{"title":"Le rôle de l’énergie nucléaire dans la lutte contre le réchauffement climatique : atouts et faiblesses dans une approche intégrée","authors":"Y. Bréchet","doi":"10.5802/crgeos.21","DOIUrl":"https://doi.org/10.5802/crgeos.21","url":null,"abstract":"","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46914088","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}
Urban policies and city inhabitants behaviors are at the forefront of global environmental issues. We live indeed in an urbanizing world, and cities are responsible for approximately two third of global energy consumptions. How buildings are built, and how cities are organized are both key drivers of greenhouse gases emissions. Making them coherent with environmental constraints often lead to co-benefits with other urban issues such as economic competitiveness or social inclusiveness. This explains why cities are globally active concerning climate change, even if much still needs to be
{"title":"Les villes et le climat : Bâtiments et urbanisme","authors":"V. Viguié","doi":"10.5802/crgeos.19","DOIUrl":"https://doi.org/10.5802/crgeos.19","url":null,"abstract":"Urban policies and city inhabitants behaviors are at the forefront of global environmental issues. We live indeed in an urbanizing world, and cities are responsible for approximately two third of global energy consumptions. How buildings are built, and how cities are organized are both key drivers of greenhouse gases emissions. Making them coherent with environmental constraints often lead to co-benefits with other urban issues such as economic competitiveness or social inclusiveness. This explains why cities are globally active concerning climate change, even if much still needs to be","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41733325","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}
Wuling Mo, Fang Liyong, Wei Guoqi, Liu Xinshe, Zhang Chunlin, L. Mancang, Su Nan, Liu Yan, Wu Saijun, Xing Fengcun
The provenance of the Upper Carboniferous Benxi Formation in North China Craton (NCC) has been considered as the northern margin of the NCC, not the North Qinling Orogenic Belt. To understand the provenance and the tectonic-sedimentary evolution during the sedimentary period of the Benxi Formation, the zircon U–Pb geochronology analysis was conducted on eleven clastic sandstone samples. The south of the NCC received clastic sediments from the North Qinling Orogenic Belt. The orogenic movements around the NCC in the Late Carboniferous period had significant impacts on the changes in paleotopography. During the early sedimentary period of the Hutian member of the Benxi Formation, the north of the Qinling Orogenic Belt was rapidly uplifted, and paleotopography was south-uplifting and north-dipping; thus, the clastic source was the North Qinling Orogenic Belt. From the late sedimentary period of the Benxi Formation Hutian member to the sedimentary period of the Jinci member, paleotopography was reversed. The northern margin of the NCC quickly uplifted, and paleotopography was north-uplifting and south-dipping. Two distinct provenances were present in the sediments of the Benxi Formation. The sediments were supplied predominately by the provenance in the north.
{"title":"Detrital zircon U–Pb geochronology from the Upper Carboniferous sediments of Benxi Formation in the North China Craton: implications for tectonic-sedimentary evolution","authors":"Wuling Mo, Fang Liyong, Wei Guoqi, Liu Xinshe, Zhang Chunlin, L. Mancang, Su Nan, Liu Yan, Wu Saijun, Xing Fengcun","doi":"10.5802/crgeos.17","DOIUrl":"https://doi.org/10.5802/crgeos.17","url":null,"abstract":"The provenance of the Upper Carboniferous Benxi Formation in North China Craton (NCC) has been considered as the northern margin of the NCC, not the North Qinling Orogenic Belt. To understand the provenance and the tectonic-sedimentary evolution during the sedimentary period of the Benxi Formation, the zircon U–Pb geochronology analysis was conducted on eleven clastic sandstone samples. The south of the NCC received clastic sediments from the North Qinling Orogenic Belt. The orogenic movements around the NCC in the Late Carboniferous period had significant impacts on the changes in paleotopography. During the early sedimentary period of the Hutian member of the Benxi Formation, the north of the Qinling Orogenic Belt was rapidly uplifted, and paleotopography was south-uplifting and north-dipping; thus, the clastic source was the North Qinling Orogenic Belt. From the late sedimentary period of the Benxi Formation Hutian member to the sedimentary period of the Jinci member, paleotopography was reversed. The northern margin of the NCC quickly uplifted, and paleotopography was north-uplifting and south-dipping. Two distinct provenances were present in the sediments of the Benxi Formation. The sediments were supplied predominately by the provenance in the north.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42512816","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}
Access to energy is a key factor in the economic development of countries. We will first examine the evolution of different ways to access to energy and their correlations with world population and countries’ GDP. We will see that the objectives of reducing carbon dioxide emissions which require a profound transformation of our access to energy will be very difficult to achieve. We will also see that the thermal improvement of buildings, and in particular the renovation of existing housing, is one of the possible objective. Mots-clés. Énergie, Climat, Efficacité énergétique, Bâtiment, Rénovation.
