Roman Botcharnikov, Max Wilke, J. Garrevoet, Maxim Portnyagin, Kevin Klimm, Stephan Buhre, S. Krasheninnikov, R. Almeev, Severine Moune, Gerald Falkenberg
Abstract. Here we present a confocal Fe K-edge μ-XANES method (where XANES stands for X-ray absorption near-edge spectroscopy) for the analysis of Fe oxidation state in heterogeneous and one-side-polished samples. The new technique allows for an analysis of small volumes with high spatial 3D resolution of <100 µm3. The probed volume is restricted to that just beneath the surface of the exposed object. This protocol avoids contamination of the signal by the host material and minimizes self-absorption effects. This technique has been tested on a set of experimental glasses with a wide range of Fe3+ / ΣFe ratios. The method was applied to the analysis of natural melt inclusions trapped in forsteritic to fayalitic olivine crystals of the Hekla volcano, Iceland. Our measurements reveal changes in Fe3+ / ΣFe from 0.17 in basaltic up to 0.45 in dacitic melts, whereas the magnetite–ilmenite equilibrium shows redox conditions with Fe3+ / ΣFe ≤0.20 (close to FMQ, fayalite–magnetite–quartz redox equilibrium) along the entire range of Hekla melt compositions. This discrepancy indicates that the oxidized nature of glasses in the melt inclusions could be related to the post-entrapment process of diffusive hydrogen loss from inclusions and associated oxidation of Fe in the melt. The Fe3+ / ΣFe ratio in silicic melts is particularly susceptible to this process due to their low FeO content, and it should be critically evaluated before petrological interpretation.
{"title":"Confocal μ-XANES as a tool to analyze Fe oxidation state in heterogeneous samples: the case of melt inclusions in olivine from the Hekla volcano","authors":"Roman Botcharnikov, Max Wilke, J. Garrevoet, Maxim Portnyagin, Kevin Klimm, Stephan Buhre, S. Krasheninnikov, R. Almeev, Severine Moune, Gerald Falkenberg","doi":"10.5194/ejm-36-195-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-195-2024","url":null,"abstract":"Abstract. Here we present a confocal Fe K-edge μ-XANES method (where XANES stands for X-ray absorption near-edge spectroscopy) for the analysis of Fe oxidation state in heterogeneous and one-side-polished samples. The new technique allows for an analysis of small volumes with high spatial 3D resolution of <100 µm3. The probed volume is restricted to that just beneath the surface of the exposed object. This protocol avoids contamination of the signal by the host material and minimizes self-absorption effects. This technique has been tested on a set of experimental glasses with a wide range of Fe3+ / ΣFe ratios. The method was applied to the analysis of natural melt inclusions trapped in forsteritic to fayalitic olivine crystals of the Hekla volcano, Iceland. Our measurements reveal changes in Fe3+ / ΣFe from 0.17 in basaltic up to 0.45 in dacitic melts, whereas the magnetite–ilmenite equilibrium shows redox conditions with Fe3+ / ΣFe ≤0.20 (close to FMQ, fayalite–magnetite–quartz redox equilibrium) along the entire range of Hekla melt compositions. This discrepancy indicates that the oxidized nature of glasses in the melt inclusions could be related to the post-entrapment process of diffusive hydrogen loss from inclusions and associated oxidation of Fe in the melt. The Fe3+ / ΣFe ratio in silicic melts is particularly susceptible to this process due to their low FeO content, and it should be critically evaluated before petrological interpretation.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139845063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Lykova, R. Rowe, G. Poirier, Henrik Friis, Kate Helwig
Abstract. The new mckelveyite group mineral bainbridgeite-(YCe), ideally Na2Ba2YCe(CO3)6 ⋅ 3H2O, was found at Mont Saint-Hilaire, Quebec, Canada. Bainbridgeite-(YCe) occurs as pseudotrigonal and pseudohexagonal hemimorphic crystals that show platy, columnar, tabular, cone-shaped, barrel-shaped, saucer-shaped, or spindle-shaped habit. They often form stacked or parallel growth aggregates, rosettes, and groups of radiating crystals. The crystals are usually less than 1 mm in size. Bainbridgeite-(YCe) varies in colour from pale yellow to yellow, grey to almost black, bluish grey, green-grey, or white. The streak is white; the lustre is vitreous. The mineral has no cleavage. The Mohs hardness is 3. Dcalc is 3.49 g cm−3. Bainbridgeite-(YCe) is optically biaxial (+), α= 1.572(2), β= 1.586(2), γ= 1.628(2), 2 V (calc.) = 62∘, 2 V (meas.) = 45(4)∘(589 nm). The IR spectrum is reported. The composition (wt %, average of five analyses) is Na2O 6.86, CaO 0.59, SrO 4.01, BaO 25.71, Y2O3 8.24, La2O3 4.96, Ce2O3 8.38, Pr2O3 0.48, Nd2O3 1.87, Sm2O3 0.23, Gd2O3 0.67, Tb2O3 0.07, Dy2O3 1.38, Ho2O3 0.32, Er2O3 0.94, Tm2O3 0.08, Yb2O3 0.49, CO2 27.03, H2O 5.67, total 97.98. The empirical formula of the holotype calculated on the basis of six cations is as follows: Na2.11Ca0.10Sr0.37Ba1.60Y0.70La0.29Ce0.49Pr0.03Nd0.11Sm0.01Gd0.03Dy0.07Ho0.02Er0.05 Yb0.02(CO3)5.86(H2O)3.00. The mineral is triclinic, P1, a= 9.1079(2) Å, b= 9.1066(3) Å, c= 6.9332(2) Å, α= 102.861(2)∘, β= 116.148(2)∘, γ= 60.181(2)∘, V= 447.85(2) Å3, and Z= 1. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are 6.22(42)(001, 1‾1‾1, 1‾01), 4.430(100)(01‾1, 2‾1‾1, 120), 4.094(37)(1‾2‾1, 1‾11, 210, 111), 3.263(26)(11‾1, 2‾1‾2, 121), 2.888(67)(1‾2‾2, 1‾12, 211), 2.633(38)(3‾01, 030, 3‾3‾1), 2.263(23)(2‾21, 2‾4‾1, 4‾2‾1). 2.010(20)(03‾2, 3‾3‾3, 3‾03, 301, 032, 331). The crystal structure, solved and refined from single-crystal X-ray diffraction data (R1= 0.040), is of the weloganite type.
