Sebastien Jego | Université d'Orléans (Loire Valley University) (original) (raw)
Papers by Sebastien Jego
Geochimica et Cosmochimica Acta, 2016
Geochmica Et Cosmochimica Acta, Jun 1, 2009
Agu Spring Meeting Abstracts, May 1, 2006
Agu Fall Meeting Abstracts, Dec 1, 2007
Geochimica et Cosmochimica Acta, 2013
We conducted multi-year analys of ice microphysics using CloudSat and CALIPSO data. Inter-annual ... more We conducted multi-year analys of ice microphysics using CloudSat and CALIPSO data. Inter-annual variability, land-ocean differences and seasonal changes of ice microphysical properties were reported for the observation periods from 2006 to 2009. CALIPSO changed the laser tilt angle from 0.3 degrees to 3 degrees off nadir direction on November 2007 and the zonal mean properties of backscattering coefficient and depolarization ratio were significantly decreased and increased, respectively, for low altitude after November 2007. ...
Geochimica et Cosmochimica Acta, 2016
The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the ma... more The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous supra-subduction zone ophiolitic complex located within the Luzon arc crust. Spinel-bearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spinel dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibole-rich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it.
Les gisements minéraux à Au-Cu-Mo constituent des ressources métalliques majeures connues pour êt... more Les gisements minéraux à Au-Cu-Mo constituent des ressources métalliques majeures connues pour être associées spatio-temporellement au magmatisme intrusif d’arc, et en particulier au magmatisme adakitique dont la pétrogenèse est singulière. Bien que la plus grande partie des métaux semble trouver son origine dans les magmas, il n’y a pas encore de consensus quant aux processus responsables de leur concentration. Le fait que les minéraux primaires contenant le minerai soient de façon prépondérante des sulfures a conduit à la suggestion que le soufre joue un rôle important dans l’enrichissement métallique au stade magmatique. Les études expérimentales précédentes ont montré que les sulfures peuvent largement fractionner Au à partir du liquide magmatique, concluant que les magmas oxydés sont potentiellement plus riches en or. Ici, nous avons effectué des expériences haute température-haute pression sur cinq roches naturelles des Philippines, sur une gamme de fO2 allant de conditions ré...
Copper-gold-molybdenum deposits represent major metal resources known to be spatially and tempora... more Copper-gold-molybdenum deposits represent major metal resources known to be spatially and temporally associated with intrusive arc magmatism (Hedenquist and Lowenstern, 1994). Although the bulk of the ore metals seem to originate from the magmas, there is as yet no consensus on processes responsible for their concentration. The fact that primary ore minerals are predominantly sulfides has led to the suggestion that sulfur may play an important role in metal enrichment processes at the magmatic stage (Sillitoe, 1997; Mungall, 2002). Previous experimental studies have shown that sulfides can largely fractionate gold from the melt, and therefore concluded that oxidized magmas are more likely to be Au-enriched. Here, we conducted high- pressure temperature experiments (4 Kbar, 1000°C) on three natural dacitic magmas from the Philippines (two adakites and one typical calc-alkaline composition) over a range of fO2 corresponding to reducing (~NNO-1), moderately oxidizing (~NNO+1.5) and str...
Subduction zone magmas are considered to be important carriers of sulfur from the sub-arc mantle ... more Subduction zone magmas are considered to be important carriers of sulfur from the sub-arc mantle wedge to the arc crust - through deposition of sulfide ores, and to the atmosphere - through volcanic degassing. Slab-derived sulfur is also proposed to be linked to the oxidation state of the mantle wedge [1]. However, the origin of the sulfur enrichment of most of arc magmas and the transport of sulfur from the subducting slab to the mantle wedge are poorly understood. Here we report experimental measurements of the sulfur content at sulfide saturation (SCSS) of slab-derived hydrous partial melts at a pressure of 2.0 GPa and a temperature range of 800-1050 °C. A synthetic MORB + 6.8 wt.% H2O doped with 1 wt% S (added as pyrite) was used as starting material. The experiments were conducted in a piston-cylinder device with samples contained in Au inner capsules and Ni-NiO (fO2 = FMQ+0.5) or Co-CoO mixtures in Au-Pd outer capsules. Sulfur concentrations in quenched silicate glass and the ...
