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| EnglandPetrology of the Volcanic Rocks ofSaintHelenaIsland, South AtlanticAbstract: Detailed field...of the two deeply eroded shield volcanoes ofSaintHelena haspermitted a reconstruction of their growth...texturalandchemical variations from basic to salic ends of the series. Major oxide contentsand a number...of known stratigraphic position.The intermediateand trachytic rocks are believed to be derived from a...processes of crystal fractionation. Volatile transferand migration of alkali-rich late-crystallizing fluids |
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| fromGough, St.Helena andTdstandaCunha lsIands;trachytes from cera:ral Victoria, Australia,and a leucitite...leucititeand phonclitic-tephrite series from Bufumbira,Uganda. In olivine crystals from basaltic lavas the...the Ca-and Mn-contents are lowand Fe shows the mostsignificant zoning from core to rim. in Fe-rich...Fe-rich oliviaes from trachytic differentiates Caand Mnfrequently show more significant variation than Fe...correlationwith Mg (and hence Mnand Ni). Whi~e someolivines showed both Ca-and Fe-enrichmemtowards |
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| 175-181. Primed in Great BritainVolcanism onGough Island: a revised stratigraphyJ. G. MAUND*, D. C....work onGough Island combined with K-Ar dating of the lavas requiresrevision of the ageand volcanic... Four main periods of volcanic activity on theisland arerecognized. These comprise the eruption of...Ma), voluminous trachyteextrusion (0.30-0.12 Ma)and finally to eruption of the Edinburgh Basalt (0.20-0...involving theeruption of pillow basaltsand hyaloclastites when theisland emerged from below sea level. This |
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| Contributions toMineralogyandPetrologyContrib. Mineral. Petrol. 66, 9 1 - 104 (1978)9 by Springer-Verlag...GroupDivision of igneous rocks into subalkalicand alkalic groups wasmade first by Iddings (I892)....Harker (1896, 1909). By his thesis, the subalkalicand alkalic groups represent two large branches of igneous...includes rocks ranging from basic to acidic compositionand represents a genetic series. The tectonic conditions...subalkalicand alkalic branches were regarded(by mistake) as being characteristic of the Pacificand Atlantic |
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| Earthand Planetary Science Letters, 110 (1992) 121- 131Elsevier Science Publishers B.V., Amsterdam...rocksfromSaintHelenaDavid W. G r a h a m a,b,* Susan E. Humphris a, William J. Jenkins aand Mark D....olivineand clinopyroxene phenocrysts in 7-15 m.y. old basaltic lavas from theisland of St.Helena. Magmatic...extraction techniques, including in vacuo crushing,and stepwise heating or fusion of the powders following...following crushing. Theinherited 3He/nile ratio at St.Helena is 4.3-5.9 R a. Helium isotope disequilibrium is |
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| phenocrysts fromTristandaCunhaandGough Island lavas: variation with fractional crystallizationand evidence...clinopyroxeneand plagioclase) present in lavas fromTristandaCunhaandGough Island. These islands...mantle plume, have enriched radiogenic isotope ratiosand are, therefore, prime candidates for an oxygen isotope...pyroxeneand feldspar in theGough lavas showthat the phenocrysts in the ma®cGough Island lavas are...isotope composition as MORB. Phenocrysts in all theGough lavas show a systematic increasein d18O value as |
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| 0022-3530/90 $3.00TristandaCunha, South Atlantic: GeochemistryandPetrogenesis of a Basanite-Phonolite...Lava Seriesby ANTON P. LE ROEX 1 , R. A. CLIFF 2AND B. J. I. ADAIR 11Department of Geology, University...University of Leeds, Leeds, UKABSTRACTTheisland ofTristandaCunha, located at 37°S, 12°W in the South Atlantic...islands, the others being Nightingaleand Inaccessible.TristandaCunha comprises acontinuous series of...from ankaramitic basanite throughphonotephriteand tephriphonolite to phonolite. Moderately porphyritic |
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| 2089^21202010doi:10.1093/petrology/egq050Shonaand Discovery Aseismic Ridge Systems,South Atlantic:...ANTON LE ROEX1*, CORNELIA CLASS2, JOHN O’CONNOR3ANDWILFRIED JOKAT41DEPARTMENT OF GEOLOGICAL SCIENCES...Ridge^Meteor Rise^AgulhasRidge^Cape Rise seamounts)and the Discovery Rise to the northhave been argued...to represent the surface expressions of the Shonaand Discovery mantle plumes, based on enriched samples...Mid-Atlantic Ridge, a single sample from Discovery Riseand tectonic reconstructions. Leg PS69 ANT XXIII/5 of |
