ORCID Profile
0000-0001-8850-397X
Current Organisation
University of Leeds
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Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-15396
Abstract: Oxide mineral phases within high-grade metamorphic rocks are often largely ignored compared to silicate minerals, except for when constraining the redox state of a s le. It is becoming increasingly apparent that unusual concentrations of oxide phases (e.g. magnetite, ilmenite and spinel) are more common in granulite facies metamorphic rocks that previously thought. However, the mechanism of their formation remains poorly constrained. For ex le, it is currently unclear what process or combination of processes result in high (over 50% oxide concentration in a s le in some cases) concentrations. There is an ongoing debate if a single process can be applied across all protoliths, with the goal that these assemblages could be used to pinpoint particular crustal process(es). A number of mechanisms have been suggested to form such extreme concentrations of oxides within metamorphic rocks. These include melt fluxing in a deformation zone (Ghatak et al., 2022), partial melt loss (Morrissey et al., 2016), deformation related metamorphic reactions and protolith composition or a combination thereof. Within a collection of high grade metapelites from Rogaland, SW Norway, we see variations in mineralogy, including changes in orthopyroxene and cordierite content with oxide concentrations, variations in grain size, variable layering as well as variable signature of the amount of deformation. Using a combination of microstructures, EBSD, EDS, XCT and other& data we will assess and illustrate the processes behind the generation of high oxide concentrations within metapelites and what this could mean for crustal processes during high-grade metamorphism.& Ghatak, H., Gardner, R. L., Daczko, N. R., Piazolo, S., & Milan, L. (2022). Oxide enrichment by syntectonic melt-rock interaction. Lithos, 414& #8211 , 106617. 0.1016/J.LITHOS.2022.106617Morrissey, L. J., Hand, M., Lane, K., Kelsey, D. E., & Dutch, R. A. (2016). Upgrading iron-ore deposits by melt loss during granulite facies metamorphism. Ore Geology Reviews, 74, 101& #8211 . ttp://0.1016/j.oregeorev.2015.11.012
Publisher: Wiley
Date: 19-05-2016
DOI: 10.1111/JMG.12192
Publisher: Elsevier BV
Date: 11-2020
Publisher: Geological Society of London
Date: 18-05-2024
Abstract: The metamorphic conditions of the Natal Metamorphic Province (NMP) have been the focus of previous studies to assist with Rodinia reconstructions but there are limited constraints on the age of metamorphism. We use a combination of modern techniques to provide new constraints on the conditions and timing of metamorphism in the two southernmost terranes: the Mzumbe and Margate. Metamorphism reached granulite facies, 780–834°C at 3.9–7.8 kbar in the Mzumbe Terrane and 850–892°C at 5.7–6.1 kbar in the Margate Terrane. The new pressure and temperature constraints are supportive of isobaric cooling in the Margate Terrane as previously proposed. Peak metamorphism of the two terranes is shown to have occurred c. 40 myr apart, which contrasts strongly with previous assumptions of coeval metamorphism. While the age of peak metamorphism of the Margate Terrane (1032.7 ± 4.7 Ma) coincides with the tectonism and magmatism associated with the emplacement of the Oribi Gorge Suite ( c. 1050–1030 Ma), the age of metamorphism of the Mzumbe Terrane (987.4 ± 8.1 Ma) occurs c. 30–40 myr after tectonism is previously thought to have finished. We propose that models of advective cooling during transcurrent shearing can explain the metamorphic conditions and timing of the NMP.
Publisher: Geological Society of London
Date: 31-05-2024
Abstract: The study of magmatic and metamorphic processes is challenged by geological complexities like geochemical variations, geochronological uncertainties and the presence/absence of fluids and/or melts. However, by integrating petrographic and microstructural studies with geochronology, geochemistry and phase equilibrium diagram investigations of different key mineral phases, it is possible to reconstruct insightful pressure–temperature–deformation–time histories. Using multiple geochronometers in a rock can provide a detailed temporal account of its evolution, as these geological clocks have different closure temperatures. Given the continuous improvement of existing and new in situ analytical techniques, this contribution provides an overview of frequently utilized petrochronometers such as garnet, zircon, titanite, allanite, rutile, monazite/xenotime and apatite, by describing the geological record that each mineral can retain and explaining how to retrieve this information. These key minerals were chosen as they provide reliable age information in a variety of rock types and, when coupled with their trace element (TE) composition, form powerful tools to investigate crustal processes at different scales. This review recommends best applications for each petrochronometer, highlights limitations to be aware of and discusses future perspectives. Finally, this contribution underscores the importance of integrating information retrieved by multi-petrochronometer studies to gain an in-depth understanding of complex thermal and deformation crustal processes.
