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Jinhui Yang - One of the best experts on this subject based on the ideXlab platform.
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mesozoic continental crustal rejuvenation of south china insights from zircon hfo isotopes of early jurassic gabbros Syenites and a type granites
Lithos, 2021Co-Authors: Jinhui Yang, Jiheng Zhang, Jingyuan Chen, Jinfeng SunAbstract:Abstract Whole rock geochemistry and Sr-Nd-Hf isotope, zircon U Pb and Hf O isotope data are reported for the early Jurassic gabbro-Syenite-alkali-feldspar granite in the inland of South China, in order to investigate their sources, petrogenesis and tectonic implication, and to further trace the rejuvenation of continental crust of South China. The zircon U Pb dating constrains the crystallization ages of 198–195 Ma for Syenites, and of about 190 Ma for alkali-feldspar granites and gabbros, respectively. The early Jurassic gabbros have low SiO2 contents and high MgO, TiO2, Cr, V and Ni concentrations, with weak negative Nb and Ta anomalies, variable whole rock initial 87Sr/86Sr ratios (0.7064–0.7117), eNd(t) values (−1.5 to +0.6), eHf(t) values (−1.6 to +5.7) and zircon eHf(t) values (+3.4 to +6.4) and mantle-like δ18O values (+4.9 to +6.2‰). They are inferred to be derived from partial melting of a fertile lithospheric mantle that had been metasomatized by subduction-related fluids/melts, with subsequent limited crustal assimilation and fractional crystallization. The early Jurassic Syenites are high-K to shoshonitic rocks with weakly negative Nb and Ta anomalies, strongly negative Sr, P and Ti anomalies, unradiogenic Sr and radiogenic Nd and Hf isotopic compositions (eNd(t) up to +5.3 and eHf(t) up to +11.5), indicating that they were generated by low-percentage partial melting of an amphibole-bearing lithospheric mantle, with subsequent crustal assimilation and extensive crystal fractionation and/or accumulation. The geochemical features of the early Jurassic K-feldspar granites suggest that they were mainly generated by mixing between mantle-derived mafic magma and crustal-derived felsic magma with extensive feldspar-dominant fractional crystallization. The early Jurassic magmatism was possibly triggered by asthenospheric upwelling following delamination of the flat-subducted Paleo-Pacific plate beneath South China, which provided heat to partial melting of above lithospheric mantle and continental crust. The underplating of depleted mantle-derived magmas changed the ancient crustal structures and modified the components of continental crust, indicating lithospheric rejuvenation during early Jurassic in South China.
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petrogenesis of an alkali Syenite granite rhyolite suite in the yanshan fold and thrust belt eastern north china craton geochronological geochemical and nd sr hf isotopic evidence for lithospheric thinning
Journal of Petrology, 2007Co-Authors: Jinhui Yang, Fuyuan Wu, Simon A Wilde, Fukun ChenAbstract:The Yanshan Fold and Thrust Belt in eastern China has been intruded by a series of alkalic igneous rocks, ranging in composition from granite and rhyolite to Syenite and trachyte. Laser ablation inductively coupled plasma mass spectrometry U^Pb analyses of zircon from three alkaline suites yield Early Cretaceous ages of 130^117Ma. Three groups of rocks have been identified based on their mineralogical, geochemical and Sr^Nd^Hf isotope characteristics. The alkali granites and rhyolites are ferroan and have low Al2O3, MgO, CaO, Sr, Ba and Eu concentrations and high SiO2, total Fe2O3, K2O, Nb, Ga, Ta, Th and heavy rare earth element abundances and Ga/Al ratios. Geochemical data and Sr-, Ndand zircon Hf-isotopic compositions [(Sr/Sr)i1⁄4 0 7050^0 7164, eNd(t)1⁄4 8 4 to 13 6 and eHf(t)1⁄4 5 7 to 16 8] indicate that they were probably generated by shallow dehydration melting of biotiteor hornblende-bearing granitoid crustal source rocks and then mixed with contemporaneous magma from a mantle and/or lower crustal source. Ferroan Syenites have distinct geochemical features from those of the alkaline granites and rhyolites, suggesting that they were produced by clinopyroxene and plagioclase fractionation of melt derived from an enriched mantle source, mixed with lower and upper crustal-derived magmas. The magnesian Syenites and trachytes have Sr-, Ndand zircon Hf-isotopic compositions that are distinct from those of the ferroan Syenites. They were mainly derived from partial melting of lower crustal materials, mixed with enriched mantle-derived alkali basaltic magma.The emplacement of an alkali Syenite^granite^rhyolite suite, coeval with the formation of metamorphic core complexes and pull-apart basins in eastern China, indicates they formed in an extensional setting, possibly as a result of lithospheric thinning.
