 | | Journal (article/letter/editorial) | | ā¢ l wne-garnet reaction in peridotites from Tanzania ARCH. M. R E I D & J. B. D A W S O N Reid,...from Tanzania. Lithos 5, 115-24. T h e composition of the p r i m a r y phases in garnet peridotite inclusions...inclusions in carbonatitic tufts from the Lashaine volcano in northern TanzarJa indicates formation at...illustrates the transition from the garnet peridotite to the spinel peridotite facies, presumably as a consequence...Neogene carbonate tuff cones ol die Monduli-Arusha area of Northern Tanzania contain a variety of ultramafic |  | | Report (chapter) | | contemporaneous volcanism in southern Kenya and northern Tanzania, the differences taking place abruptly at a latitude...contemporary volcanism in south Kenya and north Tanzania Table 8.1 summarizes the volcanic stratigraphy...northern Tanzania, mainly from c. 8 Ma, i.e. the age of the oldest known activity in northern Tanzania at Essimingor...case of Essimingor, the oldest of the northern Tanzania volcanoes, are similar to the peralkaline volcanoes...basaltic rocks show some resemblances to those in Tanzania (Appendix 2, Dawson 2008) in terms of the dominance |  | | Report (chapter) | | have resulted from later regional mapping by the Tanzania Geological Survey, together with radiometric dating...Extrusive basaltic centres. The term āperalkaline volcanoā is used here to indicate that the structure is...(unpublished) state that the oldest lavas from this volcano are melanephelinites and melilitites of the Bast...Bast Hills and Birera, to the west of the main volcano. These, as with early lavas from some other centres...Ngorongoro, Oldeani, Gelai, Ketumbeine, Tarosero, Monduli and the Shira and Mawenzi centres of Kilimanjaro) |  | | Journal (article/letter/editorial) | | Ultrabasic Xenoliths and Lava from the Lashaine Volcano, Northern Tanzania by J. B. DAWSON,1 D. G. POWELL...INTRODUCTION T H E Neogene volcanic province of northern Tanzania, which is part of the more extensive volcanic...of Winnipeg on September 6, 2015 ABSTRACT The Lashaine tuff-ring consists of carbonatite tuff and glassy...lherzolite and its phases resembles that of garnet peridotite nodules in kimberlite diatremes, and the A1,O...per cent TiO,. The other group of ultramafic xenoliths, characterized by cumulate and idiomorphic textures |  | | Journal (article/letter/editorial) | | Metasomatised and veined upper-mantle xenoliths from Pello Hill, Tanzania: evidence for anomalously-light mantle...Abstract. Peridotite xenoliths from the Pello tuff cone in the Rift Valley of northern Tanzania, bear witness...previously depleted peridotite. Chemical and mineralogical gradients are present in the peridotite wall rocks...rocks, and hydrous phases developed in the peridotite are generally lower in Ti and Fe, but higher in Mg and...metasomatism has reduced the density of affected peridotite by up to 4.5%, supporting earlier geophysical |  | | Journal (article/letter/editorial) | | L I T H S A N D H O S T - R O C K S , LASHAINE VOLCANO, TANZANIA R. HUTCHISON* Department of Earth Sciences...the ankaramitic and carbonatitic pyroclastics of Lashaine there is a suite of unaltered, ultrabasic fragments...includinggarnet-lherzolite, which typically occurs as xenoliths in kimberlite pipes. STSr/86Sr ratios and Rb and...host-rocks suggestingaccidenthLincorporationin the Lashaine magmas. Rb/Sr ratios are discussed and the conclusion...relatively high Rb content. 1. Introduction Lashaine volcano contains a wide variety of ultrabasic fragments |  | | Journal (article/letter/editorial) | | MAJOR ELEMENT GEOCHEMISTRY OF PERIDOTITE NODULES FROM SAMBURU DISTRICT, KENYA KEN-ICHIRO AOKI Instituteof...garnet-freeperidotitenodulesfromLashainevolcano,Tanzania,whichare clearlydifferent from chromianspinelperiodtitesin...Rift Valley in Kenya, eastern Uganda and northern Tanzania during the Miocene to Recent periods. Mafic rocks...nodules, of peridotite Ndonyuo Nairobi, chemical mantle the from Samburu the district, Kenya. A...Ridley to of represent fragments in the this region, included. GEOLOGY Ndonyuo situated area of |  | | Journal (article/letter/editorial) | | structures up to the thermobarometry data of mantle xenoliths V.A. Glebovitsky, L.P. Nikitina, V.Ya. Khiltova...equilibria in garnet and garnet ā spinel peridotite xenoliths from kimberlites (East Siberia, Northeastern...Geologic Processes and Objects 2000 44) for all xenoliths allowed us to avoid discrepancies in estimation...estimation of P ā T equilibrium conditions of deep xenoliths, correspond to the age of crust tectonic structures...Elsevier B.V. All rights reserved. Keywords: Mantle; Xenoliths; Thermobarometry; Upper mantle; Geotherms; Thermal |  | | Journal (article/letter/editorial) | | investigation of carbonates in peridotite xenoliths from northeastern Tanzania Received: 30 July 1999 / Accepted:...carbonates in peridotite xenoliths from the East African Rift in northeastern Tanzania occur as intergranular...microprobe analyses of mantle-derived carbonates (in xenoliths, xenocrysts, and megacrysts) reveals compositional...melts. Because most carbonate inclusions in peridotite xenoliths are calcitic, these authors are of the opinion...opinion that most, if not all, carbonates in mantle xenoliths are cumulates. Likewise, Ionov (1998) has argued |  | | Journal (article/letter/editorial) | | Mantle beneath the Tanzanian Craton: Evidence from Lashaine Pre-metasomatic Garnet-bearing Peridotites S....previously been identified in global suites of mantle xenoliths or diamond inclusions. They occur in certain harzburgite...xenolith suite from the Lashaine tuff cone, northern Tanzania. The Lashaine ultra-depleted garnets are...Metasomatism of refractory mantle is recorded in the Lashaine xenoliths by an almost continuous variation from ultra-depleted...depths (125 km) in the lithosphere than most Lashaine lherzolites and we suggest that long-term survival |  | Casagli, Alessio, Frezzotti, Maria Luce, Peccerillo, Angelo, Tiepolo, Massimo, De Astis, Gianfilippo (2017) (Garnet)-spinel peridotite xenoliths from Mega (Ethiopia): Evidence for rejuvenation and dynamic thinning of the lithosphere beneath the southern Main Ethiopian Rift. Chemical Geology, 455. 231-248 doi:10.1016/j.chemgeo.2016.11.001 | Journal (article/letter/editorial) | | (Garnet)-spinel peridotite xenoliths from Mega (Ethiopia): Evidence for rejuvenation...Massimo, De Astis, Gianļ¬lippo, (Garnet)-spinel peridotite xenoliths from Mega (Ethiopia): Evidence for rejuvenation...pertain. ACCEPTED MANUSCRIPT (Garnet)-spinel peridotite xenoliths from Mega (Ethiopia): Evidence for rejuvenation...(garnet)-spinel peridotite and pyroxenite xenoliths in Quaternary alkali-basalts at Mega (Sidamo region, Ethiopia)...adiabatic decompression path of about 40 km. Peridotite chemical compositions plot in an off-craton trend |  | | Journal (article/letter/editorial) | | 1992 ABSTRACT Peridotite xenoliths from the Olmani cinder cone, northern Tanzania, possess distinctive...to result from interaction of ultra-refractory peridotite residues with carbonatite melts. Chief among...unusually low AI20 3 clinopyroxene and the lack enstatite in refractory dunites (with olivines up to Fo94)...apatite in refractory harzburgite and wehrlite xenoliths, respectively. (3) LREE enrichment and strong...strong Ti depletion relative to Eu in all but one peridotite. Ca/AI ratios of the clinopyroxene-bearing dunites |  | | Journal (article/letter/editorial) | | within the ranges 89.-93% fayalite and 90-94% enstatite, respectively. Garnets when present are chrome...Sobolev 1977) and the Colorado-Wyoming state line region of the U.S.A. (McCallum et al. 1975), a slightly...LITHOS 13 (1980) mantle geotherm beneath that region at the time of carbonatite emplacement was closely...hand, the Lasha~ne carbonatite/ankaramite volcano in Tanzania (Dawson et al. 1970; Reid et al. 1975) contains...present day upper mantle geotherm beneath the Lashaine volcano closely similar to that beneath southern Africa |  | Teng, Fang-Zhen, Li, Wang-Ye, Ke, Shan, Marty, Bernard, Dauphas, Nicolas, Huang, Shichun, Wu, Fu-Yuan, Pourmand, Ali (2010) Magnesium isotopic composition of the Earth and chondrites. Geochimica et Cosmochimica Acta, 74 (14) 