{"title":"Énergie et climat : défis et innovations","authors":"D. Roux","doi":"10.5802/crgeos.25","DOIUrl":"https://doi.org/10.5802/crgeos.25","url":null,"abstract":"Access to energy is a key factor in the economic development of countries. We will first examine the evolution of different ways to access to energy and their correlations with world population and countries’ GDP. We will see that the objectives of reducing carbon dioxide emissions which require a profound transformation of our access to energy will be very difficult to achieve. We will also see that the thermal improvement of buildings, and in particular the renovation of existing housing, is one of the possible objective. Mots-clés. Énergie, Climat, Efficacité énergétique, Bâtiment, Rénovation.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42251081","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}
Saâd Soulaimani, S. Chakiri, A. Manar, Ayoub Soulaimani, A. Miftah, M. Bouiflane
Geophysical data inversion is a tool, which can be used to recover the subsurface distribution of physical properties from field data. Each type of geophysical data can be inverted using one or more inversion algorithms. In this paper, a set of geophysical magnetic and gravity data of the Hajjar area in Morocco, covering an extent of 3.2× 1.6 km2, were used to make a 3D model of an orebody and to estimate the mineral reserve by potential-field geophysical data inversion and excess mass estimation. We thus promote the development and application of potential-field geophysical data inversion using the softwares Geosoft Oasis Montaj and Voxi Earth ModellingTM and the evaluation of its power compared to the excess mass estimation method. The process of inversion begins with data processing, then moves to analysis and interpretation, and ends with unconstrained Cartesian cut cell inversion. The results show a variation of −0.22 mGal to 1.59 mGal for the gravity residual anomaly map, leading to have density variations from 2.45 g/cm3 to 4.22 g/cm3, and a variation of −232 nT to 1018 nT for the reduced magnetic anomaly map. Moreover, data inversion allowed us to create a 3D model of the orebody and of the adjacent geological formation, and to estimate the different parameters that characterize the orebody derived from the inversion results, which have been confirmed from survey data: (depth ≈ 160 m; maximum ∗Corresponding author. ISSN (electronic) : 1778-7025 https://comptes-rendus.academie-sciences.fr/geoscience/ 140 Saâd Soulaimani et al. density ≈ 4.22 g/cm3; minimum density ≈ 3 g/cm3; mean density ≈ 3.61 g/cm3; thickness of the overburden ≈120 m; dip ≈ 45◦; morphology ≈ lens; volume ≈ 4.8×106 m3). It was therefore possible to evaluate the reserve, and to validate the reliability of the inversion by having a root mean square error between the exploited reserve and the calculated reserve of 13.5%, i.e. an insignificant difference between the real and calculated magnetic and gravity orebody responses, which support the validity of the results.
{"title":"Potential-field geophysical data inversion for 3D modelling and reserve estimation (Example of the Hajjar mine, Guemassa massif, Morocco): magnetic and gravity data case","authors":"Saâd Soulaimani, S. Chakiri, A. Manar, Ayoub Soulaimani, A. Miftah, M. Bouiflane","doi":"10.5802/crgeos.10","DOIUrl":"https://doi.org/10.5802/crgeos.10","url":null,"abstract":"Geophysical data inversion is a tool, which can be used to recover the subsurface distribution of physical properties from field data. Each type of geophysical data can be inverted using one or more inversion algorithms. In this paper, a set of geophysical magnetic and gravity data of the Hajjar area in Morocco, covering an extent of 3.2× 1.6 km2, were used to make a 3D model of an orebody and to estimate the mineral reserve by potential-field geophysical data inversion and excess mass estimation. We thus promote the development and application of potential-field geophysical data inversion using the softwares Geosoft Oasis Montaj and Voxi Earth ModellingTM and the evaluation of its power compared to the excess mass estimation method. The process of inversion begins with data processing, then moves to analysis and interpretation, and ends with unconstrained Cartesian cut cell inversion. The results show a variation of −0.22 mGal to 1.59 mGal for the gravity residual anomaly map, leading to have density variations from 2.45 g/cm3 to 4.22 g/cm3, and a variation of −232 nT to 1018 nT for the reduced magnetic anomaly map. Moreover, data inversion allowed us to create a 3D model of the orebody and of the adjacent geological formation, and to estimate the different parameters that characterize the orebody derived from the inversion results, which have been confirmed from survey data: (depth ≈ 160 m; maximum ∗Corresponding author. ISSN (electronic) : 1778-7025 https://comptes-rendus.academie-sciences.fr/geoscience/ 140 Saâd Soulaimani et al. density ≈ 4.22 g/cm3; minimum density ≈ 3 g/cm3; mean density ≈ 3.61 g/cm3; thickness of the overburden ≈120 m; dip ≈ 45◦; morphology ≈ lens; volume ≈ 4.8×106 m3). It was therefore possible to evaluate the reserve, and to validate the reliability of the inversion by having a root mean square error between the exploited reserve and the calculated reserve of 13.5%, i.e. an insignificant difference between the real and calculated magnetic and gravity orebody responses, which support the validity of the results.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42713758","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}
