 | | Report (chapter) | | peralkaline silicic rocks and caldera volcanoes of Kenya R. Macdonald Geological Society, London, Special...of Kenya R. Macdonald S U M M A R Y: The late-Quaternary trachytic caldera volcanoes of the Kenya rift...northern set of centres (the Barrier, Emuruangogolak, Silali and Paka) basalt is a major component and mugearites...plutonic processes while the volcano is at the magmatic stage. In Kenya the late-Quaternary caldera volcanoes...on the seven centres of the inner trough of the Kenya rift (Fig. 1) but, where relevant, information from |  | | Report (issue) | | activity and geology of the northern sector of the Kenya Rift Valley British Geological Survey Research...activity and geology of the northern sector of the Kenya Rift Valley P N Dunkley, M Smith, D J Allen and...activity and geology of the northern sector of the Kenya Rift Valley P N Dunkley, M Smith, D J Allen and...springs along its western shores. Geographic index Kenya Suf>jecr index Geothermal exploration, geology...activity and geology of the northern sector of the Kenya Rift Valley. British Geological Survey Research |  | | Journal (article/letter/editorial) | | situated, 12 km apart, on the western flank of the Kenya Rift Valley (McCall, 1964; Jennings, 1971; Jones...lavas; Londiani of trachyte lavas with a few late alkali rhyolite flows. Early flows on both volcanoes are...porphyritic. They overlie the Saos Mugearite, a series of alkali basalts, hawaiites, and mugearites. Petrography...Kilombe are indistinguishablein thin section. Feldspar phenocrysts, which are larger and more abundant...to 35% of the later flows. The groundmass alkali feldspar has a pronounced fluidal texture and often |  | | Journal (article/letter/editorial) | | a c t Young (b 1 Ma) volcanic complexes in the Kenya Rift Valley are used to outline recent progress...magma mixing, remobilisation of crystal mushes and feldspar resorption, exsolution of carbonate phases and...dome complexes, e.g. the Olkaria complex in the Kenya (Gregory) rift with an estimated volume of ~13 km...Ma) silicic complexes in the inner trough of the Kenya Rift Valley to outline recent progress in our understanding...group, comprising the Barrier, Emuruangogolak, Silali and Paka, E-mail address: r.macdonald@lancaster |  | Black, Stuart, Macdonald, Ray, Barreiro, Barbara A., Dunkley, Peter N., Smith, Martin (1998) Open system alkaline magmatism in northern Kenya: evidence from U-series disequilibria and radiogenic isotopes. Contributions to Mineralogy and Petrology, 131 (4) 364-378 doi:10.1007/s004100050398 | Journal (article/letter/editorial) | | Smith Open system alkaline magmatism in northern Kenya: evidence from U-series disequilibria and radiogenic...(<10 ka) and trachytes from the volcano Emuruangogolak in the Kenya Rift Valley. The basalts are mildly...conduits closely spaced around the summit of the volcano. Introduction The nature and eciency of dierentiation...Azores, that the time from formation of a parental alkali basalt by partial melting of mantle to generation...evolution of the basanite-phonolite Laacher See volcano in Germany. Dierentiation of parental basanite |  | | Report (chapter) | | Special Publications Outline of the petrology of the Kenya rift alkaline province B.H. Baker Geological Society...October 28, 2014 Outline of the petrology of the Kenya rift alkaline province B. H. Baker S U M M A R Y...melilitites and melanephelinites to transitional alkali basalts and their differentiates. Individual volcanoes...principal magmatic suites: (i) nephelinitic; (ii) alkali basaltic; (iii) transitional basaltic. However...eastern branch of the E African rift system in Kenya and northern Tanzania contains nearly the whole |  | REN, M, OMENDA, P, ANTHONY, E, WHITE, J, MACDONALD, R, BAILEY, D (2006) Application of the QUILF thermobarometer to the peralkaline trachytes and pantellerites of the Eburru volcanic complex, East African Rift, Kenya. Lithos, 91 (1) 109-124 doi:10.1016/j.lithos.2006.03.011 | Journal (article/letter/editorial) | | the Eburru volcanic complex, East African Rift, Kenya Minghua Ren a,⁎, Peter A. Omenda b , Elizabeth Y...785, KenGen, Moi South Lake Road, Naivasha 20117, Kenya c Department of