The Cenozoic Alpine, and Paleozoic Variscan and eo-Variscan collisional belts are compared in the framework of the Wilson cycle considering differences between cold and hot orogens. The W. Alps result of the opening and closure of the Liguro-Piemonte ocean, whereas the Paleozoic Eo-variscan and Variscan orogenies document multiple ocean openings and collisions in space and a polyorogenic history in time. Jurassic or Early Ordovician break-up of Pangea or Pannotia megacontinents led to the formation of passive continental margins, and the opening of Liguro-Piemonte, or Rheic, Tepla-Le Conquet, and Medio-European oceans, respectively. In Paleozoic or Mesozoic, microcontinents such as Apulia and Sesia or Armorica and Saxo-Thuringia were individualized. The oceanic convergence stage was associated with the development of arcs and back-arc basins in the Variscan belt but magmatic arcs are missing in the W. Alps, and inferred in the Eo-variscan one. Though the nappe stack is mainly developed in the subducted European or Gondwana crust in the western Alps and Eo-variscan cases, the Moldanubian nappes formed in the upper plate in the Variscan case. The Alpine and Variscan metamorphic evolutions occurred under ca. 8 °C/km and 30 °C/km gradients, respectively. During the late- to post-orogenic stages, all belts experienced “unthickening” accommodated by extensional tectonics, metamorphic retrogression, and intramontane basin opening. The importance of crustal melting, represented by migmatites, granites, and hydrothermal circulations in the Variscan and Eo-Variscan belts is the major difference with the W. Alpine one. The presence, or absence, of a previous Variscan or Cadomian continental basement might have also influenced the rheological behavior of the crust.
{"title":"Alpine, Variscan, eo-Variscan belts: comparison between hot and cold orogens from the examples of French segments","authors":"Michel Faure","doi":"10.5802/crgeos.215","DOIUrl":"https://doi.org/10.5802/crgeos.215","url":null,"abstract":"The Cenozoic Alpine, and Paleozoic Variscan and eo-Variscan collisional belts are compared in the framework of the Wilson cycle considering differences between cold and hot orogens. The W. Alps result of the opening and closure of the Liguro-Piemonte ocean, whereas the Paleozoic Eo-variscan and Variscan orogenies document multiple ocean openings and collisions in space and a polyorogenic history in time. Jurassic or Early Ordovician break-up of Pangea or Pannotia megacontinents led to the formation of passive continental margins, and the opening of Liguro-Piemonte, or Rheic, Tepla-Le Conquet, and Medio-European oceans, respectively. In Paleozoic or Mesozoic, microcontinents such as Apulia and Sesia or Armorica and Saxo-Thuringia were individualized. The oceanic convergence stage was associated with the development of arcs and back-arc basins in the Variscan belt but magmatic arcs are missing in the W. Alps, and inferred in the Eo-variscan one. Though the nappe stack is mainly developed in the subducted European or Gondwana crust in the western Alps and Eo-variscan cases, the Moldanubian nappes formed in the upper plate in the Variscan case. The Alpine and Variscan metamorphic evolutions occurred under ca. 8 °C/km and 30 °C/km gradients, respectively. During the late- to post-orogenic stages, all belts experienced “unthickening” accommodated by extensional tectonics, metamorphic retrogression, and intramontane basin opening. The importance of crustal melting, represented by migmatites, granites, and hydrothermal circulations in the Variscan and Eo-Variscan belts is the major difference with the W. Alpine one. The presence, or absence, of a previous Variscan or Cadomian continental basement might have also influenced the rheological behavior of the crust.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135300468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Laurent Guillou-Frottier, Gaétan Milesi, Vincent Roche, Hugo Duwiquet, Audrey Taillefer
The potential of high-temperature (>150°C) geothermal systems in crustal fault zones (fault cores and hundreds of meters wide networks of interconnected fractures in the damage zone) is underestimated. Based on numerical models, we show that topography-driven, poroelasticity-driven as well as buoyancy-driven forces play a significant role in the establishment of shallow (1–4 km) thermal anomalies in fault zones. We investigate the role of permeability, topography, fault dip, tectonic regime and fault geometry on the amplitude of thermal anomalies. Favorable conditions include: (i) a damage zone thickness > 100 m, (ii) a minimum cumulative displacement of 100–150 m and (iii) fault zone lengths of at least one kilometer. Based on these parameters, we propose new potential targets for the geothermal exploration of fault zones in Western Europe.
