The Cerro Durazno, Brealito, and Cobres granitoid plutons belong to the eastern Ordovician magmat... more The Cerro Durazno, Brealito, and Cobres granitoid plutons belong to the eastern Ordovician magmatic belt of northwest Argentina and are associated with a network of NW-and N-striking ductile shear zones. A structural analysis of these plutons and their metamorphic host rocks was conducted to elucidate mid-to upper-crustal magmatism and tectonism at the western margin of Gondwana. Pluton emplacement took place at 480-455 Ma, toward the end of a ca. 75-Ma-long episode of regional deformation and high-temperature metamorphism. The Cerro Durazno and Brealito plutons were probably emplaced as NE-SW-striking, vertical magma sheets that coalesced into large magma bodies under overall E-W shortening that generated SW-dipping metamorphic foliations at a later stage of pluton formation. These fabrics were superimposed to the magmatic structures in the granite plutons and to the high-grade metamorphic structures of the host rocks. At the northern pluton margins, ductile high-strain zones, notably the Agua Rosada Shear Zone north of the Cerro Durazno pluton, further localized ascent of granitoid magma. Similarly, emplacement of the Brealito and Cobres plutons is genetically related to prominent shear zones. Geometry and metamorphic character of the shear zone network in the eastern Ordovician magmatic belt point to orogen-parallel extension and transverse shortening of the belt under variable metamorphic conditions. The width as well as protracted deformation, high-temperature metamorphism, anatexis, and granitoid magmatism of the magmatic belt are key characteristics of a hot, wide orogen that evolved during the lower Paleozoic at the western margin of Gondwana. Remarkable geotectonic similarities with respect to the modern Andes point to comparable plate-tectonic conditions at the lower Paleozoic and the Cenozoic convergent plate margins.
Introduction: Structural, petrological and geophysical work [1, 2, 3], as well as numerical model... more Introduction: Structural, petrological and geophysical work [1, 2, 3], as well as numerical modeling [4], have been conducted on the Vredefort impact structure to understand the mechanism of rock deformation during crater modification of large terrestrial impacts. In order to bridge the gap between geological ground truth and dynamic, numerical modeling, we aim to construct a 3D structural model of the impact structure followed by kinematic restoration of deformation that leads to formation and collapse of its central uplift. The Vredefort Dome is the eroded remnant of a collapsed central uplift of a Paleoproterozoic impact structure[1]. The central part of the Dome, approximately 40 km wide, consists of Archean (>3.0 Ga) granitoids and is surrounded by steeply dipping and overturned sedimentary and volcanic strata of Proterozoic (3.0-2.1 Ga) age, known as the collar around the crystalline core. To the north and west, the collar rocks are well exposed and form a series of concentric morphological quartzite ridges and valleys along less resitant shale horizons around the core, whereas to the east and the south, the central uplift is covered by the Phanerozoic Karoo Supergroup. Methods: Using the software GOCAD and Geo-Modeller (Intrepid Geophysics), we attempt to construct a 3D model of the collar rocks. The modell will include the attitude of prominent marker surfaces (sedimentary strata and lithological interfaces) as well as impact-induced discontinuities known from field analysis and geophysical imaging. Exposure of preimpact rocks is largely limited to the northwestern quadrant of the impact structure and will, thus, constrain the 3D model. The construction of a multisurface model from this portion of the collar will not only involve marker surfaces but also take into account the volume of lithological groups, e.g. the West Rand Group (Fig. 1), in between major lithological interfaces. As more structural information becomes available from the field and geophysical imaging, the model will consider also the geometry of major discontinuiuties and local deformation on lithological interfaces. Following construction of a 3D model, the data set will be imported into 3DMove (Midland Valley Inc.) to conduct further structural analyses and 3D kinematic restoration. The first step in this procedure will be to eliminate possible effects of post-impact deformation by restoring displacements on post-impact faults, and will result in the geometry of rocks attained upon the
The Southern Andes are regarded as a typical subduction orogen formed by oblique plate convergenc... more The Southern Andes are regarded as a typical subduction orogen formed by oblique plate convergence. However, there is considerable uncertainty as to how deformation is kinematically partitioned in the upper plate. Here we use analogue experiments conducted in the MultiBox (Multifunctional analogue Box) apparatus to investigate dextral transpression in the Southern Andes between 34 °S and 42 °S. We find that transpression in our models is caused mainly by two prominent fault sets; transpression zone-parallel dextral oblique-slip thrust faults and sinistral oblique-slip reverse faults. The latter of these sets may be equivalent to northwest-striking faults which were believed to be pre-Andean in origin. We also model variable crustal strength in our experiments and find that stronger crust north of 37 °S and weaker crust to the south best reproduces the observed GPS velocity field. We propose that transpression in the Southern Andes is accommodated by distributed deformation rather th...
