A LREE-depleted component in the Afar plume; further evidence from Quaternary Djibouti basalts

doi:10.1016/J.LITHOS.2009.09.008

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A LREE-depleted component in the Afar plume; further evidence from Quaternary Djibouti basalts

Journal Article•DOI•

A LREE-depleted component in the Afar plume; further evidence from Quaternary Djibouti basalts

Mohamed Ahmed Daoud¹, René C. Maury¹, Jean-Alix Barrat¹, Rex N. Taylor², Bernard Le Gall¹, Hervé Guillou³, Joseph Cotten¹, Joël Rolet¹ - Show less +4 more•Institutions (3)

European University of Brittany¹, University of Southampton², Centre national de la recherche scientifique³

01 Feb 2010-Lithos (Elsevier)-Vol. 114, Iss: 3, pp 327-336

TL;DR: In this paper, trace element and isotopic (Sr, Nd, Pb) data and unspiked K-Ar ages are presented for Quaternary (0.90-0.95 Ma old) basalts from the Hayyabley volcano, Djibouti.

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About: This article is published in Lithos.The article was published on 2010-02-01 and is currently open access. It has received 22 citations till now. The article focuses on the topics: Basalt & Trace element.

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Figures (8)

Table 3 Click here to download Table: Hayy_Table 3nb.doc

Table 1. Unspiked 40K-40Ar datings of Hayyabley basalts. See text for the analytical 1 procedures. 2 3

Table 4. Sr, Nd and Pb isotopic compositions of Hayyabley basalts (B: bulk rock; R: residue 1 after leaching). See text for the analytical procedures. Δ7/4 and Δ 8/4 denote the deviation (in 2 0/00) of

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Journal Article•DOI•

The size of plume heterogeneities constrained by Marquesas isotopic stripes

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Catherine Chauvel¹, René C. Maury², Sylvain Blais², Eric Lewin¹, Hervé Guillou¹, Gérard Guille, Philippe Rossi, Marc-André Gutscher² - Show less +4 more•Institutions (2)

Centre national de la recherche scientifique¹, European University of Brittany²

01 Jul 2012-Geochemistry Geophysics Geosystems

TL;DR: In this paper, the authors present new Sr, Nd, Pb, Hf and Hf isotopes as well as trace element data on lavas from several Marquesas Islands and demonstrate that this archipelago consists of two adjacent and distinct rows of islands with significantly different isotopic compositions.

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Abstract: The scale and geometry of chemical and isotopic heterogeneities in the source of plumes have important scientific implications on the nature, composition and origin of plumes and on the dynamics of mantle mixing over time. Here, we address these issues through the study of Marquesas Islands, one of the Archipelagoes in Polynesia. We present new Sr, Nd, Pb, Hf isotopes as well as trace element data on lavas from several Marquesas Islands and demonstrate that this archipelago consists of two adjacent and distinct rows of islands with significantly different isotopic compositions. For the entire 5.5 Ma construction period, the northern islands, hereafter called the Ua Huka group, has had systematically higher 87Sr/86Sr and lower 206Pb/204Pb ratios than the southern Fatu Hiva group at any given 143Nd/144Nd value. The shape and curvature of mixing arrays preclude the ambient depleted MORB mantle as one of the mixing end-members. We believe therefore that the entire isotopic heterogeneity originates in the plume itself. We suggest that the two Marquesas isotopic stripes originate from partial melting of two adjacent filaments contained in small plumes or "plumelets" that came from a large dome structure located deep in the mantle under Polynesia. Low-degree partial melting under Marquesas and other "weak" Polynesian hot spot chains (Pitcairn-Gambier, Austral-Cook, Society) sample small areas of the dome and preserve source heterogeneities. In contrast, more productive hot spots build up large islands such as Big Island in Hawaii or Reunion Island, and the higher degrees of melting blur the isotopic variability of the plume source.

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62 citations

Cites background from "A LREE-depleted component in the Af..."

...…Thirlwall et al., 2004; Kokfelt et al., 2006], the Galapagos [White et al., 1993;Hoernle et al., 2000; Blichert-Toft and White, 2001; Saal et al., 2007], Afar [Furman et al., 2006; Beccaluva et al., 2009; Daoud et al., 2010] and Hawaii [Yang et al., 2003; Frey et al., 2005; Fekiacova et al., 2007]....
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Journal Article•DOI•

Young rift kinematics in the Tadjoura rift, western Gulf of Aden, Republic of Djibouti

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Mohamed Ahmed Daoud¹, Bernard Le Gall¹, René C. Maury¹, Joël Rolet¹, Philippe Huchon², Hervé Guillou³ - Show less +2 more•Institutions (3)

European University of Brittany¹, University of Paris², Centre national de la recherche scientifique³

01 Feb 2011-Tectonics

TL;DR: In this paper, the Tadjoura rift is interpreted as an asymmetrical south-facing half-gr aben, about 40 km wide, dominated by a large boundary fault zone to the north.

