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Flow of Canary Mantle Plume Material Through a Subcontinental Lithospheric Corridor Beneath Africa to the Mediterranean: REPLY

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Flow of Canary Mantle Plume Material Through a Subcontinental Lithospheric Corridor Beneath Africa to the Mediterranean: REPLY Flow of Canary mantle plume material through a subcontinental lithospheric corridor beneath Africa to the Mediterranean: REPLY REPLY: doi: 10.1130/G30653Y.1 alone is inappropriate to evaluate the composi- Islands hotspot.” There are several reasons why tion of the sublithospheric mantle source(s) of our model does not require an age progression S. Duggen1,2,*, K.A. Hoernle2, F. Hauff2,1, northern African intraplate volcanic fi elds. As in Atlas volcanism with increasing distance A. Kluegel3, M. Bouabdellah4, and illustrated in the 206Pb/204Pb versus 207Pb/204Pb from the Canary Islands: 1) Delamination of M.F. Thirlwall5 isotope diagram (Fig. 1), mafi c lavas from the subcontinental lithosphere since ca. 25–45 Ma 1A.P. Møller Skolen—Upper Secondary Canary Islands and those from volcanic fi elds probably occurred in multiple events, causing School and Sixth Form College of the Danish above the lithospheric corridor form a trend discontinuous infl ow of Canary-type mantle National Minority in Germany, “Auf der that extends from below the Northern Hemi- material; 2) decompression melting of the later- Freiheit,” 24837 Schleswig, Germany sphere Reference Line toward the lithosphere ally migrating sublithospheric mantle requires 2IFM-GEOMAR, Leibniz Institute of Marine with higher 207Pb/204Pb (metasomatized sub- a vertical fl ow component, thus only when the Sciences, Research Division Dynamics of continental lithospheric mantle and/or conti- extent of thinning lithosphere of a particular the Ocean Floor, Wischhofstrasse 1-3, 24148 nental crust). Mafi c intraplate lavas (ca. 70 Ma part of the corridor allowed suffi cient upwell- Kiel, Germany to Recent) found in Oujda, Hoggar, and Egypt/ ing did decompression melting occur; and 3) 3Universität Bremen, Fachbereich 5, Sudan clearly defi ne separate trends toward much of the residual Canary plume mantle Geowissenschaften, Postfach 33 04 40, 28334 higher 206Pb/204Pb. Therefore, the isotopic data was too depleted after earlier melt extraction Bremen, Germany available is consistent with derivation of the beneath the Canary hotspot track to produce 4Department of Geology, Faculty of Sciences, volcanism above the lithospheric corridor from melts everywhere beneath the corridor. B.P. 524, 60000 Oujda, Morocco a Canary-type sublithospheric mantle source, Finally, we note that there is no contradic- 5Department of Earth Sciences, Royal which cannot be inferred for the lavas outside tion between a mantle fl ow model as proposed Holloway University of London, Egham, the corridor. Further high-quality major and by Duggen et al. (2009) and substantial in- Surrey TW20 OEX, UK trace element, Sr-Nd-Pb-Hf-isotope, and age volvement of lithospheric processes in magma In their Comment, Berger et al. (2009) data (allowing precise age correction) of north- generation and ascent as suggested by Berger question the model of fl ow of Canary mantle ern African lavas, however, will be required to et al. (2009): the temporal and spatial distribu- plume material through a subcontinental litho- address these issues in more detail. tion of intraplate volcanism above the north- spheric corridor beneath northwest Africa to 3) Concerning timing, Berger et al. argue west African lithospheric corridor most likely the Mediterranean proposed by Duggen et al. that progressive infl ow of mantle material into results from an interplay between delamination (2009). They question 1) if a plume exists be- the lithospheric corridor should produce “a of subcontinental lithospheric mantle material, neath the Canary Islands, 2) if the geochemical correlation between the ages of the Atlas vol- infl ow of Canary-type mantle plume material, composition of intraplate lavas allows distinc- canic episodes and the distance to the Canary and reactivation of inherited geological struc- tion between Canary and other northern Afri- tures, possibly driven by the African-Europe can (from Morocco to Egypt/Sudan) sublitho- convergence. HIMU spheric mantle sources, and 3) if the timing of 15.75 Egypt/Sudan volcanism in northwest Africa is consistent REFERENCES CITED with a lateral infl ow of mantle plume material. 15.70 Hoggar Allegre, C.-J., Dupre, B., Lambret, B., and Richard, NW African Oujda 1) As we presented (Duggen et al., 2009), lithosphere P., 1981, The subcontinental versus suboceanic Pb 15.65 debate: I. Lead-neodymium-strontium isotopes there is strong evidence supporting the pres- Gou- 204 in primary alkali basalts from a shield area: The rougou Rekkam ence of a mantle plume beneath the Canary Ahaggar volcanic suite: Earth and Planetary Pb/ 15.60 Islands. No other model has been proposed Middle Atlas Science Letters, v. 52, p. 85–92. 207 Guilliz thus far that can adequately explain the geo- Berger, J., Liégeois, J.-P., Ennih, N., and Bonin, B., 15.55 Canary Islands physical, geochronological, geochemical, and Atlantic 2009, Flow of Canary mantle plume material MORB through a subcontinental lithospheric corridor geological data of the region. NHRL 15.50 beneath Africa to the Mediterranean: Comment: 2) Berger et al. argue, on the basis of the 18.5 19.0 19.5 20.0 20.5 206 204 Geology, doi: 10.1130/G30516C.1. Pb-Sr-isotope diagram, that the geochemical Pb/ Pb Duggen, S., Hoernle, K., Hauff, F., Klügel, A., composition of mafi c intraplate lavas, located Figure 1. Pb-isotope diagram showing the Bouabdellah, M., and Thirlwall, M.F., 2009, outside the northwest African lithospheric cor- composition of lavas from volcanic fi elds Flow of Canary mantle plume material through a subcontinental lithospheric corridor beneath ridor (such as Pliocene Oujda, Oligocene to above (Gourougou, Guilliz, Middle Atlas, Tamazert) and outside (Oujda, Hoggar, and Africa to the Mediterranean: Geology, v. 37, Miocene Algerian Hoggar, and Late Mesozoic Egypt/Sudan) the lithospheric corridor in p. 283–286, doi: 10.1130/G25426A.1. to Quaternary Egypt/Sudan volcanism), point northern Africa. Data sources: Duggen et al., Lucassen, F., Franz, G., Romer, R.L., Pudlo, D., to the same sublithospheric mantle source (2009, and references therein); Hoggar lavas and Dulski, P., 2008, Nd, Pb, and Sr isotope as tapped by mafi c lavas above the corridor (age corrected to 27 Ma using the average composition of Late Mesozoic to Quaternary Pb, Th, U concentrations of mafi c Oujda intra-plate magmatism in NE-Africa (Sudan, (Gourougou, Guilliz, Middle Atlas) and thus lavas) (Allegre et al., 1981); Egypt/Sudan Egypt): High-l signatures from the mantle as those from the Canary Islands (Berger et al., lavas <70 Ma (corrected to the respective lithosphere: Contributions to Mineralogy and 2009). We note that the Pb-Sr-isotope diagram age) (Lucassen et al., 2008). Petrology, v. 156, p. 765–784. *E-mail: [email protected] © 2009 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or [email protected]. e203 Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/38/1/e203/3538033/e203.pdf by guest on 02 October 2021.
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