2022
41.
Dhar, A.; Ghosh, B.; Bandyopadhyay, D.; Morishita, T.; Tamura, A.; France, L.; Nguyen, Du K.; Boulanger, M.; Koley, M.; Roy, S.; Chattopadhaya, S.
The lower oceanic crust at ultraslow-spreading Southwest Indian Ridge: The inside story Journal Article
In: Gondwana Research, vol. 111, pp. 223–248, 2022.
@article{Dhar_etal2022,
title = {The lower oceanic crust at ultraslow-spreading Southwest Indian Ridge: The inside story},
author = {A. Dhar and B. Ghosh and D. Bandyopadhyay and T. Morishita and A. Tamura and L. France and Du K. Nguyen and M. Boulanger and M. Koley and S. Roy and S. Chattopadhaya},
doi = {10.1016/j.gr.2022.08.008},
year = {2022},
date = {2022-01-01},
journal = {Gondwana Research},
volume = {111},
pages = {223--248},
abstract = {Owing to the lack of persistent magma chamber and the complex interplay between magmatism and tectonism at slow- to ultraslow-spreading ridges, the likeliness of fractional crystallization being the predominant process of evolution of crustal magmas is weak. Here, we report a detailed petro-geochemical investigation from the lower crustal gabbroic rocks recovered from Hole U1473A in Atlantis Bank oceanic core complex, Southwest Indian Ridge that may potentially provide new insights on the dynamic accretion process at ultraslow-spreading ridge. Sampling the entire lithological spectrum encompassing a single geochemical cycle in this study permit us to probe the underlying magmatic processes in ultraslowspreading lower crust. Grain-size variation is ubiquitously recorded in the gabbroic lithologies of Hole U1473A, where fine-grained intervals represent relatively evolved chemistry than the coarser domains. This suggests that, they were crystallized from a common genetic melt during different degrees of evolution. The forward geochemical modelling approach have not only affirmed the long-established theory of assimilation (of early mushes’ crystals)-fractional crystallization to be the key mechanism in lower crust formation, but also provided explanation for the restricted whole rock geochemical cluster observed throughout all the rock types. We demonstrate for the first time the relationship between the progressive modal mineralogical evolution with respect to the different assimilation/fractionation ratios (r). The observed trend has been successfully replicated for the experiments with high r values = 0.8--0.9, previously predicted from this region. Integrating all results, our study supports the model of lower crustal formation via reactive porous flow of the squeezed-out melt percolating throughout the cumulate pile and segregated into different horizons.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Owing to the lack of persistent magma chamber and the complex interplay between magmatism and tectonism at slow- to ultraslow-spreading ridges, the likeliness of fractional crystallization being the predominant process of evolution of crustal magmas is weak. Here, we report a detailed petro-geochemical investigation from the lower crustal gabbroic rocks recovered from Hole U1473A in Atlantis Bank oceanic core complex, Southwest Indian Ridge that may potentially provide new insights on the dynamic accretion process at ultraslow-spreading ridge. Sampling the entire lithological spectrum encompassing a single geochemical cycle in this study permit us to probe the underlying magmatic processes in ultraslowspreading lower crust. Grain-size variation is ubiquitously recorded in the gabbroic lithologies of Hole U1473A, where fine-grained intervals represent relatively evolved chemistry than the coarser domains. This suggests that, they were crystallized from a common genetic melt during different degrees of evolution. The forward geochemical modelling approach have not only affirmed the long-established theory of assimilation (of early mushes’ crystals)-fractional crystallization to be the key mechanism in lower crust formation, but also provided explanation for the restricted whole rock geochemical cluster observed throughout all the rock types. We demonstrate for the first time the relationship between the progressive modal mineralogical evolution with respect to the different assimilation/fractionation ratios (r). The observed trend has been successfully replicated for the experiments with high r values = 0.8--0.9, previously predicted from this region. Integrating all results, our study supports the model of lower crustal formation via reactive porous flow of the squeezed-out melt percolating throughout the cumulate pile and segregated into different horizons.
42.
Ferrando, C.; Tribuzio, R.; Lissenberg, C. J.; France, L.; MacLeod, C. J.; Basch, V.; Villeneuve, J.; Deloule, E.; Sanfilippo, A.
Brown amphibole as tracer of tectono-magmatic evolution of the Atlantis Bank Oceanic Core Complex (IODP Hole U1473A) Journal Article
In: Journal of Petrology, vol. 63, pp. 1–27, 2022.
