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1
Potgieter, J. E. "Anorogenic alkaline ring-type complexes of the Damaraland Province, Namibia, and their economic potential." Thesis, Rhodes University, 1987. http://hdl.handle.net/10962/d1001567.
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Anorogenic alkaline ring-type complexes form within continental plate settings. Alkaline magmatism is derived from the upper mantle, in which mantle metasomatism plays an important part, as well as from partial melting of the lower crust. Radial and concentric fractures develop during the ascent of alkaline magma. Extrusion of basic and felsic magma takes place along these fractures with felsic volcanics building-up central volcanoes. As a result of emptying of the magma chamber, the superstructure of the volcano collapses and a caldera is formed. During the caldera stage syenitic and granitic material are intruded into ring fractures. Alkaline ring-type complexes may be classified as (i) alkaline qranite and syenite-type and (ii) carbonatite and undersaturated-type. These ring-type complexes occur as distinct igneous provinces. Some major provinces occur in Brazil, Corsica, Namibia, Nigeria, Norway, Saudi-Arabia and Sudan. In Namibia the Damaraland igneous province is of Mesozoic aqe and it contains 15 alkaline ring-type complexes . These complexes are situated along north-eastern trends which correspond to transform directions of the South Atlantic. During the opening of the South Atlantic (Gondwana breakup) Pan-African age lineaments were reactivated which allowed emplacement of anorogenic alkaline magmatism. A zonation of alkaline granite and syenitetype in the west and carbonatite and undersaturated-type ring-complexes in the east correlates with down- and upwarp axes parallel to the line of Gondwana fragmentation. Alkali- and H⁺-metasomatism is related to the alkaline and syenite-type whereas alkali metasomatism (fenitization) is associated with carbonatite and undersaturated-type ring-complexes. Sn, W and Ta mineralization is associated with alkaline granites of some of the alkaline granite and syenite-type ring-complexes. Fe, F, PO₄ , Nb, Th, REE, Sr, Zn and Pb mineralization is associated with carbonatite complexes. Potential exists for: (i) porphyry Cu-Mo and epithermal-type (Au, Ag, Pt-metals, base metals) mineralization in the alkaline granite and syenite-type ring-complexes and (ii) disseminated Cu, Au, Aq and Pt-metals in carbonatite and undersaturated-type ring-complexes
2
Smithies, Robert Hugh. "The geochemical evolution of three alkaline complexes in the Kuboos-Bremen igneous province, southern Namibia." Thesis, Rhodes University, 1992. http://hdl.handle.net/10962/d1005564.
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The Kuboos-Bremen Igneous Province comprises a linear zone of alkaline complexes that intrude Proterozoic and Pan-African rocks and trends in a northeast direction from the northwest of the Cape Province in South Africa into southern Namibia. Of the three most southerly complexes in Namibia. two comprise silicate rocks ranging from nepheline syenite to alkali-granite and are called the Grootpenseiland and Marinkas Kwela Complexes (GPC and MKC). The Marinkas Kwela Carbonatite Complex is the third and most northerly of the complexes. Isotopic age determinations on a number of rock types from both the silicate complexes yield ages around 520Ma and are consistent with published Pan-African ages for the Province. Each silicate complex shows a migrating locus of intrusion from Siundersaturated rocks in the southwest to Si-oversaturated rocks in the northeast. The complexes overlap in outcrop. The rocks are moderately to highly felsiC and none reflects primary magma compositions. The Si-undersaturated rocks from both complexes include side-wall cumulates formed from magmas that fractionated alkali-feldspar, clinopyroxene and amphibole. Foyaites also occur in the MKC and have a compositional range reflecting alkali-feldspar fractionation and, probably, some interaction with dolomite country rocks. Major and trace element data suggest that critically saturated alkali syenites occurring in both complexes evolved via protracted feldspar fractionation, and that critically saturated alkali-feldspar syenite occurring only in the GPC is a cumulate. The two rock types cannot be related genetically. Of the SI-oversaturated rocks in both complexes, those in the compositional range monzonite to granite were intruded before alkali-granites. Compositional diversity amongst the former reflects fractionation of feldspar and of mafic phases, but that process cannot genetically link the rocks to the alkali-granites. Isotopic compositions of Sr and Nd indicate that the silicate magmas were derived from an upper mantle source region characterised by low time-integrated Rb/Sr ratios and high time-Integrated Sm/Nd