{"title":"Heat flow, thermal anomalies, tectonic regimes and high-temperature geothermal systems in fault zones","authors":"Laurent Guillou-Frottier, Gaétan Milesi, Vincent Roche, Hugo Duwiquet, Audrey Taillefer","doi":"10.5802/crgeos.213","DOIUrl":"https://doi.org/10.5802/crgeos.213","url":null,"abstract":"The potential of high-temperature (>150°C) geothermal systems in crustal fault zones (fault cores and hundreds of meters wide networks of interconnected fractures in the damage zone) is underestimated. Based on numerical models, we show that topography-driven, poroelasticity-driven as well as buoyancy-driven forces play a significant role in the establishment of shallow (1–4 km) thermal anomalies in fault zones. We investigate the role of permeability, topography, fault dip, tectonic regime and fault geometry on the amplitude of thermal anomalies. Favorable conditions include: (i) a damage zone thickness > 100 m, (ii) a minimum cumulative displacement of 100–150 m and (iii) fault zone lengths of at least one kilometer. Based on these parameters, we propose new potential targets for the geothermal exploration of fault zones in Western Europe.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134988638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Outdoor recreational activities for leisure and for sport training have grown in popularity. Their environmental impacts remain little studied, especially the waste generated by over-frequentation. Our objective was to document how frequentation of a short mountain hiking trail can lead to significant quantities of waste. To this aim, all small objects found along a three-kilometer trail were collected and their origin determined. Polymers were predominant, and were mostly shoe sole fragments. This has never been documented and must be publicized due to the potential harmfulness to terrestrial and riparian ecosystems, and to increase the walkers’ awareness.
{"title":"Plastics on the rocks: the invisible but harmful footprint of shoe soles","authors":"Philippe Cecchi","doi":"10.5802/crgeos.199","DOIUrl":"https://doi.org/10.5802/crgeos.199","url":null,"abstract":"Outdoor recreational activities for leisure and for sport training have grown in popularity. Their environmental impacts remain little studied, especially the waste generated by over-frequentation. Our objective was to document how frequentation of a short mountain hiking trail can lead to significant quantities of waste. To this aim, all small objects found along a three-kilometer trail were collected and their origin determined. Polymers were predominant, and were mostly shoe sole fragments. This has never been documented and must be publicized due to the potential harmfulness to terrestrial and riparian ecosystems, and to increase the walkers’ awareness.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136292902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mafalda M. Miranda, Jasmin Raymond, Chrystel Dezayes
In remote northern regions, lacking deep geothermal exploratory boreholes, a theoretical approach to provide a first-order estimate of the stress regime seems a useful tool. Literature data was used in this context to evaluate the orientation of the stress components and empirical relationships were applied to calculate their magnitude in a community of Nunavik, northern Quebec. A Monte Carlo-based sensitivity analysis was carried out due to the uncertainty of the input parameters. Mohr–Coulomb friction and slip tendency analyses were additionally undertaken to assess the stress state and potential reactivation of existing fractures. The results highlight how the poor knowledge of the stress field has an important impact on the design and development of engineered geothermal energy systems in the Canadian off-grid community of Kuujjuaq.