@article{Ferrando_etal2022,
title = {Brown amphibole as tracer of tectono-magmatic evolution of the Atlantis Bank Oceanic Core Complex (IODP Hole U1473A)},
author = {C. Ferrando and R. Tribuzio and C. J. Lissenberg and L. France and C. J. MacLeod and V. Basch and J. Villeneuve and E. Deloule and A. Sanfilippo},
doi = {10.1093/petrology/egac089},
year = {2022},
date = {2022-01-01},
journal = {Journal of Petrology},
volume = {63},
pages = {1--27},
abstract = {Brown amphibole is a minor but common mineral component in lower oceanic crust. It is generally interpreted as products of migrating SiO2 and H2O-rich fluids or melts, which can be either residual melts from advanced magmatic differentiation of Mid-Ocean Ridge Basalt (MORB), or hydrothermal fluids including a seawater component. Within the lower oceanic crust exhumed at the Atlantis Bank Oceanic Core Complex, along the ultraslow Southwest Indian Ridge, brown amphibole is ubiquitous in all lithologies from olivine- to oxide-gabbros and diorites, including both undeformed and plastically deformed varieties. We here show the results of a systematic petrological study conceived to unravel the nature of the H2O-rich component recorded in brown amphiboles and document: (i) the evolution of migrating melts during the magmatic stage and (ii) different extents of melt-bearing deformation events recorded throughout the entire crustal transect. The low Cl contents and the light over heavy rare earth elements (LREE/HREE) ratios and high Ti contents in brown amphiboles indicate they crystallized from melts with a magmatic hydrous component. Consistently, their $delta$18O values are in equilibrium with Mid-Ocean Ridge Basalt (MORB) composition, except for diorite amphiboles that possibly record the local assimilation of altered minerals. In undeformed olivine gabbros, interstitial pargasite crystallized at hypersolidus conditions (textasciitilde1000textdegreeC) from the melt residual after late stages of MORB differentiation. We speculate that before the olivine gabbro crystal mush reached fully solid state, some aliquots of residual melts were extracted and accumulated within discrete intervals. There, ferrobasaltic melts differentiated through the early crystallization of Fe-Ti oxides and clinopyroxene as liquidus phases, ultimately forming the oxide gabbros. This process promoted rapid Si enrichment and depletion in Fe, Ti, V in the residual melt, later extracted to form the crosscutting diorite veins. The mylonitic olivine gabbros record high-temperature plastic deformation (textasciitilde900textdegreeCthinspacetextpmthinspace50textdegreeC) under hypersolidus conditions, involving melts residual from previous crystallization of the gabbroic rock. Further solid-state plastic deformation led to substantial grain size reduction and, consequently, to an increase in porosity. This created pathways for subsequent melt focusing, which likely represent late-stage differentiated melts migrating throughout the lower crustal section. This study shows that brown amphibole in the Atlantis Bank lower oceanic crust is the crystallization product of melts residual from advanced magmatic differentiation, which are also locally involved in the plastic deformation events during crustal accretion.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Brown amphibole is a minor but common mineral component in lower oceanic crust. It is generally interpreted as products of migrating SiO2 and H2O-rich fluids or melts, which can be either residual melts from advanced magmatic differentiation of Mid-Ocean Ridge Basalt (MORB), or hydrothermal fluids including a seawater component. Within the lower oceanic crust exhumed at the Atlantis Bank Oceanic Core Complex, along the ultraslow Southwest Indian Ridge, brown amphibole is ubiquitous in all lithologies from olivine- to oxide-gabbros and diorites, including both undeformed and plastically deformed varieties. We here show the results of a systematic petrological study conceived to unravel the nature of the H2O-rich component recorded in brown amphiboles and document: (i) the evolution of migrating melts during the magmatic stage and (ii) different extents of melt-bearing deformation events recorded throughout the entire crustal transect. The low Cl contents and the light over heavy rare earth elements (LREE/HREE) ratios and high Ti contents in brown amphiboles indicate they crystallized from melts with a magmatic hydrous component. Consistently, their $delta$18O values are in equilibrium with Mid-Ocean Ridge Basalt (MORB) composition, except for diorite amphiboles that possibly record the local assimilation of altered minerals. In undeformed olivine gabbros, interstitial pargasite crystallized at hypersolidus conditions (textasciitilde1000textdegreeC) from the melt residual after late stages of MORB differentiation. We speculate that before the olivine gabbro crystal mush reached fully solid state, some aliquots of residual melts were extracted and accumulated within discrete intervals. There, ferrobasaltic melts differentiated through the early crystallization of Fe-Ti oxides and clinopyroxene as liquidus phases, ultimately forming the oxide gabbros. This process promoted rapid Si enrichment and depletion in Fe, Ti, V in the residual melt, later extracted to form the crosscutting diorite veins. The mylonitic olivine gabbros record high-temperature plastic deformation (textasciitilde900textdegreeCthinspacetextpmthinspace50textdegreeC) under hypersolidus conditions, involving melts residual from previous crystallization of the gabbroic rock. Further solid-state plastic deformation led to substantial grain size reduction and, consequently, to an increase in porosity. This created pathways for subsequent melt focusing, which likely represent late-stage differentiated melts migrating throughout the lower crustal section. This study shows that brown amphibole in the Atlantis Bank lower oceanic crust is the crystallization product of melts residual from advanced magmatic differentiation, which are also locally involved in the plastic deformation events during crustal accretion.
43.
Beck, N.; Flahaut, J.; Breton, S.
En avant Mars ! Histoire et avenir de l’exploration martienne Book
2022.
@book{Beck_etal2022,
title = {En avant Mars ! Histoire et avenir de l’exploration martienne},
author = {N. Beck and J. Flahaut and S. Breton},
year = {2022},
date = {2022-01-01},
series = {EDP Sciences},
keywords = {},
pubstate = {published},
tppubtype = {book}
}
44.
Losekamm, M. J.; Biswas, J.; Chupin, T.; Deiml, M.; Deremetz, M.; Evagora, A. M.; Fau, G.; Flahaut, J.; Gancet, J.; Glier, M.; Gscheidle, C.; M.,; Joulaud,
Assessing the distribution of water ice and other volatiles at the Lunar South Pole with LUVMI-X: A mission concept Journal Article
In: The Planetary Science Journal, vol. 3, pp. 229, 2022.
