caa a22 4500 465791360 CHVBK 20180323112025.0 cr unu---uuuuu 170327e19900601xx s 000 0 eng 10.1007/BF00320965 doi (NATIONALLICENCE)springer-10.1007/BF00320965 Ti-rich komatiites from northern Norway [Elektronische Daten] [Sarah-Jane Barnes, Morten Often] Komatiites of the Karasjok Greenstone Belt, northern Norway, show two unusual features: they have certain compositional differences compared with other komatiites, and they are largely volcaniclastic in origin. Their geological setting suggests that the komatiites were crupted into shallow water, thus permitting phreatomagmatic eruption, in a small ocean basin that opened in the Baltic Shield. The major oxides (except for TiO2), the trace elements Y, Sc, V, heavy rare earth elements (HREE), Cr, Co, Ni and the platinum group elements (PGE) cover similar ranges to those observed in other komatiites, but TiO2, Sm, Zr and Hf (Ti-associated elements, TAE) are enriched compared with abundances commonly reported for komatiites. Thus, the Karasjok komatiites have interelement ratios 2 to 3 times greater than chondritic between the TAE and the HREE, PGE, Sc, V, Y, Al (HRE-associated elements, HAE). The light rare earth elements (LREE), Ta and Th are enriched in some samples relative to Ti, Sm, Zr, and Hf, but are depleted in others. One group of rocks that is similar to the Karasjok komatiites both in terms of geological setting and geochemistry is the Baffin Bay picrites. The reason for the high concentrations of TAE in the Karasjok komatiites could be that they formed at lower degrees of partial melting than most komatiites. The greater-than-chondritic TAE/HAE ratios indicate that garnet was a residual phase during their formation, requiring that the melt formed at a pressure greater than 40 kb. A model involving decompression melting of a mantle plume rising in a rifting environment, can explain the main features of the Karasjok komatiites. Springer-Verlag, 1990 Barnes Sarah-Jane Sciences de la Terre, Université du Québéc, G7H 2B1, Chicoutimi, Canada aut Often Morten Norges geologiske Undersøkelse, Postboks 3006, N-7002, Trondheim, Norway aut Contributions to Mineralogy and Petrology Springer-Verlag 105/1(1990-06-01), 42-54 0010-7999 105:1<42 1990 105 410 https://doi.org/10.1007/BF00320965 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00320965 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Barnes Sarah-Jane Sciences de la Terre, Université du Québéc, G7H 2B1, Chicoutimi, Canada aut NATIONALLICENCE 700 1- Often Morten Norges geologiske Undersøkelse, Postboks 3006, N-7002, Trondheim, Norway aut NATIONALLICENCE 773 0- Contributions to Mineralogy and Petrology Springer-Verlag 105/1(1990-06-01), 42-54 0010-7999 105:1<42 1990 105 410 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer