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TitleGeochemical-textural analysis of palagonitized basaltic glass in a lapilli tuff dredged from the Alpha Ridge, Arctic Ocean
AuthorMassey, E; Williamson, M -CORCID logo; MacDonald, D; Locock, A; Carey, R; Oakey, G; Wilton, D; Harris, J
SourceChapman Conference: Large-Scale Volcanism in the Arctic: The Role of the Mantle and Tectonics, abstracts; 2019 p. 39-40 Open Access logo Open Access
LinksOnline - En ligne (complete volui\me - volume complet, PDF, 3.32 MB)
Alt SeriesNatural Resources Canada, Contribution Series 20190263
PublisherAmerican Geophysical Union
MeetingAmerican Geophysical Union Chapman Conference: Large-scale Volcanism in the Arctic: The Role of the Mantle and Tectonics; Selfoss; IS; October 13-18, 2019
Mediaon-line; digital
File formatpdf
ProvinceNorthern offshore region; Nunavut
NTS49F; 49G; 59E; 59F; 59G; 59H; 340B; 340C; 560A; 560D
AreaArctic Ocean; Alpha Ridge
Lat/Long WENS-180.0000 -60.0000 90.0000 76.0000
Subjectsgeochemistry; igneous and metamorphic petrology; mineralogy; Science and Technology; Nature and Environment; bedrock geology; lithology; igneous rocks; volcanic rocks; tuffs; clasts; basalts; paleoenvironment; depositional environment; emplacement; tectonic history; magmatism; volcanism; dredge sampling; geochemical analyses; mineralogical analyses; textural analyses; microscopic analyses; electron probe analyses; Canada-Sweden Polar Expedition; United Nations Convention On The Law Of The Sea (Unclos); Phanerozoic; Cenozoic; Quaternary; Mesozoic; Cretaceous
ProgramDelineating Canada's Continental Shelf Under UNCLOS
Released2019 10 01
AbstractPalagonitized volcanic glass deposits, whether formed from basaltic submarine, glaciovolcanic, or lacustrine magma-water interaction, are paleoenvironment proxies of eruptive style, pressure depths of ice or water, and microbial ecosystems. In August 2016, the collaborative Canada-Sweden Polar Expedition under Canada's UNCLOS (United Nations Convention on Law of the Sea) Program dredged approximately 100 kg of volcanic rocks from the Alpha Ridge. The recovered samples consist of lapilli tuff with rounded glass-rich lapilli and angular basaltic clasts. The vitric fragments consist of fresh sideromelane glass of alkali basalt composition, and plagioclase microlites. Cognate, angular clasts incorporated in the juvenile magma during eruption are cogenetic. Together with the dominance of glassy vitric clasts in the tuff, this feature suggests a primary, phreatomagmatic eruption. Basaltic glass lapilli display a fresh glassy core surrounded by Fe- and Ti-rich zones and palagonite rims formed by rapidly cooled and quenched magma. Geochemical-textural relationships were investigated on glass, palagonite, and secondary phases by optical microscopy, electron microprobe (EMP) and mineral mapping techniques. Three distinct zones are evident: (1) fresh sideromelane; (2) an Fe-rich phase; and (3) Ti-rich inclusions mixed with clays. Commonly, a Si-Fe rich phase forms a film along the outer edge of zeolite growth and a Mn-phase with a filamentous morphology infills voids. In the palagonite rim, an inner zone is elevated in SiO2 (51.2 wt%) relative to sideromelane and an outer zone increases in FeO, MnO, MgO, and H2O. Water content in palagonite rims range from 7.5 wt% to 11.9 wt%, less than commonly reported for younger Pleistocene samples (15 wt% to 40 wt%). Among the materials discussed, the zeolite has the highest values of SiO2 (59.4 wt%), Al2O3 (22.5 wt%), and Na2O (4.8 wt%). The composition and geochemical-textural zoning observed in Alpha Ridge basaltic glass differs from other palagonitization studies. Further work may shed light on the climate that prevailed in the Late Cretaceous and on the timing for submergence of the Alpha Ridge.
Summary(Plain Language Summary, not published)
In August 2016, a collaborative Canada-Sweden Polar Expedition under Canada¿s UNCLOS (United Nations Convention on Law of the Sea) Program recovered approximately 100 kg of volcanic rocks from the Alpha Ridge. The samples consist of pyroclastic rocks with glass-rich lapilli and basalt fragments. We present a detailed study of the alteration process from fresh basaltic glass to palagonite. The composition and geochemical-textural zoning in the Alpha Ridge basaltic glass is distinct from previously published palagonitization studies. The results help us better define the geological evolution of the Alpha Ridge.

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