Strontium and oxygen isotope evidence relating to the petrogenesis of the Kangerdlugssuaq alkaline instrusion, East Greenland

Pankhurst, R. J.; Beckinsale, R. D.; Brooks, C. Kent

doi:10.1007/bf00370870

Cited by 62 publications

(34 citation statements)

References 26 publications

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Section: Copyright the Mineralogical Societymentioning

confidence: 99%

“…Kempe and Deer (1976), treating the intrusion as a closed system, discussed several mechanisms by which the magma composition might have crossed the thermal barrier in this system, but reached no conclusion as to which, if any, had operated. On the basis of isotopic evidence, however, Pankhurst et al (1976) demonstrated that the outer parts of the intrusion had undergone considerable chemical interaction with the surrounding gneisses, and the notion of simple differentiation of an isolated magma in situ could no longer be regarded as an acceptable explanation of the development of the intrusion.In view of the important bearing of the Kangerdlugssuaq intrusion on the petrogenesis of alkaline rocks, we are undertaking more detailed mineralogical and chemical studies, and present here an electron microprobe investigation of the pyroxenes and amphiboles of the intrusion. The work supplements by microprobe methods the study of Kempe…”

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confidence: 99%

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Compositional variation in the pyroxenes and amphiboles of the Kangerdlugssuaq intrusion, East Greenland: further evidence for the crustal contamination of syenite magma

Brooks

Gill

1982

Mineral. mag.

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ABSTRACT. Pyroxenes and amphiboles from the undersaturated to over-saturated syenites of the Kangerdlugssuaq intrusion have been examined to see what light they throw on the two contrasting petrogenetic models for the intrusion. Pyroxene crystals are strongly zoned outwards from augitic to more acmitic compositions, with the most calcic cores present in the foyaite, contrary to the expected pattern if the foyaite is the most evolved rock type as previously postulated. Amphiboles, which are absent in the foyaites, show an exceptionally wide compositional field varying from actinolite through richterite and katophorite to arfvedsonite. Many are manganoan and potassian varieties. However, there is no consistent variation throughout the intrusion as previous work has suggested. These results are not favourable to the idea of a crystal fractionation model for the intrusion and we suggest that the foyaite is closest to the original magma which has hybridized with the enclosing gneisses and basalts to produce the over-saturated rocks. Such a model is consistent with the existing isotopic data.T n E Kangerdlugssuaq alkaline intrusion, described first by Wager (1965), who regarded it as having formed by gravitational sinking of early formed crystals, has been regarded as a typical example of a syenite intrusion in which a range of rock types has developed by simple differentiation in situ (Sorensen, 1974, p. 38). In surface outcrop it is a large circular body, 30 km in diameter, having a volume estimated to be about 6500 km 3. It is therefore the largest Tertiary pluton in East Greenland. Trains of basalt blocks and the lamination of platy feldspars together define a gross layering * Present address: Department of Geology, Chelsea College, University of London, 552 Kings Road, London SW10 0UA. Copyright the Mineralogical Societyresembling a pile of saucers (Kempe et al., 1970), within which the distribution of rock types appears to be concordant. Silica contents are found to decrease inwards and upwards, the rock types varying from quartz nordmarkite at the margins through nordmarkite and pulaskite to foyaite at the centre of the intrusion. There is no field evidence for more than one phase of injection, and the intrusion is a prominent example of the class of alkaline complexes in which a homogeneous syenite magma appears to have differentiated from an initially over-saturated composition to an undersaturated residual liquid, in apparent violation of phase relations in the system NaA1SiO4 KAISiO4-SiO2 (see Tilley, 1957). Kempe and Deer (1976), treating the intrusion as a closed system, discussed several mechanisms by which the magma composition might have crossed the thermal barrier in this system, but reached no conclusion as to which, if any, had operated. On the basis of isotopic evidence, however, Pankhurst et al. (1976) demonstrated that the outer parts of the intrusion had undergone considerable chemical interaction with the surrounding gneisses, and the notion of simple differentiation of an isolated magma in sit...

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Section: Copyright the Mineralogical Societymentioning

confidence: 99%

mentioning

confidence: 99%

Compositional variation in the pyroxenes and amphiboles of the Kangerdlugssuaq intrusion, East Greenland: further evidence for the crustal contamination of syenite magma

Brooks

Gill

1982

Mineral. mag.

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“…Holm and Praegel include quartz nordmarkites, nordmarkites, pulaskites and foyaites from the Kangerdlugssuaq intrusion in this plot. All the Kangerdlugssuaq intrusion rocks plot within the same band as the samples from K~erven, even though the oversaturated and undersaturated syenites of the Kangerdlugssuaq intrusion (on the basis of major, trace and isotope chemistry and mineral chemistry) cannot be assumed to represent simple evolutionary trends from a common parent (Pankhurst et al, 1976;Brooks and Gill, 1982;Nielsen, 1987). The Th vs. Ce plot cannot, therefore, be used as evidence for comagmatism.…”

Section: Age Of the Kcerven Syenite Complex Thementioning

confidence: 93%

“…K~erven complex is one of several, both older and younger, satellite intrusions to the 800 km 2 50 + 1Ma old syenitic Kangerdlugssuaq intrusion (Kempe et al, 1970;Pankhurst et al, 1976). Holm and Prregel quote an Ar4~ 39 age of 58 Ma for the K~erven syenite complex.…”

Section: Age Of the Kcerven Syenite Complex Thementioning

confidence: 99%

Comments on ‘The Tertiary Kærven syenite complex, Kangerdlugssuaq, East Greenland: mineral chemistry and geochemistry’ by P. M. Holm and N.-O. Prægel

Nielsen¹

1989

Mineral. mag.

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“…Tarling et al, 1988). Only a crude concept of the timing of the Tertiary magmatic evolution in the Kangerdlugssuaq area has hitherto been published (Brooks and Gleadow, 1977;Pankhurst et al, 1976;Gleadow and Brooks, 1979). In the light of this incompleteness of knowledge we do not think it is wise to consider, as Nielsen appears to do (Nielsen and Brooks, 1981;Brooks and Nielsen, 1982;Nielsen, 1989), all the syenite complexes more or less contemporaneous at 50Ma.…”

Section: Age Of the Complexmentioning

confidence: 99%

Reply to comments by T. F. D. Nielsen on ‘The Tertiary Kærven syenite complex, Kangerdlugssuaq, East Greenland: Mineral Chemistry and Geochemistry’

Holm¹

1989

Mineral. mag.

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Strontium and oxygen isotope evidence relating to the petrogenesis of the Kangerdlugssuaq alkaline instrusion, East Greenland

Cited by 62 publications

References 26 publications

Compositional variation in the pyroxenes and amphiboles of the Kangerdlugssuaq intrusion, East Greenland: further evidence for the crustal contamination of syenite magma

Compositional variation in the pyroxenes and amphiboles of the Kangerdlugssuaq intrusion, East Greenland: further evidence for the crustal contamination of syenite magma

Comments on ‘The Tertiary Kærven syenite complex, Kangerdlugssuaq, East Greenland: mineral chemistry and geochemistry’ by P. M. Holm and N.-O. Prægel

Reply to comments by T. F. D. Nielsen on ‘The Tertiary Kærven syenite complex, Kangerdlugssuaq, East Greenland: Mineral Chemistry and Geochemistry’

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