CHICXULUB IMPACT BASIN? Clive R. Neal David Burney. David A Kring, Martin Schmieder, Sonia Tikoo,... more CHICXULUB IMPACT BASIN? Clive R. Neal David Burney. David A Kring, Martin Schmieder, Sonia Tikoo, Ulrich Peter Riller, Sarah L. Simpson, Gordon Osinski, Charles S Cockell, Marco Coolen, Sean P S Gulick, Joanna V Morgan and Expedition 364 Scientists, University of Notre Dame, Notre Dame IN, 46556; Center for Lunar Science and Exploration, Lunar and Planetary Institute, Houston, TX 77058; Universities Space Research Association Houston, Houston, TX, United States; Rutgers University, Piscataway, NJ, United States, Geologisch-Pal. Institut, Hamburg, Germany, University of Western Ontario, London, ON, Canada, University of Edinburgh, Edinburgh, EH9, United Kingdom, Curtin University, Perth, WA, Australia, The University of Texas at Austin, Department of Geological Sciences, Austin, TX, United States, Imperial College London, London, United Kingdom. [email protected]; [email protected].
Models of intra-arc deformation in the Southern Andean Volcanic Zone (SAVZ) between 42◦S and 47◦S... more Models of intra-arc deformation in the Southern Andean Volcanic Zone (SAVZ) between 42◦S and 47◦S commonly focus on the kinematics of the Liquiñe-Ofqui Fault Zone (LOFZ), which cuts the SAVZ along-strike for more than 1000 km. Northward displacement of the Chiloé Block, a detached fore-arc sliver to the west of the LOFZ, points to an overall dextral displacement on the LOFZ. In this tectonic framework, which is based on limited ground truth, the LOFZ is commonly regarded as the main, if not the only, discontinuity accommodating oblique plate convergence. Recent paleomagnetic and fault-kinematic studies, however, challenge this concept as they provide independent evidence for distributed deformation along a number of additional first-order faults resulting in heterogeneous vertical-axis rotation of upper crustal blocks. Following this concept, we highlight the complexity of deformation in the SAVZ and discuss the role of the LOFZ. Our conclusions are based on detailed lineament analy...
