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Eileen M. Mcgowan - One of the best experts on this subject based on the ideXlab platform.
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spatial distribution of putative water related features in southern acidalia cydonia mensae mars
Icarus, 2009Co-Authors: Eileen M. McgowanAbstract:Abstract Many putative water-related features exist in the northern lowlands of Mars. These features may provide clues to the abundance and timing of water or ice that existed there in the past. The Cydonia Mensae and Southern Acidalia area was chosen as the Study area owing to the abundance of two of these features: giant polygons and pitted cones. In addition a section of the Deuteronilus shoreline is located there. The abundance and close proximity of the features makes this area an excellent Place to Study the spatial relationships between these landforms, as well as the morphological characteristics of pitted cones. The features were mapped into a GIS for spatial analyses. The highest densities of pitted cones and giant polygons are adjacent but distinctly separated by a knobby ridge that is surrounded by the Deuteronilus putative shoreline. Pitted cones were measured and examined to determine if a classification by morphology is possible, but the results were inconclusive. Statistical tests on pit-to-cone diameter ratios and tests of surface temperatures of cone material suggest, but do not verify, a single cone origin. The various shapes, sizes, and putative ages of pitted cones may be attributed to temporal variation in emPlacement and spatial variation in material properties. Among the possible scenarios put forth for pitted cone genesis on Mars two are likely candidates in Cydonia Mensae: (1) the sublimation of a cold-based glacier, and (2) a buried lens of methane and/or CO2 clathrates.
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Spatial distribution of putative water related features in Southern Acidalia/Cydonia Mensae, Mars
Icarus, 2009Co-Authors: Eileen M. McgowanAbstract:Abstract Many putative water-related features exist in the northern lowlands of Mars. These features may provide clues to the abundance and timing of water or ice that existed there in the past. The Cydonia Mensae and Southern Acidalia area was chosen as the Study area owing to the abundance of two of these features: giant polygons and pitted cones. In addition a section of the Deuteronilus shoreline is located there. The abundance and close proximity of the features makes this area an excellent Place to Study the spatial relationships between these landforms, as well as the morphological characteristics of pitted cones. The features were mapped into a GIS for spatial analyses. The highest densities of pitted cones and giant polygons are adjacent but distinctly separated by a knobby ridge that is surrounded by the Deuteronilus putative shoreline. Pitted cones were measured and examined to determine if a classification by morphology is possible, but the results were inconclusive. Statistical tests on pit-to-cone diameter ratios and tests of surface temperatures of cone material suggest, but do not verify, a single cone origin. The various shapes, sizes, and putative ages of pitted cones may be attributed to temporal variation in emPlacement and spatial variation in material properties. Among the possible scenarios put forth for pitted cone genesis on Mars two are likely candidates in Cydonia Mensae: (1) the sublimation of a cold-based glacier, and (2) a buried lens of methane and/or CO2 clathrates.
Baptiste Debret - One of the best experts on this subject based on the ideXlab platform.
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Redox state of iron during high-pressure serpentinite dehydration
Contributions to Mineralogy and Petrology, 2015Co-Authors: Baptiste Debret, Fatima Martin-hernandez, Vicente Lopez Sanchez-vizcaino, M. T. Gómez-pugnaire, Nathalie Bolfan-casanova, Manuel Muñoz, José Alberto Padrón-navarta, C J Garrido, Muriel Andreani, Nicolas TrceraAbstract:The Cerro del Almirez massif (Spain) represents a unique fragment of serpentinized oceanic lithosphere that has been first equilibrated in the antigorite stability field (Atg-serpentinites) and then dehydrated into chlorite–olivine–orthopyroxene (Chl-harzburgites) at eclogite facies conditions during subduction. The massif preserves a dehydration front between Atg-serpentinites and Chl-harzburgites. It constitutes a suitable Place to Study redox changes in serpentinites and the nature of the released fluids during their dehydration. Relative to abyssal serpentinites, Atg-serpentinites display a low Fe3+/Fetotal(BR) (=0.55) and magnetite modal content (=2.8–4.3 wt%). Micro-X-ray absorption near-edge structure (μ-XANES) spectroscopy measurements of serpentines at the Fe–K edge show that antigorite has a lower Fe3+/Fetotal ratio (=0.48) than oceanic lizardite/chrysotile assemblages. The onset of Atg-serpentinites dehydration is marked by the crystallization of a Fe3+-rich antigorite (Fe3+/Fetotal = 0.6–0.75) in equilibrium with secondary olivine and by a decrease in magnetite amount (=1.6–2.2 wt%). This suggests a preferential partitioning of Fe3+ into serpentine rather than into olivine. The Atg-breakdown is marked by a decrease in Fe3+/Fetotal(BR) (=0.34–0.41), the crystallization of Fe2+-rich phases and the quasi-disappearance of magnetite (=0.6–1.4 wt.%). The observation of Fe3+-rich hematite and ilmenite intergrowths suggests that the O2 released by the crystallization of Fe2+-rich phases could promote hematite crystallization and a subsequent increase in fo2 inside the portion of the subducted mantle. Serpentinite dehydration could thus produce highly oxidized fluids in subduction zones and contribute to the oxidization of the sub-arc mantle wedge.
