Rare-earth element distribution and K/Rb ratios in granulites, mangerites and anorthosites, Lofoten-Vesteraalen, Norway

Green, T.H.; Brunfelt, A.O.; Heier, K.S.

doi:10.1016/0016-7037(72)90008-7

Cited by 88 publications

(12 citation statements)

References 25 publications

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“…These authors, however, failed to decide between a mixing process or magmatic differentiation to explain the observed trend; they interpreted the high K/Rb values in anorthosites as indicating a mantle or a deep crustal origin without noticing, as Murthy and Griffin [36] did, that this ratio is essentially controlled by plagioclase ; they also showed that K/Rb ratios in acidic rocks are higher than the crustal average. This peculiarity was later confirmed by Green et al [49] who considered these rocks as residual product of partial fusion of the crust. They thus considered a genetic relationship between mangerite and anorthosite as unlikely.…”

Section: Potassium and Rubidiummentioning

confidence: 70%

“…Data for whole rocks: Lofoten from Green et al [49], (an) = anorthosite; (mang) = mangerite; Marcy from Reynolds et al [50] ; jotunite (), mangerite () and gneiss ( ) of Snowy Mountain, Adirondacks, from Reynolds et al [50]. The main trend of Shaw [48] (MT) describes the K-Rb fractionation in average magmatic rocks.…”

Section: Fig 4 Plot Of K Vs Rb In Rocks and Plagioclases From The mentioning

confidence: 99%

“…Mangerites from the Lofoten Islands [49] show a positive Eu anomaly which would result from feldspar accumulation or be produced by fusion involving feldspar of the residue of a previous anatexis, as the high K/Rb ratios would also indicate. Moreover, Green et al [49] are unable to decide between an intermediate (dioritic) and a basic nature of the parental magma, or between different processes of formation of the dioritic magma.…”

Section: Rare Earth Elementsmentioning

confidence: 99%

“…Moreover, Green et al [49] are unable to decide between an intermediate (dioritic) and a basic nature of the parental magma, or between different processes of formation of the dioritic magma.…”

Section: Rare Earth Elementsmentioning

confidence: 99%

“…According to the proportions of the different lithological terms, deduced from the Bjerkrem-Sogndal modelling, the acidic rocks constitute about 20% in volume compared to 55% for the anorthosites and leuconorites and 25% for the norites. The hypothesis of an origin by melting of a residue of a previous crustal anatexis [49], put forward to justify the high K/Rb ratios, is not necessary. High values can simply be derived from fractional crystallization.…”

Section: The Anorthosite-norite Series and The Acidic Rocksmentioning

confidence: 99%

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Trace elements and anorthosite genesis

Duchesne

Demaiffe

1978

Earth and Planetary Science Letters

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Terrestrial massif anorthosites have gained new interest for the understanding of the deep zones of the crust and for the reconstitution of its history in Proterozoic time. The purpose of this paper is to show how trace elements can enlighten two controversial questions in the problem of anorthosites, namely the nature of the parental magma and the process which gives rise to related acidic rocks. Data obtained on rocks and minerals coming from the Rogaland anorthositic province, South Norway, are presented together with those available in the literature. The Sr and Ba in plagioclase and their relationship with Ca and K, K and Rb in rocks and plagioclases, rare earth elements (REE) in cumulate minerals and in various liquids, 87 Sr/ 86 Sr initial ratios on rocks and minerals as well as a few data on transition elements and on 18 O/ 16 O ratios are discussed in the different sections. Quantitative modelling of the behaviour of trace elements is realized mainly by graphical methods in the Bjerkrem-Sogndal layered lopolith and in the Hidra body, both andesine-type massifs. The major conclusions are as follows:(1) The parental magma of the andesine-type massifs has a jotunitic (hypersthene-monzodioritic) composition characterized by variable K/Rb ratios (from 480 to 1700), by the absence of an Eu anomaly, by variable REE contents (from 50 to 220 for La chondrite-normalized content) and by La/Yb ratios almost constant (from 6 to 12), as well as by high Ti and Fe contents, by transition elements indicating calc-alkaline affinities and by 87 Sr/ 86 Sr initial ratios similar to those of rocks derived from the upper mantle or the deep crust.(2) A jotunitic composition appears not to be compatible with the parental magma of the labradorite-type massif anorthosite. The relationship between andesine anorthosite and labradorite anorthosite cannot be described simply in terms of fractional crystallization.(3) Fractional crystallization can explain the succession of rocks from andesine anorthosite to leuconorite, to norite and finally to acidic rocks. In some cases however, namely the Bjerkrem-Sogndal lopolith in Rogaland, contamination by supracrustal material must be invoked and seems to have superimposed its effects on those of fractional crystallization.(4) Deformation, granulation and recrystallization do not appear to fractionate both the major and trace elements of the plagioclase, except Ti which is lowered.

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Section: Potassium and Rubidiummentioning

confidence: 70%

Section: Fig 4 Plot Of K Vs Rb In Rocks and Plagioclases From The mentioning

confidence: 99%