Alexander Cruden | Monash University (original) (raw)

Papers by Alexander Cruden

EGU General Assembly Conference Abstracts, Apr 1, 2017

AGU Fall Meeting Abstracts, Dec 1, 2004

Immense volumes of plutonic rocks exposed in magmatic arcs challenge our ability to understand fu... more Immense volumes of plutonic rocks exposed in magmatic arcs challenge our ability to understand fundamental interactions between deformation and magma emplacement at convergent margins. Although close temporal and spatial relationships between fault activity and emplacement of arc plutons have been inferred, the hypothesis that there is always a direct link between faults and plutons in magmatic arcs remains controversial. It

GSA 2020 Connects Online, 2020

Canadian Journal of Earth Sciences, Jul 1, 2006

The English River subprovince is one of two metasediment-dominated terranes in the western Superi... more The English River subprovince is one of two metasediment-dominated terranes in the western Superior Province. It has been interpreted as an accretionary complex, a foreland, or a fore-arc basin that developed and was subsequently deformed between the metavolcanic-rich Uchi subprovince and the orthogneiss- and metaplutonic-dominated Winnipeg River subprovince during a prolonged transpressive orogeny. To test these hypotheses, we combined a satellite image, aeromagnetic image, and Lithoprobe reflection seismic profile interpretation with detailed structural mapping to better characterize the internal geometry and significance of structural features in the western part of the subprovince in Ontario. Northward-directed subduction and collision of the Winnipeg River subprovince with the Uchi subprovince at ca. >2713–2698 Ma can account for the deposition of the sedimentary rocks, initial metamorphism, and the main phase of deformation in the subprovince, whereas the subduction of Wabigoon crust generated extensive tonalite magmatism in the Winnipeg River and English River subprovinces during the same period. A period of extension, after the docking of the Winnipeg River and Wabigoon subprovinces at ca. 2698 Ma, punctuated the compressive phases of the orogeny and was responsible for high-grade metamorphism, upward bending of the Moho, and localized deposition of late, coarse, alluvial–fluvial metasedimentary rocks. Renewed compression caused by the docking of the Wawa subprovince at ca. 2689–2684 Ma is likely responsible for a largely unrecognized regional upright folding and faulting event that controls the dominant structural geometry of the subprovince. Late in its tectonic evolution, strain was partitioned into dextral deformation that was strongly domainal and limited to the subprovince margins.

Tectonics, May 1, 2021

During rifting, pre‐existing penetrative basement fabrics can affect new faults in cover rocks by... more During rifting, pre‐existing penetrative basement fabrics can affect new faults in cover rocks by a mechanism that does not appear to involve reactivation. This subtle form of inheritance can significantly impact fault network architecture in rift basins above laterally variable basement domains with geomechanical anisotropies. Here we use multi‐layer, brittle‐ductile, crustal‐scale analogue experiments to study the influence of penetrative basement anisotropies on fault patterns in the overlying cover during a single phase of orthogonal rifting. The experiments were designed to test whether basement anisotropies, oriented 45° to the extension direction, can lead to the formation of rift faults that are oblique to both the imposed extension direction and basement anisotropies. Our experiments show that a penetrative, vertically layered, mm‐wide basement anisotropy creates extension‐oblique faults in the overlying cover. We interpret this to arise when local strike‐slip kinematics along the interfaces of mechanically contrasting materials in the basement combine with the regional imposed orthogonal extension, creating a transtensional regime. The width and spacing of alternating “strong” and “weak” basement zones interact with rift kinematics, impacting the orientation, kinematics and spacing of new faults in the cover. New insights on the influence of penetrative, pre‐existing basement fabrics on localized re‐orientation of 3D strain in the cover have implications for understanding complex fault systems in rift basins and transfer zones.

Geology, 1995

Volcanic and plutonic rocks of Archean greenstone belts in the Abitibi subprovince become younger... more Volcanic and plutonic rocks of Archean greenstone belts in the Abitibi subprovince become younger southward; plutonic rocks are ϳ10-30 m.y. younger than volcanic rocks. The Abitibi greenstone belt has an upper crust of ϳ2.75-2.70 Ga oceanic supracrustal assemblages and a middle crust of ϳ2.70-2.68 Ga granitic and gneissic rocks. The greenstone belt upper crust is greenschist facies with upright structures and low reflectivity, and the middle crust is amphibolite facies with moderate to shallowly dipping structures and strong reflectivity. We propose that the age progression and crustal layering resulted from accretion of oceanic assemblages followed by extensive mid-crustal magmatism linked to southward migration of an arc-trench system. Thermal softening of the middle crust during magmatism caused ductile flow now represented by strong, mid-crustal reflectivity. Upward heat flow following magmatism caused late-tectonic (2.67-2.65 Ga) low-pressure metamorphism observed in the upper crust.