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Abstract: The Tadjoura rift forms the westernmost edge of the westerly-propagating Sheba ridge, between Arabia a nd Somalia, as it enters into the Afar depression. Fro m structural and remote sensing dataset, the Tadjou ra rift is interpreted as an asymmetrical south-facing half-gr aben, about 40 km-wide, dominated by a large boundary fault zone to the north. It is partially filled up by the 1-3 Ma-old Gulf Basalts which onlapped the older S omali Basalts along its shallower southern flexural margin. The m ajor and trace element analysis of 78 young onshore lavas allows us to distinguish and map four distinct basa ltic types, namely the Gulf, Somali, Goumarre and H ayyabley Basalts. These results, together with radiometric a ge data, lead us to propose a revised volcano-strat igraphic sketch of the two exposed Tadjoura rift margins, an d to discriminate and date several distinct fault n etworks of this oblique rift. Morphological and statistical an alyses of onshore extensional fault populations sho w marked changes in structural styles along-strike, in a dir ection parallel to the rift axis. These major fault disturbances are assigned to the arrest of axial fault tip propagati on against pre-existing discontinuities in the NS-o riented Arta transverse zone. According to our model, the sinist ral jump of rifting into the Asal-Ghoubbet rift seg ment results from structural inheritance, in contrast with the en echelon or transform mechanism of propagation that prevail ed along the entire length of the Gulf of Aden extensi onal system.

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46 citations

Journal Article•DOI•

The Cenozoic magmatism of East Africa: Part V – Magma sources and processes in the East African Rift

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Tyrone O. Rooney¹•Institutions (1)

Michigan State University¹

01 May 2020-Lithos

TL;DR: In this paper, the isotopic systematics of East African magmatism reveal significant complexity as to the specific reservoirs that may participate in the melting processes noted above, and the isotope characteristics of magma suites from throughout the region form arrays that broadly converge on the composition of the Afar Plume, despite some complexity where the plume material has formed a hybrid plume-lithosphere component.

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45 citations

Journal Article•DOI•

At the Age

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M. Hesselman

01 Jan 1982-Michigan Historical Review

43 citations

Journal Article•DOI•

Palaeoproterozoic Continental MORB-type Tholeiites in the Karelian Craton: Petrology, Geochronology, and Tectonic Setting

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A. V. Stepanova, A. V. Samsonov, E. B. Sal’nikova, Igor S. Puchtel¹, Yu. O. Larionova, A. N. Larionov², V. S. Stepanov, Y. B. Shapovalov, S. V. Egorova - Show less +5 more•Institutions (2)

University of Maryland, College Park¹, Unitary enterprise²

01 Sep 2014-Journal of Petrology

TL;DR: In this paper, the authors used the results of U^Pb (zircon) and Sm^Nd internal isochron dating for MORB-type tholeiitic dikes in the Karelian Craton, eastern Fennoscandian Shield.

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Abstract: Major-element, lithophile trace element, and Sm^Nd and U^Pb zircon isotopic data are presented for Palaeoproterozoic mid-ocean ridge basalt (MORB)-type tholeiitic dikes ranging in age from 2140 3 to 2126 5 Ma studied at six localities within three terranes in the Karelian Craton, eastern Fennoscandian Shield. All the studied dikes have remarkably uniform geochemical and isotope characteristics.They are tholeiitic basalts with low contents of large ion lithophile elements, high field strength elements, and rare earth elements (REE), nearly flat chondrite-normalized REE patterns [(La/Sm)n1⁄4 0·9^1·2, (Gd/Yb)n1⁄41·0^1·2], and positive Ti, Nb, and Zr anomalies in the primitive mantle-normalized diagrams. The dikes also show relatively uniform initial Nd isotope compositions, with eNd values ranging fromþ1·4 toþ3·0, despite the occurrence of these dikes within Archaean terranes with different crustal history. According to the results of U^Pb (zircon) and Sm^Nd internal isochron dating the crystallization age of the dikes is constrained to be c. 2·14 Ga. The studied MORB-type tholeiitic dikes are probably comagmatic with Palaeoproterozoic MORB-type basalts that have previously been recognized in the Karelian Craton, and might represent relicts of their magma feeder system.The uniformity of ages and geochemical and isotope characteristics of the MORB-type dikes and volcanic rocks suggest that they are probably related to a common magmatic event.This event was nearcontemporaneous with the eruption of high-Ti plume-related basalts and intrusion of dikes in the c. 2·1 Ga Jatulian continental flood basalt province. Geochemical modelling indicates that the chemical and isotopic compositions of the dikes are best explained by derivation of their parental magmas by partial melting of a uniformly depleted mantle source in the spinel peridotite stability field, followed by fractional crystallization and minor (56%) assimilation of continental crustal material. This suggests that magma-storage processes in upper crustal chambers were very short-lived; this could be the