ratios, However, the evidence of Sr and 0 isotopic data is that the Si-oversaturated melts possibly interacted with a crustal component. presumably the Proterowlc rocks of the Namaqua Metamorphic Province. This interaction may explain the occurrence of apparently co-genetic rock series that evolved on opposite sides of the feldspar join in Petrogeny's Residua System. The Marinkas Kwela Carbonatite Complex was emplaced before the final intrusive phases of the MKC and exhibits unusually pronounced late-stage enrichment in manganese. The earliest intrusive rocks in the complex were nepheline syenites which were fenitised by later intrusions of sôvites. Although the commonly occurring magmatic sequence of sôvite-beforsite-ferrocarbonatite is observed at Marinkas Kwela, sôvites do not appear to have been parental to beforsites. Removal of apatite and early crystallisation of magnetite distinguish magnetite-rich beforsite from co-genetic apatite-rich beforsite. Two further magmatic sequences. the first from apatite-rich beforsite through ferrocarbonatite to Mn-rich ferrocarbonatite (high Fe/Mn) and the second from magnetite-rich beforsite to Mn-rich ferrocarbonatite (low Fe/Mn). reflect fractionation of dolomite and of dolomite+magnetite respectively.
3
Lum, Clinton Chew Lun. "Aspects of the petrogenesis of alkali basalts from the Lunar Crater volcanic field, Nevada." Connect to resource, 1986. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1230660431.
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4
Johnson, Geoffrey I. "The petrology, geochemistry and geochronology of the felsic alkaline suite of the eastern Yilgarn Block, Western Australia /." Title page, contents and abstract only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09phj67.pdf.
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Thesis (Ph. D.)--Dept. of Geology and Geophysics, University of Adelaide, 1992.Typescript (Photocopy). Includes copies of 4 papers by the author as appendix 4 (v. 1). Errata slip inserted. Includes bibliographical references (leaves 170-192 (v. 1)).
5
Wilt, Jan Carol. "Geochemical patterns of hydrothermal mineral deposits associated with calc-alkalic and alkali-calcic igneous rocks as evaluated with neural networks." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186500.
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Six alkalinity and oxidation classes of fresh igneous rocks were correlated with trace elements in rock chip samples from temporally and spatially associated ore deposits. Learning vector quantization and back-propagation artificial neural networks correctly classified 100 percent of whole rock oxides and 99 percent of mineralized samples; discriminant analysis correctly classified 96 and 83 percent, respectively. The high degree of correlation between chemistries of igneous rocks and related mineralization implies genetic links between magmatic processes or sources and the ore deposits studied. The petrochemical classification was evaluated by assigning 43 deposits to classes defined on eight variation diagrams, training neural networks to classify analyses of 569 igneous and 887 mineralized samples, and testing the networks on their ability to classify new data. Whole rock analyses were obtained from mining districts in which trace element geochemistry was also available. Half the data was eliminated using five alteration filter graphs. The K₂O and Fe₂O₃/FeO versus SiO₂ diagrams and iron mineralogy best defined alkalinity and oxidation classes. Neural networks trained with 90, 80, 70, or 50 percent of the samples correctly classified 81 to 100 percent of randomly withheld data. SiO₂/K₂O ratios of alkali-calcic igneous rocks are 14-20 and of calc-alkalic 20-30. Fe₂O₃/FeO ratios are >0.8 with abundant magnetite and sphene for oxidized, 0.5-1.2 with magnetite, sphene, and rare ilmenite for weakly oxidized, and <0.6 with ilmenite only in reduced subclasses. Lead-zinc-silver deposits as at Tombstone and Tintic are related to oxidized alkali-calcic igneous rocks. Polymetallic lead-zinc-copper-tin-silver deposits, such as Santa Eulalia and Tempiute, Nevada, are associated with weakly oxidized alkali-calcic rocks. Tin-silver deposits of Llallagua and Potosi are correlated with reduced alkali-calcic intrusives. Porphyry copper deposits as at Ray and Sierrita are connected with oxidized calc-alkalic plutons. Gold-rich porphyry copper deposits, such as Copper Canyon and Morenci are linked to weakly oxidized calc-alkalic plutons. Disseminated gold deposits, such as Chimney Creek, Nevada, are temporally and chemically correlated with reduced calc-alkalic igneous rocks, although physical connections between plutons and Carlin-type deposits remain unconfirmed. Magma series classification and neural networks have profound applications and implications to exploration, alteration and zoning studies, and metallogenesis.
