Macquarie University
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Migmatite delineates zones of melt flux through the upper crust, Wongwibinda, NSW

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posted on 2022-03-28, 16:54 authored by Michael James Farmer
The small (<20km wide) high-temperature - low-pressure (HTLP) Wongwibinda MetamorphicComplex (WMC), southern New England Orogen, is characterised by an irregular elevatedmetamorphic field gradient (<100°C/km). An examination of the migmatite rocks shows they didnot experienced significant in-situ partial melting, suggesting the abundant leucocratic veins anddykes observed in outcrop are externally derived. Using a combined field and petrographic study,augmented by targeted electron backscatter diffraction (EBSD) and whole-rock geochemicalanalyses, two types of melt pathways through the migmatite have been identified: (i) veining anddyking, and (ii) grain-scale channelled porous flow. The pathways of porous flow are recognisedacross the field area as cm- to outcrop-scale channels, characterised by rare-earth element (REE)metasomatism, mineral mode changes, a randomisation of host crystallographic preferredorientation fabrics and the presence of cuspate K-feldspar pockets. The identification of collapsestructures, due to volume loss as melt-filled dykes and voids drained, demonstrates that some of theinjected melt escaped to structurally higher levels. The two types of melt pathways and theircharacteristics supports a melt flux hypothesis, which is interpreted to drive migmatisation and promote the formation of the elevated thermal field gradient.



Theoretical thesis. Bibliography: pages 49-52

Awarding Institution

Macquarie University

Degree Type

Thesis MRes


MRes, Macquarie University, Faculty of Science and Engineering, Department of Earth and Planetary Sciences

Department, Centre or School

Department of Earth and Planetary Sciences

Year of Award


Principal Supervisor

Nathan Daczko

Additional Supervisor 1

Sandra Piazolo


Copyright Michael James Farmer 2017 Copyright disclaimer:




1 online resource (iv, 52, [2] pages) illustrations, maps

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