Relevant bibliographies by topics / Alkalic igneous rocks – Namibia

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Academic literature on the topic 'Alkalic igneous rocks – Namibia'

Author: Grafiati
Published: 4 June 2021
Last updated: 17 February 2022

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Journal articles on the topic "Alkalic igneous rocks – Namibia"

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Aspiotis, S., S. Jung, F. Hauff, and R. L. Romer. "Petrogenesis of a late-stage calc-alkaline granite in a giant S-type batholith: geochronology and Sr–Nd–Pb isotopes from the Nomatsaus granite (Donkerhoek batholith), Namibia." International Journal of Earth Sciences 110, no. 4 (April 7, 2021): 1453–76. http://dx.doi.org/10.1007/s00531-021-02024-w.

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AbstractThe late-tectonic 511.4 ± 0.6 Ma-old Nomatsaus intrusion (Donkerhoek batholith, Damara orogen, Namibia) consists of moderately peraluminous, magnesian, calc-alkalic to calcic granites similar to I-type granites worldwide. Major and trace-element variations and LREE and HREE concentrations in evolved rocks imply that the fractionated mineral assemblage includes biotite, Fe–Ti oxides, zircon, plagioclase and monazite. Increasing K2O abundance with increasing SiO2 suggests accumulation of K-feldspar; compatible with a small positive Eu anomaly in the most evolved rocks. In comparison with experimental data, the Nomatsaus granite was likely generated from meta-igneous sources of possibly dacitic composition that melted under water-undersaturated conditions (X H2O: 0.25–0.50) and at temperatures between 800 and 850 °C, compatible with the zircon and monazite saturation temperatures of 812 and 852 °C, respectively. The Nomatsaus granite has moderately radiogenic initial 87Sr/86Sr ratios (0.7067–0.7082), relatively radiogenic initial εNd values (− 2.9 to − 4.8) and moderately evolved Pb isotope ratios. Although initial Sr and Nd isotopic compositions of the granite do not vary with SiO2 or MgO contents, fSm/Nd and initial εNd values are negatively correlated indicating limited assimilation of crustal components during monazite-dominated fractional crystallization. The preferred petrogenetic model for the generation of the Nomatsaus granite involves a continent–continent collisional setting with stacking of crustal slices that in combination with high radioactive heat production rates heated the thickened crust, leading to the medium-P/high-T environment characteristic of the southern Central Zone of the Damara orogen. Such a setting promoted partial melting of metasedimentary sources during the initial stages of crustal heating, followed by the partial melting of meta-igneous rocks at mid-crustal levels at higher P–T conditions and relatively late in the orogenic evolution.
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Milner, Simon C., Anton P. Le Roex, and Ronald T. Watkins. "Rb-Sr age determinations of rocks from the Okenyenya igneous complex, northwestern Namibia." Geological Magazine 130, no. 3 (May 1993): 335–43. http://dx.doi.org/10.1017/s001675680002001x.

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AbstractThe Okenyenya igneous complex is one of a suite of intrusions which define a prominent northeast-trending linear feature in Damaraland, northwestern Namibia. Precise Rb–Sr internal isochron ages range from 128.6 ± 1 to 123.4 ± 1.4 Ma for the major phases of intrusion identified within the complex. The tholeiitic gabbros forming the outer rings of the complex, and the later alkali gabbros which form the central hills, cannot be distinguished in terms of Rb–Sr ages, although field relations clearly indicate the younger age of the latter. The intrusionsof nepheline-syenite and essexite comprising the mountain of Okenyenya Bergon the northern edge of the complex give ages of 123.4 ± 1.4 and 126.3 ± 1 Ma, respectively, and form the final major phase of intrusion. The ages obtained for early and late intrusive phases define a minimum magmatic ‘life-span’ of approximately 5 Ma for the complex. The determined age of the Okenyenya igneous complex (129–123 Ma), when taken together with the few reliable published ages for other Damaraland complexes (130–134 Ma), suggests that these sub-volcanic complexes were emplaced contemporaneously with the widespread Etendeka volcanics (˜ 130 Ma), and relate to magmatism associated with the breakup of southern Africa and South America with the opening of the South Atlantic Ocean. The linear distributionof intrusions in Damaraland is interpreted to be due to magmatism resultingfrom the upwelling Tristan plume being focused along a structural discontinuity between the Pan-African, Damaran terrain to the south, and Proterozoiccratonic basement to the north.
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Reid, D. L., A. F. Cooper, D. C. Rex, and R. E. Harmer. "Timing of post–Karoo alkaline volcanism in southern Namibia." Geological Magazine 127, no. 5 (September 1990): 427–33. http://dx.doi.org/10.1017/s001675680001517x.