6
Liu, Junsuo. "Pétrogénèse des roches alcalines mafiques d'âge méso-cénozoique dans les provinces de Hunan et Guangxi, Chine septentrionale = petrogenesis of the mesosoic-cenozoic mafic alkaline subvolcanic rocks in Hunan-Guangxi provinces, southern China /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1992. http://theses.uqac.ca.
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7
Dillet, Brigitte. "Petrography and mineralogy of the granitic rocks associated with questa caldera (new mexico, u. S. A. )." Clermont-Ferrand 2, 1987. http://www.theses.fr/1989CLF21051.
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L'etude petrographique des neuf plutons granitiques associes a la caldera de questa (nouveau mexique) a permis de mettre en evidence l'existence d'une lignee alcaline et d'une lignee calcoalcaline granodioritique a monzonitique l'existence de ces deux series peut etre reliee a l'evolution geodynamique regionale a l'epoque de leur mise en place. Les donnees geochimiques confirment les resultats de l'etude petrographique. Les relations ilmenite-magnetite-sphene et la composition de l'ilmenite, de la magnetite, de la biotite et de l'amphibole ont permis de mettre en evidence des conditions de cristallisation differentes dans les deux series. Les mineraux de la serie alcaline indiquent une cristallisation sous faibles fugacites d'oxygene, souvent fluctuantes, et a des temperatures relativement elevees. Des fugacites d'oxygene plus elevees et des temperatures generalement plus basses sont typiques de la serie calcoalcaline
8
BOISSON, DOMINIQUE. "Etude geologique du massif du nord d'haiti (hispaniola - grandes antilles)." Paris 6, 1987. http://www.theses.fr/1987PA066771.
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Le massif du nord est un edifice cretace et tertiaire polyphase appartenant a la bordure nord de l'orogene caraibe. Son etude stratigraphique et petrographique permet d'y distinguer : une logique de depot post-danienne caracterisee par : une sedimentation neogene essentiellement detritique : deux cycles de plate-forme carbonatee (l'un a l'eocene et l'autre au miocene inferieur) separes par une discordance fini-eocene et une lacune locale de sedimentation oligocene. Tous ces terrains sont supportes par l'ensemble volcano-sedimentaire de l'arc cretace recoupe par plusieurs generations d'intrusifs; le chimisme de cet ensemble indique clairement son appartenance a une lignee calco-alcaline d'arc insulaire. Le substratum de cet ensemble affleure tres peu et est constitue de roches basiques et ultrabasiques d'age inconnu. L'inventaire des differentes structures qui affectent les terrains du massif du nord combine aux contraintes stratigraphiques conduit a y retenir six episodes de deformation
9
Laporte, Didier. "Un exemple d'intrusion syntectonique : l'intrusion d'Ile-Rousse, Corse du nord-ouest : étude pétrographique, minéralogique et géochimique, analyse structurale." Saint-Etienne, 1987. http://www.theses.fr/1987STET4001.