Publisher: Elsevier BV
Date: 2017
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 04-2019
Publisher: Wiley
Date: 09-2021
DOI: 10.1111/JMG.12630
Abstract: The extent to which solid‐state volume diffusion modifies rare earth element (REE) abundances in accessory minerals during high‐temperature metamorphism governs our ability to link recorded trace‐element compositions to particular thermal events. We model diffusion of REE in zircon under different temperature–time conditions and show that, for both short‐lived (e.g. 1100°C for 1–5 Ma) and more prolonged (e.g. 1050°C for 10–30 Ma or 1000°C for 200 Ma) episodes of ultra‐high‐temperature (UHT) metamorphism, REE diffusion in igneous zircon is sufficiently rapid for REE in a ~50‐μm grain to equilibrate with the new metamorphic mineral assemblage of the host rock. By contrast, unless diffusion is accelerated by recrystallization, the presence of fluids or other processes at temperatures below 900°C zircon will largely retain its original pre‐metamorphic REE abundance pattern, even when the thermal event is long lived (≥100 Ma). Where volume diffusion is dominant, for instance, in the absence of a fluid phase, the sensitivity of REE mobility to temperature can help constrain the temperature–time path of high‐grade metamorphic rocks. Modelling of well‐characterized natural s les from the regional‐scale aureole surrounding the Rogaland Igneous Complex (RIC) in SW Norway shows that variations in REE concentration patterns in zircon indicate a T–t evolution that is consistent with independent P–T–t estimates for regional metamorphism based on phase equilibrium modelling (850–950°C at 7–8 kbar for ~100 Ma). Greater modification of REE abundance patterns in zircons within 2 km of the RIC contact, however, indicates that UHT conditions persisted for ~150 Ma close to the intrusion, with a temperature of ~1100°C for 1–5 Ma at the RIC contact. Thermal modelling suggests that the inferred T–t histories of s les from different distances from the RIC contact are best explained if the complex was emplaced incrementally over 1–5 Ma.
Publisher: Wiley
Date: 15-06-2020
DOI: 10.1111/JMG.12532
Publisher: Elsevier BV
Date: 05-2020
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-14458
Abstract: & & During his long career in ionprobe geochemistry, Professor Neal McNaughton built up an impressive collection of s les. Professor McNaughton served as SHRIMP geochronologist for the Centre of Global Metallogeny at the University of Western Australia (1994-2005), the Western Australia Centre for Exploration Targeting (2005-2007), and the John de Laeter Centre (JdLC) at Curtin University (2007-2019), and upon his retirement he donated his collection of epoxy mounted s les to the GSWA. This collection of over 1000 mounts containing over 4000 s les is full of irreplaceable s les, representing over 20 years of geochronological research and development on the SHRIMP II in the JdLC. The collection is a highly valuable resource for future geochemical and geochronological research however, the entire collection lacked a digital footprint. When this project started there was a distinct lack of a unified approach for geoscience metadata or a template for preserving such a collection. In a jointly funded effort by AuScope, GSWA and Curtin University a digital s le catalogue of the collection with digitised materials was successfully created. We operated under the FAIR data principals and utilised International Geo S le Numbers (IGSNs) as persistent identifiers to create the most impactful, accessible and visible product. The final catalogue, associated metadata and digital materials are now publicly available online on a number of digital platforms such as Research Data Australia and GSWA& #8217 s GeoVIEW.WA and the mounts are able to be borrowed from GSWA for future analysis. These efforts allowed the preservation of physical materials for future loans and analysis as well as visibility in our digital age. We will outline the template and workflow utilised by this project that can be used to preserve similarly high value collections and by current facilities, universities and researchers in their ongoing research, as well as insights for future efforts.& &
Publisher: Elsevier BV
Date: 11-2021
Publisher: Wiley
Date: 11-04-2019
DOI: 10.1111/JMG.12480
Publisher: Springer Science and Business Media LLC
Date: 05-11-2020
DOI: 10.1007/S00410-020-01752-7
Abstract: Accessory mineral thermometry and thermodynamic modelling are fundamental tools for constraining petrogenetic models of granite magmatism. U–Pb geochronology on zircon and monazite from S-type granites emplaced within a semi-continuous, whole-crust section in the Georgetown Inlier (GTI), NE Australia, indicates synchronous crystallisation at 1550 Ma. Zircon saturation temperature ( T zr ) and titanium-in-zircon thermometry ( T (Ti–zr) ) estimate magma temperatures of ~ 795 ± 41 °C ( T zr ) and ~ 845 ± 46 °C ( T (Ti-zr) ) in the deep crust, ~ 735 ± 30 °C ( T zr ) and ~ 785 ± 30 °C ( T (Ti-zr) ) in the middle crust, and ~ 796 ± 45 °C ( T zr ) and ~ 850 ± 40 °C ( T (Ti-zr) ) in the upper crust. The differing averages reflect ambient temperature conditions ( T zr ) within the magma chamber, whereas the higher T (Ti-zr) values represent peak conditions of hotter melt injections. Assuming thermal equilibrium through the crust and adiabatic ascent, shallower magmas contained 4 wt% H 2 O, whereas deeper melts contained 7 wt% H 2 O. Using these H 2 O contents, monazite saturation temperature ( T mz ) estimates agree with T zr values. Thermodynamic modelling indicates that plagioclase, garnet and biotite were restitic phases, and that compositional variation in the GTI suites resulted from entrainment of these minerals in silicic (74–76 wt% SiO 2 ) melts. At inferred emplacement P–T conditions of 5 kbar and 730 °C, additional H 2 O is required to produce sufficient melt with compositions similar to the GTI granites. Drier and hotter magmas required additional heat to raise adiabatically to upper-crustal levels. S-type granites are low- T mushes of melt and residual phases that stall and equilibrate in the middle crust, suggesting that discussions on the unreliability of zircon-based thermometers should be modulated.
Location: Australia
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 2021
End Date: 2023
Funder: European Commission
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