Extensive bimodal plutonism accompanied and followed the Acadian deformation in New Brunswick. These Acadian plutons define a Central Plutonic Belt, which is largely confined to a terrain with an Acadian trend of 030°, and a Southern Plutonic Belt, which occurs within a structural province with an Acadian and Variscan trend of 060". It has been possible to classify the Acadian plutons north of the Avalonian Platform according to their structures, textures, field relationships, mineralogy, and chemical characteristics; supplemented by radiometric age dates. Plutonic rock types include: A-B a mafic-felsic association; C-syntectonic tonalite and granodiorite; D-muscovite-bearing; F-megacrystic granitoids; H-equigranular biotite granites; and E and G-'transitional' granites. The magmatism, regardless of location, follows a common evolutionary trend and appears to comprise a sequence of intrusions from early Devonian to Carboniferous time with no significant break in the evolution. These characteristics along with the bimodal chemistry and the lack of compositional polarity suggest that the development of these Acadian plutons was not subduction-related. A time-dependent process such as radioactive heating of a thickened crust is a more probable mechanism for their genesis. Au Nouveau-Brunswick, la deformation acadienne fut accompagnee puis suivie d'un plutonisme bimodal tres etendu. Ces plutons acadiens definissent une zone intrusive centrale et une zone intrusive meridionale: la premiere se confine en grande partie dans une region qui presente une orientation acadienne de 030° alors que la seconde se trouve a 1'interieur d'une province structurale marquee par une orientation acadienne et varisque de 060°. Au nord de la plate-forme avalonlenne, les plutons acadiens ont pu etre classifies selon leurs structures, textures, relations de terrain ainsi que leurs caracterisques mineralogiques et chimiques, le tout etant complete par des datatlons radiometriques. Les roches intrusives comprennent: A-B une association mafique et felsique; C-une granodiorite et une tonalite syntectoniques; D-roches intrusives £ muscovite; F-granitoides & biotite equigranulaire; et E et G-granites "de transition". Peu importe l'endroit, on observe une tendance evolutive commune ace magmatisme qui semble comprendre une suite d'intrusions, evoluant sans interruption du Devonien inferieur au CarbonifSre. Ces caracteristiques, en plus de la bimodalite du chlmisme et de 1*absence de polarite de composition, auggerent que ces plutons acadeins ne furent pas formes par subduction. Pour engendrer ceux-cl, un processus IIS au temps, tel que le rechauffement radioactlf d'une croute qui s'est epaissie, est plus probable. [Traduit par le journal] GEOLOGIC SETTING The pre-Carboniferous rocks north of the exposed Avalonian Platform can be divided into four tectonostratigraphic zones (Ruitenberg et at. 1977). These are, from southeast to northwest, the Fredericton Trough, the Miramichi Massif, the Elmtree Inlier and the Matapedia Basin (Fig. 1). The plutonic ...
SummaryThe variation in the structural state of potassium feldspars from the St. George pluton, New Brunswick, Canada, is discussed. Monoclinic potassium feldspars occur near the eastern end of the pluton whereas the granites at the western end contain triclinic potassium feldspars. Although the bulk compositions of the host rocks are all very near the granite minimum melt composition there is a systematic increase in the degree of ordering for both the triclinic and monoclinic suites of feldspars with the more ordered variants tending to occur within rocks nearest the minimum melt composition. There is more abundant textural evidence for the presence of a late-stage fluid phase in the granites containing the monoclinic potassium feldspars. It is proposed that a slower post-crystallization cooling rate was also a factor in the nucleation of triclinic domains in the potassium feldspars at the western end of the pluton.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.