Abstract
Olivine clinopyroxenite xenoliths in a basalt flow at Krokskogen in the Oslo rift consist mainly of Al-Ti-rich clinopyroxene and alteration products after olivine (possibly also orthopyroxene). The clinopyroxene contains primary inclusions of Cr-Al-bearing titanomagnetite, pyrite and devitrified glass, and secondary fluid inclusions rich in CO2. On the basis of petrography, mineral compositions and bulk major and trace element chemistry, it is concluded that the xenoliths represent cumulates with about 5% trapped liquid, formed from a mildly alkaline basaltic magma. Microthermometrical analysis of secondary or pseudosecondary fluid inclusions give a minimum pressure of formation of 5.5 to 6 kbars, that is a depth greater than 16–17 km. The host lava has initial ɛ Nd=+4.16±0.17 and ɛ Sr=−5.50±0.26, which is believed to reflect the isotopic composition of the lithospheric mantle source region under south Norway in early Permian time. The isotopic character of the magma which gave rise to the xenoliths is preserved in clinopyroxenes which have ɛ tNd =+1.9 to +2.6 and ɛ tSr = −1.1 to −1.8. The isotopic differences between the host magma and the xenoliths reflect some degree of crustal contamination of the xenolith's parent magma.
The xenoliths of this study represent an important source of information about the large masses of dense cumulates found at depth in the crust under the Oslo rift.
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References
Andersen T (1987) Mantle and crustal components in a carbonatite complex, and the evolution of carbonatite magma: REE and isotopic evidence from the Fen complex, S.E. Norway. Chem Geol 65:147–166
Andersen T, O'Reilly SY, Griffin WE (1984) The trapped fluid phase in upper mantle xenoliths from Victoria Australia: implications for mantle metasomatism. Contrib Mineral Petrol 88:72–85
Andersen T, Griffin WL, O'Reilly SY (1987) Primary sulphide melt inclusions in mantle-derived megacrysts and pyroxenites. Lithos 20:279–294
Brunfelt AO, Steinnes E (1969) Instrumental activation analysis of silicate rocks with epithermal neutrons. Anal Chim Acta 48:13–24
Burke EAJ, Lustenhouwer WL (1987) The application of a multichannel laser Raman microprobe (Microdil-28) to the analysis of fluid inclusions. Chem Geol 61:11–17
Burrus RC (1981) Analysis of equilibria in C-O-H-S fluid inclusions. In: Hollister LS, Crawford ME (eds) Min Assoc of Canada, Short Course in Fluid Inclusions: Application to Petrology. MAC Short Course Handbook 6:34–74
Frey FA, Prinz M (1978) Ultramafic inclusions from San Carlos, Arizona: Petrological and Geochemical data bearing on their petrogenesis. Earth Planet Sci Lett 38:129–176
Fujimaki H, Tatsumoto M, Aoki K (1984) Partition coefficients of Hf, Zr and REE between phenocrysts and groundmasses. J Geophys Res 89:B662-B672
Gordon GC, Randle K, Goles GG, Corliss JB, Beeson MH, Oxley SS (1968) Instrumental activation analysis of standard rocks with high-resolution gammaray detectors. Geochim Cosmochim Acta 32:369–396
Green DH, Ringwood AE (1967) The genesis of basaltic magma. Contrib Mineral Petrol 15:103–190
Holloway J (1981) Compositions and volumes of supercritical fluids in the earth's crust. In: Hollister LS, Crawford ML (eds) Min Assoc Canada Short Course in Fluid Inclusions: Application to Petrology. MAC Short Course Handbook 6:13–38
Irving AJ (1978) A review of experimental studies of crustal/liquid trace element partitioning. Geochim Cosmochim Acta 42:743–770
Jacobsen SB, Wasserburg GJ (1978) Nd and Sr isotopic study of the Permian Oslo rift. Short Papers of the Fourth International Conf, Geochronology Cosmochronology, Isotope geology: Geol Surv Open-file Rep 78-71:194–196
