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See detailDifferentiation of tholeiitic basalt to A-type granite in the Sept Iles layered intrusion, Canada
Namur, Olivier ULg; Charlier, Bernard; Toplis, Michael et al

in Journal of Petrology (2011)

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See detailCrystallization sequence and magma chamber processes in the ferrobasaltic Sept Iles layered intrusion, Canada
Namur, Olivier ULg; Charlier, Bernard ULg; Toplis, Michael et al

in Journal of Petrology (2010), 51

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See detailPhase equilibria of the Lyngdal granodiorite (Norway): Implications for the origin of metaluminous ferroan granitoids
Bogaerts, Michel; Scaillet, Bruno; Vander Auwera, Jacqueline ULg

in Journal of Petrology (2006), 47

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See detailU-Pb zircon calendar for Namaquan (Grenville) crustal events in the granulite-facies terrane of the O'okiep Copper District of South Africa
Clifford, Tom N.; Barton, Erika S; Stern, Richard A. et al

in Journal of Petrology (2004), 45(4), 669-691

The O'okiep Copper District is underlain by voluminous 1035-1210 Ma granite gneiss and granite with remnants of metamorphosed supracrustal rocks. This assemblage was intruded by the 1030 Ma copper-bearing ... [more ▼]

The O'okiep Copper District is underlain by voluminous 1035-1210 Ma granite gneiss and granite with remnants of metamorphosed supracrustal rocks. This assemblage was intruded by the 1030 Ma copper-bearing Koperberg Suite that includes jotunite, anorthosite, biotite diorite and hypersthene-bearing rocks ranging from leuconorite to hypersthenite. New sensitive high-resolution ion microprobe age data demonstrate the presence of 1700-2000 Ma zircon as xenocrysts in all of the intrusive rocks, and as detrital zircon in the metasediments of the Khurisberg Subgroup. These data are consistent with published Sm-Nd model ages of c. 1700 Ma (T-CHUR) and c. 2000 Ma (T-DM) of many of the intrusives that support a major crust-forming event in Eburnian (Hudsonian) times. In addition, U-Th-Pb analyses of zircons from all major rock units define two tectono-magmatic episodes of the Namaquan Orogeny: (1) the O'okiepian Episode (1180-1210 Ma), represented by regional granite plutonism, notably the Nababeep and Modderfontein Granite Gneisses and the Concordia and Kweekfontein Granites that accompanied and outlasted (e.g. Kweekfontein Granite) regional tectonism [F-2(D-2)] and granulite-facies metamorphism (M-2); (2) the Klondikean Episode (1020-1040 Ma), which includes the intrusion of the porphyritic Rietberg Granite and of the Koperberg Suite that are devoid of regional planar or linear fabrics. Klondikean tectonism (D-3) is reflected by major east-west-trending open folds [F-3(D-3a)], and by localized east-west-trending near-vertical ductile folds ['steep structures'; F-4(D-3b)] whose formation was broadly coeval with the intrusion of the Koperberg Suite. A regional, largely thermal, amphibolite- to granulite-facies metamorphism (M-3) accompanied D-3. This study demonstrates, inter alia, that the complete spectrum of rock-types of the Koperberg Suite, together with the Rietberg Granite, was intruded in a short time-interval (<10 Myr) at c. 1030 Ma, and that there were lengthy periods of about 150 Myr of tectonic quiescence within the Namaquan Orogeny: (1) between the O'okiepian and Klondikean Episodes; (2) from the end of the latter to the formal end of Namaquan Orogenesis 800-850 Ma ago. [less ▲]

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See detailSome phase equilibrium constraints on the origin of Proterozoic (massif) anorthosites and related rocks
Longhi, John ULg; Vander Auwera, Jacqueline ULg; Fram, Miranda S. et al

in Journal of Petrology (1999), 40

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See detailIgneous charnockites and related rocks from the Bjerkreim-Sogndal layered intrusion (Southwest Norway): a jotunite (hypersthene monzodiorite)-derived A-type granitoid suite
Duchesne, Jean-Clair ULg; Wilmart, Edith

in Journal of Petrology (1997), 38(3), 337-369

The upper part of the Bjerkreim-Sokndal layered intrusion (BKSK) comprises a suite of charnockitic granitoids (mangerite, quartz mangerite and charnockite) with some jotunites. The petrology and ... [more ▼]

