ORCID Profile
0000-0001-9759-4754
Current Organisation
University of Sydney
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Inorganic Geochemistry | Geology | Tectonics | Electrical and Electromagnetic Methods in Geophysics
ANZSRC Socio-Economic Objective (SEO)
Titanium Minerals, Zircon, and Rare Earth Metal Ore (e.g. Monazite) Exploration | Mineral Exploration not elsewhere classified | Copper Ore Exploration |
Related Links
Publications
Reply to comments of referee #2, Luca Menegon
Publisher: Copernicus GmbH
Date: 08-2017
Reply to comments of referee #1, Scott Johnson
Publisher: Copernicus GmbH
Date: 08-2017
U–Pb zircon and biostratigraphic data of high-pressure/low-temperature metamorphic rocks of the Talea Ori: tracking the Paleotethys suture in central Crete, Greece
Publisher: Springer Science and Business Media LLC
Date: 03-03-2016
Seismic anisotropy of the lithospheric mantle beneath Marie Byrd Land, West Antarctica: Constraints from peridotite xenoliths
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-11597
Abstract: & & Constraining the seismic structure of the West Antarctic mantle is important for understanding its viscosity structure, and thus for accurately predicting the evolution of the West Antarctic Ice Sheet.& Seismic anisotropy, which is the dependence of seismic velocities on the propagation and polarization direction of seismic waves, is a valuable tool for understanding mantle deformation and flow. & We provide petrological and microstructural data from a suite of 44 spinel peridotite xenoliths entrained in Cenozoic (1.4 Ma) basalts of 7 volcanic centers located in Marie Byrd Land, West Antarctica.& Equilibration temperatures obtained from three different calibrations of the two-pyroxene geothermometer and the olivine-spinel Fe-Mg exchange geothermometer range from 780& #176 C to 1200& #176 C, calculated at a pressure of 1500 MPa.& This range of temperatures corresponds to extraction depths between 39 and 72 km, constraining the source of the xenoliths within the lithospheric mantle above the low velocity zone modelled by seismic studies.& & & & The Marie Byrd Land xenoliths are fertile with average clinopyroxene mode that ranges between 15 and 24%.& Based on their modal composition, xenoliths are predominantly classified as lherzolites (n=30), with lesser occurrences of harzburgite (n=4), wehrlite (n=3), dunite (n=3), olivine websterite (n=1), websterite (n=1), and clinopyroxenite (n=2).& Petrological data suggest that the xenoliths have been affected by various degrees of partial melting as well as by reaction with silicate melts or fluids.& For ex le, clinopyroxenes in the more fertile lherzolites and wehrlites show a constant TiO& sub& & /sub& concentration at 0.65 wt% and 0.8 wt% over a range of olivine Mg# values, while TiO& sub& & /sub& decreases rapidly with increasing Mg#, down to 0.01 wt% in the more refractory harzburgites and dunites.& The observed trend is interpreted to indicate a refertilization process.& Microstructures also indicate multiple episodes of reactive melt percolation under either static conditions or during the late stages of deformation.& Pyroxenes may enclose rounded olivine grains in crystallographic continuity with neighbouring grains, cross-cut the subgrain boundaries of olivine grains, or show an interstitial habit, either forming cuspate-shaped grains in olivine triple junctions or films along olivine-olivine grain boundaries.& Olivine shows a range of crystallographic preferred orientation (CPO) patterns, including the A-type, axial-[010], axial-[100], and B-type.& Pyroxenes have weaker but not random CPOs with [001] axes having similar orientation to olivine [100] axes in the majority of the xenoliths.& Calculated P and S waves anisotropy is variable (2& #8211 %) and increases with olivine fraction but decreases with both increasing ortho- or clinopyroxene content. & P-wave anisotropy is correlated with the strength of olivine CPO expressed with the M-index and increases with increasing strength of the orthopyroxene CPO, but seems to be less correlated with the strength of the clinopyroxene CPO.& &
Constraints on the rheology of lower crust in a strike-slip plate boundary: Evidence from the San Quintin xenoliths, Baja California, Mexico
Publisher: Copernicus GmbH
Date: 11-05-2017
DOI: 10.5194/SE-2017-45
Abstract: Abstract. The rheology of lower crust and its time-dependent behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of mafic granulite and lherzolite xenoliths from the Holocene San Quintin volcanic field, of northern Baja California, Mexico. The San Quintin volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. Combining microstructural observations, geothermometry and phase equilibria modeling we constrain that crystal-plastic deformation took place at temperatures of 750–900 °C and pressures of 400–580 MPa, corresponding to 15–22 km depth. A hot crustal geothermal gradient of 40 °C/km is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is dry. Microstructural evidence suggests that the mafic granulite and peridotite xenoliths were dominantly deforming by processes transitional between dislocation creep and diffusion creep. Recrystallized grain size paleopiezometry yields similar differential stresses in both the uppermost lower crust and upper mantle. Using dry-plagioclase and dry-olivine flow laws we demonstrate that the viscosity of the lower crust and upper mantle is low (2.2 × 1018 – 1.4 × 1020 Pa s). Comparing the viscosity structure of the lithosphere constrained from the San Quintin xenoliths with results from post-seismic relaxation studies from western US, we suggest that lower crust is stronger during transient deformation (e.g., post-seismic relaxation period) while the upper mantle is stronger during long-term deformation (e.g., interseismic period).
