Mantle Dynamics: A Nd, Sr, Pb and O Isotopic Study of the Cameroon Line Volcanic Chain

Halliday, Alex N.; Dickin, A. P.; Fallick, Anthony E.; Fitton, J. Godfrey

doi:10.1093/petrology/29.1.181

Cited by 228 publications

(172 citation statements)

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“…This similarity, which may also be extended to the un contaminated lamprophyres and associated dykes from Tamazert in Morocco (Bernard Griffiths et al, 1991) and to basalts from the Canary Islands Hoer nle et al, 1991), supports the presence of a large scale continental domain of similar isotopic char acteristics in this region (Halliday et al, 1988).…”

Section: Nd and Sr Isotopic Datamentioning

confidence: 63%

“…In comparison with the isotopic composition of other basalts from northern Africa, the basanites and basalts from Atakor are similar to basalts from Jebel Marra in Sudan (Davidson and Wilson, 1989), Cameroon line (Halliday et al, 1988) and Hoggar (Allegre et al, 1981). This similarity, which may also be extended to the un contaminated lamprophyres and associated dykes from Tamazert in Morocco (Bernard Griffiths et al, 1991) and to basalts from the Canary Islands Hoer nle et al, 1991), supports the presence of a large scale continental domain of similar isotopic char acteristics in this region (Halliday et al, 1988).…”

Section: Nd and Sr Isotopic Datamentioning

confidence: 81%

“…This apparent contradiction is Paolo (1981). Primitive basalt composition is given by sample 2501; crustal con taminant has Sr=522 ppm, Ce=35.2 ppm (average granulite xenoliths from Hoggar; Leyreloup et al ., 1982), '43 Nd/'44Nd=0.511644 and Nd= 17.5 ppm (granulite C74F; Halliday et al ., 1988); F=fraction of liquid remain ing. The assimilation/ crystallization ratio is taken as 0 .4 with the bulk partition coeff icients DNd=0 .3, DCe=0.2,Dsr=3. common to most intraplate basalts; several hypotheses have been proposed to account for it.…”

Section: Mantle Source Of Basaltsmentioning

confidence: 99%

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Trace element and isotopic geochemistry of Cenozoic alkali basaltic lavas from Atakor (Central Sahara).

1993

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The Late Miocene to Recent Atakor volcanic complex of the Hoggar (southern Algeria, central Sahara) is composed of alkali basalts and related rocks (mainly phonolites and trachytes). Most lavas have a restricted spread of their Sr and Nd isotopic ratios. 87Sr/86Sr ratios range from 0.70318 to 0.70422 and '43Nd /'44Nd ratios range from 0.512776 to 0.512937. An exception is peralkaline trachyte which has the highest Sr (0.71271) and the lowest Nd (0.512593) isotope values and was formed by an assimilation-fractional crystallization process from basaltic magma. The basaltic rocks have trace ele ment and isotopic compositions similar to ocean island basalts. It is suggested that the parent basaltic magmas were derived from a mantle plume which was modified during its ascent by interaction involv ing infiltration of a subcontinental lithospheric peridotite by plume-derived melts.

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Section: Nd and Sr Isotopic Datamentioning

confidence: 63%

Section: Nd and Sr Isotopic Datamentioning

confidence: 81%

Section: Mantle Source Of Basaltsmentioning

confidence: 99%

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Trace element and isotopic geochemistry of Cenozoic alkali basaltic lavas from Atakor (Central Sahara).

1993

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“…Models involving crustal recycling into the mantle appear to explain a wide range of geochemical features of OIB [Hofmann, 1997]. An alternative set of models accounts for certain geochemical characteristics of OIB by intramantle enrichment processes alone [e.g., Halliday et al, 1988Halliday et al, , 1990Halliday et al, , 1995 but not to lithophile isotopic compositions).…”

Section: Models For Himu Genesismentioning

confidence: 99%

Noble gases in the Cameroon line and the He, Ne, and Ar isotopic compositions of high μ (HIMU) mantle

