The thermal evolution of the east-Gondwanan subduction zone: evidence of long-lived subduction preserved at Port Macquarie, NSW

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dc.contributor.authorLee B. R.
dc.contributor.schoolSchool of Physical Sciencesen
dc.date.issued2023
dc.descriptionThis item is only available electronically. Whole thesis (as available).
dc.description.abstractThe thermal evolution of subduction zones is not well understood. Numerical models show that subduction zones thermally evolve from hot temperatures at initiation and then cool over time until they reach a steady state (maturity). These models typically show this occurring over periods of 20–40 Myr. However, these models need to be tested using natural examples. There are relatively few examples of naturally occurring long-lived subduction systems preserving accumulated subduction products over those time ranges but the Port Macquarie Serpentinite Mélange in the southern New England Orogen is one example. The mélange contains a comprehensive and diverse suite of exhumed high-pressure (high–P), low-temperature (low–T) metamorphic rocks, including eclogite, blueschist and meta-conglomerate. U–Pb titanite, garnet Lu–Hf and Rb–Sr phengite geochronology document ~100 Myr of thermal evolution in the east-Gondwanan subduction zone. Mineral equilibria modelling of ca. 490 Ma lawsonite eclogite and ca. 400 Ma meta-conglomerate suggests thermal gradients were 219°C/GPa and 200°C/GPa respectively, revealing that over this extended duration the geothermal gradient was between 6–7°C/km and did not significantly change. The high–P rocks from this long-lived palaeo-subduction system reveal that the east-Gondwanan subduction zone had reached a steady state by ca. 490 Ma, and models suggest that subduction of the palaeo-Pacific oceanic lithosphere beneath the east-Gondwanan margin initiated earlier than the Cambrian.
dc.description.dissertationThesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, YEAR
dc.identifier.urihttps://hdl.handle.net/2440/146702
dc.language.isoen
dc.provenanceThis 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/legalsen
dc.subjectHonours
dc.subjectGeology
dc.subjectthermal evolution
dc.subjectsubduction
dc.subjecteclogite
dc.subjectblueschist
dc.subjectslab cooling
dc.subjectserpentinite mélange
dc.subjectRocky Beach Metamorphic Mélange
dc.titleThe thermal evolution of the east-Gondwanan subduction zone: evidence of long-lived subduction preserved at Port Macquarie, NSW
dc.typeThesis

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