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petrogenesis of an alkali Syenite granite rhyolite suite in the yanshan fold and thrust belt eastern north china craton geochronological geochemical and nd sr hf isotopic evidence for lithospheric thinning
Journal of Petrology, 2007Co-Authors: Jinhui Yang, Fuyuan Wu, Simon A Wilde, Fukun ChenAbstract:The Yanshan Fold and Thrust Belt in eastern China has been intruded by a series of alkalic igneous rocks, ranging in composition from granite and rhyolite to Syenite and trachyte. Laser ablation inductively coupled plasma mass spectrometry U^Pb analyses of zircon from three alkaline suites yield Early Cretaceous ages of 130^117Ma. Three groups of rocks have been identified based on their mineralogical, geochemical and Sr^Nd^Hf isotope characteristics. The alkali granites and rhyolites are ferroan and have low Al2O3, MgO, CaO, Sr, Ba and Eu concentrations and high SiO2, total Fe2O3, K2O, Nb, Ga, Ta, Th and heavy rare earth element abundances and Ga/Al ratios. Geochemical data and Sr-, Ndand zircon Hf-isotopic compositions [(Sr/Sr)i1⁄4 0 7050^0 7164, eNd(t)1⁄4 8 4 to 13 6 and eHf(t)1⁄4 5 7 to 16 8] indicate that they were probably generated by shallow dehydration melting of biotiteor hornblende-bearing granitoid crustal source rocks and then mixed with contemporaneous magma from a mantle and/or lower crustal source. Ferroan Syenites have distinct geochemical features from those of the alkaline granites and rhyolites, suggesting that they were produced by clinopyroxene and plagioclase fractionation of melt derived from an enriched mantle source, mixed with lower and upper crustal-derived magmas. The magnesian Syenites and trachytes have Sr-, Ndand zircon Hf-isotopic compositions that are distinct from those of the ferroan Syenites. They were mainly derived from partial melting of lower crustal materials, mixed with enriched mantle-derived alkali basaltic magma.The emplacement of an alkali Syenite^granite^rhyolite suite, coeval with the formation of metamorphic core complexes and pull-apart basins in eastern China, indicates they formed in an extensional setting, possibly as a result of lithospheric thinning.