This contribution describes maps of the Copper Cliff Embayment (CCE) and Offset (CCO) dyke. The a... more This contribution describes maps of the Copper Cliff Embayment (CCE) and Offset (CCO) dyke. The associated study attempts to unravel the mode of melt emplacement and the role of pre-impact faults in the deformation of the southern part of the Sudbury Igneous Complex (SIC). This contribution summarizes field observations (maps and images) and structural measurements. In addition, perspective views of the 3D Move model of the CCE and CCO dyke are provided. This data can be used by researchers and exploration geologists working in the Sudbury mining camp as a basis for future mapping, research and exploration efforts in the Copper Cliff area. This article is a co-submission to the following article: L. Mathieu, U. Riller, L. Gibson, P. Lightfoot (2021) Structural controls on the localization of the mineralized Copper Cliff embayment and the Copper Cliff offset dyke, Sudbury Igneous Complex, Canada, Ore Geol. Rev., https://doi.org/10.1016/j.oregeorev.2021.104071
The timescale of the modification stage of basin-sized impact structures is not well understood. ... more The timescale of the modification stage of basin-sized impact structures is not well understood. Owing to ca. 10 km of erosion since its formation, the Vredefort impact structure, South Africa, is an ideal testing ground for deciphering post-impact modification. Here, we present geophysical and geochemical evidence from the Vredefort Granophyre Dikes, which were derived from the-now eroded-Vredefort impact melt sheet. The dikes have been studied mostly in terms of their composition, while the timing and duration of their emplacement remain controversial. We examined the modern depth extent of five dikes, with three from the inner crystalline core of the central uplift, and two from the boundary between the core and the supracrustal collar of the central uplift, using two-dimensional electrical resistivity tomography. We found that the core dikes terminate near the present erosion surface (i.e., <5 m depth). In contrast, the dikes at the core-collar boundary extend to a depth ≥ 9 m. These observations suggest that the core dikes are exposed near their lowermost terminus. In addition, we obtained bulk geochemical composition of the dikes, finding that the andesitic composition phase is present in the core-collar dikes that is not found in the core dikes. The presence of this phase indicates the episodic emplacement of impact melt into subvertical crater floor fractures. We conclude that the dike formation was protracted and occurred over a time span of at least 10 4 years. The sequential formation of the Vredefort Granophyre Dikes points to horizontal extension of crust below the impact melt sheet above a kinematic velocity discontinuity, a crustal instability resulting from the dynamic collapse of the transient cavity.
The synformal geometry of the 1.85 Ga Sudbury Igneous Complex (SIC), an impact melt sheet resulti... more The synformal geometry of the 1.85 Ga Sudbury Igneous Complex (SIC), an impact melt sheet resulting from largemagnitude meteorite impact, attests to post-impact deformation. However, in contrast to the overlying Onaping Formation, a heterolithic impact melt breccia, the SIC shows little evidence for pervasive ductile strain. This pertains in particular to its NE-lobe characterized by a curvature of about 100° in plain view. This curvature has been interpreted either as a fold or as a primary feature. In order to test these scenarios, a detailed structural analysis was conducted in the core of the NE-lobe, which consists of rocks of the Onaping Formation. Structural measurements and lithological observations made at a total of 700 stations collectively led to the construction of a detailed structural map of the Onaping Formation in the NE-lobe. The map displays a non-systematic fold pattern evident by individual units of the Onaping Formation, which from bottom to top are known as th...
CRATER: IMPLICATIONS FOR PEAK RING FORMATION. L. Xiao, J.W. Zhao, H.S. Liu, Z.Y. Xiao, J. Morgan,... more CRATER: IMPLICATIONS FOR PEAK RING FORMATION. L. Xiao, J.W. Zhao, H.S. Liu, Z.Y. Xiao, J. Morgan, S. Gulick, D. Kring, P. Claeys, U. Riller, and the Expedition 364 Scientists. Planetary Science Institute, China University of Geosciences, Wuhan, 430074, P. R. China, Space Science Institute, Macau University of Science and Technology, Avenida Wai Long, Taipa, Macau, China ([email protected]). 3 Department of Earth Science and Engineering, Imperial College London, SW7 2AZ, UK. Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, TX 78758-4445,USA. Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, USA, 6 Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium. Institut für Geologie, Universität Hamburg, Bundesstrasse 55, Hamburg, 20146, Germany.
Large impact structures with peak rings are common landforms across the solar system, and their f... more Large impact structures with peak rings are common landforms across the solar system, and their formation has implications for both the interior structure and thermal evolution of planetary bodies. Numerical modeling and structural studies have been used to simulate and ground truth peak-ring formative mechanisms, but the shock metamorphic record of minerals within these structures remains to be ascertained. We investigated impact-related microstructures and high-pressure phases in zircon from melt-bearing breccias, impact melt rock, and granitoid basement from the Chicxulub peak ring (Yucatán Peninsula, Mexico), sampled by the International Ocean Discovery Program (IODP)/International Continental Drilling Project (IODP-ICDP) Expedition 364 Hole M0077A. Zircon grains exhibit shock features such as reidite, zircon twins, and granular zircon including “former reidite in granular neoblastic” (FRIGN) zircon. These features record an initial high-pressure shock wave (>30 GPa), subsequ...
