Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/130624
Type: Thesis
Title: Late Cambrian adakitic granite at Kinchina Quarry: implications for the evolution of the Delamerian Orogen
Author: George, C. M.
Issue Date: 2018
School/Discipline: School of Physical Sciences
Abstract: The Monarto Granite is exposed as 0.2-3 metre sills at the Kinchina Quarry west of Murray Bridge. These medium-fine grained granite sheets intrude migmatite formed from Early Cambrian Kanmantoo Group turbidites and are interleaved with meta-dolerite sills of similar thickness. The granites and mafic sills appear to be synchronous with the late stages of Delamerian folding and metamorphism and the granite was dated at 495.4 ± 0.6 Ma using U-Pb on monazite. Kinchina granite sills have geochemical features that make them unique amongst other Delamerian granites. They are peralumious, with very low Y (<10ppm) and with high Sr/Y ratios and steep, LREEenriched and HREE-depleted rare earth patterns without any Eu anomalies. Their geochemical characteristics clearly define them as silica-rich adakites. With initial εNd values of +1 -+2, similar to the interleaved mafic sills (εNd +2-+3), these granites have the most primitive (mantle-like) isotopic compositions of all the Delamerian granites. The composition of the Kinchina metadolerites is consistent with a MORB-like parent melt contaminated by about 5-8% continental crust. Geochemical modelling demonstrates that these adakite melts can form by partial melting of mafic rocks with compositions exactly the same as those of their near contemporary Kinchina sills (including their crustal contamination). Modelling is best matched by ~20% melting in the plagioclase-absent, garnet –CPX-rutile stable field. This eclogite facies melting must occur at pressures >1.4GPa (>50 Km depth) and ~980oC. Such upper mantle pressures suggest that the crustal-contaminated mafic parents were partially melted following delamination from the lower crust. There is good evidence that the Delamerian Orogeny was terminated by a latest Cambrian phase of rapid uplift, exhumation and erosion, prior to the post-tectonic (480± 5 Ma) phase of voluminous type magmatism. The evidence provided by the timing and petrogenesis of the Kinchina adakites strongly support the suspicion that this terminal Delamerian exhumation was driven by delamination of dense, mafic crustal underplate.
Dissertation Note: Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2018
Where: Kanmantoo Trough, east Mt Lofty Ranges, South Australia
Keywords: Honours; Geology; adakite; Delamerian Orogeny; geochemistry; partial melting; eclogite; Kinchina; Sr; Y; delamination
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 SizeFormat 
GeorgeCM2018_Hons.pdf28.34 MBAdobe PDFView/Open


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.