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petrogenesis of post orogenic Syenites in the sulu orogenic belt east china geochronological geochemical and nd sr isotopic evidence
Chemical Geology, 2005Co-Authors: Jinhui Yang, Simon A Wilde, Sunlin Chung, Mei Fei Chu, Hongrui FanAbstract:Abstract The Jiazishan alkaline complex in the eastern Sulu ultrahigh pressure (UHP) metamorphic orogenic belt of eastern China is composed of potassic to ultrapotassic pyroxene Syenite, quartz Syenite and associated mafic dikes. A SHRIMP zircon 206Pb/238U age of 215±5 Ma was obtained for the quartz Syenite and mineral 40Ar/39Ar dating gave emplacement ages of 214.4±0.3 and 214.6±0.6 Ma for the pyroxene Syenite and 200.6±0.2 Ma for the mafic dike. These dates establish that the Jiazishan Complex was emplaced shortly after the UHP metamorphic event at 240 to 220 Ma due to the continental collision between the North China and Yangtze cratons. The ultrapotassic mafic dikes, with K2O≈4.4–6.4 wt.% and K2O/Na2O≈3.5, have high MgO (8.06–12.44 wt.%), Ni (119–319 ppm) and Cr (477–873 ppm) and moderately low CaO/Al2O3 (∼0.76) and TiO2 (∼1.12 wt.%). They also have high Sr (87Sr/86Sr∼0.7073), low Nd (ɛNd=∼−16.5) isotopic ratios, enriched LILE (Ba/La=66–74), LREE [(La/Yb)N=28–33] and depleted HFSE (La/Nb=4–6). It appears that the mafic dikes were derived from a refractory, re-enriched lithospheric mantle source. The Syenites have Sr and Nd isotopic compositions similar to the mafic dikes, implying a common origin. Geochemical and isotopic modeling suggests that the pyroxene Syenites may have been generated by early fractionation of clinopyroxene and olivine, coupled with minor amounts of crustal contamination, of a mafic magma that had a similar composition to the mafic dikes. Subsequent fractionation of feldspar-dominated assemblages, with minor or no contamination, would result in the quartz Syenites. This post-orogenic magmatism, resulting most likely in an extensional setting, provides time constraints on the major geodynamic transition from convergence to extension at the eastern margin of the North China craton. The Jiazishan potassic magmatism and geodynamic transition from convergence to extension can be explained by convective removal of the lower lithospheric mantle.
Fukun Chen - One of the best experts on this subject based on the ideXlab platform.
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petrogenesis of an alkali Syenite granite rhyolite suite in the yanshan fold and thrust belt eastern north china craton geochronological geochemical and nd sr hf isotopic evidence for lithospheric thinning
Journal of Petrology, 2007Co-Authors: Jinhui Yang, Fuyuan Wu, Simon A Wilde, Fukun ChenAbstract:The Yanshan Fold and Thrust Belt in eastern China has been intruded by a series of alkalic igneous rocks, ranging in composition from granite and rhyolite to Syenite and trachyte. Laser ablation inductively coupled plasma mass spectrometry U^Pb analyses of zircon from three alkaline suites yield Early Cretaceous ages of 130^117Ma. Three groups of rocks have been identified based on their mineralogical, geochemical and Sr^Nd^Hf isotope characteristics. The alkali granites and rhyolites are ferroan and have low Al2O3, MgO, CaO, Sr, Ba and Eu concentrations and high SiO2, total Fe2O3, K2O, Nb, Ga, Ta, Th and heavy rare earth element abundances and Ga/Al ratios. Geochemical data and Sr-, Ndand zircon Hf-isotopic compositions [(Sr/Sr)i1⁄4 0 7050^0 7164, eNd(t)1⁄4 8 4 to 13 6 and eHf(t)1⁄4 5 7 to 16 8] indicate that they were probably generated by shallow dehydration melting of biotiteor hornblende-bearing granitoid crustal source rocks and then mixed with contemporaneous magma from a mantle and/or lower crustal source. Ferroan Syenites have distinct geochemical features from those of the alkaline granites and rhyolites, suggesting that they were produced by clinopyroxene and plagioclase fractionation of melt derived from an enriched mantle source, mixed with lower and upper crustal-derived magmas. The magnesian Syenites and trachytes have Sr-, Ndand zircon Hf-isotopic compositions that are distinct from those of the ferroan Syenites. They were mainly derived from partial melting of lower crustal materials, mixed with enriched mantle-derived alkali basaltic magma.The emplacement of an alkali Syenite^granite^rhyolite suite, coeval with the formation of metamorphic core complexes and pull-apart basins in eastern China, indicates they formed in an extensional setting, possibly as a result of lithospheric thinning.
