Experimental metasomatic alteration of titanite in a series of metamorphic fluids at 700 °C and 200 MPa.
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| Title: | Experimental metasomatic alteration of titanite in a series of metamorphic fluids at 700 °C and 200 MPa. |
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| Authors: | Gmochowska, Wiktoria1 (AUTHOR) wiktoria.gmochowska@twarda.pan.pl, Harlov, Daniel2,3,4 (AUTHOR), Słaby, Ewa5 (AUTHOR), Jokubauskas, Petras6 (AUTHOR), Sláma, Jiří7 (AUTHOR), Łącki, Marcin6 (AUTHOR) |
| Source: | Mineralogy & Petrology. Sep2024, Vol. 118 Issue 3, p321-344. 24p. |
| Subjects: | Rare earth metals, Sphene, Metasomatism, Perovskite, Wollastonite, Garnet |
| Abstract: | Seven experiments exploring the reaction of titanite with various hydrothermal solutions have been carried out at 700 °C and 200 MPa for a run duration of 16 days. In experiments involving fluids consisting of NaCl+H2O, KCl+H2O, CaCl2+H2O, 2M NaOH, or 2M KOH, no reaction of the titanite with the fluid was observed other than a slight dissolution of the titanite. Experiments involving NaF+H2O and Ca(OH)2+H2O resulted in visible alteration of the titanite in texture and composition, coupled with the formation of perovskite. In the NaF+H2O experiment, perovskite, enriched with rare earth elements (REE), formed as euhedral to subhedral crystals on the surface of the recrystallized titanite. In the Ca(OH)2+H2O experiment perovskite took in minor amounts of REE, and formed as a reaction rim partially replacing the titanite via a coupled dissolution-reprecipitation reaction. Wollastonite, along with minor calcite, and grossular garnet, formed as an outer rim on the perovskite. In the NaF+H2O experiment major and trace elements were leached from the titanite, whereas in the Ca(OH)2+H2O experiment no leaching of major or trace elements was observed. Nb/Ta, Th/U, and Y/Ho were investigated as potential indicators of hydrothermal processes. While the Nb/Ta ratio was altered in the experimentally metasomatised titanite, the degree of alteration was the same for both fluids. In contrast, only small changes in the Th/U and Y/Ho ratios between the altered and original titanite were seen for either experiment. The formation of perovskite at the expense of titanite in NaF+H2O or Ca(OH)2+H2O fluids demonstrates how titanite reacts with these fluids in simple, low silica activity systems under mid to upper crustal P-T conditions. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Seven experiments exploring the reaction of titanite with various hydrothermal solutions have been carried out at 700 °C and 200 MPa for a run duration of 16 days. In experiments involving fluids consisting of NaCl+H2O, KCl+H2O, CaCl2+H2O, 2M NaOH, or 2M KOH, no reaction of the titanite with the fluid was observed other than a slight dissolution of the titanite. Experiments involving NaF+H2O and Ca(OH)2+H2O resulted in visible alteration of the titanite in texture and composition, coupled with the formation of perovskite. In the NaF+H2O experiment, perovskite, enriched with rare earth elements (REE), formed as euhedral to subhedral crystals on the surface of the recrystallized titanite. In the Ca(OH)2+H2O experiment perovskite took in minor amounts of REE, and formed as a reaction rim partially replacing the titanite via a coupled dissolution-reprecipitation reaction. Wollastonite, along with minor calcite, and grossular garnet, formed as an outer rim on the perovskite. In the NaF+H2O experiment major and trace elements were leached from the titanite, whereas in the Ca(OH)2+H2O experiment no leaching of major or trace elements was observed. Nb/Ta, Th/U, and Y/Ho were investigated as potential indicators of hydrothermal processes. While the Nb/Ta ratio was altered in the experimentally metasomatised titanite, the degree of alteration was the same for both fluids. In contrast, only small changes in the Th/U and Y/Ho ratios between the altered and original titanite were seen for either experiment. The formation of perovskite at the expense of titanite in NaF+H2O or Ca(OH)2+H2O fluids demonstrates how titanite reacts with these fluids in simple, low silica activity systems under mid to upper crustal P-T conditions. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 09300708 |
| DOI: | 10.1007/s00710-024-00862-5 |