Kovalenko VI, Solovova IP, Ryabchikov ID, Ionov DA, Bogatikov OA, Naumov VB (1987) Fluidized CO2-sulphide-silicate media as agents of mantle metasomatism and megacrysts formation: evidence from a large druse in a spinel-lherzolite xenolith. Phys Earth Planet Inter 45:280–293
Kushiro I (1960) Si-Al relation in clinopyroxene from igneous rocks. Am J Sci 258:548–554
Larsen BT (1978) Krokskogen lava area. Nor Geol Unders 337:143–162
Mearns EW (1986) Sm-Nd ages for Norwegian garnet peridotites. Lithos 19:269–278
Neumann E-R (1980) Petrogenesis of the Oslo Region larvikites and associated rocks. J Petrol 21:498–531
Neumann E-R, Schilling JG (1984) Petrology of basalts from the Mohns-Knipovich Ridge; the Norwegian — Greenland Sea. Contrib Mineral Petrol 85:209–223
Neumann E-R, Larsen BT, Sundvoll B (1985) Compositional variations among gabbroic intrusions in the Oslo rift. Lithos 18:35–59
Neumann E-R, Pallesen S, Andresen P (1986) Mass estimates of cumulates and residues after anatexis in the Oslo graben. J Geophys Res 91:11629–11640
Neumann E-R, Tilton GR, Tuen E (1988) Sr, Nd and Pb isotope geochemistry of the Oslo rift igenous province, southern Norway. Geochim Cosmochim Acta 52 (in press)
Newitt DM, Pai MV, Kuloor NR, Hugill JAW (1956) Carbon dioxide. In: Din F (ed) Thermodynamic functions of gasses. Butterworthes Sci Publ London, Vol 1, pp 102–134
Nisbet EG, Pearce JA (1977) Clinopyroxene composition in mafic lavas from different tectonic settings. Contrib Mineral Petrol 63:149–160
Ramberg IB (1976) Gravity interpretation of the Oslo Graben and associated igneous rocks. Nor Geol Unders 325:1–194
Ramberg IB, Larsen BT (1978) Tectonomagmatic evolution. Nor Geol Unders 337:55–73
Rasmussen E, Neumann E-R, Andersen T, Sundvoll B, Fjerdingstad V, Stabel A (1988) Petrogenetic processes associated with intermediate and silicic magmatism in the Oslo rift, southeast Norway. Min Mag 52 (in press)
Roedder E (1984) Fluid inclusions. Reviews in Mineralogy. Mineral Soc Am 12:644 pp
Schou-Jensen E, Neumann E-R (1988) Volcanic rocks on Jeløya, central Oslofjord: The mafic lavas. Nor Geol Tidsskr (in press)
Segalstad TV (1979) Petrology of the Skien basaltic rocks, southwestern Oslo Region, Norway. Lithos 12:221–239
Sundvoll B (1978a) Isotope- and trace-element chemistry, geochronology. Norg Geol Unders 337:35–40
Sundvoll B (1978b) Rb/Sr-relationship in the Oslo igneous rocks. In: Neumann E-R, Ramberg IB (eds) Petrology and Geochemistry of Continental Rifts. D Reidel, Dordrecht, pp 181–184
Thompson RN (1974) Some high-pressure pyroxenes. Mineral Mag 39:768–787
Touret J (1982) An empirical phase diagram for a part of the N2-CO2 system at low temperatures. Chem Geol 37:49–58
Weigand PW (1975) Geochemistry of the Oslo basaltic rocks. Skr Nor Vidensk Akad Oslo I. Mat-Natur Kl Ny Serie No 34:38 p
Wessel P, Husebye ES (1987) The Oslo Graben gravity high and taphrogenesis. Tectonophysics 142:15–26
Wilshire HG, Shervais JW (1975) Al-augite and Cr-diopside ultramafic xenoliths in basaltic rocks from western United States. Phys Chem Earth 9:257–272
Woerner G, Beusen JM, Duchateau N, Gijbels R, Schmincke H-U (1983) Trace element abundances and mineral/melt partition coefficients in phonolites from the Laacher See Volcano (Germany). Contr Mineral Petrol 84:152–173
Wood DA (1979) A variably veined suboceanic upper mantle — genetic significance for mid-ocean ridge basalts from geochemical evidence. Geology 7:499–503
Øverli PE (1985) En stratigrafisk og petrologisk undersøkelse av Horten-basalten, B1-nivået, det Sørlige Oslofelt. Cand scient thesis University of Oslo, 108 pp
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Neumann, E.R., Andersen, T. & Mearns, E.W. Olivine clinopyroxenite xenoliths in the Oslo Rift, SE Norway. Contrib Mineral Petrol 98, 184–193 (1988). https://doi.org/10.1007/BF00402111
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DOI: https://doi.org/10.1007/BF00402111