is dominated by folds with a west-north-west vergence, sub-horizontal, moderately – gently inclined, open, asymmetrical geometry; with a north-east south-west extensional component. 206Pb/238U data for Abt Schist samples within the Ad Dawadimi Terrane give a maximum depositional age of 594 ±14 Ma (2σ error at 95-105% concordance). Two 40Ar/39Ar metamorphic muscovite step-heating analyses yield peak metamorphic of ages ~616 ± 3 Ma and ~613 ± 6 Ma thus being within error of the youngest 206Pb/238U detrital zircon age. A number of zircon grains yield 206Pb/238U ages >1 Ga suggest a Mesoproterozoic, or older, influence on the source for the Abt sediments. This is supported by TIMS TDM model ages ~1154 ± 19 Ma suggesting Abt Schist protolith sediments were influenced by late Mesoproterozoic sources. Sedimentary geochemical analyses of immobile elements suggest sediments derived from the Afif Terrane were deposited into a fore-arc setting above a west dipping subducting slab. The very short time period between deposition and basin closure also suggests a fore-arc setting. Post deformation mafic dykes cross-cut the dominant foliation of the Ad Dawadimi Terrane, suggesting a period of extension after basin closure. |
Dissertation Note: | Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2009 |
Where: | Arabian-Nubian Shield |
Keywords: | Honours; Geology; Arabian-Nubian Shield; Abt Schist; structure; metamorphism; geochemistry; geochronology; zircon |
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 |
Files in This Item:
File | Size | Format | |
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LewisCJ2009_Hons.pdf | 8.45 MB | Adobe PDF | View/Open |
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