{"title":"Estimating theoretical stress regime for engineered geothermal energy systems in an arctic community (Kuujjuaq, Canada)","authors":"Mafalda M. Miranda, Jasmin Raymond, Chrystel Dezayes","doi":"10.5802/crgeos.193","DOIUrl":"https://doi.org/10.5802/crgeos.193","url":null,"abstract":"In remote northern regions, lacking deep geothermal exploratory boreholes, a theoretical approach to provide a first-order estimate of the stress regime seems a useful tool. Literature data was used in this context to evaluate the orientation of the stress components and empirical relationships were applied to calculate their magnitude in a community of Nunavik, northern Quebec. A Monte Carlo-based sensitivity analysis was carried out due to the uncertainty of the input parameters. Mohr–Coulomb friction and slip tendency analyses were additionally undertaken to assess the stress state and potential reactivation of existing fractures. The results highlight how the poor knowledge of the stress field has an important impact on the design and development of engineered geothermal energy systems in the Canadian off-grid community of Kuujjuaq.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135963447","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study analyzed the sensitivity of the double-moment normalization of rain drop size distributions (DSDs) to their integration time steps. Six DSD datasets measured at different integration time steps were modeled by the double-moment normalization method. Six couples of reference moments are used for the normalization. Three DSD models (gamma, generalized gamma and lognormal) are used for modeling. Statistical criteria are used to assess the estimation of the moments of the DSDs made by the models. As results, the analysis highlighted the dependence of the shape function parameters on the DSD integration time step. It is also noted that the three DSD models are well adapted to the data used. Nevertheless, the generalized gamma model is recommended because of the independence of the moment estimation errors with respect to the integration time step, which is not the case for the other models.
{"title":"Impact of integration time steps of rain drop size distribution on their double-moment normalization: a case study in northern Benin","authors":"Sounmaïla Moumouni, Fulgence Payot Akponi, Eric-Pascal Zahiri, Agnidé Emmanuel Lawin, Marielle Gosset","doi":"10.5802/crgeos.200","DOIUrl":"https://doi.org/10.5802/crgeos.200","url":null,"abstract":"This study analyzed the sensitivity of the double-moment normalization of rain drop size distributions (DSDs) to their integration time steps. Six DSD datasets measured at different integration time steps were modeled by the double-moment normalization method. Six couples of reference moments are used for the normalization. Three DSD models (gamma, generalized gamma and lognormal) are used for modeling. Statistical criteria are used to assess the estimation of the moments of the DSDs made by the models. As results, the analysis highlighted the dependence of the shape function parameters on the DSD integration time step. It is also noted that the three DSD models are well adapted to the data used. Nevertheless, the generalized gamma model is recommended because of the independence of the moment estimation errors with respect to the integration time step, which is not the case for the other models.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136172364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anne Jost, Shuaitao Wang, Thomas Verbeke, François Colleoni, Nicolas Flipo
Supply of aggregate materials for every construction requires mining of sand and gravel, which leads to the formation of a myriad of freshwater lakes, a now common feature of the landscape in the valleys of large rivers. Typically small in size and shallow, they are filled with waters from the adjacent aquifers and directly exposed to the atmosphere. The creation of gravel pit lakes has various and contrasting effects on their immediate environment. This article first provides a review of these impacts from the hydrodynamic point of view, and illustrates them on simple numerical test cases. It also introduces the gravel pit lake module developed for the occasion within the integrated modelling platform CaWaQS, which formulation was tested on the same test cases against the Lak package, its Modflow counterpart. By accurately simulating gravel pit lake interactions with groundwater in different configurations, this modelling exercise also aims to identify the preponderant factors leading water level fluctuations of those artificial lakes, whose temporal monitoring will soon be accessible to satellite observation.