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L'intrusion d'Ile Rousse est une association intime de granitoïdes aux caractéristiques plus ou moins fortement contrastées, juxtaposés en lames subméridiennes à fort pendage. On y distingue des granitoïdes calcoalcalins magnésio-potassiques et des granitoïdes n'appartenant pas à l'association magnésiopotassiques dont les mieux types sont les granodivrités de Corbara. Analyse statistique de la sous-fabrique des mégacristaux de Feldspath potassique accompagnée d'une modélisation mathématique
10
Dupont, Pierre-Luc. "Pétrologie et géochimie des ensembles magmatiques pharusien I et II, dans le rameau oriental de la chaîne pharusienne (Hoggar, Algérie) : Implications géodynamiques pour l'évolution d'une chaîne mobile au protérozoïque supérieur." Nancy 1, 1987. http://www.theses.fr/1987NAN10332.
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Au pharusien I, la série de timesselarsine révèle l'épanchement de basaltes, d'affinité transitionnelle a faiblement alcaline dont le site géodynamique serait celui d'un "rift" en domaine continental. Vient ensuite une série ultrabasique/basique dont le site le plus probable est celui d'arc insulaire ou de bassin marginal. Le troisième épisode est représenté par deux ensembles : un lié à un domaine de type arc insulaire, l'autre montrant une évolution vers une marge continentale active. Au pharusien II, la série d'anded est intrudée par des dolérites et des roches volcaniques en liaison avec un site de type arc insulaire. La série d'Irrellouchem est liée à un site d'arc insulaire ou de marge continentale active. Les données isotopiques du strontium obtenues sur ces deux séries impliquent une contribution mantellique importante. Le dernier épisode pharusien est représenté par les roches du batholite de Tin Tekadiouit
11
Dissler, Eric. "Evolution geodynamique cadomienne du nord-cotentin (massif armoricain)." Caen, 1987. http://www.theses.fr/1987CAEN2048.
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La structuration actuelle des terrains brioveriens resulte en grande partie de l'evolution tectono-metamorphique varisque. La chaine cadomienne accuse une vergence nord-ouest. L'identification geochimique des series volcaniques brioveriennes revele une affinite tholeitique generalisee. Une tendance calcoalcaline s'exprime en revanche au sein du batholite de la hague. L'enchainement des premieres etapes de l'evolution geodynamique cadomienne est ainsi etablie, le magmatisme du brioverien inferieur traduisant le fonctionnement d'un dispositif arcs insulaires-bassins marginaux de type marge ouest du pacifique, installe sur des lambeaux de croute pentevrienne
12
Mboungou-Kongo, Jean-Baptiste. "Les formations metamorphiques devono-dinantiennes et les roches plutoniques de la region sud-ouest de clermont-ferrand (massif central francais) : etudes petrographique, geochimique et structurale." Clermont-Ferrand 2, 1987. http://www.theses.fr/1987CLF21027.
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Le socle hercynien au sud-ouest de clermont-ferrand comporte une serie volcano-sedimentaire. Des corps plutoniques y sont intrusifs et la metamorphisent. Diorites et gabbros resultent d'une lignee de differenciation calco-alcaline, avec des facies de cumulats. Les etudes geochimiques soulignent le contraste entre le cortege gabbro-dioritique essentiellement mantellique, et les granites crustaux. L'analyse structurale de la serie volcano-sedimentaire montre deux phases de deformation
13
Costarella, René. "Le complexe annulaire alcalin de Combeynot ( Massifs cristallins externes, Alpes françaises), témoin d'un magmatisme en régime distensif. Pétrogéochimie et signification géodynamique." Phd thesis, Grenoble 1, 1987. http://tel.archives-ouvertes.fr/tel-00539879.