Copper-gold-molybdenum deposits represent major metal resources known to be spatially and tempora... more Copper-gold-molybdenum deposits represent major metal resources known to be spatially and temporally associated with intrusive arc magmatism (Hedenquist and Lowenstern, 1994). Although the bulk of the ore metals seem to originate from the magmas, there is as yet no consensus on processes responsible for their concentration. The fact that primary ore minerals are predominantly sulfides has led to the suggestion that sulfur may play an important role in metal enrichment processes at the magmatic stage (Sillitoe, 1997; Mungall, 2002). Previous experimental studies have shown that sulfides can largely fractionate gold from the melt, and therefore concluded that oxidized magmas are more likely to be Au-enriched. Here, we conducted high-pressure temperature experiments (4 Kbar, 1000°C) on three dacitic and two rhyolitic natural magmas from the Philippines (both adakitic and typical calc-alkaline compositions were used) over a range of fO2 corresponding to reducing (~NNO-1), moderately oxi...
Au-Cu-Mo deposits represent major metal resources known to be spatially and temporally associated... more Au-Cu-Mo deposits represent major metal resources known to be spatially and temporally associated with intrusive arc magmatism and, according to some studies, notably with adakites. Although the bulk of the ore metals seems to originate from the magmas, there is as yet no consensus on processes responsible for their concentration. The fact that primary ore minerals are predominantly sulfides has led to the suggestion that sulfur may play an important role in metal enrichment processes at the magmatic stage. Besides, although no previous study has focused so far on its pressure-dependency, the solubility of gold in silicate melts is expected to vary with depth in a significant way, independently of any fractionation process. If this is true, it may lead to important implications for the gold budget of arc magmas rising up through the mantle wedge and the crust. In addition to recently published gold solubility data at 1000°C and 0.4 GPa (Jego et al., 2010, GCA, In press), we present ...
Resource Geology, 2007
Baguio, in the Central Cordillera of Northern Luzon, is a district that displays porphyry copper ... more Baguio, in the Central Cordillera of Northern Luzon, is a district that displays porphyry copper and epithermal gold mineralization, associated with Early Miocene -Pliocene -Quaternary calc-alkaline and adakitic intrusions. Systematic sampling, K-Ar dating, major and trace elements, and Sr, Nd, Pb isotopic analyses of fresh magmatic rocks indicate three magmatic pulses: an Early Miocene phase (21.2 -18.7 Ma), a Middle -Late Miocene phase (15.3 -8 Ma) and fi nally a Pliocene -Quaternary event (3 -1 Ma). The fi rst phase emplaced evolved calc-alkaline magmas, essentially within the Agno Batholith complex, and is thought to be related to the westward-dipping subduction of the West Philippine Basin. After a quiescence period during which the Kennon limestone was deposited, magmatic activity resumed at 15.3 Ma, in connection with the start of the subduction of the South China Sea along the Manila Trench. It emplaced fi rst petrogenetically related and relatively unradiogenic low-K calc-alkaline lavas and intermediate adakites. Temporal geochemical patterns observed from 15.3 to 1 Ma include progressive enrichment in K and other large ion lithophile elements, increase in radiogenic Sr and Pb and corresponding decrease in radiogenic Nd. These features are thought to refl ect the progressive addition to the Luzon arc mantle wedge of incompatible elements largely inherited from South China Sea sediments. The origin of the long quiescence period, from 8 to 3 Ma, remains problematic. It might represent a local consequence of the docking of the Zambales ophiolitic terrane to Northern Luzon. Then, magmatic activity resumed at 3 Ma, emplacing chemically diversifi ed rocks ranging from low K to high K and including a large proportion of adakites, especially during the Quaternary (dacitic plugs). The authors tentatively relate this diversity to the development of a slab tear linked with the subduction of the fossil South China Sea ridge beneath the Baguio area.
Lithos, 2008
The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the ma... more The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous suprasubduction zone ophiolitic complex located within the Luzon arc crust. Spinelbearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spinel dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibolerich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it.