Barfod¹,

Ballentine²,

Halliday³

et al. 1999

J. Geophys. Res.

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reproduce the data with minimum He/ Ne fractionation at reasonable U/3He ratios.However, diffusive exchange of He and to a lesser extent Ne between aged MORB source and aged plume veins could explain the occurrence of low 3He/4He compositions in all HIMU centers and the apparent low time-integrated 3He/22Ne of the Cameroon line. IntroductionThe majority of terrestrial volcanism is the direct result of plate tectonic processes, with the notable exception of intraplate volcanism. Isotopic heterogeneity among ocean island basalts (OIB) results from the isolation of source reservoirs having distinct time-integrated chemical compositions. These requirements have led to the development of several models for generating these reservoirs including delamination of continental lithosphere, metasomatism of the upper mantle, and melting of a primitive mantle or "predominant" mantle. The most widely accepted model is recycling and storage of oceanic Treatment of noble gas systematics is conspicuously absent from recycling models, despite a considerable database for oceanic islands and MORB. As the oceanic crust is strongly degassed of primitive volatiles upon formation, by hydrothermal alteration near the surface, and by dehydration during subduction, it should possess a highly fractionated set of parent/daughter ratios (U + Th/He, U + Th/Ne, K/Ar). In a simple closed system, recycled oceanic crust should therefore rapidly acquire noble gas isotopic compositions that are highly radiogenic rather than retain primitive (MORB-like, R a = 8 _+ 1) compositions [Hart, 1984a;Farley, 1995]. In no case has any mantle sample produced isotopic compositions equivalent to the estimated mantle production ratios of He (R/R a • 0.01-0.02) and Ne (2•Ne/22Ne -0.4 to 32, see below). , 1995]. In this respect, it is essential to also identify the role of the lithosphere in controlling the observed noble gas isotopic compositions. Straddling both oceanic and continental lithosphere, the volcanic province of the Cameroon line is the ideal setting to evaluate the effects of migration through the lithosphere on the noble gas composition of HIMU magmas. We present results of the first combined HeNe-Ar isotopic study of a HIMU system using the Cameroon line as a study area. Geologic Setting and Sample SelectionThe Cameroon line is an intraplate, alkaline volcanic province extending 1600 km from the African continental interior into the Gulf of Guinea to the island of Annobon Analytical ProceduresBoth xenolith and lava samples were coarsely crushed and sieved to 300 to 850 /•m and then passed through a FrantzIsodynamic magnetic separator. The minerals were ultrasonically cleaned for 30 min in 3.0 N HC1 followed by 30 min in deionized H20 to remove basalt adhering to crystal surfaces. Finally, samples were hand picked in ethanol under a binocular microscope using oblique illumination. In the early stages of this study, noble gases were extracted from mineral phases using an off-line crushing device. The device utilized two 1-cm stainless steel ball be...

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“…The presence of such a large variety of alkaline rocks, conveniently divided into a sodic and a potassic series, is also known from several other islands with OIB signatures as well as on continental settings (e.g., Fitton & Upton 1987;Halliday et al 1988;Briot et al 1991;Foland et al 1993;Wilson et al 1995]; cf. details in the section on Geochemistry).…”

Section: Rocks Of the Remédios Formationmentioning

confidence: 99%

Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

Lopes

Ulbrich

2015

Braz. J. Geol.

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ABSTRACT:The Fernando de Noronha Archipelago presents, on its main island, a centrally-located stratigraphic unit, the Remédios Formation (age around 8 -12 Ma) constituted by basal pyroclastic rocks intruded by dikes, plugs and domes of varied igneous rocks, capped by flows and pyroclastics of mafic to ultramafic rocks of the Quixaba Formation (age around 1 -3 Ma), which is limited from the underlying unit by an extensive irregular erosion surface. A predominant sodic Remédios series (basanites, tephrites, tephriphonolites, essexite, phonolites) can be separated from a moderately potassic Remédios sequence (alkali basalts, trachyandesites, trachytes), both alkaline series showing mostly continuous geochemical trends in variation diagrams for major as well as trace elements, indicating evolution by crystal fractionation (mainly, separation of mafic minerals, including apatites and titanites). There are textural and mineralogical evidences pointing to hybrid origin of some intermediate rocks (e.g., resorbed pyroxene phenocrysts in basaltic trachyandesites, and in some lamprophyres). The primitive Quixaba rocks are mostly melanephelinites and basanites, primitive undersaturated sodic types. Geology (erosion surface), stratigraphy (two distinct units separated by a large time interval), petrography (varied Remédios Formation, more uniform Quixaba unit) and geochemistry indicate that the islands represent the activity of a protracted volcanic episode, fueled by intermittent melting of an enriched mantle, not related to asthenospheric plume activity. KEYWORDS:OIB; South Atlantic Ocean; Mafic to ultramafic volcanic-subvolcanic rocks; Sodic and potassic series. RESUMO: O Arquipélago de Fernando de Noronha mostra na sua ilha principal, na parte central, a Formação Remédios (idade em torno de 8 -12 Ma) constituída por rochas piroclásticas basais invadidas por diques, plugs e domos de variadas rochas ígneas, capeadas por derrames e piroclásticas das rochas máficas a ultramáficas da Formação Quixaba (idade de 1 a 3 Ma), separada da unidade inferior por uma superfície de erosão extensa e irregular. Uma série predominante sódica de Remédios (basanitos, tefritos, tefrifonolitos, essexito, fonolitos) pode ser diferenciada da série moderadamente potássica (álcali basaltos, traquiandesitos, traquitos), pertencente à mesma unidade. Ambas as séries mostram tendências geoquímicas geralmente contínuas em diagramas de variação de elementos maiores e traços, indicando origem por cristalização fracionada (principalmente, separação de minerais máficos, incluindo apatitas e titanitas). São encontradas evidências mineralógicas e texturais apontando

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Mantle Dynamics: A Nd, Sr, Pb and O Isotopic Study of the Cameroon Line Volcanic Chain

Cited by 228 publications

References 0 publications

Trace element and isotopic geochemistry of Cenozoic alkali basaltic lavas from Atakor (Central Sahara).

Trace element and isotopic geochemistry of Cenozoic alkali basaltic lavas from Atakor (Central Sahara).

Noble gases in the Cameroon line and the He, Ne, and Ar isotopic compositions of high μ (HIMU) mantle

Geochemistry of the alkaline volcanicsubvolcanic rocks of the Fernando de Noronha Archipelago, southern Atlantic Ocean

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