{"title":"Hydrodynamic relationships between gravel pit lakes and aquifers: brief review and insights from numerical investigations","authors":"Anne Jost, Shuaitao Wang, Thomas Verbeke, François Colleoni, Nicolas Flipo","doi":"10.5802/crgeos.181","DOIUrl":"https://doi.org/10.5802/crgeos.181","url":null,"abstract":"Supply of aggregate materials for every construction requires mining of sand and gravel, which leads to the formation of a myriad of freshwater lakes, a now common feature of the landscape in the valleys of large rivers. Typically small in size and shallow, they are filled with waters from the adjacent aquifers and directly exposed to the atmosphere. The creation of gravel pit lakes has various and contrasting effects on their immediate environment. This article first provides a review of these impacts from the hydrodynamic point of view, and illustrates them on simple numerical test cases. It also introduces the gravel pit lake module developed for the occasion within the integrated modelling platform CaWaQS, which formulation was tested on the same test cases against the Lak package, its Modflow counterpart. By accurately simulating gravel pit lake interactions with groundwater in different configurations, this modelling exercise also aims to identify the preponderant factors leading water level fluctuations of those artificial lakes, whose temporal monitoring will soon be accessible to satellite observation.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136197938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Agathe Roullé, Marie Baillet, Didier Bertil, Cécile Cornou
Since the 2000s, local seismic hazard studies have shown that Mayotte Island presented superficial geological formations prone to lithological site effects. The seismic sequence initiated in May 2018 confirmed the importance of such effects, both in terms of intensity and spatial extension. The analysis of the recorded strong motions showed that weathered volcanic formations are prone to significant site effects with mean amplification factors for peak ground acceleration (PGA) between 1.4 and 4.9 and that a complex combination of lithological and topographic site effects is in action. We thus implement a regional scale map of site effects for the fast calculation of strong motion and damage maps for crisis management purposes. We also provide a first estimate of key site parameters for eight stations: surface geology, resonance frequency, an amplification factor proxy for PGA, a V S,30 value, if available, and an estimated EC8 soil class. Supplementary Materials: Supplementary material for this article is supplied as a separate file: crgeos-151-suppl.pdf Depuis les années 2000, les études d’aléa sismique local réalisées à Mayotte ont montré que les formations géologiques superficielles présentes sur l’île étaient susceptibles de présenter des effets de site lithologiques. La séquence sismique initiée en mai 2018 a confirmé l’importance de ces effets, aussi bien en termes d’intensité que d’étendue spatiale. L’analyse des enregistrements des mouvements forts a montré notamment que les formations volcaniques altérées pouvaient être soumises à des effets de site significatifs avec des facteurs d’amplification moyens du PGA compris entre 1,4 et 4,9, et que ces effets résultaient probablement d’une combinaison complexe d’effets lithologiques et topographiques. Nous avons ensuite produit une carte d’effets de site à l’échelle régionale pour permettre le calcul en temps réel de cartes de mouvements forts et de dommages à des fins de gestion de crise. Enfin, pour les 8 sites de stations sismologiques étudiés dans cet article, nous proposons une première estimation des paramètres de sites clefs, à savoir : la géologie superficielle, la fréquence de résonance, un facteur d’amplification du PGA, une valeur du paramètre V S,30 , si disponible, et une estimation de la classe de sol EC8 au site. Compléments : Des compléments sont fournis pour cet article dans le fichier séparé : crgeos-151-suppl.pdf
自2000年代以来，当地的地震灾害研究表明，马约特岛的浅层地质构造容易受到岩性场地效应的影响。2018年5月开始的地震序列证实了这种影响在强度和空间扩展方面的重要性。对强运动记录的分析表明，风化火山岩地层容易产生显著的场地效应，其峰值地面加速度(PGA)的平均放大因子在1.4 ~ 4.9之间，是岩性和地形场地效应的复杂组合。因此，我们实现了一个区域比例尺地图的现场效果，以快速计算强运动和破坏地图的危机管理目的。我们还提供了8个站点的关键站点参数的初步估计:地表地质，共振频率，PGA的放大因子代理，V S,30值(如果可用)，以及估计的EC8土壤等级。补充材料:辅料为本文提供作为一个单独的文件:crgeos - 151 suppl.pdf从莱斯2000年排,les练习曲d 'alea sismique当地意识到马约特岛位于安大略省的东西,les形成geologiques superficielles现在苏尔凭易感人群de主持人des是运用lithologiques德网站。La ssamquence sismique initisame en mai 2018证实了mise ' importance de ces effects, aussi bien en termes d ' intensitesque d ' spatiale。分析des enregistrements des所属的堡垒一个装饰音管尤其是变量形成volcaniques alterees pouvaient可能soumises des运用de站点没有意义用影响d 'amplification办法du PGA之间的1、4和4,9日,et, ces运用resultaient probablement一combinaison complexe d 'effets lithologiques topographiques。现在，我们的产品已经被定义为“影响”，例如，我们的网站，我们的网站，我们的网站，我们的网站，我们的网站，我们的网站，我们的网站，我们的网站，我们的网站，我们的网站，我们的网站。最后，对8个站点的数据进行了采样，提出了1个参数的先验估计，1个站点的数据进行了采样，1个站点的数据进行了采样，1个站点的数据进行了采样，1个站点的数据进行了采样，1个站点的数据进行了采样，1个站点的数据进行了采样，1个站点的数据进行了采样。恭维:恭维者的恭维者的恭维者的恭维者的恭维者的恭维者的恭维者的恭维者的恭维者的恭维者的恭维者
