Phase relations of amphibole, amphibole-carbonate, and phlogopite-carbonate peridotite: petrologic constraints on the asthenosphere

Ólafsson, Magnús; Eggler, David H.

doi:10.1016/0012-821x(83)90212-1

Cited by 314 publications

(100 citation statements)

References 34 publications

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“…La présence des phases riches en volatiles (kaersutite) décrites dans les basaltes, en conformité avec les travaux expérimentaux (Olafsson et Eggler, 1983), suggère que les magmas parentaux à l'origine des laves basaltiques de Ngaoundéré proviennent d'une source mantellique métasomatisée. Les faibles valeurs des teneurs en Sr (<30 ppm) et des rapports Rb/Sr (<0,05) des basaltes de Ngaoundéré caractérisent une source mantellique métasomatisée comme en atteste la présence des poches de carbonate dans les échantillons de basalte.…”

Section: Source Métasomatiséeunclassified

Géochimie des laves basaltiques récentes des zones Nord et Est de Ngaoundéré (Cameroun, Plateau de l’Adamaoua, Afrique centrale): pétrogenèse et nature de la source

Nkouandou¹,

Ngounouno²,

Dennielou³

2011

International Journal of Biological and Chemical Sciences

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Section: Source Métasomatiséeunclassified

Géochimie des laves basaltiques récentes des zones Nord et Est de Ngaoundéré (Cameroun, Plateau de l’Adamaoua, Afrique centrale): pétrogenèse et nature de la source

Nkouandou¹,

Ngounouno²,

Dennielou³

2011

International Journal of Biological and Chemical Sciences

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“…An estimated (but constrained) and extrapolated solidus curve for amphibole-dolomite-peridotite is compared with curves for peridotite dry and with HzO in Figure 20. This is modified from a previous version [Wyllie, 1980J incorporating new data [Olafsson andEggler, 1983;Wyllie, 1987a]. Despite differences in experimental results in Figure 19, the existence of the solidus ledge near Q, where the solidus changes slope and becomes subhorizontal, appears to be established (level 4 in Figure 20).…”

Section: Phase Diagrams and Their Interpretationmentioning

confidence: 99%

Magma genesis, plate tectonics, and chemical differentiation of the Earth

Wyllie¹

1988

Reviews of Geophysics

130

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Magma genesis, migration, and eruption have played prominent roles in the chemical differentiation of the Earth. Plate tectonics has provided the framework of tectonic environments for different suites of igneous rocks and the dynamic mechanisms for moving masses of rock into melting regions. Petrology is rooted in geophysics. Petrological and geophysical processes are calibrated by the phase equilibria of the materials. The geochemistry of basalts and mantle xenoliths demonstrates that the mantle is heterogeneous. The geochemical reservoirs are related to mantle convection, with interpretation of a mantle layered or stratified or peppered with blobs. Seismic tomography is beginning to reveal the density distribution of the mantle in three dimensions, and together with fluid mechanical models and interpretation of the geoid, closer limits are being placed on mantle convection. Petrological cross sections constructed for various tectonic environments by transferring phase boundaries for source rocks onto assumed thermal structures provide physical frameworks for consideration of magmatic and metasomatic events, with examples being given for basalts, andesites, and granites at ocean-continent convergent plate boundaries, basalts and nephelinites from a thermal plume beneath Hawaii, kimberlites in cratons, nephelinites from continental rifts, and anorogenic granites. The fluid dynamics of rock-melt-vapor systems exerts strong control on igneous processes and chemical differentiation. Unravelling the processes during subduction remains one of the major problems for understanding mantle heterogeneities and the evolution of continents. INTRODUCTIONThe Union Lecture on which this review is based was pre- the magmatic processes occurring nearer the source of magma generation. There remains a gap between volcanoes, their plutonic roots, and the magma sources which has to be filled by indirect studies including geophysics, geochemistry, and fluid dynamics. Lavas reach the surface through volcanoes, and lavas can provide information about the source rocks from which they were derived if the materials and processes can be suitably calibrated in the laboratory. The calibration involves the geochemistry of major, minor, and trace element distributions (including isotopes) between minerals and melts and the conditions for melting of the various source materials under various conditions. Some lavas also bring to the surface samples of the host rocks from which they were derived by partial melting or of the rocks through which they rose. The lavas release gases to the atmosphere and hydrosphere which also provide clues about the nature of the source material at depth.The theme common to the different parts of this review relates to the conditions for melting, transfer, storage, and eruption of melts. The approach is as follows. Plate tectonics provides a framework of tectonic environments and internal processes, which can be calibrated by laboratory experiments at high pressures. Within this framework I next outline the developm...