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| Mineralogyand Magmatic Evolutionof the Basalticand Trachytic Lavas fromGough Island, South Atlantic...AtlanticDepartments of Geologyand Geochemistry, University of Cape Town, Rondebosch 7700,South Africa...ABSTRACTTheGough Island lavas range from picrite basalt through to sodalite-bearingaegirine-augitetrachyte...lavas on theisland, represented by theLower Basalt series, are approximately 10 m.y. oldand the youngest...basalticand trachytic lavas with respect to bothbulk rock majorand trace element geochemistryand mineral |
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| de LuxembourgWith 106 Figuresand 95 Tables=ein the textand on 8 FoldersGEBRUDER1970UNIV...character-ized, with scarce an exception, by vulcanism,and the yulcanological evolution, rocksuites, geomorphological...intimate acquaintance with all the Atlantic islands,and thereis every reason to believe this applies even...southern islands separate, forreasons given above,and no less to furnish a volume of reasonable magnitude...general, shownlittle interest,and indeed the American J.C. Brannerand the Belgian, A. RENARD, arethe |
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| Lineagesand Fractionation Trends inUndersaturated Volcanic Rocks from the EastOtago Volcanic Province...Province (New Zealand)andRelated Rocksby D. s. COOMBSand j . F. G. WILKINSONABSTRACTThe petrology...sodic lavasand shallow intrusives whose compositions range from alkali basalt, basanite,and nephelinite...nephelinite to trachyteand phonolite.A range of relatively potassic volcanic rocks is also developed in the... The degreeof undersaturationand ratios such as (FeO+Fe2O3):MgOand K,O:Na,O vary widely inrocks with |
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| m / l o c a t e / l i t h o sThe geochemistryand evolution of Palaeogene phonolites, central Namibia...collectively exhibit a narrow compositional rangeand represent asingle magma system of highly evolved...Na2O, Rb, Th, Zr, Zn, Pb,and REEandvery low abundances of MgO, P2O5, Srand Ba. No mafic rocks are associated...associated with the Aris phonolitesand theirultimate petrogenetic origin remains obscure. The more abundant...sanidine (andnepheline)and pyroxene. The behaviour of REE is decoupled from Zr, Nb,and Th in this |
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| Contr. Mineral.and Petrol. 26, 124~160 (1970)The Petrology of the Las Canadas Volcanoes, Tenerife...islands that makeup the Canary Archipelago. Theisland is composed of volcanics belonging to the basa...development of intermediateand salic volcanics has been in the centre of theisland wherethe Las Canadas...shield composed mainly of basaniteandankaramite flows, tuftsand agglomerates. The initial post-shield...activity built the Vilaflorvolcanic complex (Lowerand Upper Canadas Series) that originally covered much |
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| Contr. Mineral.and Petrol. 39, 309--326 (1973)9 by Springer-Verlag 1973A Basalt-Trachyte-Phonolite...Marquesas Islands, Pacific OceanArthur Clive Bishopand Alan Robert Woolleywith analyses byVictor Kingsley...Abstract. The paper describes a suite of volcanicand intrusive rocks from Ua Pu, one of theMarquesas...mugearites, trachytes,and phonolites. Their petrographic characters arebriefly describedand 24 new chemical...analyses presented. The rocks fall into a sodicand apotassic series, since some rocks are richer in |
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| Contributions toMineralogyandPetrologyContrib. Mineral. Petrol. 67, 11 - 15 (1978)9 by Springer-Verlag...Crystallization of Pyroxenesand Amphiboles in Some Alkaline Rocksand the Presence of a Pyroxene Compositional... AustraliaAbstract. Ca-and Na-rich pyroxene-amphibole compositionsand textures from a range of felsic...amphibole crystallizes,a gap is observed between Ca-and Na-rich pyroxenecompositions. This break in composition..."immiscibility gap" between Caand Na-rich pyroxenesand can be overlooked whenconsidering pyroxene compositions |
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| CarltonVictoria 3053, AustraliaDISTRIBUTORSUSAand CanadaBlackwell Scientific Publications IncPO Box...grantedby The Geological Society for librariesand otherusers registered with the Copyright Clearance...Typeset, printedand bound in Great Britain byWilliam Clowes Limited, Becclesand LondonLibrary of...metasomatism--perspectiveand prospect1MENZIES, M. Alkaline rocksand their inclusions: a window...experimental studies29LE Bhs, M. J. Nephelinitesand carbonatites53TWYMAN, J. D. & GITTINS, J. Alkalic |
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| Kaersutite-bearing plutonic xenoliths fromTristandaCunha, South Atlantic R. W. LE M A I T R E Department... titanaugite, plagioclase,and iron ore in variable amounts. Biotiteand olivine are also occasionally...occasionally present. New analysesand trace element data are given for two xenolithsand their coexisting kaersutite...kaersutite, titanaugite,and plagioclase. After discussing several possible origins with the aid of a principal...phases that crystallized from theTristan magma at depths between 5and 25 km. Evidence is also presented |