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Le massif de Combeynot, sur la bordure nord-orientale du massif du Haut-Dauphiné (massifs cristallins externes, Alpes Françaises) est constitué de deux unités fondamentales (1) un socle, déformé et métamorphisé, représenté par un ensemble migmatitique et un orthogneiss oeillé ; ce socle se rattache aux formations du noyau du massif du Haut-Dauphiné, (2) un complexe annulaire subvolcanique, intrusif dans le socle, composé de formations volcaniques et volcano-détritiques, d'un réseau filonien microgranitique et rhyolitique très dense, de deux unités granitiques disposées de manière concentrique et de filons doléritiques tardifs terminant l'épisode magmatique. Une étude comparative sur la pétrographie, la structure, la typologie des zircons et la géochimie des éléments majeurs, en traces (Y, Nb, Zr, Rb, Sr, U, Th, Hf, Sc, Cs et Ta) et Terres Rares du complexe de Combeynot ont permis de retracer l'histoire magmatique de la série et de tester sa signification géodynamique. Le magmatisme de Combeynot est de nature alcaline intraplaque et traduit un environnement géotectonique de distension. Il trouve son origine dans le manteau à partir duquel plusieurs magmas subcontemporains s'individualisent par des taux de fusion partielle différents et conduisent aux unités acides par cristallisation fractionnée. Leur mise en place superficielle dans une zone orogénique encore non consolidée, riche en fluides et la participation des phases fluides juvéniles et/ou des eaux météoriques conditionnent la nature pétrographique acide, sursaturée et subsolvus des unités granitiques du complexe ainsi que les processus d'altération hydrothermale post- et tardi- magmatiques.
14
Benzakour, Abderrahim. "Le volcanisme permien des Vosges du Nord : un témoin d'une évolution dans le cycle orogénique varisque de l'Europe occidentale." Nancy 1, 1988. http://www.theses.fr/1988NAN10252.
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Cette thèse présente une étude pétrographique et géochimique des roches volcaniques (diabases, trachy-andésites, rhyodacites, rhyolites, ignimbrites) permienne des Vosges du Nord en vue de connaître les relations pétrogénétiques entre les différents faciès et le cadre géodynamique de leur mise en place. Deux séries calcoalcalines sont distinguées et l'enrichissement en K::(2)O qui représente un caractère généralisé de ces roches est discuté
15
Bassahak, Jean. "Le complexe plutonique du Massif de Kogue (Poli-nord Cameroun) : Pétrologie, géochimie, pétrologie structurale, sa place dans le plutonisme de la chaîne panafricaine au Nord Cameroun." Nancy 1, 1988. http://www.theses.fr/1988NAN10017.
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L'architecture, la mise en place et la pétrogénèse du Massif du Kogue (Poli, Nord Cameroun) s'intègrent dans l'évolution tectonique et plutonique de la zone mobile panafricaine du Nord Cameroun. Intrusion dans les formations métamorphiques de Poli, le complexe plutonique de Kogue est formé de deux unités constituées par deux lignées de différenciation magmatique, d'affinité calco-alcaline. L'agencement et l'analyse des trajectoires des fluidalités planaires soulignent une mise en place syntectonique sous forme de dome diapir dans un couloir de cisaillement. L'état rhéologique des magmas granitique et dioritique, dans les zones de brèches magmatiques montre que ceux-ci sont contemporains et ont une mise en place synchrone
16
Shamberger, Patrick J. "Leucocratic & gabbroic xenoliths from Hualālai Volcano, Hawaiʻi /." 2004. http://hdl.handle.net/10125/10461.
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17
Scogings, Andrew John. "Alkaline intrusives from the Tugela terrane, Natal metamorphic province." Thesis, 1991. http://hdl.handle.net/10413/11162.
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Three gneissose alkaline granitoid intrusives at Ngoye, Bulls Run and
Wangu are described. They are located within the Nkomo Nappe of the
Tugela Terrane, near the northern margin of the Natal Metamorphic
Province.
The Ngoye Complex comprises alkaline granites, with minor syenite and
monzodiorite phases. According to modal am geochemical criteria the
Ngoye granites range from peraluminous (muscovite-bearing), through
metaluminous (biotite- and/or hornblende-bearing), to peralkaline
(riebeckite-, aegirine- and magnetite-bearing). The granites are
A-types according to their modal and geochemical characteristics. Rb-Sr
isotopic data for the hornblende granites indicate an age of 1063 ± 17
Ma and the initial ratio (R๐ = 0.7025) provides evidence for
derivation from a mantle source. Plotting of the Ngoye geochemistry on
tectonic-discrimination diagrams suggests intrusion into rifted
continental crust. It is concluded that the gneissose Ngoye granites
constitute a deformed central complex, similar to anorogenic complexes
in Nigeria and the Sudan.