Earth Sciences, Eastern Kentucky...Quaternary Eburru volcanic complex in the south-central Kenya Rift consists of pantelleritic trachytes and pantellerites...2006 Elsevier B.V. All rights reserved. Keywords: Kenya; Eburru volcanic complex; Trachyte; Pantellerite;...Olkaria Volcanic Complex (GOVC) in the south-central Kenya rift, where Pb isotopes and U-series disequilibria |  | | Report (chapter) | | Quaternary volcanoes Longonot and Suswa, south Kenya Rift STUART C. S C O T T 1 and IAN P. SKILLING...volcanoes Longonot and Suswa, located in the south Kenya Rift, each have a caldera formed by incremental...fissures and the caldera collapse centre at each volcano are parallel to rift faults, suggesting that rift...complexes in the central trough of the Gregory Rift, Kenya (Figs t & 2). Syn- and post-catdera pyroclastics...r61e of regional tectonics as a major control on volcano-structural events (Skilling 1993; C a m b r a y |  | Macdonald, R., Bagiński, B., Belkin, H.E., White, J.C., Noble, D.C. (2019) The Gold Flat Tuff, Nevada: Insights into the evolution of peralkaline silicic magmas. Lithos, 328. 1-13 doi:10.1016/j.lithos.2019.01.017 | Journal (article/letter/editorial) | | cognate xenoliths point to the presence of alkali feldspar SC accumulation zones. The pantellerite contains...complexly twinned euhedral phenocrysts of alkali AC feldspar up to 3 cm long. The deposit also contains...also studied in detail a cluster of intergrown feldspar crystals (sample MA FC) which may represent...10 s on each of two background positions. For feldspar, a beam spot diameter of 5 μm was used, to reduce...our experience, for example, contamination by feldspar and FeTi-oxide microlites can cause some scatter |  | Macdonald, Ray, Sumita, Mari, Schmincke, Hans-Ulrich, Bagiński, Bogusław, White, John C., Ilnicki, Sławomir S. (2015) Peralkaline felsic magmatism at the Nemrut volcano, Turkey: impact of volcanism on the evolution of Lake Van (Anatolia) IV. Contributions to Mineralogy and Petrology, 169 (4) doi:10.1007/s00410-015-1127-6 | Journal (article/letter/editorial) | | PAPER Peralkaline felsic magmatism at the Nemrut volcano, Turkey: impact of volcanism on the evolution of...open access at Springerlink.com Abstract Nemrut volcano, adjacent to Lake Van (Turkey), is one of the most...intermediate-rhyolitic magmas. Keywords Nemrut volcano · Peralkaline magmatism · Magma mixing · Open-system...peralkaline eruptive rocks at the Nemrut caldera volcano, Turkey. Nemrut is the most active centre in Turkey...both Nemrut and the adjacent subalkaline Süphan volcano. We have selected a suite of tephra samples covering |  | | Journal (article/letter/editorial) | | elsevier.com/locate/lithos The volcano–pluton interface; The Longonot (Kenya) and Kûngnât (Greenland) peralkaline...Available online 18 March 2014 Keywords: Longonot volcano Kûngnât syenite complex Evolution of complementary...magma reservoir(s). The trachytic caldera volcano Longonot (Kenya Rift Valley) and the Kûngnât syenite complex...Kelleher and Cameron, 1990) and the Olkaria complex, Kenya (Macdonald et al., 2008; Marshall et al., 2009)...which can be considered to be a complementary volcano–pluton pair. Although the histories of the two |  | | Journal (article/letter/editorial) | | interactions in volcanic rocks from the northern Kenya rift: geochemical evidence Kurkura Kabeto a,b,)...2 ) 54 wt.%. lavas from Samburu Hills, northern Kenya rift, exhibit significant variations in major and...The evolved lavas are divisible into evolved high-alkali ŽNa 2 O q K 2 O ) 9 wt.%. early Miocene latites...Miocene and Pliocene trachytes; less evolved low-alkali ŽNa 2 O q K 2 O - 9 wt.