{"title":"Mckelveyite group minerals – Part 3: Bainbridgeite-(YCe), Na2Ba2YCe(CO3)6 ⋅ 3H2O, a new species from Mont Saint-Hilaire, Canada","authors":"I. Lykova, R. Rowe, G. Poirier, Henrik Friis, Kate Helwig","doi":"10.5194/ejm-36-183-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-183-2024","url":null,"abstract":"Abstract. The new mckelveyite group mineral bainbridgeite-(YCe), ideally Na2Ba2YCe(CO3)6 ⋅ 3H2O, was found at Mont Saint-Hilaire, Quebec, Canada. Bainbridgeite-(YCe) occurs as pseudotrigonal and pseudohexagonal hemimorphic crystals that show platy, columnar, tabular, cone-shaped, barrel-shaped, saucer-shaped, or spindle-shaped habit. They often form stacked or parallel growth aggregates, rosettes, and groups of radiating crystals. The crystals are usually less than 1 mm in size. Bainbridgeite-(YCe) varies in colour from pale yellow to yellow, grey to almost black, bluish grey, green-grey, or white. The streak is white; the lustre is vitreous. The mineral has no cleavage. The Mohs hardness is 3. Dcalc is 3.49 g cm−3. Bainbridgeite-(YCe) is optically biaxial (+), α= 1.572(2), β= 1.586(2), γ= 1.628(2), 2 V (calc.) = 62∘, 2 V (meas.) = 45(4)∘(589 nm). The IR spectrum is reported. The composition (wt %, average of five analyses) is Na2O 6.86, CaO 0.59, SrO 4.01, BaO 25.71, Y2O3 8.24, La2O3 4.96, Ce2O3 8.38, Pr2O3 0.48, Nd2O3 1.87, Sm2O3 0.23, Gd2O3 0.67, Tb2O3 0.07, Dy2O3 1.38, Ho2O3 0.32, Er2O3 0.94, Tm2O3 0.08, Yb2O3 0.49, CO2 27.03, H2O 5.67, total 97.98. The empirical formula of the holotype calculated on the basis of six cations is as follows: Na2.11Ca0.10Sr0.37Ba1.60Y0.70La0.29Ce0.49Pr0.03Nd0.11Sm0.01Gd0.03Dy0.07Ho0.02Er0.05 Yb0.02(CO3)5.86(H2O)3.00. The mineral is triclinic, P1, a= 9.1079(2) Å, b= 9.1066(3) Å, c= 6.9332(2) Å, α= 102.861(2)∘, β= 116.148(2)∘, γ= 60.181(2)∘, V= 447.85(2) Å3, and Z= 1. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are 6.22(42)(001, 1‾1‾1, 1‾01), 4.430(100)(01‾1, 2‾1‾1, 120), 4.094(37)(1‾2‾1, 1‾11, 210, 111), 3.263(26)(11‾1, 2‾1‾2, 121), 2.888(67)(1‾2‾2, 1‾12, 211), 2.633(38)(3‾01, 030, 3‾3‾1), 2.263(23)(2‾21, 2‾4‾1, 4‾2‾1). 2.010(20)(03‾2, 3‾3‾3, 3‾03, 301, 032, 331). The crystal structure, solved and refined from single-crystal X-ray diffraction data (R1= 0.040), is of the weloganite type.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139850440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Lykova, R. Rowe, G. Poirier, Henrik Friis, Kate Helwig
Abstract. The new mckelveyite group mineral bainbridgeite-(YCe), ideally Na2Ba2YCe(CO3)6 ⋅ 3H2O, was found at Mont Saint-Hilaire, Quebec, Canada. Bainbridgeite-(YCe) occurs as pseudotrigonal and pseudohexagonal hemimorphic crystals that show platy, columnar, tabular, cone-shaped, barrel-shaped, saucer-shaped, or spindle-shaped habit. They often form stacked or parallel growth aggregates, rosettes, and groups of radiating crystals. The crystals are usually less than 1 mm in size. Bainbridgeite-(YCe) varies in colour from pale yellow to yellow, grey to almost black, bluish grey, green-grey, or white. The streak is white; the lustre is vitreous. The mineral has no cleavage. The Mohs hardness is 3. Dcalc is 3.49 g cm−3. Bainbridgeite-(YCe) is optically biaxial (+), α= 1.572(2), β= 1.586(2), γ= 1.628(2), 2 V (calc.) = 62∘, 2 V (meas.) = 45(4)∘(589 nm). The IR spectrum is reported. The composition (wt %, average of five analyses) is Na2O 6.86, CaO 0.59, SrO 4.01, BaO 25.71, Y2O3 8.24, La2O3 4.96, Ce2O3 8.38, Pr2O3 0.48, Nd2O3 1.87, Sm2O3 0.23, Gd2O3 0.67, Tb2O3 0.07, Dy2O3 1.38, Ho2O3 0.32, Er2O3 0.94, Tm2O3 0.08, Yb2O3 0.49, CO2 27.03, H2O 5.67, total 97.98. The empirical formula of the holotype calculated on the basis of six cations is as follows: Na2.11Ca0.10Sr0.37Ba1.60Y0.70La0.29Ce0.49Pr0.03Nd0.11Sm0.01Gd0.03Dy0.07Ho0.02Er0.05 Yb0.02(CO3)5.86(H2O)3.00. The mineral is triclinic, P1, a= 9.1079(2) Å, b= 9.1066(3) Å, c= 6.9332(2) Å, α= 102.861(2)∘, β= 116.148(2)∘, γ= 60.181(2)∘, V= 447.85(2) Å3, and Z= 1. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are 6.22(42)(001, 1‾1‾1, 1‾01), 4.430(100)(01‾1, 2‾1‾1, 120), 4.094(37)(1‾2‾1, 1‾11, 210, 111), 3.263(26)(11‾1, 2‾1‾2, 121), 2.888(67)(1‾2‾2, 1‾12, 211), 2.633(38)(3‾01, 030, 3‾3‾1), 2.263(23)(2‾21, 2‾4‾1, 4‾2‾1). 2.010(20)(03‾2, 3‾3‾3, 3‾03, 301, 032, 331). The crystal structure, solved and refined from single-crystal X-ray diffraction data (R1= 0.040), is of the weloganite type.
