| Titre | Temporal variation of titanite morphology and chemistry in a long-lived shear zone: the Clarke Head syenite in the Minas Fault Zone, Nova Scotia |
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| Auteur | Pe-Piper, G; Piper, D J W ; Nagle, J |
| Source | Lithos vol. 372-373, 105670, 2020 p. 1-18, https://doi.org/10.1016/j.lithos.2020.105670 |
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| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200052 |
| Éditeur | Elsevier |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.lithos.2020.105670 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Nouvelle-Écosse |
| SNRC | 21H/08 |
| Région | Clarke Head |
| Lat/Long OENS | -64.5000 -64.0000 45.5000 45.2500 |
| Sujets | géologie du substratum rocheux; caractéristiques structurales; zones de cisaillement; zones de failles; titanite; cristallographie; morphologie cristalline; altération hydrothermale; syenites; dynamique
des fluides; antécédents tectoniques; magmatisme; système hydrothermal; tectonique; minéralogie; géochimie; Sciences et technologie; Nature et environnement; Phanérozoïque; Paléozoïque; Carbonifère; Mississippien |
| Illustrations | cartes géolscientiques généralisées; photographies; photomicrographies; tableaux; graphiques; histogrammes; coupes schématiques transversales; cartes géochronologiques |
| Diffusé | 2020 07 12 |
| Résumé | (disponible en anglais seulement)
The mineral chemistry of titanite has been studied in a hydrothermally altered syenite preserved as blocks in a salt wall within a regional intracontinental
shear zone. The study focusses on the controls on temporal variation in REEs, Zr, Nb, U and Th. Several generations of titanite are recognised on the basis of morphology, chemistry, and relationship to other secondary minerals. Magmatic euhedral to
subhedral titanite has Ti and Zr contents characteristic of magmatic titanite in other studies, but does not have a magmatic abundance of REE. Rather, it is 102-104 times depleted in LREE and only slightly depleted in HREE. The leaching of LREE began
during a regionally recognised phase of potassic alteration, as amphiboles and biotites in gabbros and diorites recrystallized along shear zones and released K, Ca, and F. Later, some 15 Ma after emplacement, the alkali feldspars in the syenite were
largely altered to scapolite and analcime by interaction with adjacent halite and gypsum deposits. Titanite formed at that time, from dissolution-reprecipitation reactions in large rutile crystals, is less depleted in LREE, as a result of the
dominance of Cl- in hydrothermal waters. Following that event, F- -dominated hydrothermal waters prevailed again, resulting in more LREE depletion in previously formed titanite and in neoformed hydrothermal titanite. At that time, there was also
depletion in Zr and U. The trace elements in hydrothermal titanite are thus very informative on the hydrothermal history of the rocks. A combination of morphology and trace-element signature allows different hydrothermal stages to be
distinguished. |
| Sommaire | (Résumé en langage clair et simple, non publié)
La titanite est un minéral mineur répandu dans les gisements de minerai commerciaux. Nous démontrons comment sa morphologie et sa composition
chimique témoignent du style d’interaction entre les fluides hydrothermaux et les roches chaudes. |
| GEOSCAN ID | 326079 |
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