Metasomatised and veined upper-mantle xenoliths from Pello Hill, Tanzania: evidence for anomalously-light mantle beneath the Tanzanian sector of the East African Rift Valley

Dawson, J. B.; Smith, J. V.

doi:10.1007/bf00371380

Cited by 138 publications

(55 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Amphibole and phlogopite have been recorded in xenoliths at Lashaine, Pello Hill and Deeti in northern Tanzania, where they occur on the craton (Dawson & Smith 1973, 1988Johnson et al 1997). Kimberlites from Nyanza province, on cratonic crust in western Kenya, contain garnet-free harzburgite and dunite, with amphibole and lesser amounts of phlogopite (Ito 1986).…”

Section: Nature Of Mantle Rocksmentioning

confidence: 99%

“…The Sr and Nd isotope systematics of lavas from the rift valley provide evidence that the compositional heterogeneity is at least partly related to one or more chemical fractionations (depletions) in the Proterozoic, and a series of metasomatic events, one of which undoubtedly occurred shortly before and during the Cenozoic activity, others of which may be the result of subduction, accretion and magmatic events related to Archaean, Proterozoic and Panafrican orogenies (Norry et al 1980;Cohen et al 1984;Davies & Macdonald 1987;RehkaÈ mper et al 1997;Dawson & Smith 1988;Rudnick et al 1993;Chesley et al 1999;Burton et al 2000;SpaÈ th et al 2000).…”

Section: Comparisons With Ocean Island Basaltsmentioning

confidence: 99%

See 1 more Smart Citation

Magmatism of the Kenya Rift Valley: a review

MacDonald

2002

Transactions of the Royal Society of Edinburgh: Earth Sciences

View full text Add to dashboard Cite

Tertiary±Recent magmatism in the Kenya Rift Valley was initiated c. 35 Ma, in the northern part of Kenya. Initiation of magmatism then migrated southwards, reaching northern Tanzania by 5±8 Ma. This progression was accompanied by a change in the nature of the lithosphere, from rocks of the Panafrican Mozambique mobile belt through reworked craton margin to rigid, Archaean craton. Magma volumes and the geochemistry of ma®c volcanic rocks indicate that magmatism has resulted from the interaction with the lithosphere of melts and/or¯uids from one or more mantle plumes. Whilst the plume(s) may have been characterised by an ocean island basalttype component, the chemical signature of this component has everywhere been heavily overprinted by heterogeneous lithospheric mantle. Primary ma®c melts have fractionated over a wide range of crustal pressures to generate suites resulting in trachytic (silica-saturated and -undersaturated) and phonolitic residua. Various Neogene trachytic and phonolitic¯ood sequences may alternatively have resulted from volatile-induced partial melting of underplated ma®c rocks. High-level partial melting has generated peralkaline rhyolites in the south±central rift. Kenyan magmatism may, at some future stage, show an increasing plume signature, perhaps associated ultimately with continental break-up. KEY WORDS: Plume±lithosphere interactionsThe Red Sea and the Gulf of Aden are two arms of a postulated triple junction centred on the Afar region (Fig. 1). Oceanic crust began to form under these arms c. 10 Ma. The third arm, the East African Rift System (EARS), extends southwards through Ethiopia, Kenya and Tanzania into Mozambique. Whilst lithospheric extension is occurring beneath the EARS, the rift has not developed to the stage of ocean crust formation. The EARS has come to be seen, therefore, as a prime location in which to investigate the early stages of continental break-up.This review focuses on the magmatism of the Kenya Rift section, used here to indicate that section of the EARS extending from northern Kenya to northern Tanzania. The primary aim is to demonstrate the complex polybaric evolutionary history of the magmatism, starting with the postulated plume-induced generation of primary magmas by variable degrees of partial melting of heterogeneous, metasomatised lithosphere, through to generation of salic magmas by assimilation±crystal fractionation processes over a range of crustal pressures and by partial melting of crustal protoliths, also over a range of pressures.