{"title":"Mckelveyite group minerals – Part 3: Bainbridgeite-(YCe), Na2Ba2YCe(CO3)6 ⋅ 3H2O, a new species from Mont Saint-Hilaire, Canada","authors":"I. Lykova, R. Rowe, G. Poirier, Henrik Friis, Kate Helwig","doi":"10.5194/ejm-36-183-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-183-2024","url":null,"abstract":"Abstract. The new mckelveyite group mineral bainbridgeite-(YCe), ideally Na2Ba2YCe(CO3)6 ⋅ 3H2O, was found at Mont Saint-Hilaire, Quebec, Canada. Bainbridgeite-(YCe) occurs as pseudotrigonal and pseudohexagonal hemimorphic crystals that show platy, columnar, tabular, cone-shaped, barrel-shaped, saucer-shaped, or spindle-shaped habit. They often form stacked or parallel growth aggregates, rosettes, and groups of radiating crystals. The crystals are usually less than 1 mm in size. Bainbridgeite-(YCe) varies in colour from pale yellow to yellow, grey to almost black, bluish grey, green-grey, or white. The streak is white; the lustre is vitreous. The mineral has no cleavage. The Mohs hardness is 3. Dcalc is 3.49 g cm−3. Bainbridgeite-(YCe) is optically biaxial (+), α= 1.572(2), β= 1.586(2), γ= 1.628(2), 2 V (calc.) = 62∘, 2 V (meas.) = 45(4)∘(589 nm). The IR spectrum is reported. The composition (wt %, average of five analyses) is Na2O 6.86, CaO 0.59, SrO 4.01, BaO 25.71, Y2O3 8.24, La2O3 4.96, Ce2O3 8.38, Pr2O3 0.48, Nd2O3 1.87, Sm2O3 0.23, Gd2O3 0.67, Tb2O3 0.07, Dy2O3 1.38, Ho2O3 0.32, Er2O3 0.94, Tm2O3 0.08, Yb2O3 0.49, CO2 27.03, H2O 5.67, total 97.98. The empirical formula of the holotype calculated on the basis of six cations is as follows: Na2.11Ca0.10Sr0.37Ba1.60Y0.70La0.29Ce0.49Pr0.03Nd0.11Sm0.01Gd0.03Dy0.07Ho0.02Er0.05 Yb0.02(CO3)5.86(H2O)3.00. The mineral is triclinic, P1, a= 9.1079(2) Å, b= 9.1066(3) Å, c= 6.9332(2) Å, α= 102.861(2)∘, β= 116.148(2)∘, γ= 60.181(2)∘, V= 447.85(2) Å3, and Z= 1. The strongest reflections of the powder X-ray diffraction pattern [d,Å(I)(hkl)] are 6.22(42)(001, 1‾1‾1, 1‾01), 4.430(100)(01‾1, 2‾1‾1, 120), 4.094(37)(1‾2‾1, 1‾11, 210, 111), 3.263(26)(11‾1, 2‾1‾2, 121), 2.888(67)(1‾2‾2, 1‾12, 211), 2.633(38)(3‾01, 030, 3‾3‾1), 2.263(23)(2‾21, 2‾4‾1, 4‾2‾1). 2.010(20)(03‾2, 3‾3‾3, 3‾03, 301, 032, 331). The crystal structure, solved and refined from single-crystal X-ray diffraction data (R1= 0.040), is of the weloganite type.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139790542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Flemetakis, Christian Renggli, P. Pangritz, J. Berndt, S. Klemme
Abstract. We present the results of B2O3 evaporation experiments from Ca- and Mg-bearing aluminoborosilicate melts. Our experiments were conducted at 1245 to 1249 ∘C and 1350 to 1361 ∘C for different run times (60–1020 min), and at oxygen fugacities (logfO2) relative to the fayalite–magnetite–quartz (FMQ) buffer of FMQ−6 to FMQ+1.5, and in air. Our results show that with increasing fO2, evaporation of B from the melt increases by a factor of 5 compared to reducing conditions. Using Gibbs free energy minimization calculations, we suggest two possible evaporation reactions for B2O3 which constrain its speciation in the gas phase to be either 3+ or 4+ (B2O3(g) and BO2(g)). The measured B2O3 contents of the B evaporated residual glasses were used to calculate evaporation rate constants (ki) for B2O3 in oxidizing conditions (air, ki=2.09×10-4 cm min−1 at 1350 ∘C) and reducing conditions (FMQ−4, ki=4.46×10-5 cm min−1 at 1350 ∘C). The absence of diffusion profiles in the experimental glasses suggests that the evaporation rates are slower than B2O3 diffusion rates and therefore the rate-limiting process. Overall, the rate of B evaporation in air is approximately a factor of 5 higher compared to reducing conditions at FMQ−4.