%. middle Miocene mugearite...Pliocene benmoreite and trachyte suites. The high-alkali trachyphonolites and trachytes are enriched in |  | Macdonald, R., Bagiński, B., Leat, P.T., White, J.C., Dzierżanowski, P. (2011) Mineral stability in peralkaline silicic rocks: Information from trachytes of the Menengai volcano, Kenya. Lithos, 125 (1) 553-568 doi:10.1016/j.lithos.2011.03.011 | Journal (article/letter/editorial) | | Information from trachytes of the Menengai volcano, Kenya R. Macdonald a,b,⁎, B. Bagiński a, P.T. Leat...Available online 17 March 2011 Keywords: Menengai volcano Peralkaline trachytes and rhyolites Mineral stability...Menengai volcano, Kenya Rift Valley. The dominant phenocryst assemblage is alkali feldspar–hedenberg...existence, of a low-temperature zone in the alkali feldspar primary phase region, the equivalent of the...East African Rift System. Volcanic centres in the Kenya Rift Valley where pantelleritic trachytes have been |  | | Journal (article/letter/editorial) | | The rock itself consists of intermediate alkali feldspar with minor titanomagnetite and interstitial...late-magmatic veins consisting of homogeneous alkali feldspar (≈ Ab50Or50), clinopyroxene evolving from sodic...hypidiomorphic granular texture built up by alkali feldspar that is turbid due to submicroscopic exsolution...Titanomagnetite and ilmenite occur as inclusions in the feldspar and interstitially, whereas clinopyroxene is found...found only in an interstitial setting between feldspar grains. Titanomagnetite has exsolved ilmenite |  | | Journal (article/letter/editorial) | | and geochemical study on the Quaternary Gedemsa volcano in the Main Ethiopian Rift, Ayalew et al. (2001)...Plateau rhyolites in that they are free of alkali feldspar, aegyrine–augite, amphibole (richterite/eckermanite)...Plagioclase from WI is clearly distinguished from feldspar of other plateau rhyolites, which consists exclusively...WI plagioclase (open circles) compared to alkali feldspar from other plateau rhyolites (open diamonds)...other Oligocene Ethiopian Plateau rhyolites (alkali feldspar, aegyrine–augite, amphibole and ilmenite), |  | Macdonald, R., Belkin, H. E., Fitton, J. G., Rogers, N. W., Nejbert, K., Tindle, A. G., Marshall, A. S. (2008) The Roles of Fractional Crystallization, Magma Mixing, Crystal Mush Remobilization and Volatile–Melt Interactions in the Genesis of a Young Basalt–Peralkaline Rhyolite Suite, the Greater Olkaria Volcanic Complex, Kenya Rift Valley. Journal of Petrology, 49 (8) 1515-1547 doi:10.1093/petrology/egn036 | Journal (article/letter/editorial) | | Rhyolite Suite, the Greater OlkariaVolcanic Complex, Kenya Rift Valley R. MACDONALD1,2*, H. E. BELKIN3, J....mixes. All rock types may carry xenocrysts of alkali feldspar, and less commonly plagioclase, derived from...magma, with ubiquitous magma mixing. KEY WORDS: alkali basalt; geochemistry; magma mixing; trace element...rhyolite dome and lava field in the south^central Kenya rift valley that has been marked over the past 20...(Olkaria), and the neighbouring centres on the Kenya Dome (Eburru, Longonot and Suswa). From Heumann |  | | Journal (article/letter/editorial) | | Suite from the Southern Part of the Gregory Rift, Kenya Brian H. Baker 1, G o r d o n G. Goles 1, William...trachytes formed from evolved magmas largely by alkali feldspar fractionation. Estimates of phenocryst and...faulting. 1. Introduction The Gregory rift in Kenya is a part of the eastern branch of the Afro-Arabian...genetic associations have been distinguished in the Kenya rift alkaline province: a strongly alkaline association...transitional basalts, trachytes, and occasional Kenya-type phonolites, pantellerites, and comendites. |  | Upton, B. G. J., Macdonald, R., Odling, N., Rämö, O. T., Bagiński, B. (2013) Kûngnât, revisited. A review of five decades of research into an alkaline complex in South Greenland, with new trace-element and Nd isotopic data. Mineralogical Magazine, 77 (4) 523-550 doi:10.1180/minmag.2013.077.4.11 | Journal (article/letter/editorial) | | The syenites are orthocumulates (cumulus alkali feldspar, olivine, pyroxene, titanomagnetite and apatite;...apatite; intercumulus phases include alkali amphibole, biotite, quartz and calcite). In the well dissected...layered sequence displays graded modal layering, feldspar lamination and cryptic layering. Modal layering...aided by the large density differential between a) feldspar and b) Fe-rich silicates and oxides. Episodic...olivine gabbro through syenite intermediaries to alkali granite, ascribed to protracted assimilation/fractional |  | | Report (volume) | | continents. Field work was conducted in Chad, Ethiopia, Kenya, Malawi, Nigeria, Sudan, Tanzania and Uganda. However...Baker, B.FL Tectonics and volcanism of the southern Kenya Rift Valley and its influence on rift sedimentation...and sedimentation in the Kenya Rift from the equator northwards to Lake Turkana ... 