The Southern Andes are often viewed as a classic example for kinematic partitioning of oblique pl... more The Southern Andes are often viewed as a classic example for kinematic partitioning of oblique plate convergence into components of continental margin-parallel strike-slip and transverse shortening. In this regard, the Liquiñe-Ofqui Fault Zone, one of Earth’s most prominent intra-arc deformation zones, is believed to be the most important crustal discontinuity in the Southern Andes taking up margin-parallel dextral strike-slip. Recent structural studies, however, are at odds with this simple concept of kinematic partitioning, due to the presence of margin-oblique and a number of other margin-parallel intra-arc deformation zones. However, knowledge on the extent of such zones in the Southern Andes is still limited. Here, we document traces of prominent structural discontinuities (lineaments) from the Southern Andes between 39° S and 46° S. In combination with compiled low-temperature thermochronology data and interpolation of respective exhumation rates, we revisit the issue of kinem...
The Chicxulub impact event generated a long-duration hydrothermal system suitable for microbial l... more The Chicxulub impact event generated a long-duration hydrothermal system suitable for microbial life.
Porosity and its distribution in impact craters has an important effect on the petrophysical prop... more Porosity and its distribution in impact craters has an important effect on the petrophysical properties of impactites: seismic wave speeds and reflectivity, rock permeability, strength, and density. These properties are important for the identification of potential craters and the understanding of the process and consequences of cratering. The Chicxulub impact structure, recently drilled by the joint International Ocean Discovery Program and International Continental scientific Drilling Program Expedition 364, provides a unique opportunity to compare direct observations of impactites with geophysical observations and models. Here, we combine small‐scale petrographic and petrophysical measurements with larger‐scale geophysical measurements and numerical simulations of the Chicxulub impact structure. Our aim is to assess the cause of unusually high porosities within the Chicxulub peak ring and the capability of numerical impact simulations to predict the gravity signature and the dist...
The Cerro Durazno, Brealito, and Cobres granitoid plutons belong to the eastern Ordovician magmat... more The Cerro Durazno, Brealito, and Cobres granitoid plutons belong to the eastern Ordovician magmatic belt of northwest Argentina and are associated with a network of NW-and N-striking ductile shear zones. A structural analysis of these plutons and their metamorphic host rocks was conducted to elucidate mid-to upper-crustal magmatism and tectonism at the western margin of Gondwana. Pluton emplacement took place at 480-455 Ma, toward the end of a ca. 75-Ma-long episode of regional deformation and high-temperature metamorphism. The Cerro Durazno and Brealito plutons were probably emplaced as NE-SW-striking, vertical magma sheets that coalesced into large magma bodies under overall E-W shortening that generated SW-dipping metamorphic foliations at a later stage of pluton formation. These fabrics were superimposed to the magmatic structures in the granite plutons and to the high-grade metamorphic structures of the host rocks. At the northern pluton margins, ductile high-strain zones, notably the Agua Rosada Shear Zone north of the Cerro Durazno pluton, further localized ascent of granitoid magma. Similarly, emplacement of the Brealito and Cobres plutons is genetically related to prominent shear zones. Geometry and metamorphic character of the shear zone network in the eastern Ordovician magmatic belt point to orogen-parallel extension and transverse shortening of the belt under variable metamorphic conditions. The width as well as protracted deformation, high-temperature metamorphism, anatexis, and granitoid magmatism of the magmatic belt are key characteristics of a hot, wide orogen that evolved during the lower Paleozoic at the western margin of Gondwana. Remarkable geotectonic similarities with respect to the modern Andes point to comparable plate-tectonic conditions at the lower Paleozoic and the Cenozoic convergent plate margins.