{"title":"The effect of oxygen fugacity on the evaporation of boron from aluminoborosilicate melt","authors":"S. Flemetakis, Christian Renggli, P. Pangritz, J. Berndt, S. Klemme","doi":"10.5194/ejm-36-173-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-173-2024","url":null,"abstract":"Abstract. We present the results of B2O3 evaporation experiments from Ca- and Mg-bearing aluminoborosilicate melts. Our experiments were conducted at 1245 to 1249 ∘C and 1350 to 1361 ∘C for different run times (60–1020 min), and at oxygen fugacities (logfO2) relative to the fayalite–magnetite–quartz (FMQ) buffer of FMQ−6 to FMQ+1.5, and in air. Our results show that with increasing fO2, evaporation of B from the melt increases by a factor of 5 compared to reducing conditions. Using Gibbs free energy minimization calculations, we suggest two possible evaporation reactions for B2O3 which constrain its speciation in the gas phase to be either 3+ or 4+ (B2O3(g) and BO2(g)). The measured B2O3 contents of the B evaporated residual glasses were used to calculate evaporation rate constants (ki) for B2O3 in oxidizing conditions (air, ki=2.09×10-4 cm min−1 at 1350 ∘C) and reducing conditions (FMQ−4, ki=4.46×10-5 cm min−1 at 1350 ∘C). The absence of diffusion profiles in the experimental glasses suggests that the evaporation rates are slower than B2O3 diffusion rates and therefore the rate-limiting process. Overall, the rate of B evaporation in air is approximately a factor of 5 higher compared to reducing conditions at FMQ−4.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139860230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Flemetakis, Christian Renggli, P. Pangritz, J. Berndt, S. Klemme
Abstract. We present the results of B2O3 evaporation experiments from Ca- and Mg-bearing aluminoborosilicate melts. Our experiments were conducted at 1245 to 1249 ∘C and 1350 to 1361 ∘C for different run times (60–1020 min), and at oxygen fugacities (logfO2) relative to the fayalite–magnetite–quartz (FMQ) buffer of FMQ−6 to FMQ+1.5, and in air. Our results show that with increasing fO2, evaporation of B from the melt increases by a factor of 5 compared to reducing conditions. Using Gibbs free energy minimization calculations, we suggest two possible evaporation reactions for B2O3 which constrain its speciation in the gas phase to be either 3+ or 4+ (B2O3(g) and BO2(g)). The measured B2O3 contents of the B evaporated residual glasses were used to calculate evaporation rate constants (ki) for B2O3 in oxidizing conditions (air, ki=2.09×10-4 cm min−1 at 1350 ∘C) and reducing conditions (FMQ−4, ki=4.46×10-5 cm min−1 at 1350 ∘C). The absence of diffusion profiles in the experimental glasses suggests that the evaporation rates are slower than B2O3 diffusion rates and therefore the rate-limiting process. Overall, the rate of B evaporation in air is approximately a factor of 5 higher compared to reducing conditions at FMQ−4.
{"title":"The effect of oxygen fugacity on the evaporation of boron from aluminoborosilicate melt","authors":"S. Flemetakis, Christian Renggli, P. Pangritz, J. Berndt, S. Klemme","doi":"10.5194/ejm-36-173-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-173-2024","url":null,"abstract":"Abstract. We present the results of B2O3 evaporation experiments from Ca- and Mg-bearing aluminoborosilicate melts. Our experiments were conducted at 1245 to 1249 ∘C and 1350 to 1361 ∘C for different run times (60–1020 min), and at oxygen fugacities (logfO2) relative to the fayalite–magnetite–quartz (FMQ) buffer of FMQ−6 to FMQ+1.5, and in air. Our results show that with increasing fO2, evaporation of B from the melt increases by a factor of 5 compared to reducing conditions. Using Gibbs free energy minimization calculations, we suggest two possible evaporation reactions for B2O3 which constrain its speciation in the gas phase to be either 3+ or 4+ (B2O3(g) and BO2(g)). The measured B2O3 contents of the B evaporated residual glasses were used to calculate evaporation rate constants (ki) for B2O3 in oxidizing conditions (air, ki=2.09×10-4 cm min−1 at 1350 ∘C) and reducing conditions (FMQ−4, ki=4.46×10-5 cm min−1 at 1350 ∘C). The absence of diffusion profiles in the experimental glasses suggests that the evaporation rates are slower than B2O3 diffusion rates and therefore the rate-limiting process. Overall, the rate of B evaporation in air is approximately a factor of 5 higher compared to reducing conditions at FMQ−4.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139800275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Dal Bo, Henrik Friis, M. Elburg, Frédéric Hatert, Tom Andersen
Abstract. The new mineral pilanesbergite, with the ideal formula Na2Ca2Fe2Ti2(Si2O7)2O2F2, was found in a nepheline syenite, locally known as green foyaite, from the Pilanesberg Complex located in the North West Province of South Africa. Pilanesbergite occurs in green foyaite in association, and partly intergrown, with aegirine. The two minerals share an assemblage of inclusions, comprising euhedral nepheline, titanite and minor sodalite. Pilanesbergite belongs to the wöhlerite group and is isomorphic with låvenite, normandite and madeiraite. It is related to these species through the homovalent chemical substitutions Mn2+↔Fe2+ and Zr4+↔Ti4+. The empirical formula calculated on the basis of 18 anions is Na2.00(Ca1.74Na0.26)Σ2.00(Fe1.00Mn0.52Ca0.49Zr0.05)Σ2.06(Ti1.69Zr0.14Mg0.09Nb0.08)Σ2.00(Si2O7)2.00O1.84F2.16 (Z=2). The new mineral is translucent with a brown orange colour and a brownish streak. The Mohs hardness is estimated between 5 and 6 by comparison with låvenite, and no cleavage is observed. Measured and calculated densities are Dmeas=3.47 g cm−3 and Dcalc=3.40 g cm−3. In the thin section the pleochroism is strong, between straw yellow and orange red, while in immersion the strong pleochroism is observed between light yellow (α) and yellowish orange (γ). The crystals are optically biaxial (+) with α=1.743(3), β=1.768(3), γ=1.795(5) and a 2 V angle close to 90∘. The crystal structure is monoclinic (P21/a), with the unit-cell parameters a=10.7811(2), b=9.7836(1), c=7.0348(1) Å, β=108.072(2)∘ and V=705.41(2) Å3, and has been refined to R1=2.06 %. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (h k l)] are 3.219 (60) (310), 2.851 (100) (12-2), 2.802 (51) (320), 2.743 (27) (22-2), 2.423 (19) (40-2) and 1.723 (19) (44-2). Pilanesbergite formed under relatively reducing conditions from an agpaitic nepheline syenite magma that had evolved by fractional crystallization mainly of aegirine. Further crystallization of arfvedsonite caused an increase in oxygen fugacity and a change towards higher Mn/Mn+Fe of the magma, causing a change of mineral composition from pilanesbergite towards normandite.