Reply to comments of referee #3, Anonymous
Publisher: Copernicus GmbH
Date: 08-2017
Heterogeneous constrictional deformation in a ductile shear zone resulting from the transposition of a lineation-parallel fold
Publisher: Elsevier BV
Date: 07-2013
Strain gradients in zones of ductile thrusting: Insights from the External Hellenides
Publisher: Elsevier BV
Date: 09-2007
Deformation within the Cycladic subduction–exhumation channel: new insights from the enigmatic Makrotantalo nappe (Andros, Aegean)
Publisher: Springer Science and Business Media LLC
Date: 12-02-0005
Mantle strength of the San Andreas fault system and the role of mantle-crust feedbacks
Publisher: Geological Society of America
Date: 21-08-2015
DOI: 10.1130/G36752.1
Vorticity of flow in ductile thrust zones: examples from the Attico-Cycladic Massif (Internal Hellenides, Greece)
Publisher: Geological Society of London
Date: 2010
DOI: 10.1144/SP335.28
Strain Localization at Constant Strain Rate and Changing Stress Conditions: Implications for Plate Boundary Processes in the Upper Mantle
Publisher: MDPI AG
Date: 30-11-2021
DOI: 10.3390/MIN11121351
Abstract: We present results from a natural deformed shear zone in the Turon de Técouère massif of the French Pyrenees that directly addresses the processes involved in strain localization, a topic that has been investigated for the last 40 years by structural geologists. Paleopiezometry indicates that differential stresses are variable both spatially across the zone, and temporally during exhumation. We have, however, also calculated strain rate, which remains constant despite changes in stress. This result appears to be at odds with recent experimental deformation on monophase (olivine) rocks, which indicate that strain localization occurs dominantly as a result of constant stress. We hypothesize that in the Turon de Técouère massif—and many natural shear zones—strain localization occurs as a result of reactions, which decrease the grain size and promote the activation of grain size sensitive deformation mechanisms. From a tectonics perspective, this study indicates that the deformation rate in a particular plate boundary is relatively uniform. Stress, however, varies to accommodate this deformation. This viewpoint is consistent with deformation at a plate boundary, but it is not the typical way in which we interpret strain localization.
Calcite pseudomorphs after aragonite: A tool to unravel the structural history of high-pressure marbles (Evia Island, Greece)
Publisher: Elsevier BV
Date: 07-2021
Stress variations in space and time within the mantle section of an oceanic transform zone: Evidence for the seismic cycle
Publisher: Geological Society of America
Date: 27-03-2020
DOI: 10.1130/G47137.1
Abstract: The Bogota Peninsula shear zone in New Caledonia (southwest Pacific Ocean) is the exhumed mantle section of an oceanic transform zone. Ductile fabrics in this zone formed at temperatures & °C, and differential stresses estimated from microstructures vary spatially and temporally. Along a transform-perpendicular transect, stresses increase toward the high-strain areas. We attribute this stress gradient to an increase in strain rate caused by imposed rather than intrinsic strain localization. Temporal stress variations are indicated by the formation of fine-grained microdeformation zones (MDZs) that truncate and offset coarser grains. We interpret the MDZs to result from zones of brittle deformation caused by earthquake fracture propagation downward in the upper mantle, which are in turn overprinted by ductile deformation at stresses 2–6 times higher (22–81 MPa) than their surrounding steady-state fabrics. We interpret the spatial and temporal variations in microstructures and stresses as reflecting different stages of the seismic cycle in oceanic lithosphere.