EGU General Assembly Conference Abstracts, Apr 1, 2019

Geochemical perspectives letters, Apr 1, 2018

Precambrian banded iron formations record the composition of Earth's atmosphere and hydrosphere d... more Precambrian banded iron formations record the composition of Earth's atmosphere and hydrosphere during the global rise of oxygen. It has been suggested that the banded texture of these rocks points to fluctuations in ocean chemistry although this remains a subject of debate. Here we show, by petrographic and electron microscopy of Palaeoproterozoic banded iron formations from the Hamersley Province, NW Australia, that not all iron oxide microbands represent primary sedimentary layers. Some iron oxide laminae are derived from abundant hematite particles that were originally encapsulated in chert layers and subsequently liberated by removal of quartz during post-depositional deformation by dissolution-precipitation creep. The liberated hematite particles progressively accumulated in layer-parallel aggregates forming microbands, with new hematite crystals forming via non-classical crystallisation pathways during diagenesis and metamorphism. Therefore, microbands do not necessarily correspond to fluctuations in the depositional environment.

When numerical and analogue models are used to investigate the evolution of deformation processes... more When numerical and analogue models are used to investigate the evolution of deformation processes in crust and lithosphere, they face specific challenges related to, among others, large contrasts in material properties, the heterogeneous character of continental lithosphere, the presence of a free surface, the occurrence of large deformations including viscous flow and offset on shear zones, and the observation that

... Saint Blanquat, M.(de), Habert, G., Horsman, E ... Jean-Louis Paquette1, Michel de Saint Blan... more ... Saint Blanquat, M.(de), Habert, G., Horsman, E ... Jean-Louis Paquette1, Michel de Saint Blanquat2, Guillaume Delpech3, Eric Horsman4 and Sven Morgan5 1 CNRS UMR6524 and Université Blaise Pascal, Clermont-Ferrand, France-JL Paquette@ opgc. univ-bpclermont. ...

Journal of the Geological Society, 2009

Quick Search: All GSW Journals, GSW + GeoRef. advanced search. ...

Australian Journal of Earth Sciences, Jul 21, 2019

Abstract Folded reservoir rocks (Eumeralla Formation) within the Otway Basin are of significant e... more Abstract Folded reservoir rocks (Eumeralla Formation) within the Otway Basin are of significant exploration interest for their geothermal and tight gas reservoir potential. Brittle deformation within the Eumeralla Formation (ca 113–100 Ma), along the Otway coastline of Victoria, reflects a protracted history of extension, contraction, erosion and uplift, since Australian–Antarctic separation in the Early Cretaceous. This paper investigates the relative timing of heterogeneously distributed fracture populations within both folded and unfolded areas along the Otway coastline. Data collection occurred across two stratigraphic units spanning the Early Cretaceous (Eumeralla Formation) to the late Cenozoic (Demons Bluff Group), in order to measure fracture geometries and determine the relative timing of fracture formation. An unmanned aerial vehicle has been used to facilitate the systematic and inexpensive acquisition of high-resolution orthophotographs along coastal platforms, in order to complement traditional field mapping of fracture populations. A NE–SW-orientated fracture set is observed exclusively within the Eumeralla Formation (St George fold hinge), while a NW–SE-orientated fracture set pre-dates hinge-parallel fractures. Significant fracture formation has been linked to a period of mid-Cretaceous uplift within the eastern Otway Basin (ca 95 Ma). The Eumeralla Formation and Demons Bluff Group also host a NNW–SSE-orientated fracture set that is inferred to largely post-date mid-Cretaceous folding. Sinistral displacement of fold hinges within the Eumeralla Formation, combined with thrust faulting within Cenozoic sediments, is interpreted to have occurred during an episode of late Miocene to early Pliocene shortening. This paper provides new insights into the history of brittle deformation in the eastern Otway Basin.