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AbstractNew radiometric age data are reported for alkaline centres in southern Namibia, and are discussed together with published age data in terms of models put forward to account for post-Karoo (Mesozoic–Recent) alkaline magmatism within the African plate. Agreement between K–Ar and Rb–Sr ages indicate emplacement of the Dicker Willem carbonatite in southern Namibia at 49 ± 1 Ma. Alkaline rocks associated with the Gross Brukkaros volcano show a discordant radiometric age pattern, but the best estimate for the age of this complex is 77 ± 2 Ma, similar to that obtained for the neighbouring Gibeon carbonatite-kimberlite province. The Dicker Willem carbonatite is therefore younger than the Luderitz alkaline province (133 ± 2 Ma), and the Gross Brukkaros volcano, but is older than the Klinghardt phonolite field (29–37 Ma). The new age data argue against a distinct periodicity in alkaline igneous activity in southern Africa, thereby ruling out possible controls by episodic marginal upwarping of the subcontinent. Although the available age data do not appear to be consistent with the passage of one or even two hotspots under southern Namibia, it is argued that the surface expression of hotspots under continents may be so large and overlapping that within-plate magmatism attributed to these thermal anomalies need not necessarily be confined to narrow linear belts or show an age progression. The role of hotspots in continental alkaline magmatism is most likely one of melt generation, while local crustal structure probably controls the distribution and timing of eruption. Major tectonic boundaries in the Precambrian basement underlying southern Namibia seem to have controlled the development of Tertiary alkaline centres in that region.
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Cuney, Michel. "Felsic magmatism and uranium deposits." Bulletin de la Société Géologique de France 185, no. 2 (February 1, 2014): 75–92. http://dx.doi.org/10.2113/gssgfbull.185.2.75.

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Abstract The strongly incompatible behaviour of uranium in silicate magmas results in its concentration in the most felsic melts and a prevalence of granites and rhyolites as primary U sources for the formation of U deposits. Despite its incompatible behavior, U deposits resulting directly from magmatic processes are quite rare. In most deposits, U is mobilized by hydrothermal fluids or ground water well after the emplacement of the igneous rocks. Of the broad range of granite types, only a few have U contents and physico-chemical properties that permit the crystallization of accessory minerals from which uranium can be leached for the formation of U deposits. The first granites on Earth, which crystallized uraninite, dated at 3.1 Ga, are the potassic granites from the Kaapval craton (South Africa) which were also the source of the detrital uraninite for the Dominion Reef and Witwatersrand quartz pebble conglomerate deposits. Four types of granites or rhyolites can be sufficiently enriched in U to represent a significant source for the genesis of U deposits: peralkaline, high-K metaluminous calc-alkaline, L-type peraluminous and anatectic pegmatoids. L-type peraluminous plutonic rocks in which U is dominantly hosted in uraninite or in the glass of their volcanic equivalents represent the best U source. Peralkaline granites or syenites are associated with the only magmatic U-deposits formed by extreme fractional crystallization. The refractory character of the U-bearing minerals does not permit their extraction under the present economic conditions and make them unfavorable U sources for other deposit types. By contrast, felsic peralkaline volcanic rocks, in which U is dominantly hosted in the glassy matrix, represent an excellent source for many deposit types. High-K calc-alkaline plutonic rocks only represent a significant U source when the U-bearing accessory minerals (U-thorite, allanite, Nb oxides) become metamict. The volcanic rocks of the same geochemistry may be also a favorable uranium source if a large part of the U is hosted in the glassy matrix. The largest U deposit in the world, Olympic Dam in South Australia is hosted by highly fractionated high-K plutonic and volcanic rocks, but the origin of the U mineralization is still unclear. Anatectic pegmatoids containing disseminated uraninite which results from the partial melting of uranium-rich metasediments and/or metavolcanic felsic rocks, host large low grade U deposits such as the Rössing and Husab deposits in Namibia. The evaluation of the potentiality for igneous rocks to represent an efficient U source represents a critical step to consider during the early stages of exploration for most U deposit types. In particular a wider use of the magmatic inclusions to determine the parent magma chemistry and its U content is of utmost interest to evaluate the U source potential of sedimentary basins that contain felsic volcanic acidic tuffs.
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Watson, Ken, Lawrence C. Rowan, Timothy L. Bowers, Carmen Anton‐Pacheco, Pablo Gumiel, and Susanne H. Miller. "Lithologic analysis from multispectral thermal infrared data of the alkalic rock complex at Iron Hill, Colorado." GEOPHYSICS 61, no. 3 (May 1996): 706–21. http://dx.doi.org/10.1190/1.1443998.