59 Swain, C.J., Skinner...R.T. Volcano-tectonic control on sedimentation in the Koobi Fora sedimentary basin. Lake Turkana. 85 ...landtorm evolution in a rift valley basin, northern Kenya. Frostick, L.E. & Reid, I. Evolution and sedimentary |  | | Report (volume) | | 273 BAKER, B. H. Outline of the petroIogy of the Kenya rift alkaline province 293 MACDONALD,R. Quaternary...peralkaline silicic rocks and caldera volcanoes of Kenya 313 WOOLLEY, A. R. & JONES, G. C. The petrochemistry...feldspathoids, sodic pyroxenes, sodic amphiboles and other alkali-rich phases. These rocks are, therefore, deficient...silica-deficient but are rarely alkali-rich. True (nepheline-normative) alkali basalts grade into hypersthene-normative...transitional basalts are often closely associated with alkali basalts in the field, they are traditionally regarded |  | | | | where layering is defined by varying amounts of alkali feldspar and mafic minerals. Petrographically, the syenites...the outer and inner zones are dominated by alkali feldspar, nepheline (rarely haüyne) and variable quantities...of the dykes are doleritic; they are commonly feldspar-phyric, possessing vesicular centres and displaying...generally green-grey in colour, porphyritic, with feldspar and nepheline phenocrysts (in some cases displaying...typically have a fine medium grained texture and are feldspar-phyric. Rare phenocrysts of augite and unaltered |  | Ayalew, Dereje, Barbey, Pierre, Marty, Bernard, Reisberg, Laurie, Yirgu, Gezahegn, Pik, Raphael (2002) Source, genesis, and timing of giant ignimbrite deposits associated with Ethiopian continental flood basalts. Geochimica et Cosmochimica Acta, 66 (8) 1429-1448 doi:10.1016/s0016-7037(01)00834-1 | Journal (article/letter/editorial) | | trap basalts. Their phenocryst assemblage (alkali feldspar, quartz, aegyrine-augite, ilmenite ⫾ Ti-magnetite...wt.%, the liquidus temperatures for quartz, alkali-feldspar, and oxides range from 850 to 900°C. Considering...plateau ignimbrites. Phases Phenocrsysts Quartz Alkali feldspar Modal % Petrographic description ⬍ 8% Generally...sometimes occurring as inclusions in quartz and alkali-feldspar. Richterite/ferro-richterite, or eckermani...cracking) to partially crystalline (with quartz and K-feldspar intergrowth); devitrification and recrystallisation |  | | Journal (article/letter/editorial) | | of the Late Pliocene (5·7 to 4·2 Ma) Mt Sidley volcano, Marie Byrd Land, is examined using major and trace...series; (b) a more silica-saturated to -oversaturated alkali basalt to trachyte series. Rock compositions in...produce primary basanite and [5% melting to produce alkali basalt from the same mantle source. The differentiation...crystallization of a similar mineral assemblage from alkali basalt is modeled for compositions in the trachyte...(AFC). The first step involved contamination of alkali basalt by calc-alkaline granitoids within the middle |  | | Book | | fossil vertebrates in tuffs of the spectacular volcano that I had mapped in 19909. Thereafter, from 1959...sedimentological and palaeontological studies in the Kenya Rift Valley project. This, indeed, worked exceedingly... GREGORY RIFT VALLEY TANZANIA; OLORGESAILIE, KENYA I51 10. MARY D, LEAKEY. Olduvai Gorge 1911-1975:...SHACKLETON. Geological Map of the Olorgesailie Area, Kenya 171 12. 13. GLYNN LL. IsAAc. The Olorgesailie...Contents B. Tue Lake Barinco Basin, KENYA 14. GREGORY R. CHAPMAN Basin, Kenya & MAUREEN BROOK. Ghronostratigraphy |  | | Report (issue) | | (Bottom) Carbonatite lava at Oldoinyo Lengai volcano, northern Tanzania. Courtesy Alexander J. Teague...upper-mantle low-velocity anomaly beneath Ethiopia, Kenya, and Tanzania: Constraints on the origin of the...and natrocarbonatite lavas at Oldoinyo Lengai volcano, Tanzania. . . . . . . . . . . . . . . . . . ....fingerprints of mantle metasomatism beneath Nyos volcano (Cameroon volcanic line) . . . . . . . . . . ....40Ar-39Ar ages and petrogenesis of the Massif d’Ambre volcano, northern Madagascar . . . . . . . . . . . . . |
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