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“…On the basis of experimental studies they appear to represent opposite ends of the volatile spectrum; carbonatites clearly require abundant CO 2 in the source (Wyllie and Huang, 1975;Olafsson and Eggler, 1983;Eggler, 1989;Wyllie, 1989), whereas lamproites require H 2 Orich sources (Arima and Edgar, 1983b;Foley et al, 1987;Edgar and Vukadinovic, 1992) in which carbon, if present in any abundance at all, probably exists as CH 4 (Foley et al, 1986;Foley, 1993). Coupled to these distinctive volatile compositions in the source regions, carbonatites and lamproites each have highly specific characteristics as regards major element composition and incompatible element distribution, indicating contrasting source enrichment styles that resulted in specific metasomatic assemblages (Green and Wallace, 1988;Meen et al, 1989;Foley, 1992a,b;Thibault et al, 1992;Mitchell, 1995;Chakhmouradian, 2006).…”

Section: Introductionmentioning

confidence: 99%

Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

Tappe

Foley

Kjarsgaard

et al. 2008

Geochimica et Cosmochimica Acta

256

104

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New U-Pb perovskite ages reveal that diamondiferous ultramafic lamprophyre magmas erupted through the Archean crust of northern Labrador and Quebec (eastern Canada) .2). These contrasting isotopic characteristics of aillikites/carbonatites and mela-aillikites, along with subtle differences in their modal carbonate, SiO 2 , Al 2 O 3 , Na 2 O, Cs-Rb, and Zr-Hf contents, are consistent with two distinctive metasomatic assemblages of different age in the mantle magma source region.Integration of petrologic, geochemical, and isotopic information leads us to propose that the isotopically enriched component originated from a reduced phlogopite-richterite-Ti-oxide dominated source assemblage that is reminiscent of MARID suite xenoliths. In contrast, the isotopically depleted component was derived from a more oxidized phlogopite-carbonate dominated source assemblage. We argue that low-degree CO 2 -rich potassic silicate melts from the convective upper mantle were preferentially channelled into an older, pre-existing MARID-type vein network at the base of the North Atlantic craton lithosphere, where they froze to form new phlogopite-carbonate dominated veins. Continued stretching and thinning of the cratonic lithosphere during the Late Neoproterozoic remobilized the carbonate-rich vein material and induced volatile-fluxed fusion of the MARID-type veins and the cold peridotite substrate. Isotopic modelling suggests that only 5-12% trace element contribution from such geochemically extreme MARID-type material is required to produce the observed compositional shift from the isotopically most depleted aillikites/carbonatites towards enriched mela-aillikites.We conclude that cold cratonic mantle lithosphere can host several generations of contrasting vein assemblages, and that each may have formed during past tectonic and magmatic events under distinctively different physicochemical conditions. Although cratonic MARID-type and carbonate-bearing veins in peridotite can be the respective sources for lamproite and carbonatite magmas when present as the sole metasome, their concomitant fusion in a complex source region may give rise to a whole new variety of deep volatile-rich magmas and we suggest that orangeites (formerly Group 2 kimberlites), kamafugites, and certain types of ultramafic lamprophyre are formed in this manner.

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Phase relations of amphibole, amphibole-carbonate, and phlogopite-carbonate peridotite: petrologic constraints on the asthenosphere

Cited by 314 publications

References 34 publications

Géochimie des laves basaltiques récentes des zones Nord et Est de Ngaoundéré (Cameroun, Plateau de l’Adamaoua, Afrique centrale): pétrogenèse et nature de la source

Géochimie des laves basaltiques récentes des zones Nord et Est de Ngaoundéré (Cameroun, Plateau de l’Adamaoua, Afrique centrale): pétrogenèse et nature de la source

Magma genesis, plate tectonics, and chemical differentiation of the Earth

Between carbonatite and lamproite—Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes

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