Abstract
Quantitative analysis of REE distribution in differentiated, clearly intrusive charnockites from southwest Norway, reveal extreme variation in both absolute abundances and fractionation patterns. The pyroxene-bearing, charnockitic facies show uniform REE patterns with slight enrichment of the light-REE (about 150x chondrites) and positive, neutral or negative Eu-anomalies. Subsequent amphibole-bearing, adamellitic facies show progressive, preferential enrichment of light-REE, reaching La-values higher than 500x chondrites, and increasingly negative Euanomalies. Finally, highly differentiated biotite-granites show a marked depletion of ight-REE, ending with chondrite-normalized La/Lu ratios about 1 and Eu/ Eu* ratios less than 0.2.
Using geochemical model calculation, relating major element variations between three main stages of differentiation in terms of refractory mineral assemblages, stepwise quantitative modelling of the REE distributions reproduces the observed changes, and support an origin of the charnockite series as progressively fractionated residual liquids.
Close similarity with the REE patterns of charnockite-rapakivi suites elsewhere implies that these may constitute a series of co-magmatic rocks, derived from related more basic source magmas. The fact that the least differentiated members of the series, the charnockites, generally display remarkably uniform REE-patterns, suggests that they equilibrated with a refractory crystal fraction that produces a uniform, bulk partition coefficient. The present analysis suggests that this would be plagioclase and orthopyroxene in a ratio of about 4∶1 and including minor apatite, which in turn points towards affinity with potentially plagioclase-rich cumulates.
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References
Arth, J.G.: Behaviour of trace elements during magmatic processes — A summary of theoretical models and their applications. J. Res. U.S. Geol. Surv. 4/1, 41–47 (1976)
Bridgwater, D., Watterson, J.S.: Igneous intrusion and associated rocks of the mangerite-charnockite suite. Nature 213, 897 (1967)
deWaard, D., Wheeler, E.P.: Chemical and petrologic trends in anorthositic and associated rocks of the Nain massif, Labrador. Lithos 4, 367–380 (1971)
deWaard, D., Duchesne, J.-C., Michot, J.: Anorthosites and their environment. Cent. Soc. Géol. Belgique 1974, 323–346 (1974)
Duchesne, J.-C., Roelands, J., Demaiffe, D., Hertogen, J., Gijbels, R., de Winter, J.: Rare-earth data on monzonitic rocks related to anorthosites and their bearing on the parental magma of the anorthositic series. Earth Planet. Sci. Lett. 24, 325–335 (1974)
Duchesne, J.-C., Demaiffe, D.: Trace elements and anorthosite genesis. Earth Planet. Sci. Lett. 38, 249–272 (1978)
Emslie, R.F.: Some chemical characteristics of anorthositic suites and their significance. Can. J. Earth Sci. 10, 54–71 (1973)
Emslie, R.F.: Anorthosite massifs, Rapakivi granites, and Late Proterozoic rifting of North America. Precambrian Res. 7, 61–98 (1978)
Falkum, T., Wilson, J.R., Annis, M.P., Fregerslev, S., Zimmermann, H.D.: The intrusive granites of the Farsund area, South Norway. Nor. Geol. Tidsskr. 52, 463–465 (1972)
Falkum, T., Petersen, J.S.: A three-fold division of the ‘farsundite’ plutonic complex at Farsund, southern Norway. Nor. Geol. Tidsskr. 54, 361–366 (1974)
Falkum, T., Wilson, J.R., Petersen, J.S., Zimmermann, H.D.: The intrusive granites of the Farsund area, south Norway: Their interrelations and relations with the Precambrian metamorphic envelope. Nor. Geol. Tidsskr. 59, 125–139 (1979)
Hanson, G.N.: The application of trace elements to the petrogenesis of igneous rocks of granitic composition. Earth Planet. Sci. Lett. 38, 26–43 (1978)
Hubbard, F.H.: The Precambrian crystalline complex of southwestern Sweden. The geology and petrogenetic development of the Varberg region. Geol. Fören. Stockh. Förh. 97, 223–236 (1975)