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trace element behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms Study of the lanzo ultramafic massif western alps
Chemical Geology, 2013Co-Authors: Baptiste Debret, Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain LafayAbstract:Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) elements that participate to elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable Place to Study trace element behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took Place in a relatively closed system without significant trace element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these elements are removed from slab to mantle wedge during subduction.
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Trace element behavior during serpentinization/de-serpentinization of an eclogitized oceanic lithosphere: A LA-ICPMS Study of the Lanzo ultramafic massif (Western Alps)
Chemical Geology, 2013Co-Authors: Baptiste Debret, Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain LafayAbstract:Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) elements that participate to elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable Place to Study trace element behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took Place in a relatively closed system without significant trace element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, < 20% serpentinization) to the paleo-Moho, composed of massive serpentinites (MS, 80% serpentinization), the trace elements mobility is reduced. The chemical composition of lizardite and antigorite is homogenized with the local degree of serpentinization: in SSP, serpentine veins composition is inherited from the host mineral while, in MS, their composition is homogenous between destabilized phases at the scale of the outcrop (~ 5 m). In the shallowest part of the oceanic lithosphere, from the paleo-Moho to the oceanic paleo-seafloor, the serpentinites are foliated (FS, > 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these elements are removed from slab to mantle wedge during subduction.
Jean-marc Daniel - One of the best experts on this subject based on the ideXlab platform.
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Structural and microstructural evolution of the Rattlesnake Mountain Anticline (Wyoming, USA): new insights into the Sevier and Laramide orogenic stress build-up in the Bighorn Basin
Tectonophysics, 2012Co-Authors: Nicolas Beaudoin, Rémi Leprêtre, Nicolas Bellahsen, Olivier Lacombe, Khalid Amrouch, Jean-paul Callot, Laurent Emmanuel, Jean-marc DanielAbstract:The Rocky Mountains in western US provide among the best examples of thick-skinned tectonics: following a period of thin-skinned tectonics related to the Sevier orogeny, the compressional reactivation of basement faults gave birth to the so-called Laramide uplifts/arches. The Bighorn basin, located in Wyoming, is therefore a key Place to Study the transition from thin- to thick-skinned tectonics in orogenic forelands, especially in terms of microstructural and stress/strain evolution. Our Study focuses on a classic Laramide structure: the Rattlesnake Mountain Anticline (RMA, Wyoming, USA), a basement-cored anticline located in the western part of the Bighorn basin. Stress and strain evolution analysis in folded sedimentary layers and underlying faulted basement rocks were performed on the basis of combined analyses of fractures, fault-slip data and calcite twinning paleopiezometry. Most of the fractures are related to three main tectonic events: the Sevier thin-skinned contraction, the Laramide thick-skinned contraction, and the Basin and Range extension. Serial balanced cross-sections of RMA and disPlacement profiles suggest that all thrust faults were coeval, evidencing strain distribution in the basement during faulting. The comparison of RMA with another structure located in the eastern edge of the Bighorn basin, i.e. the Sheep Mountain Anticline (SMA), allows to propose a conceptual model for the geometric and kinematic evolution of Laramide-related basement-cored anticlines. Finally, the stress evolution is reconstructed at both the fold scale and the basin scale. We show that the evolution of stress trends and magnitudes was quite similar in both structures (RMA and SMA) during Laramide times (thick-skinned tectonics), in spite of different stress regimes. During Sevier (thin-skinned tectonics) and post-Laramide times, stress trends and fracture patterns were different in these two structures. These results suggest that the distance to the orogenic front influenced the fracture patterns but not the foreland stress magnitudes, which were likely controlled by the structural style.