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Airborne thermal‐infrared multispectral scanner (TIMS) data of the Iron Hill carbonatite‐alkalic igneous rock complex in south‐central Colorado are analyzed using a new spectral emissivity ratio algorithm and confirmed by field examination using existing 1:24 000‐scale geologic maps and petrographic studies. Color composite images show that the alkalic rocks could be clearly identified and that differences existed among alkalic rocks in several parts of the complex. An unsupervised classification algorithm defines four alkalic rock classes within the complex: biotitic pyroxenite, uncompahgrite, augitic pyroxenite, and fenite + nepheline syenite. Felsic rock classes defined in the surrounding country rock are an extensive class consisting of tuff, granite, and felsite, a less extensive class of granite and felsite, and quartzite. The general composition of the classes can be determined from comparisons of the TIMS spectra with laboratory spectra. Carbonatite rocks are not classified, and we attribute that to the fact that dolomite, the predominant carbonate mineral in the complex, has a spectral feature that falls between TIMS channels 5 and 6. Mineralogical variability in the fenitized granite contributed to the nonuniform pattern of the fenite‐nepheline syenite class. The biotitic pyroxenite, which resulted from alteration of the pyroxenite, is spatially associated and appears to be related to narrow carbonatite dikes and sills. Results from a linear unmixing algorithm suggest that the detected spatial extent of the two mixed felsic rock classes was sensitive to the amount of vegetation cover. These results illustrate that spectral thermal infrared data can be processed to yield compositional information that can be a cost‐effective tool to target mineral exploration, particularly in igneous terranes.
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West, David P., Dwight Bradley, and Raymond Coish. "The Litchfield Pluton in South-Central Maine: Carboniferous Alkalic Magmatism in northern New England, USA." Atlantic Geology 52 (June 30, 2016): 169. http://dx.doi.org/10.4138/atlgeol.2016.008.

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The Litchfield pluton is a poorly exposed 7 km2 composite alkalic intrusive complex that cuts previously deformed and metamorphosed Silurian turbidites in south-central Maine. The pluton includes a variety of alkaline syenites, including the type locality of “litchfieldite”, a coarse-grained cancrinite, sodalite, and lepidomelane bearing nepheline syenite first recognized over 150 years ago and common in many petrologic collections. A new U-Pb zircon age of 321 ± 2 Ma from the nepheline syenite is interpreted to represent the crystallization age of the plutonic complex. A new biotite 40Ar/39Ar age of 239 ± 1 Ma from the syenite is similar to previously published mica ages from the surrounding country rocks and dates the time of regional cooling in the area below ~ 300°C. Whole rock geochemical analyses from rocks of the Litchfield pluton are compatible with strongly alkaline A-type granitoid rocks that formed in a within plate or continental rift tectonic setting. The age and geochemical characteristics of the alkalic igneous rocks near Litchfield are consistent with a model that invokes the generation of a small volume of alkalic magma beneath south-central Maine during a period of Carboniferous transcurrent tectonism in the northern Appalachian orogen.
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Barr, Sandra M., Daniel Brisebois, and Alan S. Macdonald. "Carboniferous volcanic rocks of the Magdalen Islands, Gulf of St. Lawrence." Canadian Journal of Earth Sciences 22, no. 11 (November 1, 1985): 1679–88. http://dx.doi.org/10.1139/e85-176.

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Volcanic rocks of Mississippian age occur on the Magdalen Islands as cap rocks and within collapse breccias above salt diapirs that have formed the islands. They consist of coarse volcaniclastic deposits and basaltic flows, intruded by minor mafic dykes and plugs. Petrologic studies of the basaltic rocks show that they are extensively altered. Original plagioclase, clinopyroxene, olivine, and interstitial glass are partially to entirely replaced by mixtures of chlorite, sericite, smectite, sphene, carbonate, epidote, albite, potassium feldspar, and iron oxides, and the samples display a relatively wide range in chemical compositions. Especially mobile were K, Na, and Ca, and most samples are classified as potash spilites (poenites). Using standard discriminant diagrams for mafic igneous rocks, it can be seen that the basalts appear to range from continental tholeiitic to continental alkalic. However, relict clinopyroxene compositions and the presence of kaersutitic amphibole and titaniferous biotite in some samples imply that the suite may originally have been more alkalic than tholeiitic.
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Buhlmann, Arndt L., Patricia Cavell, Ronald A. Burwash, Robert A. Creaser, and Robert W. Luth. "Minette bodies and cognate mica-clinopyroxenite xenoliths from the Milk River area, southern Alberta: records of a complex history of the northernmost part of the Archean Wyoming craton." Canadian Journal of Earth Sciences 37, no. 11 (November 1, 2000): 1629–50. http://dx.doi.org/10.1139/e00-058.