Hubbard, F.H., Whitley, J.E.: Rapakivi granite, anorthosite and charnockitic plutonism. Nature 271, 439–440 (1978)
Hubbard, F.H., Whitley, J.E.: REE in charnockite and associated rocks, southwest Sweden. Lithos 12, 1–11 (1979)
Jensen, B.B.: Patterns of trace element partitioning. Geochim. Cosmochim. Acta 37, 2227–2242 (1973)
Joron, J.-L.: Contribution à l'analyse des éléments en traces dans les roches et les minéraux par activation neutronique, 101 pp. Thèse 3e cycle. Univ. Paris-sud, d'Orsay 1974
Koljonen, T., Rosenberg, R.J.: Rare-earth elements in granitic rocks. Lithos 7, 249–261 (1974)
Malm, O., Ormåsen, D.E.: Mangerite-charnockite intrusions in the Lofoten-Vesterålen area, north Norway. Nor. Geol. Unders. 338, 83–114 (1978)
Nagasawa, H.: Rare-earth concentrations in zircons and apatites and their host dacites and granites. Earth Planet. Sci. Lett. 9, 359–364 (1970)
Nagasawa, H.: Partitioning of Eu and Sr between co-existing plagioclase and K-feldspar. Earth Planet. Sci. Lett. 13, 139–144 (1971)
Nagasawa, H., Schnetzler, C.C.: Partitioning of rare-earth, alkali and alkaline earth elements between phenocrysts and acidic igneous magma. Geochim. Cosmochim. Acta 35, 953–968 (1971)
Ormåsen, D.E.: Petrology of the Hopen mangerite-charnockite intrusion, Lofoten, north Norway. Lithos 10, 291–310 (1977)
Pasteels, P., Demaiffe, D., Michot, J.: U-Pb and Rb-Sr geochronology of the eastern parth of the south Rogaland igneous complex, southern Norway. Lithos 12, 199–208 (1979)
Pedersen, S., Falkum, T.: Rb-Sr isochrons for the granitic plutons around Farsund, southern Norway. Chem. Geol. 15, 97–101 (1975)
Petersen, J.S.: The Precambrian basament complex near Lyngdal, South Norway (in Danish), 249 pp. Thesis, Univ. of Aarhus, 1973
Petersen, J.S.: The zoned Kleivan granite — An end member of the anorthosite suite in SW Norway. Lithos 13, 79–95 (1980)
Petersen, J.S., Pedersen, S.: Strontium-isotope study of the Kleivan granite, southern Norway. Nor. Geol. Tidsskr. 58, 97–102 (1978)
Philpotts, J.A.: Redox estimation from a calculation of Eu2+ and Eu3+ concentrations in natural phases. Earth Planet. Sci. Lett. 9, 257–268 (1970)
Philpotts, J.A., Schnetzler, C.C., Thomas, H.H.: Rare earth abundances in an anorthosite and a mangerite. Nature 212, 805–806 (1966)
Schnetzler, C.C., Philpotts, J.A.: Partition coefficients of rare-earth elements between igneous matrix material and rock-forming mineral phenocrysts. Geochim. Cosmochim. Acta 34, 331–340 (1970)
Shaw, D.M.: Trace element fractionation during anatexis. Geochim. Cosmochim. Acta 34, 237–243 (1970)
Treuil, M., Jaffrezic, H., Deschamps, N., Derre, C., Guichard, F., Joron, J.L., Pelletier, B., Nevatny, S., Courtois, C.: Analyse des Lanthanides, du Hafnium, du Scandium, du Chrome, du Manganèse, du Cobalt, du Cuivre et du Zinc dans les minéraux et les roches par Activation neutronique. J. Radioanal. Chem. 18, 55–68 (1973)
Vorma, A.: Alkali feldspars of the Wiborg rapakivi massif in southeastern Finland. Bull. Comm. Géol. Finlande 246, 72 pp. (1971)
Vorma, A.: On the petrochemistry of rapakivi granites with special reference to the Laitila massif, southwestern Finland. Bull. Geol. Surv. Finland 285, 98 pp. (1976)
Weaver, S.D., Sceal, J.S.C., Gibson, I.L.: Trace-element data relevant to the origin of trachytic and panterleritic lavas in the East African Rift System. Contrib. Mineral. Petrol. 36/3, 181–194 (1972)
Wilson, J.R.: Farsundite — a suitable term for charnockite nomenclature? Neues Jahrb. Mineral., Monatsh. 7, 324–331 (1977)
Wright, T.L., Doherty, P.C.: A linear programming and least squares computer method for solving petrological mixing problems. Geol. Soc. Am. 81, 1995–2008 (1970)
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Petersen, J.S. Rare-earth element fractionation and petrogenetic modelling in charnockitic rocks, southwest Norway. Contr. Mineral. and Petrol. 73, 161–172 (1980). https://doi.org/10.1007/BF00371391
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DOI: https://doi.org/10.1007/BF00371391