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Geochemical Systema...
Geochemical Systematics of High Arctic Large Igneous Province Continental Tholeiites from Canada-Evidence for Progressive Crustal Contamination in the Plumbing System
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- Bedard, Jean H. (författare)
- Geol Survey Canada, 490 Couronne, Quebec City, PQ G1K 9A9, Canada.
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- Saumur, Benoit Michel (författare)
- Univ Quebec Montreal, Dept Sci Terre & Atmosphere, 201 Av President Kennedy, Montreal, PQ H2X 3Y7, Canada.
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- Tegner, Christian (författare)
- Aarhus Univ, Ctr Earth Syst Petrol, Dept Geosci, Aarhus, Denmark.
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- Troll, Valentin R. (författare)
- Uppsala universitet,Mineralogi, petrologi och tektonik,Naturresurser och hållbar utveckling
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- Deegan, Frances (författare)
- Uppsala universitet,Mineralogi, petrologi och tektonik,Naturresurser och hållbar utveckling
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- Evenchick, Carol A. (författare)
- Geol Survey Canada, 605 Robson St, Vancouver, BC V6B 5J3, Canada.
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- Grasby, Stephen E. (författare)
- Geol Survey Canada, 3303 33Rd St Nw, Calgary, AB T2L 2A7, Canada.
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- Dewing, Keith (författare)
- Geol Survey Canada, 3303 33Rd St Nw, Calgary, AB T2L 2A7, Canada.
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Geol Survey Canada, 490 Couronne, Quebec City, PQ G1K 9A9, Canada Univ Quebec Montreal, Dept Sci Terre & Atmosphere, 201 Av President Kennedy, Montreal, PQ H2X 3Y7, Canada. (creator_code:org_t)
- 2021-06-09
- 2021
- Engelska.
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Ingår i: Journal of Petrology. - : Oxford University Press. - 0022-3530 .- 1460-2415. ; 62:9
- Relaterad länk:
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https://doi.org/10.4...
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https://uu.diva-port... (primary) (Raw object)
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https://urn.kb.se/re...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- Cretaceous High Arctic large igneous province (HALIP) sub-alkaline magmatic rocks in Canada are mostly evolved (MgO 2-7 wt%), sparsely plagioclase + clinopyroxene +/- olivine-phyric tholeiitic basalts. There were two main HALIP continental flood basalt (CFB) eruption episodes: 135-120 Ma (Isachsen Fm.) and 105-90 Ma (Strand Fiord Fm.), both associated with cogenetic doleritic sills and dykes. Building on a large modern database, 16 HALIP tholeiite types are defined and grouped into genetic series using Ce vs Sm/Yb-NMORB distributions. Comparison with model melting curves implies that higher-Sm/Yb HALIP basalt types record low-degree melting of garnet-bearing mantle sources. More voluminous intermediate- and low-Sm/Yb HALIP basalt types separated from the mantle at shallower levels after further extensive melting in the spinel-peridotite field. Within a given Sm/Yb range, increases in incompatible elements such as Ce are coupled with progressive clockwise rotation of normalized incompatible trace element profiles. Trace element modeling implies this cannot be due to closed-system fractional crystallization but requires progressive and ubiquitous incorporation of a component resembling continental crust. The fractionation models imply that low-Sm/Yb HALIP basalts (similar to 7 wt% MgO) initially crystallized olivine gabbro assemblages, with lower-MgO basalts successively crystallizing gabbro and ilmenite-gabbro assemblages. In contrast, higher-Sm/Yb basalts fractionated more clinopyroxene and ilmenite, but extensive plagioclase fractionation is still required to explain developing negative Sr-Eu anomalies. Backfractionation models require about 40% addition of olivine to bring the most primitive HALIP basalts (similar to 7% MgO) into equilibrium with Fo(89) mantle. Inverse fractionation-assimilation modeling shrinks the CFB signature, making decontaminated model parental melts more similar to enriched mid-ocean ridge basalt. The progressive increase of the contamination signature within each HALIP tholeiitic differentiation series is not consistent with models involving derivation of HALIP basalts from a mantle source previously enriched by subduction. Strong interaction of basalt with Sverdrup Basin sedimentary rocks may cause localized over-enrichment in K-Rb-Th-U, but cannot explain strong Ba enrichment in the absence of concomitant K-Rb-Th-U enrichment. The localized Ba enrichment could reflect either a Ba-rich lithospheric mantle component that is strongly manifested in the coeval HALIP alkaline suites, or syn- to post-emplacement fluid-mediated transfer from Ba-rich host rocks.
Ämnesord
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geology (hsv//eng)
Nyckelord
- basalt
- contamination
- continental LIP
- HALIP
- plumbing system
Publikations- och innehållstyp
- ref (ämneskategori)
- art (ämneskategori)
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