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Minettes exposed in southern Alberta near the Milk River are the northern outliers of the Eocene Sweet Grass Hills igneous complex of the Montana alkalic igneous province. These minettes often contain coarse-grained xenoliths of phlogopite + clinopyroxene ± apatite. The parent magmas of the minettes were generated at pressures [Formula: see text]17 kbar in equilibrium with clinopyroxene + phlogopite ± olivine. Fractional crystallization and mixing provided a spectrum of evolved minettes and cumulates, the latter of which were sampled by subsequent minette magmas as xenoliths. Two xenoliths were dated at 49.0 ± 0.8 Ma and 52 ± 1.7 Ma. The host dyke of the latter xenolith gave an age of 50 ± 0.3 Ma. The minettes and their xenoliths have overlapping values of 87Sr/86Sri, εNdT, 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb, similar to those of alkaline igneous rocks from farther south in the Montana alkalic igneous province. The Sweet Grass Hills lie north of the Great Falls Tectonic Zone, previously interpreted as a Proterozoic suture zone separating the Archean Medicine Hat block from the Archean Wyoming craton to the south. Geochemical data for the Milk River minettes provide evidence for a history of the mantle underneath the Medicine Hat block, similar to that found previously for mantle-derived rocks of the Wyoming craton, including a significant Proterozoic mantle enrichment event. Given this similarity, we suggest that the Wyoming craton extends into southern Alberta, and that the Great Falls Tectonic Zone does not represent a Proterozoic suture of two Archean blocks.
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Morris, Paul A., Tetsumaru Itaya, Shigeru Iizumi, Hiroo Kagami, R. John Watling, and Hisashi Murakami. "Age relations and petrology of alkalic igneous rocks from Oki Dozen, Southwest Japan." GEOCHEMICAL JOURNAL 31, no. 3 (1997): 135–54. http://dx.doi.org/10.2343/geochemj.31.135.

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Barr, Sandra M. "Geochemistry and tectonic setting of late Precambrian volcanic and plutonic rocks in southeastern Cape Breton Island, Nova Scotia." Canadian Journal of Earth Sciences 30, no. 6 (June 1, 1993): 1147–54. http://dx.doi.org/10.1139/e93-097.

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Late Precambrian volcanic–sedimentary belts in the Mira (Avalon) terrane of southeastern Cape Breton Island display differences in rock types, petrochemistry, and age, showing that they did not form contemporaneously above a single northwest-dipping subduction zone, as proposed in earlier models. The oldest rocks are 680 Ma mafic and felsic flows and tuffs, and abundant, mainly tuffaceous, sedimentary rocks in the Stirling belt. They are interpreted to have formed in a trough within or peripheral to a volcanic-arc complex. Northwest of the Stirling belt, the East Bay Hills, Coxheath Hills, and Sporting Mountain belts consist of ca. 620 Ma mafic to felsic subaerial pyroclastic rocks and flows and contemporaneous dioritic to granitic plutons. Both volcanic and plutonic rocks are calc-alkalic to high-K calc-alkalic suites, formed in a continental margin volcanic arc. A correlative 620 Ma plutonic suite intruded the western margin of the Stirling belt, suggesting that subduction may have been toward the present southeast. The ca. 575 Ma Coastal belt, located southeast of the Stirling belt, is significantly younger than the other belts and appears to represent a less evolved calc-alkalic to low-K continental margin volcanic-arc and intra-arc basin formed above a northwest-dipping subduction zone. These various volcanic–sedimentary belts were juxtaposed by lateral movements along major faults in the late Precambrian to form this part of the Avalon composite terrane. Subduction-related, calc-alkalic magmatism at ca. 620 Ma was apparently widespread throughout the Avalon terrane of the northern Appalachian Orogen. However, ca. 680 Ma magmatism like that in the Stirling belt has been documented elsewhere only in the Connaigre Bay Group of Newfoundland. Circa 575 Ma and younger subduction-generated igneous activity like that in the Coastal belt has been recognized in southern New Brunswick, but alkaline magmas were forming in extensional regimes in other areas of the Avalon terrane at that time.
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Dissertations / Theses on the topic "Alkalic igneous rocks – Namibia"

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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
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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.
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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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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)).
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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.
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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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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
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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
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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
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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
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Books on the topic "Alkalic igneous rocks – Namibia"

1

Diehl, M. Geology, mineralogy, geochemistry, and hydrothermal alteration of the Brandberg Alkaline Complex, Namibia. Winhoek, Namibia: Ministry of Mines and Energy, Geological Survey of Namibia, 1990.