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petrogenesis of an alkali Syenite granite rhyolite suite in the yanshan fold and thrust belt eastern north china craton geochronological geochemical and nd sr hf isotopic evidence for lithospheric thinning
Journal of Petrology, 2007Co-Authors: Jinhui Yang, Fuyuan Wu, Simon A Wilde, Fukun ChenAbstract:The Yanshan Fold and Thrust Belt in eastern China has been intruded by a series of alkalic igneous rocks, ranging in composition from granite and rhyolite to Syenite and trachyte. Laser ablation inductively coupled plasma mass spectrometry U^Pb analyses of zircon from three alkaline suites yield Early Cretaceous ages of 130^117Ma. Three groups of rocks have been identified based on their mineralogical, geochemical and Sr^Nd^Hf isotope characteristics. The alkali granites and rhyolites are ferroan and have low Al2O3, MgO, CaO, Sr, Ba and Eu concentrations and high SiO2, total Fe2O3, K2O, Nb, Ga, Ta, Th and heavy rare earth element abundances and Ga/Al ratios. Geochemical data and Sr-, Ndand zircon Hf-isotopic compositions [(Sr/Sr)i1⁄4 0 7050^0 7164, eNd(t)1⁄4 8 4 to 13 6 and eHf(t)1⁄4 5 7 to 16 8] indicate that they were probably generated by shallow dehydration melting of biotiteor hornblende-bearing granitoid crustal source rocks and then mixed with contemporaneous magma from a mantle and/or lower crustal source. Ferroan Syenites have distinct geochemical features from those of the alkaline granites and rhyolites, suggesting that they were produced by clinopyroxene and plagioclase fractionation of melt derived from an enriched mantle source, mixed with lower and upper crustal-derived magmas. The magnesian Syenites and trachytes have Sr-, Ndand zircon Hf-isotopic compositions that are distinct from those of the ferroan Syenites. They were mainly derived from partial melting of lower crustal materials, mixed with enriched mantle-derived alkali basaltic magma.The emplacement of an alkali Syenite^granite^rhyolite suite, coeval with the formation of metamorphic core complexes and pull-apart basins in eastern China, indicates they formed in an extensional setting, possibly as a result of lithospheric thinning.
Simon A Wilde - One of the best experts on this subject based on the ideXlab platform.
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petrogenesis of an alkali Syenite granite rhyolite suite in the yanshan fold and thrust belt eastern north china craton geochronological geochemical and nd sr hf isotopic evidence for lithospheric thinning
Journal of Petrology, 2007Co-Authors: Jinhui Yang, Fuyuan Wu, Simon A Wilde, Fukun ChenAbstract:The Yanshan Fold and Thrust Belt in eastern China has been intruded by a series of alkalic igneous rocks, ranging in composition from granite and rhyolite to Syenite and trachyte. Laser ablation inductively coupled plasma mass spectrometry U^Pb analyses of zircon from three alkaline suites yield Early Cretaceous ages of 130^117Ma. Three groups of rocks have been identified based on their mineralogical, geochemical and Sr^Nd^Hf isotope characteristics. The alkali granites and rhyolites are ferroan and have low Al2O3, MgO, CaO, Sr, Ba and Eu concentrations and high SiO2, total Fe2O3, K2O, Nb, Ga, Ta, Th and heavy rare earth element abundances and Ga/Al ratios. Geochemical data and Sr-, Ndand zircon Hf-isotopic compositions [(Sr/Sr)i1⁄4 0 7050^0 7164, eNd(t)1⁄4 8 4 to 13 6 and eHf(t)1⁄4 5 7 to 16 8] indicate that they were probably generated by shallow dehydration melting of biotiteor hornblende-bearing granitoid crustal source rocks and then mixed with contemporaneous magma from a mantle and/or lower crustal source. Ferroan Syenites have distinct geochemical features from those of the alkaline granites and rhyolites, suggesting that they were produced by clinopyroxene and plagioclase fractionation of melt derived from an enriched mantle source, mixed with lower and upper crustal-derived magmas. The magnesian Syenites and trachytes have Sr-, Ndand zircon Hf-isotopic compositions that are distinct from those of the ferroan Syenites. They were mainly derived from partial melting of lower crustal materials, mixed with enriched mantle-derived alkali basaltic magma.The emplacement of an alkali Syenite^granite^rhyolite suite, coeval with the formation of metamorphic core complexes and pull-apart basins in eastern China, indicates they formed in an extensional setting, possibly as a result of lithospheric thinning.