The upper part of the Bjerkreim-Sokndal layered intrusion (BKSK) comprises a suite of charnockitic granitoids (mangerite, quartz mangerite and charnockite) with some jotunites. The petrology and geochemistry (major and trace elements) of 8 main rock types (88 samples) are considered. The rocks form a suite of K2O-rich alkali-calcic granitoids of A-type, deriving from jotunitic magma. Two trends of inferred liquids are distinguished: the main liquid line of descent which passes from jotunites through 2-pyroxene quartz mangerites to amphibole charnockites, the second one which encompasses olivine-bearing quartz mangerites and charnockites and is rooted into mangeritic liquids. Comparison with the Tellnes rock series reveals that contamination by leucogranitic material has taken place simultaneously with fractional crystallization in both BKSK trends. Zr, Rb, Cs, and Th are particularly sensitive to assimilation and the higher water content in BKSK. Zircon and apatite have saturated at the liquidus of quartz mangerite around 900°C, close to the FMQ buffer. The two-pyroxene quartz mangerites cannot have been equilibrated with the mangerite cumulates on which they rest. A major influx of magma took place when mangeritic cumulates were being deposited. It mingled and partly mixed with the resident contaminated magma. [less ▲]

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See detailIron-Titanium oxide minerals in the Bjerkrem-Sogndal massif, south-western Norway
Duchesne, Jean-Clair ULg

in Journal of Petrology (1972), 13(1), 57-81

Ilmenite and magnetite are investigated from the point of view of their distribution, micro-texture, and chemical composition (major and minor elements) in the Bjerkreim-Sokndal massif (Egersund area ... [more ▼]

Ilmenite and magnetite are investigated from the point of view of their distribution, micro-texture, and chemical composition (major and minor elements) in the Bjerkreim-Sokndal massif (Egersund area, South-Rogaland, SW. Norway). This massif is an igneous layered lopolith made up of cumulates of the anorthosite-mangerite suite. The lower part of the massif presents a rhytmic structure. The microtextures of ilmenite result from simple exsolution of ilmenite-hematite solid solution. Magnetite contains intergrowths of ilmenite formed by oxidation-exsolution of ulvöspinel-magnetite solid-solution. In the stratigraphic sequence, on a large scale, ilmenite appears first alone, and is then accompanied by magnetite; its hematite content decreases towards the top of the massif, while the titanium content of the magnetite increases. On the scale of the rhythms, similar trends but of a lesser amplitude are also observed. Evidence of deuteric readjustment of the orthomagmatic composition of the two oxides is provided (1) by the observation of microtextures at the contact betwen grains (zoning of primary ilmenite and rim of secondary ilmenite) (2) by the existence of differences in chemical composition between isolated grains and grains in contact, and (3) bythe determination of the equilibrium temperature by means of the Buddington and Lindsley geothermonmeter. Reconstruction of the T-fO2 orthomagmatic conditions is provided in two particular levels of the massif shows that the reducing character of the magma increases during differentiation. The sudden changes in the oxide assembalge at the base of the rythmic units reflect a sudden increase in the fO2 of the magma. These increases, as shown by variation in Cr, Ni and Co, are due to recurrences of the basic character of the magma. The variations of the minor elements Mn, V, Ga, and Zn are interpreted in terms of the influence of the deuteric readjustment. It follows that the ratios Mn/Fe2+ ; Ga/Fe3+, and Zn/Fe2+ increase and that the ratio V/Fe3+ decreases in the magma in the course of differentiation. The distribution of Mn between ilmenite and magnetite is discussed. Intermittent supplies of undifferentiated magma are proposed as the geological mechanism controlling the chemical recurrencess associated with the rhythmic structure. [less ▲]

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See detailFe-Ti oxide minerals in the Bjerkrem-Sogndal massif (Norway)
Duchesne, Jean-Clair ULg

in Journal of Petrology (1972), 13

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