show abstract

Section: Nature Of Mantle Rocksmentioning

confidence: 99%

Section: Comparisons With Ocean Island Basaltsmentioning

confidence: 99%

Magmatism of the Kenya Rift Valley: a review

MacDonald

2002

Transactions of the Royal Society of Edinburgh: Earth Sciences

View full text Add to dashboard Cite

show abstract

“…The mineralogical and chemical enrichment in peridotite associated with metasomatic vein intrusion was studied in detail in outcrops of mantle rocks (Bodinier et al 2004;McPherson et al 1996;Woodland et al 1996;Zanetti et al 1996) and in mantle xenoliths (Dawson and Smith 1988;Irving 1980;Kempton 1987;Neumann et al 2002Neumann et al , 2004Nielson and Noller 1987;Wilshire et al 1980;WulffPedersen et al 1999). However, the mechanism of vein formation has received less attention and is the prime target of this experimental study.…”

Section: Introductionmentioning

confidence: 99%

Liquid line of descent of a basanitic liquid at 1.5 Gpa: constraints on the formation of metasomatic veins

Pilet

Ulmer

Villiger

2009

Contrib Mineral Petrol

View full text Add to dashboard Cite

“…Amphibole analyses from the Ataq xenoliths have been reported by Varne (1970), Varne and Graham (1971), Menzies and Murthy (1980), and Chazot et al (1994Chazot et al ( , 1996aChazot et al ( , 1996b. They show compositions of chromian pargasite -edenite with intermediate Na 2 O/K 2 O = 2.5, which are similar to those in ordinary metasomatic amphiboles from mantle rocks (e.g., Francis, 1976;Dawson and Smith, 1982;Arai, 1986;Wilkinson and Le Maitre, 1987;O'Reilly and Griffin, 1988;Dawson, et al, 1988;Witt and Seck, 1989). Here, we report the petrographic and chemical characteristics of an unusual amphibole, magnesiokatophorite, and discuss its importance in mantle metasomatism.…”

Section: Introductionmentioning

confidence: 70%

Cr-rich magnesiokatophorite as an indicator of mantle metasomatism by hydrous Na-rich carbonatite

Ali

Arai

2013

Journal of Mineralogical and Petrological Sciences

View full text Add to dashboard Cite

Na -and Cr -rich amphibole and clinopyroxene are commonly observed in hydrous mantle xenoliths hosted by Pliocene -Quaternary basalts from Yemen. The amphibole is Cr -rich magnesiokatophorite high in Na 2 O (3.66 -5.65 wt%) and Cr 2 O 3 (2.21 -3.09 wt%), relatively low in K 2 O (0.23 -0.66 wt %) and almost free of Cl and F. The clinopyroxene is characterized by high Cr 2 O 3 (up to 5.64 wt%) and Na 2 O (up to 2.97 wt%), indicating appreciable amounts of kosmochlor. Both minerals show high REE concentrations as well as HFSE depletion, suggesting an involvement of carbonatitic melt in their formation. The magnesiokatophorites and kosmochlor -bearing diopside possibly formed through metasomatism by hydrous Na -rich carbonatite melt. Magnesiokatophorite is an indicator of metasomatism by hydrous Na -rich carbonatite in the upper mantle.

show abstract

Metasomatised and veined upper-mantle xenoliths from Pello Hill, Tanzania: evidence for anomalously-light mantle beneath the Tanzanian sector of the East African Rift Valley

Cited by 138 publications

References 54 publications

Magmatism of the Kenya Rift Valley: a review

Magmatism of the Kenya Rift Valley: a review

Liquid line of descent of a basanitic liquid at 1.5 Gpa: constraints on the formation of metasomatic veins

Cr-rich magnesiokatophorite as an indicator of mantle metasomatism by hydrous Na-rich carbonatite

Contact Info

Product

Resources

About