摘要。在位于南非西北省的皮兰斯贝格复合体中的霞石正长岩（当地称为绿福安岩）中发现了新矿物皮兰斯贝格岩，其理想分子式为Na2Ca2Fe2Ti2(Si2O7)2O2F2。Pilanesbergite 出现在绿色萤石中，与黑云母伴生，部分与黑云母互生。这两种矿物具有共同的包裹体组合，包括八面体霞石、榍石和少量钠长石。Pilanesbergite 属于沃勒石组，与洛芬石、诺曼底石和马德拉石同构。它通过 Mn2+↔Fe2+ 和 Zr4+↔Ti4+ 的同价化学置换与这些矿种建立了联系。根据 18 个阴离子计算得出的经验公式为 Na2.00（Ca1.74Na0.26）Σ2.00（Fe1.00Mn0.52Ca0.49Zr0.05）Σ2.06（Ti1.69Zr0.14Mg0.09Nb0.08）Σ2.00（Si2O7）2.00O1.84F2.16（Z=2）。这种新矿物呈半透明状，褐橙色，有褐色条纹。莫氏硬度估计在 5 至 6 之间，与洛芬石相比较，没有观察到裂隙。测量和计算得出的密度分别为 Dmeas=3.47 g cm-3 和 Dcalc=3.40 g cm-3。薄片上的褶皱很强烈，介于稻草黄和橘红色之间，而在浸入水中则观察到强烈的褶皱，介于浅黄色（α）和黄橙色（γ）之间。晶体具有光学双轴性 (+)，α=1.743(3)，β=1.768(3)，γ=1.795(5)，2 V 角接近 90∘。晶体结构为单斜（P21/a），单位晶胞参数为 a=10.7811(2)，b=9.7836(1)，c=7.0348(1) Å，β=108.072(2)∘，V=705.41(2) Å3。粉末 X 射线衍射图样[d, Å (I, %) (h k l)] 的最强线是 3.219 (60) (310)、2.851 (100) (12-2)、2.802 (51) (320)、2.743 (27) (22-2)、2.423 (19) (40-2) 和 1.723 (19) (44-2)。皮兰斯贝格岩是在相对还原的条件下由芒硝霞石正长岩岩浆形成的，该岩浆主要由芒硝分馏结晶而成。Arfvedsonite 的进一步结晶导致氧富集度增加，岩浆的锰/锰+铁含量变高，使矿物成分从皮兰斯贝格岩变为诺曼底岩。
{"title":"Pilanesbergite: a new rock-forming mineral occurring in nepheline syenite from the Pilanesberg Alkaline Complex, South Africa","authors":"F. Dal Bo, Henrik Friis, M. Elburg, Frédéric Hatert, Tom Andersen","doi":"10.5194/ejm-36-73-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-73-2024","url":null,"abstract":"Abstract. The new mineral pilanesbergite, with the ideal formula Na2Ca2Fe2Ti2(Si2O7)2O2F2, was found in a nepheline syenite, locally known as green foyaite, from the Pilanesberg Complex located in the North West Province of South Africa. Pilanesbergite occurs in green foyaite in association, and partly intergrown, with aegirine. The two minerals share an assemblage of inclusions, comprising euhedral nepheline, titanite and minor sodalite. Pilanesbergite belongs to the wöhlerite group and is isomorphic with låvenite, normandite and madeiraite. It is related to these species through the homovalent chemical substitutions Mn2+↔Fe2+ and Zr4+↔Ti4+. The empirical formula calculated on the basis of 18 anions is Na2.00(Ca1.74Na0.26)Σ2.00(Fe1.00Mn0.52Ca0.49Zr0.05)Σ2.06(Ti1.69Zr0.14Mg0.09Nb0.08)Σ2.00(Si2O7)2.00O1.84F2.16 (Z=2). The new mineral is translucent with a brown orange colour and a brownish streak. The Mohs hardness is estimated between 5 and 6 by comparison with låvenite, and no cleavage is observed. Measured and calculated densities are Dmeas=3.47 g cm−3 and Dcalc=3.40 g cm−3. In the thin section the pleochroism is strong, between straw yellow and orange red, while in immersion the strong pleochroism is observed between light yellow (α) and yellowish orange (γ). The crystals are optically biaxial (+) with α=1.743(3), β=1.768(3), γ=1.795(5) and a 2 V angle close to 90∘. The crystal structure is monoclinic (P21/a), with the unit-cell parameters a=10.7811(2), b=9.7836(1), c=7.0348(1) Å, β=108.072(2)∘ and V=705.41(2) Å3, and has been refined to R1=2.06 %. The strongest lines of the powder X-ray diffraction pattern [d, Å (I, %) (h k l)] are 3.219 (60) (310), 2.851 (100) (12-2), 2.802 (51) (320), 2.743 (27) (22-2), 2.423 (19) (40-2) and 1.723 (19) (44-2). Pilanesbergite formed under relatively reducing conditions from an agpaitic nepheline syenite magma that had evolved by fractional crystallization mainly of aegirine. Further crystallization of arfvedsonite caused an increase in oxygen fugacity and a change towards higher Mn/Mn+Fe of the magma, causing a change of mineral composition from pilanesbergite towards normandite.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139527893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Quentin Bollaert, Mathieu Chassé, Guillaume Morin, Benoît Baptiste, Alexandra Courtin, L. Galoisy, Gautier Landrot, Cécile Quantin, Georges Calas
Abstract. The mineralogy of niobium (Nb) is characterized by multicomponent oxides such as AB2O6, A2B2O7, ABO4, and ABO3 in which Nb is incorporated in the B site. Such complex crystal-chemistry prevents their unambiguous identification in ore deposits such as hydrothermal rocks and laterites which exhibit complex and fine-grained textures. The understanding of the processes controlling Nb ore deposit formation in various geological settings is therefore limited, although Nb is a critical element. In this study, we use X-ray absorption spectroscopy (XAS) at the Nb K-edge to investigate the local atomic-scale structure around Nb in a large set of natural and synthetic minerals of geological and technological importance. Our X-ray absorption near-edge structure (XANES) data at the Nb K-edge show three major features of variable position and intensity and then can be related to the local distortion and coordination number of the Nb site. Shell-by-shell fits of the extended X-ray absorption fine structure (EXAFS) data reveal that the NbO6 octahedra are distorted in a variety of pyrochlore species. At least two distinct first shells of O atoms are present while reported crystallographic data yield regular octahedra in the same minerals. Next-nearest Nb–Nb distances in pyrochlore and Nb-bearing perovskite mirror a corner-sharing NbO6 network, whereas the two Nb–Nb distances in columbite are typical of edge- and corner-sharing NbO6 octahedra. Such a resolution on the Nb site geometry and the intersite relationships between the next-nearest NbO6 octahedra is made possible by collecting EXAFS data under optimal conditions at 20 K and up to 16 Å−1. The local structure around substituted Nb5+ in Fe3+, Ti4+, and Ce4+ oxides suffers major changes relative to the unsubstituted structures. The substitution of Nb5+ for Ti4+ in anatase leads to the increase in the interatomic distances between Nb and its first and second Ti4+ neighbors. The substitution of Nb5+ for Ce4+ in cerianite reduces the coordination number of the cation from eight to four, and the Nb–O bonds are shortened compared to Ce–O ones. In hematite, Nb5+ occupies a regular site, whereas the Fe3+ site is strongly distorted suggesting major site relaxation due to charge mismatch. The sensitivity of XANES and EXAFS spectroscopies at the Nb K-edge to the local site geometry and next-nearest neighbors demonstrated in this study would help decipher Nb speciation and investigate mineralogical reactions of Nb minerals in deposit-related contexts such as hydrothermal and lateritic deposits.