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| The Petrology of RodriguezIsland, Indian OceanAbstract: RodriguezIsland is offset from the center...phonoliticsegregation veinsand occasional pyroclastic deposits. Gabbroic xenolithsand xenocrysts, whichare...are widely distributedand locally abundant, areinterpreted as fragments of a layered intrusion(cryptic...chamber at an earlier period of the volcano'shistory,and brought to the surface during a rejuvenation phase...activity. This phase,which has produced the presentisland, seems to haveoccurred after marine planation |
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| corresponding to the Departmentsof the Museum,and an Historical series.Parts will appear at irregular...will contain about three orfour hundred pages,and will not necessarily becompleted within one calendar...Antarctic TerritoryBerthaIsland, Sheehan NunatakiScullin MonolithChemistryand discussionThe Scotia...ClarenceIslandSouth Orkney IslandsInaccessible Islands(a)CoronationIsland(b)SignyIsland(c)Powell...Powelland Michelsen Islands(d)FredriksenIsland(e)(/) LaurieIslandGraptoliteIsland.(g).Basaltic |
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| OVERSEAS GEOLOGYAND M I N E R A LRESOURCESVOLUME 7, N U M B E R 4INCLUDINGINDEX FOR VOLUME 7LONDON...T ERUTILE I L M E N I T E B E R Y L Z I R C O NAND O T H E R MINERALS•FERRO-ALLOYS•BUYERS A N D...of ocular.I K. & B. Laboratory EquipmentHandand Motor Driven Jaw CrushersPulverizers, Grinding Mills...Agitators, Feeders. E l e c t r a -magnetsFiltersand Dryers. Continuous Plants500 Lbs/hour capacity....S , R A R EEARTHS, B A S E M E TA L S , O R E SAND R E S I D U E S , E T C .ii ,-..1.-.-•,,..,. |
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| Mountainsand Messum Igneous Complex,Namibia. Part I: Geochemical Evidence ofEarly CretaceousTristan Plume...Plume Meltsandthe Role of Crustal Contamination in theParana´–Etendeka CFBA. EWART1∗, S. C. MILNER2†...MILNER2†, R. A. ARMSTRONG2‡AND A. R. DUNCAN21DEPT. OF EARTH SCIENCES, UNIVERSITY OF QUEENSLAND, ST. LUCIA...ACCEPTED JULY 30, 1997The Goboboseb Mountainsand Messum Complex represent a majorCretaceous (132...province. The eruptivescomprise the Awahab Formationand are represented by a lowersequence of mafic lavas |
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| PART OF JAPAN MAKOTO SAWAI Anjo High School, Aichiand MITSUO SHIMAZU Niigata University, Niigata In...distributed, numerous alkali basalt dikesand sheets occurand some of them were studied by Kuno (1960)...(1960). A trachyte dike also occur in the areaand it is most alkaline among the rocks of the area. The trachyte...rohedenbergite, fayalite, arfvedsonite, plagioclaseand alkali feldspar. Groundmass minerals are alkali feldspar...feldspar sodic ferrohedenbergite, aenimgatiteand titanomagnetite. The trachyte includes small xenoliths |
 | R. Halama, , Wenzel, T., Upton, B. G. J., Siebel, W., Markl, G. (2003) A geochemical and Sr-Nd-O isotopic study of the Proterozoic Eriksfjord Basalts, Gardar Province, South Greenland: Reconstruction of an OIB signature in crustally contaminated rift-related basalts.Mineralogical Magazine, 67 (5) 831-853doi:10.1180/0026461036750147 | Journal (article/letter/editorial) |
| October 2003, Vol. 67(5), pp. 831–853A geochemicaland Sr-Nd-O isotopic study of theProterozoic Eriksfjord...HALAMA1, T. WENZEL1, B. G. J. UPTON2, W. SIEBEL1AND G. MARKL1,*12Universität Tübingen, Institut...D-72074 Tübingen, GermanyDepartment of Geologyand Geophysics, The University of Edinburgh, West Mains...transitionalbetween tholeiiteand alkaline basalt with MgO contents<7 wt.%and they display LREE-enrichment...to a chondritic source. Most of the trace elementand REE characteristics are similar to those ofbasalts |
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| EARTHAND PLANETARY SCIENCE LETTERS 1 (1966} 361-368. NORTH-HOLLAND PUBL. COMP., AMSTERDAM OXYGEN ISOTOPE...ratios of coexisting silicate minerals in igneousand metamorphic rocks are approximately proportional...differences in their chemical indices. Apparently, solidand liquid silicates of equivalent chemistry do not fractionate...one another. Isotopic zoning within phenoerystsand whole-rock isotopic variations accompanying magmatic...differentiation are thus expected to be minimaland chiefly due to variations in chemical index. Isotopic |
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| Crustal ContaminationCHRIS HARRIS1∗, JULIAN S. MARSH2AND SIMON C. MILNER31DEPARTMENT OF GEOLOGICAL SCIENCES...sub-alkalinesuite, (2) an outer quartz syenite suite,and (3) an inner silicaundersaturated suite dominated...explained byfractional crystallization, but Sr-and O-isotope data indicate thatthese rocks contain...syenites trend towards the 0·1 GPa phonoliteminimumand appear to have evolved by closed system fractional...elementand Nd-and Sr-isotopecharacteristics that are similar to those of basanites fromTristanda Cunha |