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42 citations

Cites background from "A LREE-depleted component in the Af..."

...Analogues of the Karelian Palaeoproterozoic continental MORB-type tholeiities have been recognized in the North Atlantic and Afar continental flood basalt provinces, where depleted MORB-type tholeiitic basalts are shown to have formed simultaneously with high-Ti basalts (Barrat et al., 2003; Daoud et al., 2010; S ager & Holm, 2011;Waight & Baker, 2012)....
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..., 2012), and dikes (this study) compared with low-Ti tholeiites from the Faroe Islands (S ager & Holm, 2011), depleted basalts from Central East Greenland (Waight & Baker, 2012), LREE-depleted basalts from Central Afar (Barrat et al., 2003; Daoud et al., 2010), Kolbeinsey Ridge and Reykjanes Ridge basalts (PetDB), and global N-MORB (PetDB)....
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...MORB-type continental tholeiitic basalts are thought to have formed as a result of melting of depleted mantle components in mantle-plume source regions (Daoud et al., 2010; S ager & Holm, 2011; Waight & Baker, 2012)....
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..., 1990; Perttunen & Hanski, 2003); Fe^Ti basalts and low-Ti basalts, Faroe Islands (S ager & Holm, 2011); Fe^Ti basalts and depleted basalts, Central East Greenland (Waight & Baker, 2012); LREE-depleted basalts, Central Afar (Barrat et al., 2003; Daoud et al., 2010)....
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Journal Article•DOI•

Trace element and isotopic geochemistry of lavas from Haleakala Volcano, east Maui, Hawaii: Implications for the origin of Hawaiian basalts

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Chu-Yung Chen, Frederick A. Frey

10 Sep 1985-Journal of Geophysical Research

TL;DR: In this article, Chen et al. propose a model in which melts from a diaper interact with incipient melts of its wall rocks, presumed to be oceanic lithosphere, and conclude that the lower lithosphere and much of the asthenosphere beneath Hawaiian volcanoes are involved in creating these volcanoes.

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Abstract: Haleakala volcano on East Maui, Hawaii, consists of a tholeiitic basalt shield which grades into a younger alkalic series that was followed by a posterosional alkalic series. Tholeiitic, transitional, and alkalic basalts range widely in Sr and Nd isotopic ratios (from mid-ocean ridge basalt to bulk earth ratios) and incompatible element (P, K, Rb, Sr, Zr, Nb, Ba, REE, Hf, Ta, and Th) abundances, but isotopic ratios and incompatible element abundance ratios (e.g., Ba/La, Nb/La, La/Ce, La/Sm) vary systematically with age. The youngest series (posterosional alkalic lavas) has the highest Rb/Sr, Ba/La, Nb/La, La/Ce, and 143Nd/144Nd ratios and the lowest 87sr/86sr ratios, whereas the oldest series (dominantly tholeiitic basalts) has the lowest Rb/Sr, Ba/La, Nb/La, La/Ce, and 143Nd/144Nd ratios and the highest 87sr/86sr ratios. The most striking features of the trace element and isotopic data are the inverse correlations between isotopic ratios and parent/daughter abundance ratios in the Sr and Nd systems. Although some of the geochemical variations can be explained by shallow level fractional crystallization (e.g., alkali basalt to mugearite [Chen et al., 1984, and manuscript in preparation, 1985]), the temporal geochemical trends require a major role for mixing. We propose a model in which melts from a diaper interact with incipient melts of its wall rocks, presumed to be oceanic lithosphere. Because of motion between the lithosphere and mantle hot spot the relative contribution of melts from the diapir (mantle plume) material to the lavas decreases with time; consequently, with decreasing age the basalts become more enriched in incompatible trace elements and acquire Sr and Nd isotopic ratios which overlap with mid-ocean ridge basalts. This model quantitatively explains the isotopic ratios and incompatible trace element abundances in representative samples from the three Haleakala volcanic series. On the basis of the degrees of melting inferred for the mixing components we conclude that the lower lithosphere and much of the asthenosphere beneath Hawaiian volcanoes are involved in creating these volcanoes.