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Lulin, Jean-Marc. Un nouveau gîte à Nb, Ta, U, T.R. d'origine magmatique en Afrique orientale: Le complexe alcalin tectonisé de Meponda, précambrien de la province du Niassa (République populaire du Mozambique). Orléans: Editions du Bureau de recherches géologiques et minières, Service géologique national, 1985.

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Flanagan, F. J. Additions and corrections for USGS bulletin 1623, three USGS mafic rock reference samples, W-2, DNC-1, and BIR-1. Reston, Va: U.S. Geological Survey, 1986.

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Krivdik, S. G. Petrologii͡a︡ shchelochnykh porod Ukrainskogo shchita. Kiev: Nauk. dumka, 1990.

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Lazarenkov, V. G. Format͡s︡ionnyĭ analiz shchelochnykh porod kontinentov i okeanov. Leningrad: "Nedra," Leningradskoe otd-nie, 1988.

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Bochkarev, V. V. Subshchelochnoĭ magmatizm Urala. Ekaterinburg: In-t geologii i geokhimii UrO RAN, 2000.

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E, Brooks William. Analyses of upper-plate volcanic rocks at Picacho Peak, Pinal County, Arizona. [Reston, Va.?]: U.S. Dept. of the Interior, Geological Survey, 1985.

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E, Brooks William. Analyses of upper-plate volcanic rocks at Picacho Peak, Pinal County, Arizona. [Reston, Va.?]: U.S. Dept. of the Interior, Geological Survey, 1985.

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Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: Wapikopa Lake Alkalic Rock Complex, district of Kenora. Toronto, Ont: Ontario Ministry of Northern Development and Mines, Mines and Minerals Division, 1988.

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Sage, R. P. Geology of carbonatite-alkalic rock complexes in Ontario: Hecla-Kilmer Alkalic Rock Complex, district of Cochrane. Toronto, Ont: Ministry of Northern Development and Mines, Mines and Minerals Division, 1988.

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Book chapters on the topic "Alkalic igneous rocks – Namibia"

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Faure, Gunter. "Alkalic Igneous Rocks on the Continents." In Origin of Igneous Rocks, 281–350. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-662-04474-2_6.

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Karner, Frank R. "IGC Field Trip T131: Devils Tower—Black Hills alkalic igneous rocks and general geology." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 1–2. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0001.

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Karner, Frank R. "IGC Field Trip T131: Geological framework of the Black Hills—Bear Lodge Mountains region." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 3–6. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0003.

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Karner, Frank R., and Richard L. Patelke. "IGC Field Trip T131: General geology of the Black Hills and Bear Lodge Mountains." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 7–20. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0007.

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Karner, Frank R., Gloria A. Pederson, and Marilyn R. Shultz. "Glossary of places and people of the Black Hills." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 21–28. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0021.

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Karner, Frank R. "Field guide day 1: Geology of the precambrian rocks of the Keystone region." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 29–32. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0029.

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Karner, Frank R., and Richard L. Patelke. "Field guide day 2: Geology of the precambrian rocks of the Custer region, Hot Springs Mammoth site and Wind Cave." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 33–40. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0033.

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Karner, Frank R., and Stanley F. White. "Field guide day 3: Geology of the Badlands region and the mesozoic-paleozoic rocks of Boulder Canyon." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 41–44. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0041.

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Karner, Frank R. "Activities guide day 4: United States Independence Day and geological and cultural features of the Deadwood region." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 45. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0045.

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Karner, Frank R., and Stanley F. White. "Field guide day 5: Geology of precambrian-cenozoic rocks of the Deadwood-Lead region, Terry Peak, and Spearfish Canyon." In Devils Tower—Black Hills Alkalic Igneous Rocks and General Geology, 46–49. Washington, D. C.: American Geophysical Union, 1989. http://dx.doi.org/10.1029/ft131p0046.

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Conference papers on the topic "Alkalic igneous rocks – Namibia"

1

Anderson, Eric D., Karen D. Kelley, Erin E. Marsh, and Wesley R. Weisberg. "THE USE OF POTENTIAL FIELD DATA IN CHARACTERIZING BASEMENT ROCKS AND IGNEOUS SUITES NEAR THE TELLURIUM-RICH CRIPPLE CREEK ALKALIC EPITHERMAL DEPOSIT, COLORADO." In GSA Annual Meeting in Denver, Colorado, USA - 2016. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016am-286629.

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