{"title":"Quelles transformations pour l’atténuation du changement climatique ? Des trajectoires d’émissions mondiales à la trajectoire française","authors":"C. Guivarch","doi":"10.5802/crgeos.23","DOIUrl":"https://doi.org/10.5802/crgeos.23","url":null,"abstract":"","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43416741","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}
The geological carbon sink consists of “putting back” the carbon into the subsurface from which it was extracted, in order to reduce incompressible residual CO2 emissions. Complementary to terrestrial (soils and forests) and oceanic carbon sinks, it is expected to play a key role in achieving carbon neutrality. 19 CO2 capture and storage (CCS) projects are already in operation worldwide. Major research and innovation efforts are being carried out to scale up and deploy this technology wherever it is needed. France, Europe and many countries believe that CCS will be essential to achieve the objectives of the Paris climate agreement and limit global warming to +1.5 ◦C. Mots-clés. Climat, Emissions, Neutralité carbone, CSC, CSCV.
{"title":"Captage et Stockage du CO 2 : le puits de carbone géologique","authors":"Isabelle Czernichowski-Lauriol","doi":"10.5802/crgeos.20","DOIUrl":"https://doi.org/10.5802/crgeos.20","url":null,"abstract":"The geological carbon sink consists of “putting back” the carbon into the subsurface from which it was extracted, in order to reduce incompressible residual CO2 emissions. Complementary to terrestrial (soils and forests) and oceanic carbon sinks, it is expected to play a key role in achieving carbon neutrality. 19 CO2 capture and storage (CCS) projects are already in operation worldwide. Major research and innovation efforts are being carried out to scale up and deploy this technology wherever it is needed. France, Europe and many countries believe that CCS will be essential to achieve the objectives of the Paris climate agreement and limit global warming to +1.5 ◦C. Mots-clés. Climat, Emissions, Neutralité carbone, CSC, CSCV.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43530052","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}
H. E. Hachimi, N. Youbi, J. Madeira, A. Marzoli, J. Mata, H. Bertrand, M. K. Bensalah, Moulay Ahmed Boumehdi, M. Doblas, F. Medina, M. Abbou, L. Martins
The best preserved and most complete lava flow sequences of the Central Atlantic Magmatic Province (CAMP) in Morocco are exposed in the Central High Atlas and can reach up to 300 m in thickness. Four distinct formations, emplaced in subaerial environments, are classically recognized: the ∗Corresponding author. ISSN (electronic) : 1778-7025 https://comptes-rendus.academie-sciences.fr/geoscience/ 456 Hind El Hachimi et al. Lower, Intermediate, Upper and Recurrent formations. These formations are separated by paleosoils and sedimentary sequences (mudstones, siltstones, sandstones, limestones), that are in general less than two meter-thick and may exceptionally reach a thickness of 80 m, representing minor periods of volcanic quiescence. CAMP lava flows of the Central High Atlas can be grouped into two main categories: subaerial compound pahoehoe flows and simple flows. The former type is exclusively confined to the Lower and Intermediate Formations, while simple flows occur in the Upper and Recurrent Formations. The dominance of compound flows in the two lowermost units of the CAMP suggests a slow emplacement during successive sustained eruptive episodes. Instead the thick single flows characterizing the Upper and Recurrent units indicate higher effusive rates. Basaltic pillow lavas (always of short lateral extent: 10 to 100 m), showing radial jointing and vitreous rinds, identical to those found in the Western Meseta, are occasionally associated with hyaloclastites in the base of the Intermediate Formation, immediately above clastic sediments, or in the Upper Formation. The occurrence of pillow lavas does not imply a generalized subaqueous environment at the time of the lava emission. Instead, they represent subaerial flows that entered small lakes occupying depressions on the volcanic topography of the Lower and Intermediate Formations. The short lateral extent of the pillow lavas and their constant stratigraphic position, the existence of lava flows with unequivocal subaerial characteristics associated to sediments containing fossilized wood, clearly indicate onshore emplacement.