@article{Losekamm_etal2022,
title = {Assessing the distribution of water ice and other volatiles at the Lunar South Pole with LUVMI-X: A mission concept},
author = {M. J. Losekamm and J. Biswas and T. Chupin and M. Deiml and M. Deremetz and A. M. Evagora and G. Fau and J. Flahaut and J. Gancet and M. Glier and C. Gscheidle and M. and Joulaud},
doi = {10.3847/PSJ/ac8cfd},
year = {2022},
date = {2022-01-01},
journal = {The Planetary Science Journal},
volume = {3},
pages = {229},
abstract = {The search for exploitable deposits of water and other volatiles at the Moon’s poles has intensified considerably in recent years, due to the renewed strong interest in lunar exploration. With the return of humans to the lunar surface on the horizon, the use of locally available resources to support long-term and sustainable exploration programs, encompassing both robotic and crewed elements, has moved into focus of public and private actors alike. Our current knowledge about the distribution and concentration of water and other volatiles in the lunar rocks and regolith is, however, too limited to assess the feasibility and economic viability of resource-extraction efforts. On a more fundamental level, we currently lack sufficiently detailed data to fully understand the origins of lunar water and its migration to the polar regions. In this paper, we present LUVMI-X, a mission concept intended to address the shortage of in situ data on volatiles on the Moon that results from a recently concluded design study. Its central element is a compact rover equipped with complementary instrumentation capable of investigating both the surface and shallow subsurface of illuminated and shadowed areas at the lunar south pole. We describe the rover and instrument design, the mission’s operational concept, and a preliminary landing-site analysis. We also discuss how LUVMI-X fits into the diverse landscape of lunar missions under development.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The search for exploitable deposits of water and other volatiles at the Moon’s poles has intensified considerably in recent years, due to the renewed strong interest in lunar exploration. With the return of humans to the lunar surface on the horizon, the use of locally available resources to support long-term and sustainable exploration programs, encompassing both robotic and crewed elements, has moved into focus of public and private actors alike. Our current knowledge about the distribution and concentration of water and other volatiles in the lunar rocks and regolith is, however, too limited to assess the feasibility and economic viability of resource-extraction efforts. On a more fundamental level, we currently lack sufficiently detailed data to fully understand the origins of lunar water and its migration to the polar regions. In this paper, we present LUVMI-X, a mission concept intended to address the shortage of in situ data on volatiles on the Moon that results from a recently concluded design study. Its central element is a compact rover equipped with complementary instrumentation capable of investigating both the surface and shallow subsurface of illuminated and shadowed areas at the lunar south pole. We describe the rover and instrument design, the mission’s operational concept, and a preliminary landing-site analysis. We also discuss how LUVMI-X fits into the diverse landscape of lunar missions under development.
45.
Cortes-Calderon, E. A.; Ellis, B. S.; Mark, D. F.; Neukampf, J.; Wolff, J. A.; Ulmer, P.; Bachmann, O.
In: Journal of Petrology, vol. 00, pp. 1–22, 2022.
@article{Cortes-Calderon_etal2022,
title = {Generation and Field Relations of Low-$delta$18O Silica-Undersaturated and Mildly Saturated Alkaline Magmas: a Case Study from the Fataga Group, Gran Canaria},
author = {E. A. Cortes-Calderon and B. S. Ellis and D. F. Mark and J. Neukampf and J. A. Wolff and P. Ulmer and O. Bachmann},
doi = {10.1093/petrology/egac090},
year = {2022},
date = {2022-01-01},
journal = {Journal of Petrology},
volume = {00},
pages = {1--22},
abstract = {The origins of felsic low-$delta$18O melts (\< +5.5 texttenthousand) are usually attributed to assimilation of high-temperature hydrothermally altered (HTHA) rocks. Very few alkaline (silica undersaturated and/or peralkaline) examples are known. Here, we classify the Miocene Fataga Group in Gran Canaria, a silica-undersaturated to mildly saturated alkaline volcanic sequence consisting of trachytic to phonolitic extra-caldera ignimbrites and lavas, as a new low-$delta$18O felsic locality. We provide new mineral, glass and bulk geochemical data linked to a well-constrained stratigraphy to assess the processes involved in the magma reservoir that fed the Fataga eruptions. New high-precision single crystal feldspar 40Ar/39Ar ages of the study area span 13.931 textpm 0.034 Ma to 10.288 textpm 0.016 Ma. Fractional crystallisation at shallow depths of sanidine/anorthoclase, biotite, augite/diopside, titanite, ilmenite and titanomagnetite is the main driving process to produce phonolitic magmas from trachytic melts. Evidence of mafic hotter recharge is not found in the field, but some units exhibit trachytic compositions characterised by positive Eu/Eu* anomalies and high Ba contents, interpreted as melts of feldspar-dominated cumulates, the solid remnants of fractional crystallisation. Hence, recharge magmas halted in the crystal mush and provided the heat needed to sustain cumulate melting and volcanic activity. This cumulate signature might be lost if fractional crystallisation continues before the eruption. The interplay among meteoric water, the caldera-fault system, intra-caldera ignimbrites (Mog\'{a}n Group) and the Fataga magma reservoir favoured assimilation of up to ca. 30% of HTHA rocks. Such assimilation is variable through time and recorded by $delta$18Omelt values down to +4.73 texttenthousand. We did not find any direct relation between assimilation and silica saturation of the Fataga volcanic deposits.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The origins of felsic low-$delta$18O melts (< +5.5 texttenthousand) are usually attributed to assimilation of high-temperature hydrothermally altered (HTHA) rocks. Very few alkaline (silica undersaturated and/or peralkaline) examples are known. Here, we classify the Miocene Fataga Group in Gran Canaria, a silica-undersaturated to mildly saturated alkaline volcanic sequence consisting of trachytic to phonolitic extra-caldera ignimbrites and lavas, as a new low-$delta$18O felsic locality. We provide new mineral, glass and bulk geochemical data linked to a well-constrained stratigraphy to assess the processes involved in the magma reservoir that fed the Fataga eruptions. New high-precision single crystal feldspar 40Ar/39Ar ages of the study area span 13.931 textpm 0.034 Ma to 10.288 textpm 0.016 Ma. Fractional crystallisation at shallow depths of sanidine/anorthoclase, biotite, augite/diopside, titanite, ilmenite and titanomagnetite is the main driving process to produce phonolitic magmas from trachytic melts. Evidence of mafic hotter recharge is not found in the field, but some units exhibit trachytic compositions characterised by positive Eu/Eu* anomalies and high Ba contents, interpreted as melts of feldspar-dominated cumulates, the solid remnants of fractional crystallisation. Hence, recharge magmas halted in the crystal mush and provided the heat needed to sustain cumulate melting and volcanic activity. This cumulate signature might be lost if fractional crystallisation continues before the eruption. The interplay among meteoric water, the caldera-fault system, intra-caldera ignimbrites (Mogán Group) and the Fataga magma reservoir favoured assimilation of up to ca. 30% of HTHA rocks. Such assimilation is variable through time and recorded by $delta$18Omelt values down to +4.73 texttenthousand. We did not find any direct relation between assimilation and silica saturation of the Fataga volcanic deposits.