摘要。铌（Nb）矿物学的特点是多组分氧化物，如 AB2O6、A2B2O7、ABO4 和 ABO3，其中铌掺杂在 B 位。这种复杂的晶体化学性质阻碍了它们在热液岩和红土等矿床中的明确识别，因为这些矿床呈现出复杂的细粒纹理。因此，尽管铌是一种关键元素，但人们对各种地质环境中控制铌矿床形成过程的了解仍然有限。在本研究中，我们利用铌 K 边的 X 射线吸收光谱 (XAS) 来研究大量具有地质和技术重要性的天然和合成矿物中铌周围的局部原子尺度结构。我们在铌 K 边的 X 射线吸收近边结构 (XANES) 数据显示了位置和强度可变的三大特征，这些特征与铌位点的局部畸变和配位数有关。扩展 X 射线吸收精细结构（EXAFS）数据的逐壳拟合显示，NbO6 八面体在各种火成岩中都发生了变形。至少存在两个不同的 O 原子第一壳，而报告的晶体学数据则显示相同矿物中存在规则的八面体。辉绿岩和含铌的透辉石中最邻近的 Nb-Nb 间距反映了共角 NbO6 网络，而铌铁矿中的两个 Nb-Nb 间距则是典型的共边和共角 NbO6 八面体。通过在 20 K 和高达 16 Å-1 的最佳条件下收集 EXAFS 数据，可以对铌位点的几何形状和最邻近的 NbO6 八面体之间的位点间关系进行这样的解析。与未取代的结构相比，Fe3+、Ti4+ 和 Ce4+ 氧化物中取代的 Nb5+ 周围的局部结构发生了重大变化。锐钛矿中 Nb5+ 对 Ti4+ 的取代导致 Nb 与其第一和第二 Ti4+ 邻域之间的原子间距增大。在铈镧矿中，Nb5+取代Ce4+后，阳离子的配位数从8个减少到4个，Nb-O键比Ce-O键更短。在赤铁矿中，Nb5+占据了一个规则的位点，而 Fe3+ 位点则强烈扭曲，这表明电荷失配导致了主要的位点松弛。本研究中展示的铌 K 边 XANES 和 EXAFS 光谱对局部位点几何形状和近邻位点的敏感性，将有助于破译铌的种类，并研究热液矿床和红土矿床等矿床相关环境中铌矿物的矿物学反应。
{"title":"Atomic-scale environment of niobium in ore minerals as revealed by XANES and EXAFS at the Nb K-edge","authors":"Quentin Bollaert, Mathieu Chassé, Guillaume Morin, Benoît Baptiste, Alexandra Courtin, L. Galoisy, Gautier Landrot, Cécile Quantin, Georges Calas","doi":"10.5194/ejm-36-55-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-55-2024","url":null,"abstract":"Abstract. The mineralogy of niobium (Nb) is characterized by multicomponent oxides such as AB2O6, A2B2O7, ABO4, and ABO3 in which Nb is incorporated in the B site. Such complex crystal-chemistry prevents their unambiguous identification in ore deposits such as hydrothermal rocks and laterites which exhibit complex and fine-grained textures. The understanding of the processes controlling Nb ore deposit formation in various geological settings is therefore limited, although Nb is a critical element. In this study, we use X-ray absorption spectroscopy (XAS) at the Nb K-edge to investigate the local atomic-scale structure around Nb in a large set of natural and synthetic minerals of geological and technological importance. Our X-ray absorption near-edge structure (XANES) data at the Nb K-edge show three major features of variable position and intensity and then can be related to the local distortion and coordination number of the Nb site. Shell-by-shell fits of the extended X-ray absorption fine structure (EXAFS) data reveal that the NbO6 octahedra are distorted in a variety of pyrochlore species. At least two distinct first shells of O atoms are present while reported crystallographic data yield regular octahedra in the same minerals. Next-nearest Nb–Nb distances in pyrochlore and Nb-bearing perovskite mirror a corner-sharing NbO6 network, whereas the two Nb–Nb distances in columbite are typical of edge- and corner-sharing NbO6 octahedra. Such a resolution on the Nb site geometry and the intersite relationships between the next-nearest NbO6 octahedra is made possible by collecting EXAFS data under optimal conditions at 20 K and up to 16 Å−1. The local structure around substituted Nb5+ in Fe3+, Ti4+, and Ce4+ oxides suffers major changes relative to the unsubstituted structures. The substitution of Nb5+ for Ti4+ in anatase leads to the increase in the interatomic distances between Nb and its first and second Ti4+ neighbors. The substitution of Nb5+ for Ce4+ in cerianite reduces the coordination number of the cation from eight to four, and the Nb–O bonds are shortened compared to Ce–O ones. In hematite, Nb5+ occupies a regular site, whereas the Fe3+ site is strongly distorted suggesting major site relaxation due to charge mismatch. The sensitivity of XANES and EXAFS spectroscopies at the Nb K-edge to the local site geometry and next-nearest neighbors demonstrated in this study would help decipher Nb speciation and investigate mineralogical reactions of Nb minerals in deposit-related contexts such as hydrothermal and lateritic deposits.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139446994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Majzlan, Anna Reichstein, Patrick Haase, M. Števko, Jiří Sejkora, Edgar Dachs
Abstract. In this work, we investigated the M3(AsO4)2⋅ 8H2O end members annabergite (M is Ni), erythrite (M is Co), and hörnesite (M is Mg) and their solid solutions. Acid-solution calorimetry and relaxation calorimetry were used to determine the solubility products (log Ksp) for annabergite (−33.7), erythrite (−32.1), and hörnesite (−22.3). Solubility products for other end members of this group were extracted from the literature and critically evaluated. The enthalpies of mixing are complex, related to subsystems M(1)3(AsO4)2⋅ 8H2O–M(1)M(2)2(AsO4)2⋅ 8H2O and M(1)M(2)2(AsO4)2⋅ 8H2O–M(2)3(AsO4)2⋅ 8H2O. They are small and positive for the annabergite–erythrite solid solution and small and negative for the annabergite–hörnesite solid solution. Autocorrelation analysis of Fourier-transform infrared (FTIR) spectra shows correlation of strain decrease in the structure with the negative enthalpies of mixing in the annabergite–hörnesite solid solution. A set of more than 600 electron microprobe analyses of the M3(AsO4)2⋅ 8H2O minerals documents the variability and complexity in this group. Most common compositions are those dominated by Ni, Co, or Ni–Co. The analytical results were used to calculate the maximal configurational entropies which could be a factor that compensates for the small enthalpies of mixing in the annabergite–erythrite solid solution. The data presented here can be used to model sites polluted with metals and arsenic and to enhance our understanding of complex solid solutions.