4150-4166 doi:10.1016/j.gca.2010.04.019 | Journal (article/letter/editorial) | | Cook-Austral chain); (3) 29 peridotite xenoliths from Australia, China, France, Tanzania and USA; and (4) 38...38 carbonaceous, ordinary and enstatite chondrites including 9 chondrite groups (CI, CM, CO, CV, L, LL...LL, H, EH and EL). Oceanic basalts and peridotite xenoliths have similar Mg isotopic compositions, with...and d26Mg = 0.25 Ā± 0.04 (2SD) for global peridotite xenoliths (n = 29). The identical Mg isotopic compositions...isotope fractionation during partial melting of peridotite mantle and magmatic differentiation of basaltic |  | | Journal (article/letter/editorial) | | 00 Metamorphic Petrology of Xenoliths from Kenya and Northern Tanzania and Implications for Geotherms...December 1991) ABSTRACT Pyroxenitic and peridotitic xenoliths from the Quaternary volcanic field of Marsabit...of transformation from the garnet peridotite to the spinel peridotite stability field. On the basis of...of one composite xenolith consisting of type I peridotite and grt pyroxenite point to a common P-7evolution...Cr/(Cr + Al) ratios of spl are similar to those of peridotite type II. Pyroxenes show minor chemical zoning |  | | Journal (article/letter/editorial) | | garnet are isotopically heavy. This indicates that peridotite whole-rock Ī“ 60 Ni may be controlled by variations...and cumulate mineralogy. Based on fertile peridotite xenoliths and Phanerozoic komatiite samples it is...1. Mantle xenoliths, peridotites and mineral separates 56 Most of the ultrama c xenoliths analysed in...the Neo- 57 gene volcanic province in Northern Tanzania, a part of the eastern Rift Valley 58 of East...61 these samples were collected from the Lashaine volcano, an area famous for 62 carbonatite lavas |  | | Journal (article/letter/editorial) | | from Pleistoceneārecent volcanism in northern Tanzania J.B. Dawson ā Grant Institute of Geosciences,...canoes in the Gregory Rift Valley of northern Tanzania (termed the Younger Extrusives) comprise one of...evidence for which is found in Tanzanian mantle xenoliths. An integrated model involves carbonated olivineānephelinite...asthenosphere by melting of carbonate-bearing peridotite. Small amounts of the melt migrate rapidly and...volcanism in northern Tanzania The Late TertiaryāRecent volcanic province of northern Tanzania is the most recently |  | | Journal (article/letter/editorial) | | 1994 Quaternary kimberlitic volcanism on the Tanzania Craton J.B. Dawson Department of Geology and Geophysics...youngest magmatic rocks on the Tanzania Craton. They consist of small xenoliths of phlogopite-calcite-garnet...degrees of melting of a carbonate-apatite-bearing peridotite source at depths in excess of 110 km. Introduction...Introduction Quaternary magmatism in northern Tanzania is mainly confined to the immediate vicinity of the...kimberlite intrusion in the past (Dawson 1970), the Tanzania Craton is virtually devoid of Quaternary igneous |  | Mana, S., Furman, T., Carr, M.J., Mollel, G.F., Mortlock, R.A., Feigenson, M.D., Turrin, B.D., Swisher, C.C. (2012) Geochronology and geochemistry of the Essimingor volcano: Melting of metasomatized lithospheric mantle beneath the North Tanzanian Divergence zone (East African Rift) Lithos, 155. 310-325 doi:10.1016/j.lithos.2012.09.009 | Journal (article/letter/editorial) | | Geochronology and geochemistry of the Essimingor volcano: Melting of metasomatized lithospheric mantle beneath...associated with the centrally located Essimingor volcano. Although major element oxides show narrow compositional...development and history of the EAR. In northern Tanzania, magmatic activity and rifting are superimposed...1994; Fig. 1). Baker et al. (1972) referred to this region as the North Tanzanian Divergence zone ā Corresponding...it extends from the Plio-Quaternary Kilimanjaro volcano in the east to the large Late Pleistocene caldera |  | | Journal (article/letter/editorial) | | reaction in the upper mantle: evidence from peridotite xenoliths in the Letseng-la-Terae kimberlites, Lesotho...Lock and J. B. Dawson ABSTRACT: Garnet-bearing xenoliths from Letseng-la-Terae