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petrogenesis of an alkali Syenite granite rhyolite suite in the yanshan fold and thrust belt eastern north china craton geochronological geochemical and nd sr hf isotopic evidence for lithospheric thinning
Journal of Petrology, 2007Co-Authors: Jinhui Yang, Fuyuan Wu, Simon A Wilde, Fukun ChenAbstract:The Yanshan Fold and Thrust Belt in eastern China has been intruded by a series of alkalic igneous rocks, ranging in composition from granite and rhyolite to Syenite and trachyte. Laser ablation inductively coupled plasma mass spectrometry U^Pb analyses of zircon from three alkaline suites yield Early Cretaceous ages of 130^117Ma. Three groups of rocks have been identified based on their mineralogical, geochemical and Sr^Nd^Hf isotope characteristics. The alkali granites and rhyolites are ferroan and have low Al2O3, MgO, CaO, Sr, Ba and Eu concentrations and high SiO2, total Fe2O3, K2O, Nb, Ga, Ta, Th and heavy rare earth element abundances and Ga/Al ratios. Geochemical data and Sr-, Ndand zircon Hf-isotopic compositions [(Sr/Sr)i1⁄4 0 7050^0 7164, eNd(t)1⁄4 8 4 to 13 6 and eHf(t)1⁄4 5 7 to 16 8] indicate that they were probably generated by shallow dehydration melting of biotiteor hornblende-bearing granitoid crustal source rocks and then mixed with contemporaneous magma from a mantle and/or lower crustal source. Ferroan Syenites have distinct geochemical features from those of the alkaline granites and rhyolites, suggesting that they were produced by clinopyroxene and plagioclase fractionation of melt derived from an enriched mantle source, mixed with lower and upper crustal-derived magmas. The magnesian Syenites and trachytes have Sr-, Ndand zircon Hf-isotopic compositions that are distinct from those of the ferroan Syenites. They were mainly derived from partial melting of lower crustal materials, mixed with enriched mantle-derived alkali basaltic magma.The emplacement of an alkali Syenite^granite^rhyolite suite, coeval with the formation of metamorphic core complexes and pull-apart basins in eastern China, indicates they formed in an extensional setting, possibly as a result of lithospheric thinning.
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petrogenesis of post orogenic Syenites in the sulu orogenic belt east china geochronological geochemical and nd sr isotopic evidence
Chemical Geology, 2005Co-Authors: Jinhui Yang, Simon A Wilde, Sunlin Chung, Mei Fei Chu, Hongrui FanAbstract:Abstract The Jiazishan alkaline complex in the eastern Sulu ultrahigh pressure (UHP) metamorphic orogenic belt of eastern China is composed of potassic to ultrapotassic pyroxene Syenite, quartz Syenite and associated mafic dikes. A SHRIMP zircon 206Pb/238U age of 215±5 Ma was obtained for the quartz Syenite and mineral 40Ar/39Ar dating gave emplacement ages of 214.4±0.3 and 214.6±0.6 Ma for the pyroxene Syenite and 200.6±0.2 Ma for the mafic dike. These dates establish that the Jiazishan Complex was emplaced shortly after the UHP metamorphic event at 240 to 220 Ma due to the continental collision between the North China and Yangtze cratons. The ultrapotassic mafic dikes, with K2O≈4.4–6.4 wt.% and K2O/Na2O≈3.5, have high MgO (8.06–12.44 wt.%), Ni (119–319 ppm) and Cr (477–873 ppm) and moderately low CaO/Al2O3 (∼0.76) and TiO2 (∼1.12 wt.%). They also have high Sr (87Sr/86Sr∼0.7073), low Nd (ɛNd=∼−16.5) isotopic ratios, enriched LILE (Ba/La=66–74), LREE [(La/Yb)N=28–33] and depleted HFSE (La/Nb=4–6). It appears that the mafic dikes were derived from a refractory, re-enriched lithospheric mantle source. The Syenites have Sr and Nd isotopic compositions similar to the mafic dikes, implying a common origin. Geochemical and isotopic modeling suggests that the pyroxene Syenites may have been generated by early fractionation of clinopyroxene and olivine, coupled with minor amounts of crustal contamination, of a mafic magma that had a similar composition to the mafic dikes. Subsequent fractionation of feldspar-dominated assemblages, with minor or no contamination, would result in the quartz Syenites. This post-orogenic magmatism, resulting most likely in an extensional setting, provides time constraints on the major geodynamic transition from convergence to extension at the eastern margin of the North China craton. The Jiazishan potassic magmatism and geodynamic transition from convergence to extension can be explained by convective removal of the lower lithospheric mantle.