摩洛哥中大西洋岩浆省(CAMP)保存最完好、最完整的熔岩流层序暴露在中部高地图集，厚度可达300 m。四种不同的地层，位于地面环境中，被经典地识别:ISSN(电子):1778-7025 https://comptes-rendus.academie-sciences.fr/geoscience/ 456 Hind El Hachimi等。下、中、上、回地层。这些地层被古土壤和沉积层(泥岩、粉砂岩、砂岩、灰岩)隔开，通常厚度不到2米，也有可能达到80米，代表了火山静止的小时期。中央高阿特拉斯的CAMP熔岩流可分为两大类:陆上复合pahoe流和简单流。前一种类型仅局限于下部和中间组，而简单的流动发生在上部和回流组。在CAMP最底部的两个单元中，复合流占主导地位，表明在连续持续的喷发事件中缓慢就位。相反，上单元和回流单元的厚单流表明较高的渗出率。玄武岩枕状熔岩(通常横向范围较短:10 - 100米)，呈放射状节理和玻璃状外壳，与在西梅塞塔发现的相同，偶尔与中间组底部、碎屑沉积物上方或上组的透明质碎屑岩相关联。枕状熔岩的出现并不意味着熔岩喷发时是一个普遍的水下环境。相反，它们代表了进入占据下、中地层火山地形洼地的小湖泊的陆上水流。枕状熔岩的横向范围短，地层位置稳定，熔岩流的存在与含有化石木材的沉积物相关联，具有明确的陆上特征，清楚地表明了陆上侵位。
{"title":"Physical volcanology and emplacement mechanism of the Central Atlantic Magmatic Province (CAMP) lava flows from the Central High Atlas, Morocco","authors":"H. E. Hachimi, N. Youbi, J. Madeira, A. Marzoli, J. Mata, H. Bertrand, M. K. Bensalah, Moulay Ahmed Boumehdi, M. Doblas, F. Medina, M. Abbou, L. Martins","doi":"10.5802/crgeos.7","DOIUrl":"https://doi.org/10.5802/crgeos.7","url":null,"abstract":"The best preserved and most complete lava flow sequences of the Central Atlantic Magmatic Province (CAMP) in Morocco are exposed in the Central High Atlas and can reach up to 300 m in thickness. Four distinct formations, emplaced in subaerial environments, are classically recognized: the ∗Corresponding author. ISSN (electronic) : 1778-7025 https://comptes-rendus.academie-sciences.fr/geoscience/ 456 Hind El Hachimi et al. Lower, Intermediate, Upper and Recurrent formations. These formations are separated by paleosoils and sedimentary sequences (mudstones, siltstones, sandstones, limestones), that are in general less than two meter-thick and may exceptionally reach a thickness of 80 m, representing minor periods of volcanic quiescence. CAMP lava flows of the Central High Atlas can be grouped into two main categories: subaerial compound pahoehoe flows and simple flows. The former type is exclusively confined to the Lower and Intermediate Formations, while simple flows occur in the Upper and Recurrent Formations. The dominance of compound flows in the two lowermost units of the CAMP suggests a slow emplacement during successive sustained eruptive episodes. Instead the thick single flows characterizing the Upper and Recurrent units indicate higher effusive rates. Basaltic pillow lavas (always of short lateral extent: 10 to 100 m), showing radial jointing and vitreous rinds, identical to those found in the Western Meseta, are occasionally associated with hyaloclastites in the base of the Intermediate Formation, immediately above clastic sediments, or in the Upper Formation. The occurrence of pillow lavas does not imply a generalized subaqueous environment at the time of the lava emission. Instead, they represent subaerial flows that entered small lakes occupying depressions on the volcanic topography of the Lower and Intermediate Formations. The short lateral extent of the pillow lavas and their constant stratigraphic position, the existence of lava flows with unequivocal subaerial characteristics associated to sediments containing fossilized wood, clearly indicate onshore emplacement.","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2020-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41480326","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}
The protracted tectonic and magmatic record of cratons over the Archaean Eon has been classically interpreted in terms of long-lived shallow-dipping subduction or repeated mantle plumes. In this paper, we use the 1D conductive heat equation to model the evolution of the geotherm of a generic felsic-dominated Archaean cratonic nuclei solely considering the secular decay of radioactive isotopes (238U, 235U, 232Th, and 40K), responsible for heat production in the crust. Using a range of plausible parameters for crustal thickness, lithospheric thickness, and surface heat flux, this modelling shows that Archaean crust was characterized by an initially high geothermal gradient at 3.5 Ga, with a Moho temperature close to 900 °C, and that it might have remained partially molten for about one billion years. The existence of a partially molten crust for an extended period of time offers an alternative option to shallow-dipping subduction or repeated mantle plumes for the understanding of the peculiar tectonic evolution of Archaean cratons marked by (i) protracted high-temperature metamorphism and magmatism associated with crustal differentiation, and (ii) widespread deformation characterized by structural domes attributed to the development of crustal-scale gravitational instabilities.