{"title":"Thermodynamics of vivianite-group arsenates M3(AsO4)2 ⋅ 8H2O (M is Ni, Co, Mg, Zn, Cu) and chemical variability in the natural arsenates of this group","authors":"J. Majzlan, Anna Reichstein, Patrick Haase, M. Števko, Jiří Sejkora, Edgar Dachs","doi":"10.5194/ejm-36-31-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-31-2024","url":null,"abstract":"Abstract. In this work, we investigated the M3(AsO4)2⋅ 8H2O end members annabergite (M is Ni), erythrite (M is Co), and hörnesite (M is Mg) and their solid solutions. Acid-solution calorimetry and relaxation calorimetry were used to determine the solubility products (log Ksp) for annabergite (−33.7), erythrite (−32.1), and hörnesite (−22.3). Solubility products for other end members of this group were extracted from the literature and critically evaluated. The enthalpies of mixing are complex, related to subsystems M(1)3(AsO4)2⋅ 8H2O–M(1)M(2)2(AsO4)2⋅ 8H2O and M(1)M(2)2(AsO4)2⋅ 8H2O–M(2)3(AsO4)2⋅ 8H2O. They are small and positive for the annabergite–erythrite solid solution and small and negative for the annabergite–hörnesite solid solution. Autocorrelation analysis of Fourier-transform infrared (FTIR) spectra shows correlation of strain decrease in the structure with the negative enthalpies of mixing in the annabergite–hörnesite solid solution. A set of more than 600 electron microprobe analyses of the M3(AsO4)2⋅ 8H2O minerals documents the variability and complexity in this group. Most common compositions are those dominated by Ni, Co, or Ni–Co. The analytical results were used to calculate the maximal configurational entropies which could be a factor that compensates for the small enthalpies of mixing in the annabergite–erythrite solid solution. The data presented here can be used to model sites polluted with metals and arsenic and to enhance our understanding of complex solid solutions.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139447529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qian Guo, Shun Guo, Yueheng Yang, Qian Mao, Jiangyan Yuan, Shitou Wu, Xiaochi Liu, K. Sein
Abstract. Fluid infiltration into (meta-)carbonate rocks is an important petrologic process that induces metamorphic decarbonation and potential mineralization of metals or nonmetals. The determination of the infiltration time and the compositional features of reactive fluids is essential to understand the mechanism and process of fluid–rock interactions. Zirconolite (ideal formula: CaZrTi2O7) is an important U-bearing accessory mineral that can develop in metasomatized metacarbonate rocks. In this study, we investigate the occurrence, texture, composition, and chronology of various types of zirconolite from fluid-infiltrated reaction zones in dolomite marbles from the Mogok metamorphic belt, Myanmar. Three types of zirconolite are recognized: (1) the first type (Zrl-I) coexists with metasomatic silicate and oxide minerals (forsterite, spinel, phlogopite) and has a homogeneous composition with high contents of UO2 (21.37 wt %–22.82 wt %) and ThO2 (0.84 wt %–1.99 wt %). (2) The second type (Zrl-II) has textural characteristics similar to those of Zrl-I. However, Zrl-II shows a core–rim zonation with a slightly higher UO2 content in the rims (average of 23.5 ± 0.4 wt % (n=8)) than the cores (average of 22.1 ± 0.3 wt % (n=8)). (3) The third type (Zrl-III) typically occurs as coronas around baddeleyite and coexists with polycrystalline quartz. Zrl-III has obviously lower contents of UO2 (0.88 wt %–5.3 wt %) than those of Zrl-I and Zrl-II. All types of zirconolite have relatively low rare earth element (REE) contents (< 480 µg g−1 for ΣREE). Microtextures and compositions of the three zirconolite types, in combination with in situ zirconolite U–Pb dating using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), reveal episodic fluid infiltration and element mobilization in the dolomite marbles. The first-stage infiltration occurred at ∼ 35 Ma, leading to the formation of Mg-rich silicates and oxides and accessory minerals (Zrl-I, baddeleyite, and geikielite). The reactive fluid was characterized by high contents of Zr, Ti, U, and Th. After that, some Zrl-I grains underwent a local fluid-assisted dissolution–precipitation process, which produced a core–rim zonation (i.e., the Zrl-II type). The final stage of fluid infiltration, recorded by the growth of Zrl-III after baddeleyite, took place at ∼ 19 Ma. The infiltrating fluid of this stage had relatively lower U contents and higher SiO2 activities than the first-stage infiltrating fluid. This study illustrates that zirconolite is a powerful mineral that can record repeated episodes (ranging from 35 to 19 Ma) of fluid influx, metasomatic reactions, and Zr–Ti–U mineralization in (meta-)carbonates. This mineral not only provides key information about the timing of fluid flow but also documents the chemical variation in reactive fluids. Thus, zirconolite is expected to play a more important role in characterizing the fluid–carbonate interaction, orogenic CO2 release, and the transfer an
