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TitleComparative amphibole chemistry of the Monteregian and White Mountain alkaline suites, and the origin of amphibole megacrysts in alkali basalts and lamprophyres
AuthorBédard, J H
SourceMineralogical Magazine vol. 52, 1988 p. 91-103, Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 2005289
Alt SeriesUniversity of Cambridge, Department of Earth Sciences, Contribution 981
PublisherMineralogical Society
Mediapaper; on-line; digital
File formatpdf
NTS21E; 31G/01; 31G/08; 31G/09; 31G/16; 31H
AreaMonteregian Hills; White Mountains; New England; Oka; île Cadieux; île Bizard; Mount Royal; Mont St-Bruno; Mont St-Hillaire; Mont Rougemont; Mont Yamaska; Mont Shefford; Mont Brome; Barber Hill; Lac Memphrémagog; Mont Mégantic; Vermont; Cuttingsville; Ascutney; New Hampshire; Pliny; Ossipee; Pliny; Belknap; Pawtuckaway; Maine; Canada; United States of America
Lat/Long WENS -74.2500 -70.0000 46.0000 42.6667
Subjectsigneous and metamorphic petrology; igneous rocks; dykes; plutonic rocks; amphibole; lamprophyres; basalts; hastingsite; hornblende; host rocks; monchiquites; magnesium; titanium; aluminum; formation pressures; mafic rocks; pressure-temperature conditions; petrogenesis; modelling; crystal fractionation; alnoites; camptonites; chemical analysis; textural analyses; phenocrysts; plutons; deuteric alteration; granites; syenites; gabbros; actinolite; arfvedsonite; felsic rocks; silica; Monteregian Series; White Mountain Magma Series; White Mountain Batholith; pargasite; kaersutite; edenite; compositions; occurrences; aillikites; tschermackites; katophorite; barroisite; richterite; winchite; riebeckite; groundmass; xenocrysts; basanite; Phanerozoic; Mesozoic; Cretaceous; Jurassic; Triassic
Illustrationsgeological sketch maps; photomicrographs; profiles; tables; plots
ProgramNSERC Natural Sciences and Engineering Research Council of Canada
ProgramFCAC - Fonds pour la Formation de Chercheurs et Action Concertée
Released2018 07 05
AbstractAmphiboles in dykes from the dominantly silica-undersaturated Monteregian series range from pargasitic megacrysts and xenocrysts to kaersutitic, pargasitic and hastingsitic phenocrysts, groundmass prisms and reaction rims. Amphiboles in dykes and plutons from the silica-oversaturated White Mountain Magma Series range from kaersutite, through hornblende, hastingsite and edenite, to sodic-calcic and sodic varieties. This contrast between the amphiboles from the two series is probably a reflection of differing melt silica activity and is a useful petrologic discriminant. In most cases, pargasitic amphibole megacrysts from Monteregian monchiquites reflect the Mg numbers of their host rocks and are considered cognate. The megacrysts are lower in Ti and higher in Mg and Al than their phenocryst mantles and rims. This is probably a result of higher pressures of formation.

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