{"title":"Secular cooling and crystallization of partially molten Archaean continental crust over 1 Ga","authors":"Olivier Vanderhaeghe , Célia Guergouz , Cécile Fabre , Stéphanie Duchêne , David Baratoux","doi":"10.1016/j.crte.2019.07.002","DOIUrl":"10.1016/j.crte.2019.07.002","url":null,"abstract":"<div><p>The protracted tectonic and magmatic record of cratons over the Archaean Eon has been classically interpreted in terms of long-lived shallow-dipping subduction or repeated mantle plumes. In this paper, we use the 1D conductive heat equation to model the evolution of the geotherm of a generic felsic-dominated Archaean cratonic nuclei solely considering the secular decay of radioactive isotopes (<sup>238</sup>U, <sup>235</sup>U, <sup>232</sup>Th, and <sup>40</sup>K), responsible for heat production in the crust. Using a range of plausible parameters for crustal thickness, lithospheric thickness, and surface heat flux, this modelling shows that Archaean crust was characterized by an initially high geothermal gradient at 3.5 Ga, with a Moho temperature close to 900 °C, and that it might have remained partially molten for about one billion years. The existence of a partially molten crust for an extended period of time offers an alternative option to shallow-dipping subduction or repeated mantle plumes for the understanding of the peculiar tectonic evolution of Archaean cratons marked by (i) protracted high-temperature metamorphism and magmatism associated with crustal differentiation, and (ii) widespread deformation characterized by structural domes attributed to the development of crustal-scale gravitational instabilities.</p></div>","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.crte.2019.07.002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41707365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We examined magma storage conditions and eruptive dynamics for the trachyandesite (~58 wt% SiO2, 9–10 wt% alkalis) of the Pavin monogenetic volcano, a maar-like explosive crater belonging to a small group of youngest volcanoes in the Massif Central. By confronting the natural samples to experimental products, we constrained pre-eruptive conditions around 950–975 °C, 150–200 MPa (~5.5–7.0 km in depth), NNO+1.5, and 4.5–5.5 wt% melt H2O. There is petrological evidence of magma crystallization in the conduit up to shallow levels (~50 MPa; 2 km in depth) before fragmentation into pumice clasts in the last kilometre of ascent. The experiments highlight the role of biotite and of crystallization pressure in defining separate compositional trends of residual liquids, i.e. alkaline (trachytes) versus sub-alkaline (dacite-rhyolite).
{"title":"The intermediate step in fractionation trends of mildly alkaline volcanic suites: An experimental insight from the Pavin trachyandesite (Massif Central, France)","authors":"Morgane Rondet, Caroline Martel, Jean-Louis Bourdier","doi":"10.1016/j.crte.2019.07.003","DOIUrl":"10.1016/j.crte.2019.07.003","url":null,"abstract":"<div><p>We examined magma storage conditions and eruptive dynamics for the trachyandesite (~58 wt% SiO<sub>2</sub>, 9–10 wt% alkalis) of the Pavin monogenetic volcano, a maar-like explosive crater belonging to a small group of youngest volcanoes in the Massif Central. By confronting the natural samples to experimental products, we constrained pre-eruptive conditions around 950–975 °C, 150–200 MPa (~5.5–7.0 km in depth), NNO+1.5, and 4.5–5.5 wt% melt H<sub>2</sub>O. There is petrological evidence of magma crystallization in the conduit up to shallow levels (~50 MPa; 2 km in depth) before fragmentation into pumice clasts in the last kilometre of ascent. The experiments highlight the role of biotite and of crystallization pressure in defining separate compositional trends of residual liquids, i.e. alkaline (trachytes) versus sub-alkaline (dacite-rhyolite).</p></div>","PeriodicalId":50651,"journal":{"name":"Comptes Rendus Geoscience","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.crte.2019.07.003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43119836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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