Precambrian Research, Aug 1, 2023

<p>Continental transform faults transition to a new plate boundary type when strike... more <p>Continental transform faults transition to a new plate boundary type when strike-slip, transpression or transtension are no longer the most efficient way to accommodate plate motion. In some instances, rather than the transform fault ‘transforming’ plate motion directly to its connecting plate boundary, the continental transform fault can become ‘misaligned’ with its connecting plate boundary. Where a plate boundary misalignment occurs, plate motion that was localised on the transform fault can become distributed over a broad, intervening transition zone between the two major plate boundary faults. In this study we use scaled analogue models to investigate the development of fault networks in regions of localised and distributed simple shear and the transition between the two. We use digital image correlation (DIC) to analyse the surface deformation of the analogue model experiment and present results as incremental shear strain maps of the surface of the analogue models.  The results are compared to natural examples of plate boundary transition zones (e.g., Alpine Fault, New Zealand; North Anatolian Fault, Turkey; San Andreas Fault, USA).  In our previous analogue model experiments, regions of localised and distributed simple shear have been generated in an analogue shear box using a four-way stretchable fabric to adjust the basal boundary conditions. These experiments were limited by the elasticity of the stretchable material, which cannot deform infinitely. Here we will present preliminary results from a new shear box apparatus that uses carbon fibre rods to adjust the basal boundary conditions. This new apparatus has been designed to minimise the boundary effects caused by the limitations of the four-way stretchable fabric in our previous experiments.</p>

Ore Geology Reviews, Nov 1, 2017

Field observations and theoretical considerations suggest that dense magmatic sulphide liquids ar... more Field observations and theoretical considerations suggest that dense magmatic sulphide liquids are injected into and/or passively infiltrate surrounding wall rocks late in the emplacement history of intrusion-hosted magmatic ore systems. Using analogies with other engineering and mineral systems, we evaluate the structural and physical controls on the ingress of sulphide liquid into brittle host rocks. Gravity-driven infiltration of sulphide liquid out of the host igneous intrusion into country rock may be analogous to the behaviour of dense immiscible fluids in groundwater systems (Dense Non Aqueous Phase Liquids; DNAPL), which is controlled by the body force of the liquid itself. Downward penetration of sulphide liquid into micro-fractures may occur once a sufficient thickness of sulphide, known as the critical accumulation height, is reached in the overlying intrusion. Upward and lateral injection of sulphide liquid is a similar process to the behaviour of crustal hydrothermal fluids, where active deformation, fluid pressure and host-rock anisotropy play critical roles. Such physical controls must be considered and integrated with well-established petrogeochemical concepts in order to better understand the genesis of magmatic Ni-Cu-PGE sulphide deposits.

EGU General Assembly Conference Abstracts, Apr 1, 2017

AGU Fall Meeting Abstracts, Dec 1, 2004

Immense volumes of plutonic rocks exposed in magmatic arcs challenge our ability to understand fu... more Immense volumes of plutonic rocks exposed in magmatic arcs challenge our ability to understand fundamental interactions between deformation and magma emplacement at convergent margins. Although close temporal and spatial relationships between fault activity and emplacement of arc plutons have been inferred, the hypothesis that there is always a direct link between faults and plutons in magmatic arcs remains controversial. It

GSA 2020 Connects Online, 2020

Canadian Journal of Earth Sciences, Jul 1, 2006

The English River subprovince is one of two metasediment-dominated terranes in the western Superi... more The English River subprovince is one of two metasediment-dominated terranes in the western Superior Province. It has been interpreted as an accretionary complex, a foreland, or a fore-arc basin that developed and was subsequently deformed between the metavolcanic-rich Uchi subprovince and the orthogneiss- and metaplutonic-dominated Winnipeg River subprovince during a prolonged transpressive orogeny. To test these hypotheses, we combined a satellite image, aeromagnetic image, and Lithoprobe reflection seismic profile interpretation with detailed structural mapping to better characterize the internal geometry and significance of structural features in the western part of the subprovince in Ontario. Northward-directed subduction and collision of the Winnipeg River subprovince with the Uchi subprovince at ca. >2713–2698 Ma can account for the deposition of the sedimentary rocks, initial metamorphism, and the main phase of deformation in the subprovince, whereas the subduction of Wabigoon crust generated extensive tonalite magmatism in the Winnipeg River and English River subprovinces during the same period. A period of extension, after the docking of the Winnipeg River and Wabigoon subprovinces at ca. 2698 Ma, punctuated the compressive phases of the orogeny and was responsible for high-grade metamorphism, upward bending of the Moho, and localized deposition of late, coarse, alluvial–fluvial metasedimentary rocks. Renewed compression caused by the docking of the Wawa subprovince at ca. 2689–2684 Ma is likely responsible for a largely unrecognized regional upright folding and faulting event that controls the dominant structural geometry of the subprovince. Late in its tectonic evolution, strain was partitioned into dextral deformation that was strongly domainal and limited to the subprovince margins.