The Bulls Run Complex is situated 30 km west of the Ngoye Complex. A
concentric outcrop pattern has been mapped, according to which an
envelope of silica-saturated biotite-muscovite syenite surrounds a core
of nepheline-bearing syenites. Minor intrusive phases include
biotite-rich dykes, sovite carbonatite sheets, silica-oversaturated
microsyenite dykes and feldspathic ijolite. The outer envelope of
muscovite-rich syenite is interpreted as fenitised pelitic country
rock. An alkali-lamprophyre origin is suggested for the biotite-rich
dykes. Geochemically the syenites are predominantly miaskitic, apart
from the microsyenite dykes which are mildly peralkaline. Rb-Sr
isotopic data for the nepheline syenites indicate an age of 1138 ± 45 Ma
(Ro = 0.70322). Carbonate separates from the carbonatites provide a
similar low initial ratio (Ra = 0.70319) which supports a comagmatic
mantle origin. A comparison is drawn between the Bulls Run Complex and
miaskitic nepheline syenite gneisses in the mid-Proterozoic Grenville
Province of canada. From this, it is suggested that the Bulls Run
Complex is pretectonic and was intruded into the rifted passive margin
of a continent.
The Wangu Granite Gneiss is situated 3 km southwest of the Bulls Run
Complex. The granites are fine grained and contain aegirine-augite
and/or magnetite, and classify as alkali-feldspar granite. Peralkaline
chemistry is characteristic of the Wangu granites, with trace-elenent
contents indicating a distinct A-type signature. Biotite-rich mafic
dykes intrude the southern part of the Wangu outcrop and, on the basis
of major- and trace-element signatures, are suggested to be
metamorphosed volatile-rich alkaline lamprophyres similar to those at
Bulls Run. Geochemical similarities between the Wangu granites and
certain comendites from the Kenya Rift are noted. It is suggested that
the Wangu granites were emplaced as high-level dykes, within rifted
continental crust.
It is proposed that the Ngoye, Bulls Run and Wangu intrusives be united
as the Nkwaleni Suite.
Comparison of the Tugela Terrane with the Grenville Province reveals
many similarities, particularly their mid- to late-Proterozoic age and
the occurrence of pre-tectonic anorogenic continental magmatism. It is
concluded that, unlike the current model which would have the Tugela
Terrane as obducted ophiolite, these new data indicate that the Tugela
Terrane is a metamorphosed continental rift system.Thesis (Ph.D.)-University of Durban-Westville, 1991.
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Schrader, Christian Michael. "Geochronology and geology of the Pebble Cu-Au-Mo porphyry and the sill Au-Ag epithermal deposits, southwest Alaska." 2001. http://purl.galileo.usg.edu/uga%5Fetd/schrader%5Fchristian%5Fm%5F200112%5Fms.
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"Paleomagnetism of Neoproterozoic Intraplate Igneous Rocks in the Southwest Kalahari Craton, Namibia and South Africa." Texas Christian University, 2008. http://etd.tcu.edu/etdfiles/available/etd-12182008-145847/.
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Johnson, Geoffrey I. (Geoffrey Ian). "The petrology, geochemistry and geochronology of the felsic alkaline suite of the eastern Yilgarn Block, Western Australia / Geoffrey I. Johnson." 1991. http://hdl.handle.net/2440/19697.
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Typescript (Photocopy)Includes copies of 4 papers by the author as appendix 4 (v. 1)
Errata slip inserted
Bibliography: leaves 170-192 (v. 1)
2 v. : ill., maps ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--Dept. of Geology and Geophysics, University of Adelaide, 1992