Geochimica et Cosmochimica Acta, 2016
Geochmica Et Cosmochimica Acta, Jun 1, 2009
Agu Spring Meeting Abstracts, May 1, 2006
Agu Fall Meeting Abstracts, Dec 1, 2007
Geochimica et Cosmochimica Acta, 2013
We conducted multi-year analys of ice microphysics using CloudSat and CALIPSO data. Inter-annual ... more We conducted multi-year analys of ice microphysics using CloudSat and CALIPSO data. Inter-annual variability, land-ocean differences and seasonal changes of ice microphysical properties were reported for the observation periods from 2006 to 2009. CALIPSO changed the laser tilt angle from 0.3 degrees to 3 degrees off nadir direction on November 2007 and the zonal mean properties of backscattering coefficient and depolarization ratio were significantly decreased and increased, respectively, for low altitude after November 2007. ...
Geochimica et Cosmochimica Acta, 2016
The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the ma... more The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous supra-subduction zone ophiolitic complex located within the Luzon arc crust. Spinel-bearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spinel dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibole-rich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it.
Les gisements minéraux à Au-Cu-Mo constituent des ressources métalliques majeures connues pour êt... more Les gisements minéraux à Au-Cu-Mo constituent des ressources métalliques majeures connues pour être associées spatio-temporellement au magmatisme intrusif d’arc, et en particulier au magmatisme adakitique dont la pétrogenèse est singulière. Bien que la plus grande partie des métaux semble trouver son origine dans les magmas, il n’y a pas encore de consensus quant aux processus responsables de leur concentration. Le fait que les minéraux primaires contenant le minerai soient de façon prépondérante des sulfures a conduit à la suggestion que le soufre joue un rôle important dans l’enrichissement métallique au stade magmatique. Les études expérimentales précédentes ont montré que les sulfures peuvent largement fractionner Au à partir du liquide magmatique, concluant que les magmas oxydés sont potentiellement plus riches en or. Ici, nous avons effectué des expériences haute température-haute pression sur cinq roches naturelles des Philippines, sur une gamme de fO2 allant de conditions ré...
Copper-gold-molybdenum deposits represent major metal resources known to be spatially and tempora... more Copper-gold-molybdenum deposits represent major metal resources known to be spatially and temporally associated with intrusive arc magmatism (Hedenquist and Lowenstern, 1994). Although the bulk of the ore metals seem to originate from the magmas, there is as yet no consensus on processes responsible for their concentration. The fact that primary ore minerals are predominantly sulfides has led to the suggestion that sulfur may play an important role in metal enrichment processes at the magmatic stage (Sillitoe, 1997; Mungall, 2002). Previous experimental studies have shown that sulfides can largely fractionate gold from the melt, and therefore concluded that oxidized magmas are more likely to be Au-enriched. Here, we conducted high- pressure temperature experiments (4 Kbar, 1000°C) on three natural dacitic magmas from the Philippines (two adakites and one typical calc-alkaline composition) over a range of fO2 corresponding to reducing (~NNO-1), moderately oxidizing (~NNO+1.5) and str...
Subduction zone magmas are considered to be important carriers of sulfur from the sub-arc mantle ... more Subduction zone magmas are considered to be important carriers of sulfur from the sub-arc mantle wedge to the arc crust - through deposition of sulfide ores, and to the atmosphere - through volcanic degassing. Slab-derived sulfur is also proposed to be linked to the oxidation state of the mantle wedge [1]. However, the origin of the sulfur enrichment of most of arc magmas and the transport of sulfur from the subducting slab to the mantle wedge are poorly understood. Here we report experimental measurements of the sulfur content at sulfide saturation (SCSS) of slab-derived hydrous partial melts at a pressure of 2.0 GPa and a temperature range of 800-1050 °C. A synthetic MORB + 6.8 wt.% H2O doped with 1 wt% S (added as pyrite) was used as starting material. The experiments were conducted in a piston-cylinder device with samples contained in Au inner capsules and Ni-NiO (fO2 = FMQ+0.5) or Co-CoO mixtures in Au-Pd outer capsules. Sulfur concentrations in quenched silicate glass and the ...
Copper-gold-molybdenum deposits represent major metal resources known to be spatially and tempora... more Copper-gold-molybdenum deposits represent major metal resources known to be spatially and temporally associated with intrusive arc magmatism (Hedenquist and Lowenstern, 1994). Although the bulk of the ore metals seem to originate from the magmas, there is as yet no consensus on processes responsible for their concentration. The fact that primary ore minerals are predominantly sulfides has led to the suggestion that sulfur may play an important role in metal enrichment processes at the magmatic stage (Sillitoe, 1997; Mungall, 2002). Previous experimental studies have shown that sulfides can largely fractionate gold from the melt, and therefore concluded that oxidized magmas are more likely to be Au-enriched. Here, we conducted high-pressure temperature experiments (4 Kbar, 1000°C) on three dacitic and two rhyolitic natural magmas from the Philippines (both adakitic and typical calc-alkaline compositions were used) over a range of fO2 corresponding to reducing (~NNO-1), moderately oxi...