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306 citations

East maui, hawaii' implications for the origin of hawaiian basalts

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Chu-Yung Chen, Frederick A. Frey

01 Jan 1985

TL;DR: Chen et al. as discussed by the authors presented a model in which melts from a diapir interpreted in terms of mantle processes were used to define the mantle source and fractional crystallization (e.g. Stu- interact with incipient melts of its wall rocks).

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Abstract: Haleakala volcano on East Maui, volcanism which has been attributed to plate Hawaii, consists of a tholeiitic basalt shield migration over a mantle hot spot (e.g., Wilson, which grades into a younger alkalic series that 1963; Morgan, 1971, 1972). Recent studies of was followed by a posterosional alkalic series. Hawaiian basalts show that Hawaiian volcanoes Tholeiitic, transitional, and alkalic basalts have distinct geochemical characteristics which range widely in Sr and Nd isotopic ratios (from require distinct mantle source compositions mid-ocean ridge basalt to bulk earth ratios) and (e.g., Leeman et al., 1977; Tatsumoto, 1978; incompatible element (P, K, Rb, St, Zr, Nb, Lanphere et al., 1980; Basaltic Volcanism Study Ba, REE, Hf, Ta, and Th) abundances, but iso- Project (BVSP), 1981; Stille et al., 1983). If topic ratios and incompatible element abundance the mineralogy and composition of the mantle ratios (e.g., Ba/La, Nb/La, La/Ce, La/Sm) vary sources for each Hawaiian volcano can be esti- systematically with age. The youngest series mated, constraints on the relative importance (posterosional alkalic lavas) has the highest of various mantle regions (e.g., lithosphere, Rb/Sr, Ba/La, Nb/La, La/Ce, and 143Nd/I44Nd asthenosphere, and lower mantle) to Hawaiian ratios and the lowest 87Sr/86Sr ratios, whereas volcanism may be obtained which will lead to an the oldest series (dominantly tholeiitic basalts) understanding of the mantle processes which has the lowest Rb/Sr, Ba/La, Nb/La, La/Ce, and create hot spot volcanism. 143Nd/144Nd ratios and the highest 87Sr/86Sr However, interpretation of geochemical dif- ratios. The most striking features of the trace ferences between Hawaiian volcanoes is only element and isotopic data are the inverse meaningful if the geochemical variations within correlations between isotopic ratios and individual volcanoes are well defined. Systema- parent/daughter abundance ratios in the Sr and tic studies of stratigraphically controlled Nd systems. Although some of the geochemical samples from mature Hawaiian volcanoes are variations can be explained by shallow level required to define the mantle source com- fractional crystallization (e.g., alkali basalt to positions involved in the generation of an mugearite (Chen et al., 1984, and manuscript in individual volcano, and such data are necessary preparation, 1985)), the temporal geochemical for several volcanoes before intervolcano trends require a major role for mixing. We pro- geochemical differences can be realistically pose a model in which melts from a diapir interpreted in terms of mantle processes. Stu- interact with incipient melts of its wall rocks, dies of stratigraphically controlled samples presumed to be oceanic lithosphere. Because of encompassing a major time fraction of the erup- motion between the lithosphere and mantle hot tion history of a mature Hawaiian volcano are spot the relative contribution of melts from the difficult because older lavas are deeply buried, diapir (mantle plume) material to the lavas and when exposed on seacliffs or in canyons, decreases with time; consequently, with they are commonly highly altered; however, decreasing age the basalts become more geochemical studies of stratigraphically enriched in incompatible trace elements and controlled samples are now being done on Mauna acquire Sr and Nd isotopic ratios which overlap Loa (Rhodes, 1983), Mauna Kea (West and Gar- with mid-ocean ridge basalts. This model quan- cia, 1982; Kwon and Wise, 1983; Frey et al., titatively explains the isotopic ratios and 1984), Kohala (Feigenson et al., 1983), East incompatible trace element abundances in repre- Molokai (Beeson, 1976; Clague and Beeson, 1980; sentative samples from the three Haleakala Clague et al., 1983) and Haleakala (Chen and volcanic series. On the basis of the degrees Frey, 1983; Chen et al., 1984, this paper; West of melting inferred for the mixing components and Leeman, 1984). The first-order evolu- we conclude that the lower lithosphere and tionary characteristics of Hawaiian volcanoes much of the asthenosphere beneath Hawaiian are known: the main shield is constructed of volcanoes are involved in creating these volca- tholeiitic basalt which is usually overlain by noes.