Introduction: Structural, petrological and geophysical work [1, 2, 3], as well as numerical model... more Introduction: Structural, petrological and geophysical work [1, 2, 3], as well as numerical modeling [4], have been conducted on the Vredefort impact structure to understand the mechanism of rock deformation during crater modification of large terrestrial impacts. In order to bridge the gap between geological ground truth and dynamic, numerical modeling, we aim to construct a 3D structural model of the impact structure followed by kinematic restoration of deformation that leads to formation and collapse of its central uplift. The Vredefort Dome is the eroded remnant of a collapsed central uplift of a Paleoproterozoic impact structure[1]. The central part of the Dome, approximately 40 km wide, consists of Archean (>3.0 Ga) granitoids and is surrounded by steeply dipping and overturned sedimentary and volcanic strata of Proterozoic (3.0-2.1 Ga) age, known as the collar around the crystalline core. To the north and west, the collar rocks are well exposed and form a series of concentric morphological quartzite ridges and valleys along less resitant shale horizons around the core, whereas to the east and the south, the central uplift is covered by the Phanerozoic Karoo Supergroup. Methods: Using the software GOCAD and Geo-Modeller (Intrepid Geophysics), we attempt to construct a 3D model of the collar rocks. The modell will include the attitude of prominent marker surfaces (sedimentary strata and lithological interfaces) as well as impact-induced discontinuities known from field analysis and geophysical imaging. Exposure of preimpact rocks is largely limited to the northwestern quadrant of the impact structure and will, thus, constrain the 3D model. The construction of a multisurface model from this portion of the collar will not only involve marker surfaces but also take into account the volume of lithological groups, e.g. the West Rand Group (Fig. 1), in between major lithological interfaces. As more structural information becomes available from the field and geophysical imaging, the model will consider also the geometry of major discontinuiuties and local deformation on lithological interfaces. Following construction of a 3D model, the data set will be imported into 3DMove (Midland Valley Inc.) to conduct further structural analyses and 3D kinematic restoration. The first step in this procedure will be to eliminate possible effects of post-impact deformation by restoring displacements on post-impact faults, and will result in the geometry of rocks attained upon the
The Southern Andes are regarded as a typical subduction orogen formed by oblique plate convergenc... more The Southern Andes are regarded as a typical subduction orogen formed by oblique plate convergence. However, there is considerable uncertainty as to how deformation is kinematically partitioned in the upper plate. Here we use analogue experiments conducted in the MultiBox (Multifunctional analogue Box) apparatus to investigate dextral transpression in the Southern Andes between 34 °S and 42 °S. We find that transpression in our models is caused mainly by two prominent fault sets; transpression zone-parallel dextral oblique-slip thrust faults and sinistral oblique-slip reverse faults. The latter of these sets may be equivalent to northwest-striking faults which were believed to be pre-Andean in origin. We also model variable crustal strength in our experiments and find that stronger crust north of 37 °S and weaker crust to the south best reproduces the observed GPS velocity field. We propose that transpression in the Southern Andes is accommodated by distributed deformation rather th...
CHICXULUB IMPACT BASIN? Clive R. Neal David Burney. David A Kring, Martin Schmieder, Sonia Tikoo,... more CHICXULUB IMPACT BASIN? Clive R. Neal David Burney. David A Kring, Martin Schmieder, Sonia Tikoo, Ulrich Peter Riller, Sarah L. Simpson, Gordon Osinski, Charles S Cockell, Marco Coolen, Sean P S Gulick, Joanna V Morgan and Expedition 364 Scientists, University of Notre Dame, Notre Dame IN, 46556; Center for Lunar Science and Exploration, Lunar and Planetary Institute, Houston, TX 77058; Universities Space Research Association Houston, Houston, TX, United States; Rutgers University, Piscataway, NJ, United States, Geologisch-Pal. Institut, Hamburg, Germany, University of Western Ontario, London, ON, Canada, University of Edinburgh, Edinburgh, EH9, United Kingdom, Curtin University, Perth, WA, Australia, The University of Texas at Austin, Department of Geological Sciences, Austin, TX, United States, Imperial College London, London, United Kingdom. [email protected]; [email protected].
