| Titre | Scapolite and analcime: monitors of magmatic fluid metasomatism in a major shear zone |
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| Auteur | Pe-Piper, G; Piper, D J W ; Nagle, J |
| Source | Chemical Geology vol. 522, 2019 p. 208-222, https://doi.org/10.1016/j.chemgeo.2019.05.014 |
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| Année | 2019 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20180270 |
| Éditeur | Elsevier BV |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.chemgeo.2019.05.014 |
| Media | papier; en ligne; numérique |
| Formats | pdf (Adobe® Reader®); html |
| Province | Nouvelle-Écosse |
| SNRC | 21H/08 |
| Région | Clarke Head; Cobequid Highlands; Parrsboro |
| Lat/Long OENS | -64.5000 -64.0000 45.5000 45.3333 |
| Sujets | géologie du substratum rocheux; lithologie; roches ignées; roches intrusives; syenites; roches granitiques; gabbros; diorites; caractéristiques structurales; zones de cisaillement; zones de failles;
altération; métasomatose; milieux tectoniques; antécédents tectoniques; intrusions; magmatisme; formation de failles; bassins; précipitation; système hydrothermal; dynamique des fluides; fluage; scapolite; analcime; hastingsite; filons; chlorure de
sodium; géochimie du chlore; géochimie du sodium; etudes isotopiques; isotopes d'oxygène; géochimie du titane; géochimie du zirconium; feldspath; géochimie du potassium; biotite; microscopie des lames minces; assemblages de minéraux; paragenèse;
analyses par microsonde électronique; conditions de pression-température; datation radiométrique; datation au uranium-plomb; datation argon-argon; Terrane d'Avalon ; Terrane de Meguma ; Zone de cisaillement de Cobequid ; pétrologie ignée et
métamorphique; minéralogie; tectonique; géochimie; géochronologie; Phanérozoïque; Paléozoïque; Carbonifère; Dévonien |
| Illustrations | cartes géolscientiques généralisées; photographies; photomicrographies; tableaux; graphiques; diagrammes ternaires; cartes géochronologiques |
| Programme | Division de la CGC atlantique |
| Diffusé | 2019 05 25 |
| Résumé | (disponible en anglais seulement)
Scapolite and analcime are uncommon alteration minerals in syenite. Here we describe a syenite body in a fault zone that hosts these minerals and we elucidate
the unusual chemical conditions that led to their formation. The Clarke Head syenite is part of a regional late Devonian-early Carboniferous back-arc A-type granitoid suite in the Cobequid Highlands of Nova Scotia, Canadian Appalachians. The syenite
contains magmatic rutile and analcime. Magmatic K-feldspar has been largely replaced by scapolite of marialite composition, which shows a temporal transition from more Cl rich to more carbonate rich varieties. Scapolite veins cut both the syenite and
associated gabbro and diorite. Analcime I occurs as a late stage interstitial magmatic mineral. Analcime II forms by alteration of albite lamellae in perthite replaced by scapolite, analcime III vugs that cross-cut scapolite and analcime IV occurs in
late veins cross-cutting earlier analcime phases and scapolite. The regional A-type granite plutonism was Na- and halogen rich, with widespread late-magmatic albitization and F-related mobility of REE minerals. However, only at Clarke Head is there
extreme Na- and Cl-rich metasomatism, indicated by scapolite and Cl-rich hastingsite (with>1 wt% Cl content). Cl-rich fluids were derived from regional halite evaporites at faulted basin margins. The main circulating fluids were likely of magmatic
origin, based on the delta-18O of both replacement and vein scapolite. As the NaCl supply was reduced, scapolite became more Ca-rich. Halogen-rich fluids also mobilized Ti and Zr, which were reprecipitated in hydrothermal rutile and zircon as the
halogen activity diminished. Scapolite replacement of K-feldspar released large amounts of K+ into the circulating fluids, which converted ferromagnesian silicates in fault zones to secondary biotite. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Une description de la scapolite et de l'analcime, deux minéraux inhabituels trouvés dans la roche granitique de la zone de la faille de Minas
près de Parrsboro (Nouvelle-Écosse) et une interprétation de leur origine tenant compte des systèmes minéralisateurs. |
| GEOSCAN ID | 313030 |
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