46.
Debret, B.; Ménez, B.; Bouquerel, H.; Bouilhol, P.; Mattielli, N.; Pisapia, C.; Rigaudier, T.; Williams, H. M.
High-pressure synthesis and storage of solid organic compounds in active subduction zones Journal Article
In: Science Advances, vol. 8, pp. eabo2397, 2022.
@article{Debret_etal2022,
title = {High-pressure synthesis and storage of solid organic compounds in active subduction zones},
author = {B. Debret and B. M\'{e}nez and H. Bouquerel and P. Bouilhol and N. Mattielli and C. Pisapia and T. Rigaudier and H. M. Williams},
doi = {10.1126/sciadv.abo2397},
year = {2022},
date = {2022-01-01},
journal = {Science Advances},
volume = {8},
pages = {eabo2397},
abstract = {Recent thermodynamic and experimental studies have suggested that volatile organic compounds (e.g., methane, formate, and acetate) can be produced and stabilized in subduction zones, potentially playing an important role in the deep carbon cycle. However, field evidence for the high-pressure production and storage of solid organic compounds is missing. Here, we examine forearc serpentinite clasts recovered by drilling mud volcanoes above the Mariana subduction zone. Notable correlations between carbon and iron stable-isotope signatures and fluid-mobile element (B, As and Sb) concentrations provide evidence for the percolation of slab-derived CO2-rich aqueous fluids through the forearc mantle. The presence of carbonaceous matter rich in aliphatic moieties within high-temperature clasts (\>350textdegreeC) demonstrates that molecular hydrogen production associated with forearc serpentinization is an efficient mechanism for the reduction and conversion of slab-derived CO2-rich fluids into solid organic compounds. These findings emphasize the need to consider the forearc mantle as an important reservoir of organic carbon on Earth.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recent thermodynamic and experimental studies have suggested that volatile organic compounds (e.g., methane, formate, and acetate) can be produced and stabilized in subduction zones, potentially playing an important role in the deep carbon cycle. However, field evidence for the high-pressure production and storage of solid organic compounds is missing. Here, we examine forearc serpentinite clasts recovered by drilling mud volcanoes above the Mariana subduction zone. Notable correlations between carbon and iron stable-isotope signatures and fluid-mobile element (B, As and Sb) concentrations provide evidence for the percolation of slab-derived CO2-rich aqueous fluids through the forearc mantle. The presence of carbonaceous matter rich in aliphatic moieties within high-temperature clasts (>350textdegreeC) demonstrates that molecular hydrogen production associated with forearc serpentinization is an efficient mechanism for the reduction and conversion of slab-derived CO2-rich fluids into solid organic compounds. These findings emphasize the need to consider the forearc mantle as an important reservoir of organic carbon on Earth.
47.
Couzinié, S.; Bouilhol, P.; Laurent, O.; Grocolas, T.; Montel, J. M.
In: BSGF- Earth Sciences Bulletin, vol. 193, no. 15, 2022.