Au-Cu-Mo deposits represent major metal resources known to be spatially and temporally associated... more Au-Cu-Mo deposits represent major metal resources known to be spatially and temporally associated with intrusive arc magmatism and, according to some studies, notably with adakites. Although the bulk of the ore metals seems to originate from the magmas, there is as yet no consensus on processes responsible for their concentration. The fact that primary ore minerals are predominantly sulfides has led to the suggestion that sulfur may play an important role in metal enrichment processes at the magmatic stage. Besides, although no previous study has focused so far on its pressure-dependency, the solubility of gold in silicate melts is expected to vary with depth in a significant way, independently of any fractionation process. If this is true, it may lead to important implications for the gold budget of arc magmas rising up through the mantle wedge and the crust. In addition to recently published gold solubility data at 1000°C and 0.4 GPa (Jego et al., 2010, GCA, In press), we present ...
Resource Geology, 2007
Baguio, in the Central Cordillera of Northern Luzon, is a district that displays porphyry copper ... more Baguio, in the Central Cordillera of Northern Luzon, is a district that displays porphyry copper and epithermal gold mineralization, associated with Early Miocene -Pliocene -Quaternary calc-alkaline and adakitic intrusions. Systematic sampling, K-Ar dating, major and trace elements, and Sr, Nd, Pb isotopic analyses of fresh magmatic rocks indicate three magmatic pulses: an Early Miocene phase (21.2 -18.7 Ma), a Middle -Late Miocene phase (15.3 -8 Ma) and fi nally a Pliocene -Quaternary event (3 -1 Ma). The fi rst phase emplaced evolved calc-alkaline magmas, essentially within the Agno Batholith complex, and is thought to be related to the westward-dipping subduction of the West Philippine Basin. After a quiescence period during which the Kennon limestone was deposited, magmatic activity resumed at 15.3 Ma, in connection with the start of the subduction of the South China Sea along the Manila Trench. It emplaced fi rst petrogenetically related and relatively unradiogenic low-K calc-alkaline lavas and intermediate adakites. Temporal geochemical patterns observed from 15.3 to 1 Ma include progressive enrichment in K and other large ion lithophile elements, increase in radiogenic Sr and Pb and corresponding decrease in radiogenic Nd. These features are thought to refl ect the progressive addition to the Luzon arc mantle wedge of incompatible elements largely inherited from South China Sea sediments. The origin of the long quiescence period, from 8 to 3 Ma, remains problematic. It might represent a local consequence of the docking of the Zambales ophiolitic terrane to Northern Luzon. Then, magmatic activity resumed at 3 Ma, emplacing chemically diversifi ed rocks ranging from low K to high K and including a large proportion of adakites, especially during the Quaternary (dacitic plugs). The authors tentatively relate this diversity to the development of a slab tear linked with the subduction of the fossil South China Sea ridge beneath the Baguio area.
Lithos, 2008
The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the ma... more The Monglo adakite contains mafic and ultramafic xenoliths, which probably originated from the mantle section of an Early Cretaceous suprasubduction zone ophiolitic complex located within the Luzon arc crust. Spinelbearing dunites are dominant among this xenolith collection and display evidence for three episodes of subduction-related melt percolation. The first one is evidenced by an undeformed clinopyroxene characterized by convex-upwards REE pattern. This clinopyroxene crystallized from a calc-alkaline basaltic magma, likely formed in the Cretaceous supra-subduction setting of the ophiolite. Then, two metasomatic events, evidenced by orthopyroxene-rich and amphibole-rich secondary parageneses, respectively, affected most of the spinel dunites. The opx-rich paragenesis is related to the circulation within the dunitic upper mantle of hydrous slab-derived melts similar to those affecting the mantle peridotite xenoliths from Papua New Guinea and Kamchatka. Finally the amphibolerich veins are related to the interaction between the studied dunite xenoliths and the host adakite or an adakitic melt similar to it.