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This contribution presents U-Pb geochronological data for Ca-Fe-Ti garnets from compositionally diverse alkaline and carbonatitic intrusive rocks ranging from Neoarchean to Permian-Triassic (Cinder Lake and Eden Lake in Manitoba, Canada; Belaya Zima and Odikhincha in Siberia, Russia; Afrikanda in the Kola Peninsula, Russia) obtained using isotope-dilution thermal-ionization mass spectrometry (ID-TIMS) and their trace-element compositions measured by laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICPMS). The studied garnets yield U-Pb concordant or subconcordant ages obtained with a precision of <0.5% owing to their relatively high content of U and negligible common Pb. The new ID-TIMS data are in excellent agreement with the previously reported zircon, baddeleyite and perovskite ages. The results of the present work demonstrate that postmagmatic alteration does not disturb or reset the U-Pb isotopic budget of these minerals, and that garnets representing the andradite-schorlomite-morimotoite system can serve as a robust reference material for micro-analytical geochronological studies of a wide spectrum of igneous and contact-metasomatic rocks. The new LA-ICPMS data demonstrate that the abundances of rare-earth, high-field-strength and other trace elements in calcic garnets from alkaline and carbonatitic rocks vary by at least two orders of magnitude and can therefore be used as reliable magma-evolution tracers. The rare-earth budget of these minerals is best described in terms of the chondrite-normalized ratios (Sm/La) cn and (Sm/Yb) cn , which are sensitive to lanthanide fractionation, and Y/Ho, which is interpreted to respond to garnet re-equilibration with a fluid. • U-Pb ID-TIMS study of calcic garnets yields precise and reliable ages. • Postmagmatic alteration does not disturb the U-Pb isotopic budget. • Ca-Fe-Ti garnets can serve as a robust isotopic reference material. [ABSTRACT FROM AUTHOR]

The article examines the historical background of the Robert B. Ferguson Museum of Mineralogy in the Department of Geological Sciences at the University of Manitoba in Winnipeg. Geologist Joseph Winthrop Spencer's collection of minerals and rocks was among the first collections of the museum. Information on the notable individuals behind the museum is presented.

This paper presents a microbeam (electron microprobe, Raman spectroscopic and X-ray microdiffraction) study of cancrinite-group minerals of relevance to alkaline igneous rocks. A solid solution is known to exist between cancrinite and vishnevite with the principal substitutions being CO32- by SO42- and Ca for Na. In the present study, several intermediate members of the cancrinite-vishnevite series from a syenitic intrusion at Cinder Lake (Manitoba, Canada), were used to examine how chemical variations in this series affect their spectroscopic and structural characteristics. The Cinder Lake samples deviate from the ideal cancrinite-vishnevite binary owing to the presence of cation vacancies. The only substituent elements detectable by electron microprobe are K, Sr and Fe (0.03-0.70, 0-0.85 and 0-0.45 wt.% respective oxides). The following Raman bands are present in the spectra of these minerals: ~631 cm-1 and ~984-986 cm-1 [SO42- vibration modes]; ~720-774 cm-1 and ~1045-1060 cm-1 [CO32- vibration modes]; and ~3540 cm-1 and 3591 cm-1 [H2O vibration modes]. Our study shows a clear relationship between the chemical composition and Raman characteristics of intermediate members of the cancrinite-vishnevite series, especially with regard to stretching modes of the CO2-3 and SO42- anions. From cancrinite-poor (Ccn6.5) to cancrinitedominant (Ccn91.3) compositions, the SO42- vibration modes disappear from the Raman spectrum, giving way to CO32- modes. X-ray microdiffraction results show a decrease in unit-cell parameters towards cancrinite-dominant compositions: a = 12.664 (1) Å, c = 5.173(1) Åfor vishnevite (Ccn22); a = 12.613 (1) Å, c = 5.132(1) Å for cancrinite (Ccn71). Our results demonstrate that Raman spectroscopy and X-ray microdiffraction are effective for in situ identification of microscopic grains of cancrinite-vishnevite where other methods (e.g. infrared spectroscopy) are inapplicable. The petrogenetic implications of cancrinite-vishnevite relations for tracing early- to late-stage evolution of alkaline magmas are discussed. [ABSTRACT FROM AUTHOR]