Fuyuan Wu - One of the best experts on this subject based on the ideXlab platform.
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petrogenesis of an alkali Syenite granite rhyolite suite in the yanshan fold and thrust belt eastern north china craton geochronological geochemical and nd sr hf isotopic evidence for lithospheric thinning
Journal of Petrology, 2007Co-Authors: Jinhui Yang, Fuyuan Wu, Simon A Wilde, Fukun ChenAbstract:The Yanshan Fold and Thrust Belt in eastern China has been intruded by a series of alkalic igneous rocks, ranging in composition from granite and rhyolite to Syenite and trachyte. Laser ablation inductively coupled plasma mass spectrometry U^Pb analyses of zircon from three alkaline suites yield Early Cretaceous ages of 130^117Ma. Three groups of rocks have been identified based on their mineralogical, geochemical and Sr^Nd^Hf isotope characteristics. The alkali granites and rhyolites are ferroan and have low Al2O3, MgO, CaO, Sr, Ba and Eu concentrations and high SiO2, total Fe2O3, K2O, Nb, Ga, Ta, Th and heavy rare earth element abundances and Ga/Al ratios. Geochemical data and Sr-, Ndand zircon Hf-isotopic compositions [(Sr/Sr)i1⁄4 0 7050^0 7164, eNd(t)1⁄4 8 4 to 13 6 and eHf(t)1⁄4 5 7 to 16 8] indicate that they were probably generated by shallow dehydration melting of biotiteor hornblende-bearing granitoid crustal source rocks and then mixed with contemporaneous magma from a mantle and/or lower crustal source. Ferroan Syenites have distinct geochemical features from those of the alkaline granites and rhyolites, suggesting that they were produced by clinopyroxene and plagioclase fractionation of melt derived from an enriched mantle source, mixed with lower and upper crustal-derived magmas. The magnesian Syenites and trachytes have Sr-, Ndand zircon Hf-isotopic compositions that are distinct from those of the ferroan Syenites. They were mainly derived from partial melting of lower crustal materials, mixed with enriched mantle-derived alkali basaltic magma.The emplacement of an alkali Syenite^granite^rhyolite suite, coeval with the formation of metamorphic core complexes and pull-apart basins in eastern China, indicates they formed in an extensional setting, possibly as a result of lithospheric thinning.