Models of intra-arc deformation in the Southern Andean Volcanic Zone (SAVZ) between 42◦S and 47◦S... more Models of intra-arc deformation in the Southern Andean Volcanic Zone (SAVZ) between 42◦S and 47◦S commonly focus on the kinematics of the Liquiñe-Ofqui Fault Zone (LOFZ), which cuts the SAVZ along-strike for more than 1000 km. Northward displacement of the Chiloé Block, a detached fore-arc sliver to the west of the LOFZ, points to an overall dextral displacement on the LOFZ. In this tectonic framework, which is based on limited ground truth, the LOFZ is commonly regarded as the main, if not the only, discontinuity accommodating oblique plate convergence. Recent paleomagnetic and fault-kinematic studies, however, challenge this concept as they provide independent evidence for distributed deformation along a number of additional first-order faults resulting in heterogeneous vertical-axis rotation of upper crustal blocks. Following this concept, we highlight the complexity of deformation in the SAVZ and discuss the role of the LOFZ. Our conclusions are based on detailed lineament analy...
This contribution describes maps of the Copper Cliff Embayment (CCE) and Offset (CCO) dyke. The a... more This contribution describes maps of the Copper Cliff Embayment (CCE) and Offset (CCO) dyke. The associated study attempts to unravel the mode of melt emplacement and the role of pre-impact faults in the deformation of the southern part of the Sudbury Igneous Complex (SIC). This contribution summarizes field observations (maps and images) and structural measurements. In addition, perspective views of the 3D Move model of the CCE and CCO dyke are provided. This data can be used by researchers and exploration geologists working in the Sudbury mining camp as a basis for future mapping, research and exploration efforts in the Copper Cliff area. This article is a co-submission to the following article: L. Mathieu, U. Riller, L. Gibson, P. Lightfoot (2021) Structural controls on the localization of the mineralized Copper Cliff embayment and the Copper Cliff offset dyke, Sudbury Igneous Complex, Canada, Ore Geol. Rev., https://doi.org/10.1016/j.oregeorev.2021.104071
The timescale of the modification stage of basin-sized impact structures is not well understood. ... more The timescale of the modification stage of basin-sized impact structures is not well understood. Owing to ca. 10 km of erosion since its formation, the Vredefort impact structure, South Africa, is an ideal testing ground for deciphering post-impact modification. Here, we present geophysical and geochemical evidence from the Vredefort Granophyre Dikes, which were derived from the-now eroded-Vredefort impact melt sheet. The dikes have been studied mostly in terms of their composition, while the timing and duration of their emplacement remain controversial. We examined the modern depth extent of five dikes, with three from the inner crystalline core of the central uplift, and two from the boundary between the core and the supracrustal collar of the central uplift, using two-dimensional electrical resistivity tomography. We found that the core dikes terminate near the present erosion surface (i.e., <5 m depth). In contrast, the dikes at the core-collar boundary extend to a depth ≥ 9 m. These observations suggest that the core dikes are exposed near their lowermost terminus. In addition, we obtained bulk geochemical composition of the dikes, finding that the andesitic composition phase is present in the core-collar dikes that is not found in the core dikes. The presence of this phase indicates the episodic emplacement of impact melt into subvertical crater floor fractures. We conclude that the dike formation was protracted and occurred over a time span of at least 10 4 years. The sequential formation of the Vredefort Granophyre Dikes points to horizontal extension of crust below the impact melt sheet above a kinematic velocity discontinuity, a crustal instability resulting from the dynamic collapse of the transient cavity.
The synformal geometry of the 1.85 Ga Sudbury Igneous Complex (SIC), an impact melt sheet resulti... more The synformal geometry of the 1.85 Ga Sudbury Igneous Complex (SIC), an impact melt sheet resulting from largemagnitude meteorite impact, attests to post-impact deformation. However, in contrast to the overlying Onaping Formation, a heterolithic impact melt breccia, the SIC shows little evidence for pervasive ductile strain. This pertains in particular to its NE-lobe characterized by a curvature of about 100° in plain view. This curvature has been interpreted either as a fold or as a primary feature. In order to test these scenarios, a detailed structural analysis was conducted in the core of the NE-lobe, which consists of rocks of the Onaping Formation. Structural measurements and lithological observations made at a total of 700 stations collectively led to the construction of a detailed structural map of the Onaping Formation in the NE-lobe. The map displays a non-systematic fold pattern evident by individual units of the Onaping Formation, which from bottom to top are known as th...