{"title":"Site effects observations and mapping on the weathered volcanic formations of Mayotte Island","authors":"Agathe Roullé, Marie Baillet, Didier Bertil, Cécile Cornou","doi":"10.5802/crgeos.151","DOIUrl":"https://doi.org/10.5802/crgeos.151","url":null,"abstract":"Since the 2000s, local seismic hazard studies have shown that Mayotte Island presented superficial geological formations prone to lithological site effects. The seismic sequence initiated in May 2018 confirmed the importance of such effects, both in terms of intensity and spatial extension. The analysis of the recorded strong motions showed that weathered volcanic formations are prone to significant site effects with mean amplification factors for peak ground acceleration (PGA) between 1.4 and 4.9 and that a complex combination of lithological and topographic site effects is in action. We thus implement a regional scale map of site effects for the fast calculation of strong motion and damage maps for crisis management purposes. We also provide a first estimate of key site parameters for eight stations: surface geology, resonance frequency, an amplification factor proxy for PGA, a V S,30 value, if available, and an estimated EC8 soil class. Supplementary Materials: Supplementary material for this article is supplied as a separate file: crgeos-151-suppl.pdf Depuis les années 2000, les études d’aléa sismique local réalisées à Mayotte ont montré que les formations géologiques superficielles présentes sur l’île étaient susceptibles de présenter des effets de site lithologiques. La séquence sismique initiée en mai 2018 a confirmé l’importance de ces effets, aussi bien en termes d’intensité que d’étendue spatiale. L’analyse des enregistrements des mouvements forts a montré notamment que les formations volcaniques altérées pouvaient être soumises à des effets de site significatifs avec des facteurs d’amplification moyens du PGA compris entre 1,4 et 4,9, et que ces effets résultaient probablement d’une combinaison complexe d’effets lithologiques et topographiques. Nous avons ensuite produit une carte d’effets de site à l’échelle régionale pour permettre le calcul en temps réel de cartes de mouvements forts et de dommages à des fins de gestion de crise. Enfin, pour les 8 sites de stations sismologiques étudiés dans cet article, nous proposons une première estimation des paramètres de sites clefs, à savoir : la géologie superficielle, la fréquence de résonance, un facteur d’amplification du PGA, une valeur du paramètre V S,30 , si disponible, et une estimation de la classe de sol EC8 au site. Compléments : Des compléments sont fournis pour cet article dans le fichier séparé : crgeos-151-suppl.pdf","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135481521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A hierarchical sequential Gaussian cosimulation method is applied in this study for modeling the variables with an inequality constraint in the bivariate relationship. An algorithm is improved by embedding an inverse transform sampling technique in the second simulation to reproduce bivariate complexity and accelerate the process of cosimulation. A heterotopic simple cokriging (SCK) is also proposed, which introduces two moving neighborhoods: single and multiple searching strategies in both steps of the hierarchical process. The proposed algorithm is tested over a real case study from an iron deposit where iron and aluminum oxide shows a strong bivariate dependency as well as a sharp inequality constraint. The results showed that the proposed hierarchical cosimulation with a multiple searching strategy provides satisfying results compared to the case when a single searching strategy is employed. Moreover, the proposed algorithm is compared to the conventional hierarchical cosimulation, which does not implement the inverse transform sampling integrated into the second simulation. The proposed methodology successfully reproduces inequality constraint, while conventional hierarchical cosimulation fails in this regard. However, it is demonstrated that the proposed methodology requires further improvement for better reproduction of global statistics (i.e., mean and standard deviation).
