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TitreMineralogy and geochemistry of an orbicular-textured ultramafic lamprophyre from the Latchford area, northeastern Ontario
AuteurTemelkovski, A; Potter, E G; Kjarsgaard, I M; Cousens, B L
SourceL'Association géologique du Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 34, 2011 p. 215; 1 CD-ROM
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20100421
ÉditeurGeological Association of Canada and the Mineralogical Association of Canada ( GACMAC)
Réunion2011 GAC-MAC-SEG-SGA Joint Annual Meeting; Ottawa; CA; mai 25-27, 2011
Documentpublication en série
Mediapapier; CD-ROM; numérique
Lat/Long OENS-80.5000 -80.0000 46.2500 46.0000
Sujetslamprophyres; roches ultramafiques; roches ignées; fluorescence aux rayons x; méthodes de fluorescence aux rayons x; analyses par microscope électronique; assemblages de minéraux; minéralogie; géochimie
ProgrammeUranium, GEM : La géocartographie de l'énergie et des minéraux
Résumé(disponible en anglais seulement)
An unusual, orbicular-textured, ultramafic lamprophyre was discovered on the western shoreline of Anima Nipissing Lake, in
Northeastern Ontario during a regional diamond exploration program. This sample was thoroughly examined using XRF, microscopy
and electron microprobe analysis. The mineral assemblage of the orbicular dyke consists of: phlogopite, diopside, Mg-ilmenite and apatite macro- and/or phenocrysts, in an altered groundmass of Ti-magnetite, carbonate, chlorite and serpentine. Compositionally, the orbicules are similar to the matrix of the dyke, suggesting that they are pelletal lapilli that formed around Mg-ilmenite and diopside macrocrysts. The mineral paragenesis has similarities to both kimberlites and ultramafic lamprophyres. Mg-ilmenite compositions show moderate MgO contents (4-5 wt%) characteristic of ultramafic lamprophyres and at the lower end of kimberlite megacryst compositional range. Phlogopite macrocrysts are Ti-rich (up to 7.7 wt% TiO2) and follow an evolutionary path similar to that of ultramafic lamprophyres. Ti-magnetite and Cr-free diopside compositions also show characteristics similar to those found in lamprophyres, particularly damtjernites. Abundant apatite is the host of the high P, Sr and LREE concentrations found in the whole rock. In addition to the orbicules, the rock contains glomerophyric, droplet-like textures that are believed to be products of liquid immiscibility. Although the whole
rock composition is similar to both kimberlites and ultramafic lamprophyres, the mineral chemistry shows a better correlation with
ultramafic lamprophyres, specifically damtjernite. Although intrusive contacts remain covered by overburden, this lamprophyre
dyke lies along strike of a Sudbury olivine diabase dyke and occurs approximately 10 km southwest of the KRVY diamond-bearing
breccia. The ultramafic KRVY body exhibits similar textures (i.e. heterolithic breccia and pelletal lapilli) and mineralogy (i.e.
phlogopite, carbonate, ilmenite, apatite and diopside) as the lamprophyre dyke. However, further study of the latter occurrence is
required to determine if a genetic relationship exists between these two unusual occurrences and to determine whether they represent
members of a larger intrusive event.