display a range of textures...throughout this temperature range but coarse xenoliths are restricted to low temperature equilibration...spinel-bearing rocks may be derived from normal garnet peridotite by a complex sequence of reaction, followed by...mainly garnet-bearing and belong to the common peridotite group as defined by Cox et al. (1973). The textures |  | Zhang, Hongfu, Menzies, Martin A, Gurney, John J, Zhou, Xinhua (2001) Cratonic peridotites and silica-rich melts: diopside-enstatite relationships in polymict xenoliths, Kaapvaal, South Africa. Geochimica et Cosmochimica Acta, 65 (19) 3365-3377 doi:10.1016/s0016-7037(01)00675-5 | Journal (article/letter/editorial) | | silica-rich melts: Diopside-enstatite relationships in polymict xenoliths, Kaapvaal, South Africa HONGFU... We report on the replacement of diopside by enstatite in polymict peridotites from Kimberley, South...minerals. The involvement of metasomatic melts in peridotite transformation was first alluded to by Quick...diopside by enstatite in basalt-borne peridotite xenoliths from the Lashaine volcano, northern Tanzania (Dawson...isotopic data from a suite of polymict mantle xenoliths (JJG1414, BD2394, BD344) from the Kaapvaal craton |  | Jung, Seung Gi, Choi, Sung Hi, Ji, Kang Hyeun, Ryu, Jong-Sik, Lee, Der-Chuen (2019) Geochemistry of volcanic rocks from Oldoinyo Lengai, Tanzania: Implications for mantle source lithology. Lithos, 350. 105223 doi:10.1016/j.lithos.2019.105223 | Journal (article/letter/editorial) | | Geochemistry of volcanic rocks from Oldoinyo Lengai, Tanzania: Implications for mantle source lithology Seung...Geochemistry of volcanic rocks from Oldoinyo Lengai, Tanzania: Implications for mantle source lithology, LITHOS...Geochemistry of volcanic rocks from Oldoinyo Lengai, Tanzania: 2 Implications for mantle source lithology...carbonatite volcano within the East African Rift Valley in 23 northern Tanzania. The volcano is dominated...relative to the compositions of modeled 37 garnet peridotite-derived melts, suggesting that they were derived |  | | Journal (article/letter/editorial) | | S0016-7037(00)00566-4 Osmium isotopic compositions of mantle xenoliths: A global perspective THOMAS MEISEL,1,* RICHARD...systematics of spinel- and garnet-bearing mantle xenoliths from North and Central America, Europe, southern...southern Africa, Asia, and the Pacific region were determined to define more precisely the isotopic composition...was defined on the basis of 117 spinel-bearing xenoliths from this work and data from the literature, including...range of compositions defined by ordinary and enstatite chondrites, not carbonaceous chondrites. Spinel-bearing |  | | Journal (article/letter/editorial) | | beneath stable cratonic areas such as Kimberley and Tanzania show gradients similar to those for the low-temperature...the equilibration temperature of xenoliths from the amount of enstatite in solid solution in the diopside...for equilibration pressures and temperatures of xenoliths. This requirement is satisfactorily fulfilled...equilibration pressures and temperatures of ultramafic xenoliths involving olivine, orthopyroxene and garnet. Palaeogeotherms...relations obtained from eqs, 6-9 for ultramafic xenoliths PHN 1569 and PHN 1611 of Boyd and Finger (1975) |  | Nicholls, I.A., Ferguson, John, Jones, H., Marks, G.P., Mutter, J.C. (1981) Ultramafic blocks from the ocean floor southwest of Australia. Earth and Planetary Science Letters, 56. 362-374 doi:10.1016/0012-821x(81)90140-0 | Journal (article/letter/editorial) | | the southern coast of Australia. In the latter region, the rise is characterized by an unusually smooth...4]. While the major structural features of the region shown in Fig. 1 are well known, their origins are...are uncertain. The Diamantina Zone is a narrow region of basement ridges and thoughts of unusually high...Eocene magnetic anomalies 22 through 19 from the region south of the Great Australian Bight westward to...122Ā°E. They believe that the rise was part of a region of major Mesozoic crustal thinning and subsidence |
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