{"title":"Assessing heterotopic searching strategy in hierarchical cosimulation for modeling the variables with inequality constraints","authors":"Sultan Abulkhair, N. Madani","doi":"10.5802/CRGEOS.58","DOIUrl":"https://doi.org/10.5802/CRGEOS.58","url":null,"abstract":"A hierarchical sequential Gaussian cosimulation method is applied in this study for modeling the variables with an inequality constraint in the bivariate relationship. An algorithm is improved by embedding an inverse transform sampling technique in the second simulation to reproduce bivariate complexity and accelerate the process of cosimulation. A heterotopic simple cokriging (SCK) is also proposed, which introduces two moving neighborhoods: single and multiple searching strategies in both steps of the hierarchical process. The proposed algorithm is tested over a real case study from an iron deposit where iron and aluminum oxide shows a strong bivariate dependency as well as a sharp inequality constraint. The results showed that the proposed hierarchical cosimulation with a multiple searching strategy provides satisfying results compared to the case when a single searching strategy is employed. Moreover, the proposed algorithm is compared to the conventional hierarchical cosimulation, which does not implement the inverse transform sampling integrated into the second simulation. The proposed methodology successfully reproduces inequality constraint, while conventional hierarchical cosimulation fails in this regard. However, it is demonstrated that the proposed methodology requires further improvement for better reproduction of global statistics (i.e., mean and standard deviation).","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2021-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45247975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jairo Guerrero, Luis Montes, E. Jaillard, A. Kammer
Geoscientists commonly focus on Tertiary units to understand the Andean uplift and deformation of the eastern Cordillera of Colombia, whereas the Cretaceous evolution remains poorly known. Cretaceous units are exposed in western Eastern Cordillera, but outcrops are scarce in the Middle Magdalena Valley. Recent seismic acquisition programs and new wells drilled through the Cretaceous succession led to a better understanding of unconformities and sequences in both the Middle Magdalena Valley and the western flank of the Eastern Cordillera. This paper identifies unconformities bounding seismic sequences and deciphers Cretaceous structural deformation in the Middle Magdalena Valley and western Eastern Cordillera based on the interpretation of sizable seismic reflection sections and well information. The analysis of sedimentary sequences and unconformity surfaces allowed identification of stages of pre-Eocene deformation. Regional correlations of sequences and unconformities recognized here with those identified by other authors support the occurrence of Cretaceous regional tectonic events.
{"title":"Seismic interpretation of the Cretaceous unconformities and sequences in the Middle Magdalena Valley and the western margin of the Eastern Cordillera, Colombia","authors":"Jairo Guerrero, Luis Montes, E. Jaillard, A. Kammer","doi":"10.5802/CRGEOS.47","DOIUrl":"https://doi.org/10.5802/CRGEOS.47","url":null,"abstract":"Geoscientists commonly focus on Tertiary units to understand the Andean uplift and deformation of the eastern Cordillera of Colombia, whereas the Cretaceous evolution remains poorly known. Cretaceous units are exposed in western Eastern Cordillera, but outcrops are scarce in the Middle Magdalena Valley. Recent seismic acquisition programs and new wells drilled through the Cretaceous succession led to a better understanding of unconformities and sequences in both the Middle Magdalena Valley and the western flank of the Eastern Cordillera. This paper identifies unconformities bounding seismic sequences and deciphers Cretaceous structural deformation in the Middle Magdalena Valley and western Eastern Cordillera based on the interpretation of sizable seismic reflection sections and well information. The analysis of sedimentary sequences and unconformity surfaces allowed identification of stages of pre-Eocene deformation. Regional correlations of sequences and unconformities recognized here with those identified by other authors support the occurrence of Cretaceous regional tectonic events.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2021-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47561393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Badro, P. Sossi, Zhengbing Deng, S. Borensztajn, N. Wehr, F. Ryerson