CRATER: IMPLICATIONS FOR PEAK RING FORMATION. L. Xiao, J.W. Zhao, H.S. Liu, Z.Y. Xiao, J. Morgan,... more CRATER: IMPLICATIONS FOR PEAK RING FORMATION. L. Xiao, J.W. Zhao, H.S. Liu, Z.Y. Xiao, J. Morgan, S. Gulick, D. Kring, P. Claeys, U. Riller, and the Expedition 364 Scientists. Planetary Science Institute, China University of Geosciences, Wuhan, 430074, P. R. China, Space Science Institute, Macau University of Science and Technology, Avenida Wai Long, Taipa, Macau, China ([email protected]). 3 Department of Earth Science and Engineering, Imperial College London, SW7 2AZ, UK. Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, TX 78758-4445,USA. Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, TX 77058, USA, 6 Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium. Institut für Geologie, Universität Hamburg, Bundesstrasse 55, Hamburg, 20146, Germany.
Large impact structures with peak rings are common landforms across the solar system, and their f... more Large impact structures with peak rings are common landforms across the solar system, and their formation has implications for both the interior structure and thermal evolution of planetary bodies. Numerical modeling and structural studies have been used to simulate and ground truth peak-ring formative mechanisms, but the shock metamorphic record of minerals within these structures remains to be ascertained. We investigated impact-related microstructures and high-pressure phases in zircon from melt-bearing breccias, impact melt rock, and granitoid basement from the Chicxulub peak ring (Yucatán Peninsula, Mexico), sampled by the International Ocean Discovery Program (IODP)/International Continental Drilling Project (IODP-ICDP) Expedition 364 Hole M0077A. Zircon grains exhibit shock features such as reidite, zircon twins, and granular zircon including “former reidite in granular neoblastic” (FRIGN) zircon. These features record an initial high-pressure shock wave (>30 GPa), subsequ...
The Southern Andes are often viewed as a classic example for kinematic partitioning of oblique pl... more The Southern Andes are often viewed as a classic example for kinematic partitioning of oblique plate convergence into components of continental margin-parallel strike-slip and transverse shortening. In this regard, the Liquiñe-Ofqui Fault Zone, one of Earth’s most prominent intra-arc deformation zones, is believed to be the most important crustal discontinuity in the Southern Andes taking up margin-parallel dextral strike-slip. Recent structural studies, however, are at odds with this simple concept of kinematic partitioning, due to the presence of margin-oblique and a number of other margin-parallel intra-arc deformation zones. However, knowledge on the extent of such zones in the Southern Andes is still limited. Here, we document traces of prominent structural discontinuities (lineaments) from the Southern Andes between 39° S and 46° S. In combination with compiled low-temperature thermochronology data and interpolation of respective exhumation rates, we revisit the issue of kinem...
The Chicxulub impact event generated a long-duration hydrothermal system suitable for microbial l... more The Chicxulub impact event generated a long-duration hydrothermal system suitable for microbial life.
Porosity and its distribution in impact craters has an important effect on the petrophysical prop... more Porosity and its distribution in impact craters has an important effect on the petrophysical properties of impactites: seismic wave speeds and reflectivity, rock permeability, strength, and density. These properties are important for the identification of potential craters and the understanding of the process and consequences of cratering. The Chicxulub impact structure, recently drilled by the joint International Ocean Discovery Program and International Continental scientific Drilling Program Expedition 364, provides a unique opportunity to compare direct observations of impactites with geophysical observations and models. Here, we combine small‐scale petrographic and petrophysical measurements with larger‐scale geophysical measurements and numerical simulations of the Chicxulub impact structure. Our aim is to assess the cause of unusually high porosities within the Chicxulub peak ring and the capability of numerical impact simulations to predict the gravity signature and the dist...
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Papers by Ulrich Riller