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302 citations

"A LREE-depleted component in the Af..." refers background in this paper

...Origin of depleted 611 components in basalt related to the Hawaiian hot spot: Evidence from isotopic and 612 incompatible element ratios....
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...Similar conclusions have been reached for the Hawaiian 418 (Frey et al., 2005) and Icelandic (Thirlwall, 1995; Kerr et al., 1995; Fitton et al., 1997; 419 Chauvel and Hémond, 2000; Thirlwall et al., 2004; Skovgaard et al., 2001; Kokfelt et al., 420 2006) plumes....
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...…al., 1997; 49 Chauvel and Hémond, 2000; Skovgaard et al., 2001; Fitton et al., 2003; Thirlwall et al., 2004; 50 Kokfelt et al., 2006); (2) Hawaii (Chen and Frey, 1985; Yang et al., 2003; Frey et al., 2005); 51 (3) the Galapagos (White et al., 1993; Hoernle et al., 2000; Blichert-Toft and White,…...
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...Trace element and isotope geochemistry of lavas from 543 Halaakala Volcano, East Maui: implications for the origin of Hawaiian basalts....
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...However, the occurrence of subordinate components characterized by a light rare 47 earth element (LREE) depletion has been suggested from the study of basalts from major 48 mantle plumes in: (1) Iceland (Zindler et al., 1979; Hémond et al., 1993; Taylor et al., 1997; 49 Chauvel and Hémond, 2000; Skovgaard et al., 2001; Fitton et al., 2003; Thirlwall et al., 2004; 50 Kokfelt et al., 2006); (2) Hawaii (Chen and Frey, 1985; Yang et al., 2003; Frey et al., 2005); 51 (3) the Galapagos (White et al., 1993; Hoernle et al., 2000; Blichert-Toft and White, 2001; 52 Saal et al., 2007); and (4) the Kerguelen Archipelago (Doucet et al., 2002)....
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Journal Article•DOI•

Isotopic and trace element signatures of Ethiopian flood basalts: evidence for plume–lithosphere interactions

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Raphaël Pik¹, Catherine Deniel¹, Christian Coulon¹, Gezahegn Yirgu², Bernard Marty¹ - Show less +1 more•Institutions (2)

Centre national de la recherche scientifique¹, Addis Ababa University²

01 Aug 1999-Geochimica et Cosmochimica Acta

TL;DR: In this article, trace element and radiogenic isotope data have been measured on Oligocene flood basalts from the northwestern Ethiopian plateau to investigate and identify the nature of mantle and crustal sources involved in the genesis of this huge volume of prerift basalts to constrain the interaction between the Afar mantle plume and the lithosphere at the onset of continental break-up.

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280 citations

"A LREE-depleted component in the Af..." refers background or methods in this paper

...Their distinct locations, emplacement ages (Oligocene for E88, ca. 1 Ma for 363 Hayyabley and less than 0.2 Ma for Manda Hararo) and underlying crustal/lithospheric 364 thickness (normal for E88, thinned for the two other occurrences) are hardly consistent with a 365 similar petrogenetic history....
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...…Afar basalts (Treuil and Joron, 1975; Joron et al., 295 1980; Deniel et al., 1994) are dominantly enriched, previous studies (Barrat et al., 1993, 2003; 296 Pik et al., 1999; Meshesha and Shinjo, 2007) have demonstrated that minor depleted 297 components were also involved in their petrogenesis....
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...Compositions of LREE-depleted basalts from Hayyabley (average of the samples 846 analysed by ICP-MS), Manda Hararo (average data from Barrat et al., 2003), Ethiopian 847 Plateau (sample E88, Pik et al., 1999), and of a N-MORB from Tadjoura Gulf (sample A3D3, 848 Joron et al., 1980; Barrat et al., 1993)....
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...Compositions of LREE-depleted basalts from Hayyabley (average of the samples 1 analysed by ICP-MS), Manda Hararo (average data from Barrat et al., 2003), Ethiopian 2 Plateau (sample E88, Pik et al., 1999), and of a N-MORB from Tadjoura Gulf (sample A3D3, 3 Joron et al., 1980; Barrat et al., 1993)....
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...…et al., 1992), (3) Erta „Ale volcanics 821 (Barrat et al., 1998), (4) LREE-depleted basalts from Manda Hararo (MH, Barrat et al., 2003), 822 and (5) some Ethiopian samples (E88: depleted Oligocene basalt; HT2: average composition 823 of high-Ti basalts, Pik et al., 1999) are shown for comparison....
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Journal Article•DOI•