@article{Couzini_etal2022,
title = {Cambro--Ordovician ferrosilicic magmatism along the northern Gondwana margin: constraints from the C\'{e}zarenque--Joyeuse gneiss complex (French Massif Central)},
author = {S. Couzini\'{e} and P. Bouilhol and O. Laurent and T. Grocolas and J. M. Montel},
doi = {10.1051/bsgf/2022010},
year = {2022},
date = {2022-01-01},
journal = {BSGF- Earth Sciences Bulletin},
volume = {193},
number = {15},
abstract = {It is well-acknowledged that the northern margin of the Gondwana supercontinent was affected by a major magmatic event at late Cambrian (Furongian) to early Ordovician (Tremadocian--Floian) times. However, an accurate assessment of its extent, origin, and significance is partly hampered by the incomplete characterization of the numerous gneiss massifs exposed in the inner part of the Variscan belt, as some of them possibly represent dismembered and deformed Furongian--Lower Ordovician igneous bodies. In this study, we document the case of the ‘‘C\'{e}zarenque--Joyeuse’’ gneiss complex in the C\'{e}vennes parautochthon domain of the French Massif Central. The gneisses form decametre- to kilometre-thick concordant massifs interlayered within a pluri-kilometric sequence of mica- and quartz schists. They encompass two main petrological types: augen gneisses and albite gneisses, both typified by their blue and engulfed quartz grains with the augen facies differing by the presence of centimetre-sized pseudomorphs after K-feldspar and the local preservation of igneous textures. Whole-rock geochemistry highlights that many gneisses have magmatic ferrosilicic (acidic with anomalously high FeOt and low CaO) compositions while others are akin to greywackes. Collectively, it is inferred that the bulk of the C\'{e}zarenque--Joyeuse gneisses represents former rhyodacite lava flows or ignimbrites and associated epiclastic tuffs. Volumetrically subordinate, finer grained, and strongly silicic leucogneisses are interpreted as microgranite dykes originally intrusive within the volcanic edifices. LA--ICP--MS U--Pb dating of magmatic zircon grains extracted from an augen gneiss and a leucogneiss brackets the crystallization age of the silicic magmas between 486.1thinspacetextpmthinspace5.5thinspaceMa and 483.0thinspacetextpmthinspace5.5thinspaceMa which unambiguously ties the C\'{e}zarenque--Joyeuse gneisses to the Furongian--Lower Ordovician volcanic belt of SW Europe. Inherited zircon date distributions, Ti-in-zircon and zircon saturation thermometry demonstrate that they formed by melting at 750--820thinspacetextdegreeC of Ediacaran sediments. Zircon Eu/Eu* and Ce/Ce* systematics indicate that the melts were strongly reduced (fO2 probably close to the values expected for the iron--w\"{u}stite buffer), possibly because they interacted during ascent with Lower Cambrian black shales. This would have enhanced Fe solubility in the melt phase and may explain the peculiar ferrosilicic signature displayed by many Furongian--Lower Ordovician igneous rocks in the northern Gondwana realm. We infer that crustal melting resulted from a combination of mantle-derived magma underplating in an intracontinental rift setting and anomalously elevated radiogenic heat production within the Ediacaran sedimentary sequences.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
It is well-acknowledged that the northern margin of the Gondwana supercontinent was affected by a major magmatic event at late Cambrian (Furongian) to early Ordovician (Tremadocian--Floian) times. However, an accurate assessment of its extent, origin, and significance is partly hampered by the incomplete characterization of the numerous gneiss massifs exposed in the inner part of the Variscan belt, as some of them possibly represent dismembered and deformed Furongian--Lower Ordovician igneous bodies. In this study, we document the case of the ‘‘Cézarenque--Joyeuse’’ gneiss complex in the Cévennes parautochthon domain of the French Massif Central. The gneisses form decametre- to kilometre-thick concordant massifs interlayered within a pluri-kilometric sequence of mica- and quartz schists. They encompass two main petrological types: augen gneisses and albite gneisses, both typified by their blue and engulfed quartz grains with the augen facies differing by the presence of centimetre-sized pseudomorphs after K-feldspar and the local preservation of igneous textures. Whole-rock geochemistry highlights that many gneisses have magmatic ferrosilicic (acidic with anomalously high FeOt and low CaO) compositions while others are akin to greywackes. Collectively, it is inferred that the bulk of the Cézarenque--Joyeuse gneisses represents former rhyodacite lava flows or ignimbrites and associated epiclastic tuffs. Volumetrically subordinate, finer grained, and strongly silicic leucogneisses are interpreted as microgranite dykes originally intrusive within the volcanic edifices. LA--ICP--MS U--Pb dating of magmatic zircon grains extracted from an augen gneiss and a leucogneiss brackets the crystallization age of the silicic magmas between 486.1thinspacetextpmthinspace5.5thinspaceMa and 483.0thinspacetextpmthinspace5.5thinspaceMa which unambiguously ties the Cézarenque--Joyeuse gneisses to the Furongian--Lower Ordovician volcanic belt of SW Europe. Inherited zircon date distributions, Ti-in-zircon and zircon saturation thermometry demonstrate that they formed by melting at 750--820thinspacetextdegreeC of Ediacaran sediments. Zircon Eu/Eu* and Ce/Ce* systematics indicate that the melts were strongly reduced (fO2 probably close to the values expected for the iron--wüstite buffer), possibly because they interacted during ascent with Lower Cambrian black shales. This would have enhanced Fe solubility in the melt phase and may explain the peculiar ferrosilicic signature displayed by many Furongian--Lower Ordovician igneous rocks in the northern Gondwana realm. We infer that crustal melting resulted from a combination of mantle-derived magma underplating in an intracontinental rift setting and anomalously elevated radiogenic heat production within the Ediacaran sedimentary sequences.
48.
Pin, J.; France, L.; Lambart, S.; Reisberg, L.
Thermodynamic modeling of melt addition to peridotite: Implications for the refertilization of the non-cratonic continental mantle lithosphere Journal Article
In: Chemical Geology, vol. 609, pp. 121050, 2022.