{"title":"Multiple growth of zirconolite in marble (Mogok metamorphic belt, Myanmar): evidence for episodes of fluid metasomatism and Zr–Ti–U mineralization in metacarbonate systems","authors":"Qian Guo, Shun Guo, Yueheng Yang, Qian Mao, Jiangyan Yuan, Shitou Wu, Xiaochi Liu, K. Sein","doi":"10.5194/ejm-36-11-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-11-2024","url":null,"abstract":"Abstract. Fluid infiltration into (meta-)carbonate rocks is an important petrologic process that induces metamorphic decarbonation and potential mineralization of metals or nonmetals. The determination of the infiltration time and the compositional features of reactive fluids is essential to understand the mechanism and process of fluid–rock interactions. Zirconolite (ideal formula: CaZrTi2O7) is an important U-bearing accessory mineral that can develop in metasomatized metacarbonate rocks. In this study, we investigate the occurrence, texture, composition, and chronology of various types of zirconolite from fluid-infiltrated reaction zones in dolomite marbles from the Mogok metamorphic belt, Myanmar. Three types of zirconolite are recognized: (1) the first type (Zrl-I) coexists with metasomatic silicate and oxide minerals (forsterite, spinel, phlogopite) and has a homogeneous composition with high contents of UO2 (21.37 wt %–22.82 wt %) and ThO2 (0.84 wt %–1.99 wt %). (2) The second type (Zrl-II) has textural characteristics similar to those of Zrl-I. However, Zrl-II shows a core–rim zonation with a slightly higher UO2 content in the rims (average of 23.5 ± 0.4 wt % (n=8)) than the cores (average of 22.1 ± 0.3 wt % (n=8)). (3) The third type (Zrl-III) typically occurs as coronas around baddeleyite and coexists with polycrystalline quartz. Zrl-III has obviously lower contents of UO2 (0.88 wt %–5.3 wt %) than those of Zrl-I and Zrl-II. All types of zirconolite have relatively low rare earth element (REE) contents (< 480 µg g−1 for ΣREE). Microtextures and compositions of the three zirconolite types, in combination with in situ zirconolite U–Pb dating using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), reveal episodic fluid infiltration and element mobilization in the dolomite marbles. The first-stage infiltration occurred at ∼ 35 Ma, leading to the formation of Mg-rich silicates and oxides and accessory minerals (Zrl-I, baddeleyite, and geikielite). The reactive fluid was characterized by high contents of Zr, Ti, U, and Th. After that, some Zrl-I grains underwent a local fluid-assisted dissolution–precipitation process, which produced a core–rim zonation (i.e., the Zrl-II type). The final stage of fluid infiltration, recorded by the growth of Zrl-III after baddeleyite, took place at ∼ 19 Ma. The infiltrating fluid of this stage had relatively lower U contents and higher SiO2 activities than the first-stage infiltrating fluid. This study illustrates that zirconolite is a powerful mineral that can record repeated episodes (ranging from 35 to 19 Ma) of fluid influx, metasomatic reactions, and Zr–Ti–U mineralization in (meta-)carbonates. This mineral not only provides key information about the timing of fluid flow but also documents the chemical variation in reactive fluids. Thus, zirconolite is expected to play a more important role in characterizing the fluid–carbonate interaction, orogenic CO2 release, and the transfer an","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jonas Toupal, D. Mauro, C. Biagioni, Federica Zaccarini, R. Gieré
Abstract. Members of the childrenite–eosphorite series, ideally (Fe1−xMnx)AlPO4(OH)2⋅H2O, from the highly evolved Homolka granite, in the southern Czech Republic, were characterized using a multi-analytical approach. They occur as anhedral grains, up to ∼0.2 mm in size, associated with quartz, muscovite, albite, and K-feldspar. Tiny inclusions of probable uraninite have been observed. Backscattered electron images reveal a patchy zoning of these members of the childrenite–eosphorite series, related to an uneven distribution of Fe and Mn. On the basis of electron microprobe analysis, the average composition of the studied material is (Fe0.68Mn0.28Ca0.03)Σ0.99Al0.96(P1.04Si0.01)Σ1.05O4.00(OH)2.09⋅0.91H2O, thus corresponding to childrenite. Unit-cell parameters of this species are a=6.9226(9), b=10.4081(13), c=13.3957(17) Å. Its crystal structure was refined in the space group Cmca down to R1=0.0295 on the basis of 602 unique reflections with Fo>4σ(Fo) and 66 refined parameters. The crystal structure analysis agrees with the results of electron microprobe analysis and suggests that, in the studied material, Fe occurs in the divalent oxidation state only. Crystal structure data are also consistent with the Raman spectrum collected on the same grain that was structurally characterized, confirming the occurrence of PO4 groups only in childrenite.
{"title":"Structural and compositional data for childrenite from the Homolka granite, Czech Republic","authors":"Jonas Toupal, D. Mauro, C. Biagioni, Federica Zaccarini, R. Gieré","doi":"10.5194/ejm-36-1-2024","DOIUrl":"https://doi.org/10.5194/ejm-36-1-2024","url":null,"abstract":"Abstract. Members of the childrenite–eosphorite series, ideally (Fe1−xMnx)AlPO4(OH)2⋅H2O, from the highly evolved Homolka granite, in the southern Czech Republic, were characterized using a multi-analytical approach. They occur as anhedral grains, up to ∼0.2 mm in size, associated with quartz, muscovite, albite, and K-feldspar. Tiny inclusions of probable uraninite have been observed. Backscattered electron images reveal a patchy zoning of these members of the childrenite–eosphorite series, related to an uneven distribution of Fe and Mn. On the basis of electron microprobe analysis, the average composition of the studied material is (Fe0.68Mn0.28Ca0.03)Σ0.99Al0.96(P1.04Si0.01)Σ1.05O4.00(OH)2.09⋅0.91H2O, thus corresponding to childrenite. Unit-cell parameters of this species are a=6.9226(9), b=10.4081(13), c=13.3957(17) Å. Its crystal structure was refined in the space group Cmca down to R1=0.0295 on the basis of 602 unique reflections with Fo>4σ(Fo) and 66 refined parameters. The crystal structure analysis agrees with the results of electron microprobe analysis and suggests that, in the studied material, Fe occurs in the divalent oxidation state only. Crystal structure data are also consistent with the Raman spectrum collected on the same grain that was structurally characterized, confirming the occurrence of PO4 groups only in childrenite.\u0000","PeriodicalId":11971,"journal":{"name":"European Journal of Mineralogy","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139386141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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