Tectonics, May 1, 2021

During rifting, pre‐existing penetrative basement fabrics can affect new faults in cover rocks by... more During rifting, pre‐existing penetrative basement fabrics can affect new faults in cover rocks by a mechanism that does not appear to involve reactivation. This subtle form of inheritance can significantly impact fault network architecture in rift basins above laterally variable basement domains with geomechanical anisotropies. Here we use multi‐layer, brittle‐ductile, crustal‐scale analogue experiments to study the influence of penetrative basement anisotropies on fault patterns in the overlying cover during a single phase of orthogonal rifting. The experiments were designed to test whether basement anisotropies, oriented 45° to the extension direction, can lead to the formation of rift faults that are oblique to both the imposed extension direction and basement anisotropies. Our experiments show that a penetrative, vertically layered, mm‐wide basement anisotropy creates extension‐oblique faults in the overlying cover. We interpret this to arise when local strike‐slip kinematics along the interfaces of mechanically contrasting materials in the basement combine with the regional imposed orthogonal extension, creating a transtensional regime. The width and spacing of alternating “strong” and “weak” basement zones interact with rift kinematics, impacting the orientation, kinematics and spacing of new faults in the cover. New insights on the influence of penetrative, pre‐existing basement fabrics on localized re‐orientation of 3D strain in the cover have implications for understanding complex fault systems in rift basins and transfer zones.

Geology, 1995

Volcanic and plutonic rocks of Archean greenstone belts in the Abitibi subprovince become younger... more Volcanic and plutonic rocks of Archean greenstone belts in the Abitibi subprovince become younger southward; plutonic rocks are ϳ10-30 m.y. younger than volcanic rocks. The Abitibi greenstone belt has an upper crust of ϳ2.75-2.70 Ga oceanic supracrustal assemblages and a middle crust of ϳ2.70-2.68 Ga granitic and gneissic rocks. The greenstone belt upper crust is greenschist facies with upright structures and low reflectivity, and the middle crust is amphibolite facies with moderate to shallowly dipping structures and strong reflectivity. We propose that the age progression and crustal layering resulted from accretion of oceanic assemblages followed by extensive mid-crustal magmatism linked to southward migration of an arc-trench system. Thermal softening of the middle crust during magmatism caused ductile flow now represented by strong, mid-crustal reflectivity. Upward heat flow following magmatism caused late-tectonic (2.67-2.65 Ga) low-pressure metamorphism observed in the upper crust.

EGU General Assembly Conference Abstracts, Apr 1, 2019

Geochemical perspectives letters, Apr 1, 2018

Precambrian banded iron formations record the composition of Earth's atmosphere and hydrosphere d... more Precambrian banded iron formations record the composition of Earth's atmosphere and hydrosphere during the global rise of oxygen. It has been suggested that the banded texture of these rocks points to fluctuations in ocean chemistry although this remains a subject of debate. Here we show, by petrographic and electron microscopy of Palaeoproterozoic banded iron formations from the Hamersley Province, NW Australia, that not all iron oxide microbands represent primary sedimentary layers. Some iron oxide laminae are derived from abundant hematite particles that were originally encapsulated in chert layers and subsequently liberated by removal of quartz during post-depositional deformation by dissolution-precipitation creep. The liberated hematite particles progressively accumulated in layer-parallel aggregates forming microbands, with new hematite crystals forming via non-classical crystallisation pathways during diagenesis and metamorphism. Therefore, microbands do not necessarily correspond to fluctuations in the depositional environment.

When numerical and analogue models are used to investigate the evolution of deformation processes... more When numerical and analogue models are used to investigate the evolution of deformation processes in crust and lithosphere, they face specific challenges related to, among others, large contrasts in material properties, the heterogeneous character of continental lithosphere, the presence of a free surface, the occurrence of large deformations including viscous flow and offset on shear zones, and the observation that

... Saint Blanquat, M.(de), Habert, G., Horsman, E ... Jean-Louis Paquette1, Michel de Saint Blan... more ... Saint Blanquat, M.(de), Habert, G., Horsman, E ... Jean-Louis Paquette1, Michel de Saint Blanquat2, Guillaume Delpech3, Eric Horsman4 and Sven Morgan5 1 CNRS UMR6524 and Université Blaise Pascal, Clermont-Ferrand, France-JL Paquette@ opgc. univ-bpclermont. ...

Journal of the Geological Society, 2009

Quick Search: All GSW Journals, GSW + GeoRef. advanced search. ...