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Structural and microstructural evolution of the Rattlesnake Mountain Anticline (Wyoming, USA): New insights into the Sevier and Laramide orogenic stress build-up in the Bighorn Basin
Tectonophysics, 2012Co-Authors: Nicolas Beaudoin, Rémi Leprêtre, Nicolas Bellahsen, Olivier Lacombe, Khalid Amrouch, Jean-paul Callot, Laurent Emmanuel, Jean-marc DanielAbstract:The Rocky Mountains in western US provide among the best examples of thick-skinned tectonics: following a period of thin-skinned tectonics related to the Sevier orogeny, the compressional reactivation of basement faults gave birth to the so-called Laramide uplifts/arches. The Bighorn basin, located in Wyoming, is therefore a key Place to Study the transition from thin- to thick-skinned tectonics in orogenic forelands, especially in terms of microstructural and stress/strain evolution. Our Study focuses on a classic Laramide structure: the Rattlesnake Mountain Anticline (RMA, Wyoming, USA), a basement-cored anticline located in the western part of the Bighorn basin. Stress and strain evolution analysis in folded sedimentary layers and underlying faulted basement rocks were performed on the basis of combined analyses of fractures, fault-slip data and calcite twinning paleopiezometry. Most of the fractures are related to three main tectonic events: the Sevier thin-skinned contraction, the Laramide thick-skinned contraction, and the Basin and Range extension. Serial balanced cross-sections of RMA and disPlacement profiles suggest that all thrust faults were coeval, evidencing strain distribution in the basement during faulting. The comparison of RMA with another structure located in the eastern edge of the Bighorn basin, i.e. the Sheep Mountain Anticline (SMA), allows to propose a conceptual model for the geometric and kinematic evolution of Laramide-related basement-cored anticlines. Finally, the stress evolution is reconstructed at both the fold scale and the basin scale. We show that the evolution of stress trends and magnitudes was quite similar in both structures (RMA and SMA) during Laramide times (thick-skinned tectonics), in spite of different stress regimes. During Sevier (thin-skinned tectonics) and post-Laramide times, stress trends and fracture patterns were different in these two structures. These results suggest that the distance to the orogenic front influenced the fracture patterns but not the foreland stress magnitudes, which were likely controlled by the structural style. © 2012 Elsevier B.V.
Romain Lafay - One of the best experts on this subject based on the ideXlab platform.
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trace element behavior during serpentinization de serpentinization of an eclogitized oceanic lithosphere a la icpms Study of the lanzo ultramafic massif western alps
Chemical Geology, 2013Co-Authors: Baptiste Debret, Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain LafayAbstract:Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) elements that participate to elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable Place to Study trace element behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took Place in a relatively closed system without significant trace element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these elements are removed from slab to mantle wedge during subduction.
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Trace element behavior during serpentinization/de-serpentinization of an eclogitized oceanic lithosphere: A LA-ICPMS Study of the Lanzo ultramafic massif (Western Alps)
Chemical Geology, 2013Co-Authors: Baptiste Debret, Muriel Andreani, Marguerite Godard, Christian Nicollet, Stephane Schwartz, Romain LafayAbstract:Serpentinites are one of the major components of the oceanic lithosphere and are stable in the slab and the mantle wedge up to 100-150 km depth in subduction zones. During oceanic mantle hydration and alteration, they trap trace and fluid mobile (FME: B, Li, As, Sb, Rb, Ba, Cs, Sr, U and Pb) elements that participate to elemental transfer occurring between the dehydrating slab and the mantle wedge in subduction context. The Lanzo massif is an eclogitized oceanic lithosphere that preserved its oceanic structure and recorded different steps of serpentinization/de-serpentinization from oceanic lizardite to prograde antigorite in subduction context, up to its dehydration and secondary olivine crystallization, and finally retrograde antigorite during massif exhumation. It constitutes a suitable Place to Study trace element behavior during serpentinization/de-serpentinization processes and associated chemical transfers between the different envelopes of the oceanic lithosphere and the mantle wedge. Geochemical analyses of serpentine and associated minerals show that the serpentinization/de-serpentinization of the Lanzo massif took Place in a relatively closed system without significant trace element transfer between the different parts of the oceanic lithosphere. In the deeper part of the lithosphere, from the slightly serpentinized mantle peridotites (SSP, < 20% serpentinization) to the paleo-Moho, composed of massive serpentinites (MS, 80% serpentinization), the trace elements mobility is reduced. The chemical composition of lizardite and antigorite is homogenized with the local degree of serpentinization: in SSP, serpentine veins composition is inherited from the host mineral while, in MS, their composition is homogenous between destabilized phases at the scale of the outcrop (~ 5 m). In the shallowest part of the oceanic lithosphere, from the paleo-Moho to the oceanic paleo-seafloor, the serpentinites are foliated (FS, > 90% serpentinization). In that zone, the alpine deformation enhances the mobility of trace elements and permits their redistribution and the homogenization of antigorite composition at massif scale. Locally, in the SSP and MS, the crystallization of metamorphic veins of ~ 1-2 m corresponds to channelized fluid flows that allowed fluid transfers - and thereby trace elements - to longer distance. The successive crystallizations of antigorite and then olivine are accompanied by a diminution of some FME (B, Li, As, Sb, Ba, Rb) and Eu contents attesting that these elements are removed from slab to mantle wedge during subduction.