Nd and Sr isotope ratios and rare earth element abundances in Reykjanes Peninsula basalts evidence for mantle heterogeneity beneath Iceland

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Alan Zindler¹, Stanley R. Hart¹, Frederick A. Frey¹, Sveinn P. Jakobsson²•Institutions (2)

Massachusetts Institute of Technology¹, American Museum of Natural History²

01 Nov 1979-Earth and Planetary Science Letters

TL;DR: In this paper, the authors conclude that the mantle beneath the Reykjanes Peninsula is heterogeneous with respect to relative rare earth element (REE) abundances and 143Nd/144Nd ratios.

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275 citations

"A LREE-depleted component in the Af..." refers background in this paper

...…by a light rare 47 earth element (LREE) depletion has been suggested from the study of basalts from major 48 mantle plumes in: (1) Iceland (Zindler et al., 1979; Hémond et al., 1993; Taylor et al., 1997; 49 Chauvel and Hémond, 2000; Skovgaard et al., 2001; Fitton et al., 2003; Thirlwall…...
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Journal Article•DOI•

Does depleted mantle form an intrinsic part of the Iceland plume

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J. Godfrey Fitton¹, Andrew D. Saunders², Pamela D. Kempton³, B S Hardarson⁴, B S Hardarson¹ - Show less +1 more•Institutions (4)

University of Edinburgh¹, University of Leicester², University of Nottingham³, University of Iceland⁴

01 Mar 2003

TL;DR: In this paper, the authors examine the case presented by Hanan et al. [2000] and conclude that their arguments are flawed and show that the data plot in their NMORB field on an eHf versus eNd diagram.

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Abstract: [1] Icelandic basalt ranges in composition from voluminous tholeiite, erupted in the rift zones, to small-volume, mildly alkaline basalt erupted off-axis. In addition, small-volume flows of primitive basalt, highly depleted in incompatible elements, are sometimes found in the actively spreading rift axes. Relative incompatible-element depletion or enrichment in Icelandic basalt is correlated with variation in radiogenic isotope ratios, implying that the mantle beneath Iceland is heterogeneous and that the relative contribution of the various mantle components relates to eruption environment (on- or off-axis) and hence to degree of melting. Thus small-degree off-axis melting preferentially samples an enriched and more fusible mantle component, whereas more extensive melting beneath the rift axes produces magma that more closely represents the bulk Iceland plume mantle composition. The small-volume flows of depleted basalt represent melts that have preferentially sampled a depleted and more refractory mantle component. A debate has arisen over the nature of the depleted component in the Iceland plume. Some authors [e.g., Hanan and Schilling, 1997] argue that the depleted component is ambient upper mantle, the source of normal mid-ocean ridge basalt (NMORB) in this region. Others [e.g., Thirlwall, 1995; Kerr et al., 1995; Fitton et al., 1997], however, have used various lines of evidence to suggest that the plume contains an intrinsic depleted component that is distinct from the NMORB source. Hanan et al. [2000] attempt to refute the existence of a depleted Iceland plume (DIP) component through a critical evaluation of the Nb-Zr-Y arguments advanced by Fitton et al. [1997] and the Hf-Nd-isotopic evidence presented by Kempton et al. [1998]. In this paper we examine the case presented by Hanan et al. [2000] and conclude that their arguments are flawed. Firstly, their trace-element data set excludes data from depleted Icelandic basalt samples and so it is not surprising that they find no evidence for a DIP component. Secondly, they present two new Hf-isotope analyses of a single depleted Icelandic basalt sample and show that the data plot in their NMORB field on an eHf versus eNd diagram. However, new data allow the resolution of distinct NMORB and depleted Icelandic basalt fields on this diagram. We conclude that trace-element and radiogenic isotope data from Iceland require the existence of a DIP component.

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264 citations