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petrogenesis of an alkali Syenite granite rhyolite suite in the yanshan fold and thrust belt eastern north china craton geochronological geochemical and nd sr hf isotopic evidence for lithospheric thinning
Journal of Petrology, 2007Co-Authors: Jinhui Yang, Fuyuan Wu, Simon A Wilde, Fukun ChenAbstract:The Yanshan Fold and Thrust Belt in eastern China has been intruded by a series of alkalic igneous rocks, ranging in composition from granite and rhyolite to Syenite and trachyte. Laser ablation inductively coupled plasma mass spectrometry U^Pb analyses of zircon from three alkaline suites yield Early Cretaceous ages of 130^117Ma. Three groups of rocks have been identified based on their mineralogical, geochemical and Sr^Nd^Hf isotope characteristics. The alkali granites and rhyolites are ferroan and have low Al2O3, MgO, CaO, Sr, Ba and Eu concentrations and high SiO2, total Fe2O3, K2O, Nb, Ga, Ta, Th and heavy rare earth element abundances and Ga/Al ratios. Geochemical data and Sr-, Ndand zircon Hf-isotopic compositions [(Sr/Sr)i1⁄4 0 7050^0 7164, eNd(t)1⁄4 8 4 to 13 6 and eHf(t)1⁄4 5 7 to 16 8] indicate that they were probably generated by shallow dehydration melting of biotiteor hornblende-bearing granitoid crustal source rocks and then mixed with contemporaneous magma from a mantle and/or lower crustal source. Ferroan Syenites have distinct geochemical features from those of the alkaline granites and rhyolites, suggesting that they were produced by clinopyroxene and plagioclase fractionation of melt derived from an enriched mantle source, mixed with lower and upper crustal-derived magmas. The magnesian Syenites and trachytes have Sr-, Ndand zircon Hf-isotopic compositions that are distinct from those of the ferroan Syenites. They were mainly derived from partial melting of lower crustal materials, mixed with enriched mantle-derived alkali basaltic magma.The emplacement of an alkali Syenite^granite^rhyolite suite, coeval with the formation of metamorphic core complexes and pull-apart basins in eastern China, indicates they formed in an extensional setting, possibly as a result of lithospheric thinning.
A Moukhsil - One of the best experts on this subject based on the ideXlab platform.
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Silicate-carbonate liquid immiscibility: insights from the Crevier alkaline intrusion (Quebec)
Journal of Petrology, 2020Co-Authors: P.-a Groulier, F Turlin, A. S. André-mayer, D. Ohnenstetter, A Crépon, Philippe Boulvais, Marc Poujol, C. Rollion-bard, A. Zeh, A MoukhsilAbstract:This contribution explores the petrogenetic relationships between silicate and carbonatitic rocks in the Crevier Alkaline Intrusion (CAI, Québec, Canada). The CAI is located in the Proterozoic Grenville Province and is composed of a suite of undersaturated peralkaline rocks from ijolite to nepheline Syenite and carbonatites. Petrogenetic relationships between different undersaturated alkaline igneous rocks, carbonate-bearing and carbonate-free nepheline Syenite and carbonatites observed in the CAI suggest that (i) carbonate-bearing and carbonate-free silicate rocks are comagmatic with carbonatite, and that (ii) both silicate and carbonatitic liquids are fractionated from an ijolitic parental magma that has undergone liquid immiscibility. One of the observed facies is characterized by spectacular ocelli of carbonate-bearing nepheline Syenite in a matrix of carbonatite. The younger nepheline Syenite facies can be divided into two groups based on the presence or absence of magmatic carbonates. Both groups are characterized by the presence of pyrochlore-group minerals that carry the Nb-Ta mineralization.We specifically use accessory minerals such as zircon, pyrochlore and apatite to constrain the temporal and physicochemical parameters of the immiscibility process. By coupling (i) mineral textures, (ii) trace elements, (iii) Ti-in-zircon thermometry, and (iv) oxygen isotope compositions, we have traced the crystallization of zircon before, during and after the immiscibility process. The results allowed us to constrain the minimum temperature of this process at ∼815-865 °C. In addition, two magmatic populations of pyrochlore are identified through their petrographic and geochemical characteristics within the younger nepheline Syenite facies. Pyrochlore from the earlier ocelli facies of carbonate-bearing nepheline Syenite follow a Nb-Ta differentiation trend, whereas pyrochlore from the younger carbonate-free nepheline Syenite follow a more classical Nb-Ti trend. Following the complete immiscibility between the silicate and carbonatitic liquids, the fractionation between Nb and Ta stopped while a new generation of Nb-rich pyrochlore grew, displaying a more classical Nb-Ti fractionation trend and a more constant Nb/Ta ratio in the nepheline Syenite.