@article{Pin_etal2022,
title = {Thermodynamic modeling of melt addition to peridotite: Implications for the refertilization of the non-cratonic continental mantle lithosphere},
author = {J. Pin and L. France and S. Lambart and L. Reisberg},
doi = {10.1016/j.chemgeo.2022.121050},
year = {2022},
date = {2022-01-01},
journal = {Chemical Geology},
volume = {609},
pages = {121050},
abstract = {In a classic model of evolution of the non-cratonic continental mantle lithosphere, harzburgites represent the refractory (\<5% clinopyroxene) residues of high degrees of partial melting of fertile mantle, while lherzolites (\>5% clinopyroxene) represent residues of lesser degrees of partial melting. However, partial melting is not the only process that could explain the peridotite compositional variability that ranges from fertile (\>2 wt% Al2O3, \<45 wt% MgO) to refractory (\<2 wt% Al2O3, \>45 wt% MgO). In the refertilization process, harzburgite is a refractory protolith (potentially previously formed by partial melting of a fertile mantle) that undergoes reactive percolation of silicate melts derived from the underlying asthenosphere, resulting in the crystallization of a new generation of minerals (mostly clinopyroxene). A simple but critical first step towards understanding therefertilization process is to examine how modal and major element compositions evolve as melts are added to peridotites. Here we use a thermodynamically-constrained two-component mixing model to independently evaluate the roles of five different parameters: pressure, temperature, redox conditions, and compositions of the initial peridotite and the added basaltic melt (hereafter referred to P-T-fO2-X$pi$-Xmelt), during melt addition. We compare the results with observed suites of peridotites. The main observations are as follows: (1) the produced model is consistent with the global peridotite database, and (2) T, fO2 and small variations of pressure have almost no impact on the evolution of the system. In contrast, the mineralogy of the percolated harzburgite has a substantial effect on the variation of the modal proportions. The parameter with the most significant impact is Xmelt, which is directly linked to the geodynamic context and melting conditions. This parameter directly controls the refertilization reaction and so, the phase proportions and the bulk-rock composition. Elements that partition preferentially in the melt phase (e.g., Na) display depletions in natural assemblages that are stronger than those predicted from the simple mixing model, consistent with the fact that the natural process occurs in an open system, and that reactive percolation likely results in incompatible element enrichment in the associated melt. Our results corroborate the suggestion that most of the spectrum of compositional variability observed in lithospheric mantle peridotites can be explained by the impregnation of primitive silicate melt in refractory harzburgites.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In a classic model of evolution of the non-cratonic continental mantle lithosphere, harzburgites represent the refractory (<5% clinopyroxene) residues of high degrees of partial melting of fertile mantle, while lherzolites (>5% clinopyroxene) represent residues of lesser degrees of partial melting. However, partial melting is not the only process that could explain the peridotite compositional variability that ranges from fertile (>2 wt% Al2O3, <45 wt% MgO) to refractory (<2 wt% Al2O3, >45 wt% MgO). In the refertilization process, harzburgite is a refractory protolith (potentially previously formed by partial melting of a fertile mantle) that undergoes reactive percolation of silicate melts derived from the underlying asthenosphere, resulting in the crystallization of a new generation of minerals (mostly clinopyroxene). A simple but critical first step towards understanding therefertilization process is to examine how modal and major element compositions evolve as melts are added to peridotites. Here we use a thermodynamically-constrained two-component mixing model to independently evaluate the roles of five different parameters: pressure, temperature, redox conditions, and compositions of the initial peridotite and the added basaltic melt (hereafter referred to P-T-fO2-X$pi$-Xmelt), during melt addition. We compare the results with observed suites of peridotites. The main observations are as follows: (1) the produced model is consistent with the global peridotite database, and (2) T, fO2 and small variations of pressure have almost no impact on the evolution of the system. In contrast, the mineralogy of the percolated harzburgite has a substantial effect on the variation of the modal proportions. The parameter with the most significant impact is Xmelt, which is directly linked to the geodynamic context and melting conditions. This parameter directly controls the refertilization reaction and so, the phase proportions and the bulk-rock composition. Elements that partition preferentially in the melt phase (e.g., Na) display depletions in natural assemblages that are stronger than those predicted from the simple mixing model, consistent with the fact that the natural process occurs in an open system, and that reactive percolation likely results in incompatible element enrichment in the associated melt. Our results corroborate the suggestion that most of the spectrum of compositional variability observed in lithospheric mantle peridotites can be explained by the impregnation of primitive silicate melt in refractory harzburgites.
49.
Schwarz, D.; Giuliani, G.
La gemmologie des émeraudes du Brésil Journal Article
In: Emeraudes, tout un monde !, pp. 303–310, 2022.
@article{Schwarz+Giuliani2022,
title = {La gemmologie des \'{e}meraudes du Br\'{e}sil},
author = {D. Schwarz and G. Giuliani},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {303--310},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
50.
Pignatelli, I.; Giuliani, G.; Morlot, Ch.; Salsi, L.; Martayan, G.
Les curiosités minéralogiques de l’émeraude colombienne Journal Article
In: Emeraudes, tout un monde !, pp. 215–226, 2022.
@article{Pignatelli_etal2022_2,
title = {Les curiosit\'{e}s min\'{e}ralogiques de l’\'{e}meraude colombienne},
author = {I. Pignatelli and G. Giuliani and Ch. Morlot and L. Salsi and G. Martayan},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {215--226},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
51.
Michelou, J. C.; Cornuz, L.; Michelou, Z.; Pardieu, V.; Giuliani, G.
Les gisements d’émeraude du Pakistan Journal Article
In: Emeraudes, tout un monde !, pp. 247–258, 2022.
@article{Michelou_etal2022,
title = {Les gisements d’\'{e}meraude du Pakistan},
author = {J. C. Michelou and L. Cornuz and Z. Michelou and V. Pardieu and G. Giuliani},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {247--258},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
52.
Giuliani, G.; Branquet, Y.; Groat, L. A.; Marshall, D. D.; Fallick, A. A.