Nicolas Beaudoin - One of the best experts on this subject based on the ideXlab platform.
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Structural and microstructural evolution of the Rattlesnake Mountain Anticline (Wyoming, USA): new insights into the Sevier and Laramide orogenic stress build-up in the Bighorn Basin
Tectonophysics, 2012Co-Authors: Nicolas Beaudoin, Rémi Leprêtre, Nicolas Bellahsen, Olivier Lacombe, Khalid Amrouch, Jean-paul Callot, Laurent Emmanuel, Jean-marc DanielAbstract:The Rocky Mountains in western US provide among the best examples of thick-skinned tectonics: following a period of thin-skinned tectonics related to the Sevier orogeny, the compressional reactivation of basement faults gave birth to the so-called Laramide uplifts/arches. The Bighorn basin, located in Wyoming, is therefore a key Place to Study the transition from thin- to thick-skinned tectonics in orogenic forelands, especially in terms of microstructural and stress/strain evolution. Our Study focuses on a classic Laramide structure: the Rattlesnake Mountain Anticline (RMA, Wyoming, USA), a basement-cored anticline located in the western part of the Bighorn basin. Stress and strain evolution analysis in folded sedimentary layers and underlying faulted basement rocks were performed on the basis of combined analyses of fractures, fault-slip data and calcite twinning paleopiezometry. Most of the fractures are related to three main tectonic events: the Sevier thin-skinned contraction, the Laramide thick-skinned contraction, and the Basin and Range extension. Serial balanced cross-sections of RMA and disPlacement profiles suggest that all thrust faults were coeval, evidencing strain distribution in the basement during faulting. The comparison of RMA with another structure located in the eastern edge of the Bighorn basin, i.e. the Sheep Mountain Anticline (SMA), allows to propose a conceptual model for the geometric and kinematic evolution of Laramide-related basement-cored anticlines. Finally, the stress evolution is reconstructed at both the fold scale and the basin scale. We show that the evolution of stress trends and magnitudes was quite similar in both structures (RMA and SMA) during Laramide times (thick-skinned tectonics), in spite of different stress regimes. During Sevier (thin-skinned tectonics) and post-Laramide times, stress trends and fracture patterns were different in these two structures. These results suggest that the distance to the orogenic front influenced the fracture patterns but not the foreland stress magnitudes, which were likely controlled by the structural style.
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Structural and microstructural evolution of the Rattlesnake Mountain Anticline (Wyoming, USA): New insights into the Sevier and Laramide orogenic stress build-up in the Bighorn Basin
Tectonophysics, 2012Co-Authors: Nicolas Beaudoin, Rémi Leprêtre, Nicolas Bellahsen, Olivier Lacombe, Khalid Amrouch, Jean-paul Callot, Laurent Emmanuel, Jean-marc DanielAbstract:The Rocky Mountains in western US provide among the best examples of thick-skinned tectonics: following a period of thin-skinned tectonics related to the Sevier orogeny, the compressional reactivation of basement faults gave birth to the so-called Laramide uplifts/arches. The Bighorn basin, located in Wyoming, is therefore a key Place to Study the transition from thin- to thick-skinned tectonics in orogenic forelands, especially in terms of microstructural and stress/strain evolution. Our Study focuses on a classic Laramide structure: the Rattlesnake Mountain Anticline (RMA, Wyoming, USA), a basement-cored anticline located in the western part of the Bighorn basin. Stress and strain evolution analysis in folded sedimentary layers and underlying faulted basement rocks were performed on the basis of combined analyses of fractures, fault-slip data and calcite twinning paleopiezometry. Most of the fractures are related to three main tectonic events: the Sevier thin-skinned contraction, the Laramide thick-skinned contraction, and the Basin and Range extension. Serial balanced cross-sections of RMA and disPlacement profiles suggest that all thrust faults were coeval, evidencing strain distribution in the basement during faulting. The comparison of RMA with another structure located in the eastern edge of the Bighorn basin, i.e. the Sheep Mountain Anticline (SMA), allows to propose a conceptual model for the geometric and kinematic evolution of Laramide-related basement-cored anticlines. Finally, the stress evolution is reconstructed at both the fold scale and the basin scale. We show that the evolution of stress trends and magnitudes was quite similar in both structures (RMA and SMA) during Laramide times (thick-skinned tectonics), in spite of different stress regimes. During Sevier (thin-skinned tectonics) and post-Laramide times, stress trends and fracture patterns were different in these two structures. These results suggest that the distance to the orogenic front influenced the fracture patterns but not the foreland stress magnitudes, which were likely controlled by the structural style. © 2012 Elsevier B.V.