We carried out evaporation experiments on a B-type calcium–aluminium-rich inclusion (CAI) melt in a gas-mixing aerodynamic levitation laser furnace, at 1873 K and an oxygen partial pressure of 10−9.1 atm, for durations ranging from 60 to 600 s. Evaporation of SiO2 and MgO follow the same trend as those observed in vacuum furnace experiments at the same temperature and starting composition, showing that their evaporation relative to one another from the melt is independent of pressure, oxygen fugacity, and hydrodynamical regime specific to the furnace. Isotopic ratios of Mg and Si in evaporation residues are used to derive fractionation factors of αMgvap−liq = 0.9906± 0.0004 and αSivap−liq = 0.9943± 0.0003, which are both significantly closer to unity than those found for evaporation in a vacuum, which translates to less isotope fractionation. The residues are also less isotopically fractionated than expected for cases in which transport of the gas species away from the melt is diffusion-controlled at 1-atm. By analysing the flow regimes in our furnace, we find that advection by the levitating gas is the primary mode of mass transport away from the melt surface, as opposed to diffusion-limited transport in a vacuum or 1-atm tube furnace. A modified Hertz– Knudsen–Langmuir formulation accounts for this process, and shows that isotopic fractionation of both Si and Mg reflect a saturation factor (ratio of the pressure of the evaporating species to vapour saturation pressure) equal to 0.75. This is in perfect accord with recent measurements of Cu isotopic fractionation using a similar furnace. The fact that three elements (Mg, Si, Cu) with varying equilibrium vapour pressures, activity coefficients in the liquid, and diffusion coefficients in the gas have the same scaling behaviour to saturation pressure is a strong indication that the mechanism controlling evaporation is driven by the hydrodynamical regime imposed in the furnace. Therefore, this class of experiments can be used to constrain processes in which advection dominates over ∗Corresponding author. ISSN (electronic) : 1778-7025 https://comptes-rendus.academie-sciences.fr/geoscience/ 102 James Badro et al. diffusion, such as (but not limited to) planetary ejecta, tektites, giant impacts, nebular condensation in a turbulent flow, or nuclear fallout material. Finally, the possibility to reach high temperatures (in excess of 3500 K) in this furnace allows it to be used to evaluate the activity coefficients of melt components in extreme conditions relevant to molten planetary interiors (i.e., magma oceans), with a specific focus on refractory elements.
{"title":"Experimental investigation of elemental and isotopic evaporation processes by laser heating in an aerodynamic levitation furnace","authors":"J. Badro, P. Sossi, Zhengbing Deng, S. Borensztajn, N. Wehr, F. Ryerson","doi":"10.5802/CRGEOS.56","DOIUrl":"https://doi.org/10.5802/CRGEOS.56","url":null,"abstract":"We carried out evaporation experiments on a B-type calcium–aluminium-rich inclusion (CAI) melt in a gas-mixing aerodynamic levitation laser furnace, at 1873 K and an oxygen partial pressure of 10−9.1 atm, for durations ranging from 60 to 600 s. Evaporation of SiO2 and MgO follow the same trend as those observed in vacuum furnace experiments at the same temperature and starting composition, showing that their evaporation relative to one another from the melt is independent of pressure, oxygen fugacity, and hydrodynamical regime specific to the furnace. Isotopic ratios of Mg and Si in evaporation residues are used to derive fractionation factors of αMgvap−liq = 0.9906± 0.0004 and αSivap−liq = 0.9943± 0.0003, which are both significantly closer to unity than those found for evaporation in a vacuum, which translates to less isotope fractionation. The residues are also less isotopically fractionated than expected for cases in which transport of the gas species away from the melt is diffusion-controlled at 1-atm. By analysing the flow regimes in our furnace, we find that advection by the levitating gas is the primary mode of mass transport away from the melt surface, as opposed to diffusion-limited transport in a vacuum or 1-atm tube furnace. A modified Hertz– Knudsen–Langmuir formulation accounts for this process, and shows that isotopic fractionation of both Si and Mg reflect a saturation factor (ratio of the pressure of the evaporating species to vapour saturation pressure) equal to 0.75. This is in perfect accord with recent measurements of Cu isotopic fractionation using a similar furnace. The fact that three elements (Mg, Si, Cu) with varying equilibrium vapour pressures, activity coefficients in the liquid, and diffusion coefficients in the gas have the same scaling behaviour to saturation pressure is a strong indication that the mechanism controlling evaporation is driven by the hydrodynamical regime imposed in the furnace. Therefore, this class of experiments can be used to constrain processes in which advection dominates over ∗Corresponding author. ISSN (electronic) : 1778-7025 https://comptes-rendus.academie-sciences.fr/geoscience/ 102 James Badro et al. diffusion, such as (but not limited to) planetary ejecta, tektites, giant impacts, nebular condensation in a turbulent flow, or nuclear fallout material. Finally, the possibility to reach high temperatures (in excess of 3500 K) in this furnace allows it to be used to evaluate the activity coefficients of melt components in extreme conditions relevant to molten planetary interiors (i.e., magma oceans), with a specific focus on refractory elements.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2021-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42662637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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