Typologie des gisements d’émeraude Journal Article
In: Emeraudes, tout un monde !, pp. 37–44, 2022.
@article{Giuliani_etal2022_2,
title = {Typologie des gisements d’\'{e}meraude},
author = {G. Giuliani and Y. Branquet and L. A. Groat and D. D. Marshall and A. A. Fallick},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {37--44},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
53.
Giuliani, G.
Géologie et gen`ese des émeraudes du Panjshir Journal Article
In: Emeraudes, tout un monde !, pp. 265–270, 2022.
@article{Giuliani2022_3,
title = {G\'{e}ologie et gen`ese des \'{e}meraudes du Panjshir},
author = {G. Giuliani},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {265--270},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
54.
Giuliani, G.
Pourquoi certains gisements d’émeraude sont-ils si particuliers Journal Article
In: Emeraudes, tout un monde !, pp. 137–148, 2022.
@article{Giuliani2022_2,
title = {Pourquoi certains gisements d’\'{e}meraude sont-ils si particuliers},
author = {G. Giuliani},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {137--148},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
55.
Giuliani, G.
Les gisements d’émeraude en environnement granitique Journal Article
In: Emeraudes, tout un monde !, pp. 45–46, 2022.
@article{Giuliani2022,
title = {Les gisements d’\'{e}meraude en environnement granitique},
author = {G. Giuliani},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {45--46},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
56.
Branquet, Y.; Giuliani, G.
Géologie et exploration de l’émeraude colombienne Journal Article
In: Emeraudes, tout un monde !, pp. 195–206, 2022.
@article{Branquet+Giuliani2022,
title = {G\'{e}ologie et exploration de l’\'{e}meraude colombienne},
author = {Y. Branquet and G. Giuliani},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {195--206},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
57.
Béziat, D.; Salvi, S.; Giuliani, G.; Rakotondrazafy, A. F. M.; Pardieu, V.; Sangsawong, S.
Les gisements d’émeraude de Madagascar Journal Article
In: Emeraudes, tout un monde !, pp. 63–70, 2022.
@article{Bziat_etal2022,
title = {Les gisements d’\'{e}meraude de Madagascar},
author = {D. B\'{e}ziat and S. Salvi and G. Giuliani and A. F. M. Rakotondrazafy and V. Pardieu and S. Sangsawong},
year = {2022},
date = {2022-01-01},
journal = {Emeraudes, tout un monde !},
pages = {63--70},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
58.
Lang, S.; Mollo, S.; France, L.; Misiti, V.; Nazzari, M.
In: Chemical Geology, vol. 601, pp. 120870, 2022.
@article{Lang_etal2022,
title = {Partitioning of Ti, Al, P, and Cr between olivine and a tholeiitic basaltic melt: Insights on olivine zoning patterns and cation substitution reactions under variable cooling rate conditions},
author = {S. Lang and S. Mollo and L. France and V. Misiti and M. Nazzari},
doi = {10.1016/j.chemgeo.2022.120870},
year = {2022},
date = {2022-01-01},
journal = {Chemical Geology},
volume = {601},
pages = {120870},
abstract = {The mechanism governing the kinetic growth of olivine in dynamic volcanic settings has been the subject of considerable attention in recent years. Under variable cooling rate (CR) and undercooling (−$Delta$T) regimes, the textual maturation of olivine proceeds from skeletal/dendritic crystals to polyhedral morphologies by infilling of the crystal framework. Owing to the establishment of a diffusion-controlled growth regime, a sharp diffusive boundary layer develops in the melt next to the advancing olivine surface. In this context, we have quantified the apparent partitioning of Ti, Al, P, and Cr between olivine and a Hawaiian tholeiitic basaltic melt at P = 1 at},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The mechanism governing the kinetic growth of olivine in dynamic volcanic settings has been the subject of considerable attention in recent years. Under variable cooling rate (CR) and undercooling (−$Delta$T) regimes, the textual maturation of olivine proceeds from skeletal/dendritic crystals to polyhedral morphologies by infilling of the crystal framework. Owing to the establishment of a diffusion-controlled growth regime, a sharp diffusive boundary layer develops in the melt next to the advancing olivine surface. In this context, we have quantified the apparent partitioning of Ti, Al, P, and Cr between olivine and a Hawaiian tholeiitic basaltic melt at P = 1 at
59.
Podda, O.; Tissandier, L.; Laplace, A.; Deloule, E.
Solubility of uranium oxide in ternary aluminosilicate glass melts Journal Article
In: Journal of Non-Crystalline Solids, vol. 595, pp. 121845, 2022.