Tectonic evolution of a crustal-scale oblique ramp, Hellenides thrust belt, Greece
Publisher: Elsevier BV
Date: 12-2013
Big data in microstructure analysis: Building a universal orientation system for thin sections
Publisher: Elsevier BV
Date: 08-2019
Tracking the late Paleozoic to early Mesozoic margin of northern Gondwana in the Hellenides: paleotectonic constraints from U–Pb detrital zircon ages
Publisher: Springer Science and Business Media LLC
Date: 25-01-2016
Effects of melt-percolation, refertilization and deformation on upper mantle seismic anisotropy: constraints from peridotite xenoliths, Marie Byrd Land, West Antarctica
Publisher: Geological Society of London
Date: 17-09-2021
DOI: 10.1144/M56-2020-16
Abstract: We report on the petrology, microstructure and seismic properties of 44 peridotite xenoliths extracted from the upper mantle beneath Marie Byrd Land (MBL), West Antarctica. The aim of this work is to understand how melt-rock reaction, refertilization, and deformation affected the seismic properties (velocities, anisotropy) of the West Antarctic upper mantle, in the context of MBL tectonic evolution and West Antarctic Rift System formation. Modal compositions, mineral major element compositions, microstructures, and crystallographic preferred orientations (CPOs) provide evidence for diachronous reactive melt percolation and refertilization. Olivine shows three main CPO patterns, the A-type, axial-[010], and axial-[100] texture types. Average seismic properties of the MBL mantle lithosphere are mainly controlled by the strength of olivine crystallographic texture. Reactive melt percolation and refertilization likely modified seismic velocities and anisotropy, as is suggested by a systematic decrease in maximum P-wave and S-wave anisotropies with increasing modal abundance of pyroxene. At larger spatial scales, the seismic properties of the MBL mantle xenoliths are dominated by the anisotropy resulting from the A-type olivine CPO. Variations between in idual volcanic centres, however, attest to spatial variations in the mantle structure, potentially related to 3D deformation and the prolonged tectonic history of MBL.
Subduction- and exhumation-related structures in the Cycladic Blueschists: Insights from south Evia Island (Aegean region, Greece)
Publisher: American Geophysical Union (AGU)
Date: 02-03-2012
DOI: 10.1029/2011TC002946
U-Pb single zircon ages and geochemistry of metagranitoid rocks in the Cycladic Blueschists (Evia Island): Implications for the Triassic tectonic setting of Greece
Publisher: Elsevier BV
Date: 06-2013
Using incremental elongation and shearing to unravel the kinematics of a complex transpressional zone
Publisher: Elsevier BV
Date: 10-2018
Exhumation of high-pressure rocks under continuous compression: A working hypothesis for the southern Hellenides (central Crete, Greece)
Publisher: Cambridge University Press (CUP)
Date: 18-09-2006
DOI: 10.1017/S0016756806002585
Abstract: Combined kinematic, structural and palaeostress (calcite twinning, fault-slip data) analyses are used to study the exhumation mechanism of the high-pressure rocks exposed on the island of Crete (southern Aegean, Greece). Our study shows that the evolution of windows in central Crete was controlled by two main contractional phases of deformation. The first phase (D 1 ) was related to the ductile-stage of exhumation. NNW–SSE compression during D 1 caused layer- and transport-parallel shortening in the upper thrust sheets, resulting in nappe stacking via low-angle thrusting. Synchronously, intracontinental subduction led to high-pressure metamorphism which, however, did not affect the most external parts of the southern Hellenides. Subsequent upward ductile extrusion of high-pressure rocks was characterized by both down-section increase of strain and up-section increase of the pure shear component. The second phase (D 2 ) was associated with the brittle-stage of exhumation. D 2 was governed by NNE–SSW compression and involved conspicuous thrust-related folding, considerable tectonic imbrication and formation of a Middle Miocene basin. The major D 2 -related Psiloritis Thrust cross-cuts the entire nappe pile, and its trajectory partially follows and reworks the D 1 -related contact between upper and lower (high-pressure) tectonic units. Eduction and doming of the Talea Window was accompanied by gravity sliding of the upper thrust sheets and by out-of-the-syncline thrusting. Late-orogenic collapse also contributed to the exhumation process. Therefore, it seems that the high-pressure rocks of central Crete were exhumed under continuous compression and that the role of extension was previously overestimated.
Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico
Publisher: Copernicus GmbH
Date: 21-12-2017
Abstract: Abstract. The rheology of lower crust and its transient behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of granulite and lherzolite xenoliths from the upper Pleistocene–Holocene San Quintín volcanic field of northern Baja California, Mexico. The San Quintín volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. The development of a strong foliation in both the mafic granulites and lherzolites, suggests that a lithospheric-scale shear zone exists beneath the San Quintín volcanic field. Combining microstructural observations, geothermometry, and phase equilibria modeling, we estimated that crystal-plastic deformation took place at temperatures of 750–890 °C and pressures of 400–560 MPa, corresponding to 15–22 km depth. A hot crustal geotherm of 40 ° C km−1 is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is relatively dry. Microstructures are interpreted to show that deformation in both the uppermost lower crust and upper mantle was accommodated by a combination of dislocation creep and grain-size-sensitive creep. Recrystallized grain size paleopiezometry yields low differential stresses of 12–33 and 17 MPa for plagioclase and olivine, respectively. The lower range of stresses (12–17 MPa) in the mafic granulite and lherzolite xenoliths is interpreted to be associated with transient deformation under decreasing stress conditions, following an event of stress increase. Using flow laws for dry plagioclase, we estimated a low viscosity of 1.1–1.3×1020 Pa ⋅ s for the high temperature conditions (890 °C) in the lower crust. Significantly lower viscosities in the range of 1016–1019 Pa ⋅ s, were estimated using flow laws for wet plagioclase. The shallow upper mantle has a low viscosity of 5.7×1019 Pa ⋅ s, which indicates the lack of an upper-mantle lid beneath northern Baja California. Our data show that during post-seismic transients, the upper mantle and the lower crust in the Pacific–Baja California plate boundary are characterized by similar and low differential stress. Transient viscosity of the lower crust is similar to the viscosity of the upper mantle.
Stress changes during exhumation of a high-pressure nappe (Phyllite-Quartzite unit, Greece): Insights from quartz microstructures and recrystallized grain size statistics
Publisher: Elsevier BV
Date: 02-2023
Mechanisms of fault mirror formation and fault healing in carbonate rocks
Publisher: Elsevier BV
Date: 2020
Supplementary material to "Constraints on the rheology of lower crust in a strike-slip plate boundary: Evidence from the San Quintin xenoliths, Baja California, Mexico"
Publisher: Copernicus GmbH
Date: 11-05-2017
Oligocene-Miocene thrusting in central Aegean: insights from the Cycladic island of Amorgos
Publisher: Wiley
Date: 17-04-2011
DOI: 10.1002/GJ.1304
Review_se-2019-28_VasileiosChatzaras
Publisher: Copernicus GmbH
Date: 13-03-2019
Transpressional deformation in the lithospheric mantle beneath the North Anatolian Fault Zone
Publisher: Elsevier BV
Date: 09-2021
Axial‐type olivine crystallographic preferred orientations: The effect of strain geometry on mantle texture
Publisher: American Geophysical Union (AGU)
Date: 07-2016
DOI: 10.1002/2015JB012628
Chapter 6 Coupled deformation and melt-migration events recording subduction initiation, Dun Mountain ophiolite, New Zealand
Publisher: Geological Society of London
Date: 2019
DOI: 10.1144/M49.5
Microstructural and textural modification of columnar calcite under increasing shear strain (Evia Island, Greece)
Publisher: Elsevier BV
Date: 07-2022
Review_se-2019-32
Publisher: Copernicus GmbH
Date: 12-04-2019
Ductile nappe stacking and refolding in the Cycladic Blueschist Unit: insights from Sifnos Island (south Aegean Sea)
Publisher: Springer Science and Business Media LLC
Date: 16-10-2016
Imposed strain localization in the mantle section of an oceanic transform zone revealed by microstructural and stress variations
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-11897
Abstract: & & Mantle earthquakes that occur deeper than the 600 & #176 C isotherm in oceanic transform faults indicate seismic rupturing at conditions where viscous deformation (bulk ductile behavior) is dominant.& However, direct geological evidence of earthquake-related deformation at ambient upper mantle conditions is rare, impeding our understanding of earthquake dynamics in plate-boundary fault systems.& The Bogota Peninsula Shear Zone (BPSZ), New Caledonia, is an ancient oceanic transform fault exhumed from upper mantle depths.& Ductile structures in the BPSZ formed at temperatures & 800 & #176 C and microstructures indicate that differential stress varies spatially and temporally.& Spatial variation is observed as an increase in differential stress with strain toward localized zones of high strain stress increases from 6& #8211 MPa in coarse grained tectonites to 11& #8211 MPa within 1& #8211 km wide mylonite zones.