Australian Journal of Earth Sciences, Jul 21, 2019

Abstract Folded reservoir rocks (Eumeralla Formation) within the Otway Basin are of significant e... more Abstract Folded reservoir rocks (Eumeralla Formation) within the Otway Basin are of significant exploration interest for their geothermal and tight gas reservoir potential. Brittle deformation within the Eumeralla Formation (ca 113–100 Ma), along the Otway coastline of Victoria, reflects a protracted history of extension, contraction, erosion and uplift, since Australian–Antarctic separation in the Early Cretaceous. This paper investigates the relative timing of heterogeneously distributed fracture populations within both folded and unfolded areas along the Otway coastline. Data collection occurred across two stratigraphic units spanning the Early Cretaceous (Eumeralla Formation) to the late Cenozoic (Demons Bluff Group), in order to measure fracture geometries and determine the relative timing of fracture formation. An unmanned aerial vehicle has been used to facilitate the systematic and inexpensive acquisition of high-resolution orthophotographs along coastal platforms, in order to complement traditional field mapping of fracture populations. A NE–SW-orientated fracture set is observed exclusively within the Eumeralla Formation (St George fold hinge), while a NW–SE-orientated fracture set pre-dates hinge-parallel fractures. Significant fracture formation has been linked to a period of mid-Cretaceous uplift within the eastern Otway Basin (ca 95 Ma). The Eumeralla Formation and Demons Bluff Group also host a NNW–SSE-orientated fracture set that is inferred to largely post-date mid-Cretaceous folding. Sinistral displacement of fold hinges within the Eumeralla Formation, combined with thrust faulting within Cenozoic sediments, is interpreted to have occurred during an episode of late Miocene to early Pliocene shortening. This paper provides new insights into the history of brittle deformation in the eastern Otway Basin.

Precambrian Research, Aug 1, 2023

<p>Continental transform faults transition to a new plate boundary type when strike... more <p>Continental transform faults transition to a new plate boundary type when strike-slip, transpression or transtension are no longer the most efficient way to accommodate plate motion. In some instances, rather than the transform fault ‘transforming’ plate motion directly to its connecting plate boundary, the continental transform fault can become ‘misaligned’ with its connecting plate boundary. Where a plate boundary misalignment occurs, plate motion that was localised on the transform fault can become distributed over a broad, intervening transition zone between the two major plate boundary faults. In this study we use scaled analogue models to investigate the development of fault networks in regions of localised and distributed simple shear and the transition between the two. We use digital image correlation (DIC) to analyse the surface deformation of the analogue model experiment and present results as incremental shear strain maps of the surface of the analogue models.  The results are compared to natural examples of plate boundary transition zones (e.g., Alpine Fault, New Zealand; North Anatolian Fault, Turkey; San Andreas Fault, USA).  In our previous analogue model experiments, regions of localised and distributed simple shear have been generated in an analogue shear box using a four-way stretchable fabric to adjust the basal boundary conditions. These experiments were limited by the elasticity of the stretchable material, which cannot deform infinitely. Here we will present preliminary results from a new shear box apparatus that uses carbon fibre rods to adjust the basal boundary conditions. This new apparatus has been designed to minimise the boundary effects caused by the limitations of the four-way stretchable fabric in our previous experiments.</p>

Ore Geology Reviews, Nov 1, 2017

Field observations and theoretical considerations suggest that dense magmatic sulphide liquids ar... more Field observations and theoretical considerations suggest that dense magmatic sulphide liquids are injected into and/or passively infiltrate surrounding wall rocks late in the emplacement history of intrusion-hosted magmatic ore systems. Using analogies with other engineering and mineral systems, we evaluate the structural and physical controls on the ingress of sulphide liquid into brittle host rocks. Gravity-driven infiltration of sulphide liquid out of the host igneous intrusion into country rock may be analogous to the behaviour of dense immiscible fluids in groundwater systems (Dense Non Aqueous Phase Liquids; DNAPL), which is controlled by the body force of the liquid itself. Downward penetration of sulphide liquid into micro-fractures may occur once a sufficient thickness of sulphide, known as the critical accumulation height, is reached in the overlying intrusion. Upward and lateral injection of sulphide liquid is a similar process to the behaviour of crustal hydrothermal fluids, where active deformation, fluid pressure and host-rock anisotropy play critical roles. Such physical controls must be considered and integrated with well-established petrogeochemical concepts in order to better understand the genesis of magmatic Ni-Cu-PGE sulphide deposits.