@article{Podda_etal2022,
title = {Solubility of uranium oxide in ternary aluminosilicate glass melts},
author = {O. Podda and L. Tissandier and A. Laplace and E. Deloule},
doi = {10.1016/j.jnoncrysol.2022.121845},
year = {2022},
date = {2022-01-01},
journal = {Journal of Non-Crystalline Solids},
volume = {595},
pages = {121845},
abstract = {Uranium solubility was measured in melts belonging to the CaO-Al2O3-SiO2 (CAS) and MgO-Al2O3-SiO2 (MAS) systems using the Pt wire loop technique, enabling independent control of the temperature (1400 \^{a}¦C), glass composition, and oxygen fugacity (-16.1\<log(fO2)\<-0.7). The low sample masses allowed the equilibrium state to be reached quickly and rapid quenching of the glasses was performed in order to immobilize each system as close as possible to the molten state. The compositions of the different quenched glasses were analyzed by EDS. Uranium solubility decreased with decreasing oxygen fugacity, highlighting the lower solubility of uranium at reduced oxidation states. For each system, uranium solubility was constant from log(fO2)\<-9.7. Moreover, different uranium behavior was evidenced between the two ternary systems. Modification of the Al content affected only uranium solubility in the CAS compositions, while uranium volatilization for oxidizing conditions was noted in the MAS system. This difference in behavior may be attributed to structural changes and probably to the variable proportions of [5]Al in each glass system.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Uranium solubility was measured in melts belonging to the CaO-Al2O3-SiO2 (CAS) and MgO-Al2O3-SiO2 (MAS) systems using the Pt wire loop technique, enabling independent control of the temperature (1400 â¦C), glass composition, and oxygen fugacity (-16.1<log(fO2)<-0.7). The low sample masses allowed the equilibrium state to be reached quickly and rapid quenching of the glasses was performed in order to immobilize each system as close as possible to the molten state. The compositions of the different quenched glasses were analyzed by EDS. Uranium solubility decreased with decreasing oxygen fugacity, highlighting the lower solubility of uranium at reduced oxidation states. For each system, uranium solubility was constant from log(fO2)<-9.7. Moreover, different uranium behavior was evidenced between the two ternary systems. Modification of the Al content affected only uranium solubility in the CAS compositions, while uranium volatilization for oxidizing conditions was noted in the MAS system. This difference in behavior may be attributed to structural changes and probably to the variable proportions of [5]Al in each glass system.
60.
Morin, G. L. F.; Marrocchi, Y.; Villeneuve, J.; Jacquet, E.
16O-rich anhydrous silicates in CI chondrites: Implications for the nature and dynamics of dust in the solar accretion disk Journal Article
In: Geochimica et Cosmochimica Acta, vol. 332, pp. 203–219, 2022.
@article{Morin_etal2022,
title = {16O-rich anhydrous silicates in CI chondrites: Implications for the nature and dynamics of dust in the solar accretion disk},
author = {G. L. F. Morin and Y. Marrocchi and J. Villeneuve and E. Jacquet},
doi = {10.1016/j.gca.2022.06.017},
year = {2022},
date = {2022-01-01},
journal = {Geochimica et Cosmochimica Acta},
volume = {332},
pages = {203--219},
abstract = {CI chondrites have nonvolatile chemical compositions closely resembling that of the Sun’s photosphere and are thus considered to have the most primitive compositions of all known solar system materials. They have, however, experienced pervasive parent-body alteration processes that transformed their primary constituents, obscuring the nature and origin of primordial CI dust. We used in-situ quantitative microprobe and secondary ion mass spectrometry techniques to characterize the chemistry and oxygen isotopic compositions of anhydrous silicates in two sections of the CI chondrites Ivuna and Alais, which contain higher abundances of those than other CI samples. These silicates are Mg-rich olivine and low-Ca pyroxene crystals mostly occurring as aggregates within sub-mm Fe-rich clasts. Our data reveal mass-independent oxygen isotopic variations with D17O values ranging from -23.63 to -0.57texttenthousand, representing the first evidence of extremely 16O-rich (D17O \< -20texttenthousand) olivine and pyroxene grains in CI chondrites. Two of these olivines are characterized by MnO/FeO textasciitilde 1,typical of low-iron, Mn-enriched silicates commonly observed in amoeboid olivine aggregates. Other anhydrous silicate grains have D17O values ranging from -6 to 0texttenthousand, probably representing chondrule fragments. Combined, these results indicate that chondrule and refractory inclusion material were incorporated into the CI parent body(ies). This conclusion is consistent with recent models showing that refractory inclusions could have formed and/or been transported at larger heliocentric distances than previously thought during the concomitant injection of material from the molecular cloud and outward extension of the disk by viscous spreading. The CI chondrules are presumably of local origin, with their isotopic systematics suggesting an affinity with the CR clan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
CI chondrites have nonvolatile chemical compositions closely resembling that of the Sun’s photosphere and are thus considered to have the most primitive compositions of all known solar system materials. They have, however, experienced pervasive parent-body alteration processes that transformed their primary constituents, obscuring the nature and origin of primordial CI dust. We used in-situ quantitative microprobe and secondary ion mass spectrometry techniques to characterize the chemistry and oxygen isotopic compositions of anhydrous silicates in two sections of the CI chondrites Ivuna and Alais, which contain higher abundances of those than other CI samples. These silicates are Mg-rich olivine and low-Ca pyroxene crystals mostly occurring as aggregates within sub-mm Fe-rich clasts. Our data reveal mass-independent oxygen isotopic variations with D17O values ranging from -23.63 to -0.57texttenthousand, representing the first evidence of extremely 16O-rich (D17O < -20texttenthousand) olivine and pyroxene grains in CI chondrites. Two of these olivines are characterized by MnO/FeO textasciitilde 1,typical of low-iron, Mn-enriched silicates commonly observed in amoeboid olivine aggregates. Other anhydrous silicate grains have D17O values ranging from -6 to 0texttenthousand, probably representing chondrule fragments. Combined, these results indicate that chondrule and refractory inclusion material were incorporated into the CI parent body(ies). This conclusion is consistent with recent models showing that refractory inclusions could have formed and/or been transported at larger heliocentric distances than previously thought during the concomitant injection of material from the molecular cloud and outward extension of the disk by viscous spreading. The CI chondrules are presumably of local origin, with their isotopic systematics suggesting an affinity with the CR clan.