& Temporal stress variation is observed by the formation of micro-deformation zones that seem to have brittle precursors, are filled with fine-grained recrystallized olivine grains and crosscut the background fabrics in the harzburgites that host them.& The micro-deformation zones are not restricted to the mylonite zones, but rather are located throughout the BPSZ, having affected the protomylonites and the coarse grained tectonites. & The micro-deformation zones record stresses of 22& #8211 MPa that are 2& #8211 times higher than the background, steady-state stresses in the surrounding mantle rocks.& We interpret the observed spatial and temporal variations in microstructures and stresses in the upper mantle to demonstrate the influence of seismic events in the upper part of the oceanic transform fault system.& We attribute the increase in stress with strain to be the result of imposed localization induced by downward propagation of the seismic rupture into the underlying mantle.& The micro-deformation zones could result from brittle fractures caused by earthquake-related deformation in the mantle section of the transform fault, which are in turn overprinted by ductile deformation.& & & & & & & & & Synthesizing the spatial and temporal variations in stresses and microstructures in the Bogota Peninsula Shear Zone we propose a conceptual model where brittle fracturing and shearing take place during coseismic rupture at increased stress, ductile flow at decaying stress is concentrated in the micro-deformation zones during postseismic relaxation, and uniformly distributed creep at low stress occurs in the host-rocks of the micro-deformation zones during interseismic deformation.& The critical result from the studied paleotransform zone is that the fine-grained micro-deformation zones and the mylonites do not represent weak zones. & Instead, they form by dislocation creep at transient high-stress deformation during the seismic cycle. & The spatial distribution of the micro-deformation zones also suggests that repeated stress cycles in oceanic transform faults may not localize strain in pre-existing shear zones but disperse strain across the structure.& &
Intra-oceanic subduction initiation recorded by the metamorphic sole of the New Caledonia ophiolite: petrological, structural and age constraints
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-11835
Abstract: & & Subduction initiation is commonly identified as a major enigma in plate tectonics. Attention to subduction initiation is growing in the community, as is our understanding of the sequences of geologic events that precede and postdate this critical stage of the Wilson cycle. Nevertheless, the direct triggers of subduction initiation and their regional to global consequences remain uncertain. The New Caledonia ophiolite has formed in a supra-subduction zone setting in the vicinity of an active spreading centre. The metamorphic sole, which represents the ancient subduction interface, is locally preserved beneath the ophiolite. Unravelling its tectono-metamorphic record is essential in order to determine the timing of subduction initiation and the tectonic processes operating at the plate interface during the early stages of subduction.& We have s led and studied hibole-bearing rocks of the metamorphic sole that crop out in three newly found and three previously known localities that are scattered across the island (160 km * 50 km in size). The hibolites form laterally discontinuous meter-size lenses that crop out within or beneath the serpentinite sole at the base of the ophiolite nappe.& Preliminary U-Pb zircon ID-TIMS geochronology yields a crystallization age of 56& #177 Ma in agreement, but with a narrower timespan compared to previously published data (Cluzel et al., 2012).& We use whole-rock geochemistry, mineral chemistry and thermodynamic modelling to constrain the Pressure-Temperature-time history of the hibolites.& Microstructural data such as dominant deformation mechanisms, crystallographic preferred orientations, grain size distributions determined by EBSD allow to constrain the deformation processes and rheological behavior of the hibolites during subduction infancy.& & & & & & & & & Cluzel, D., Jourdan, F., Meffre, S., Maurizot, P., and Lesimple, S., 2012. The metamorphic sole of New Caledonia ophiolite: 40Ar/39Ar, U-Pb, and geochemical evidence for subduction inception& at a spreading ridge. Tectonics, VOL. 31, TC3016, doi:10.1029/2011TC003085.& &
Closure of the Paleotethys in the External Hellenides: Constraints from U-Pb ages of magmatic and detrital zircons (Crete)
Publisher: Elsevier BV
Date: 09-2015
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Funder: European Commission
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