Else Ragnhild Neumann

• Hyung, Eugenia; Sedaghatpour, Fatemeh; Larsen, Bjørn Tore; Neumann, Else Ragnhild; Eriksen, Zachary T. & Petaev, Michail I. [Vis alle 7 forfattere av denne artikkelen] (2023). A peridotite source for strongly alkalic ultrabasic HIMU lavas of the Oslo Rift, Norway. Chemical Geology. ISSN 0009-2541. 622. doi: 10.1016/j.chemgeo.2023.121377.
• Callegaro, Sara; Svensen, Henrik Hovland; Neumann, Else Ragnhild; Polozov, Alexander G.; Jerram, Dougal Alexander & Deegan, Frances M. [Vis alle 10 forfattere av denne artikkelen] (2021). Geochemistry of deep Tunguska Basin sills, Siberian Traps: correlations and potential implications for the end-Permian environmental crisis. Contributions to Mineralogy and Petrology. ISSN 0010-7999. 176. doi: 10.1007/s00410-021-01807-3. Fulltekst i vitenarkiv
• Neumann, Else Ragnhild; Marsh, J.S.; Galerne, Christophe Yann; Polteau, Stephane; Svensen, Henrik & Planke, Sverre (2020). Co-existing low-Ti and high-Ti dolerites in two large dykes in the Gap Dyke swarm, southeastern Karoo Basin (South Africa). South African Journal of Geology. ISSN 1012-0750. 123(1), s. 19–34. doi: 10.25131/sajg.123.0003.
• Neumann, Else Ragnhild (2019). Origin and evolution of the early magmatism in the Oslo Rift (Southeast Norway): Evidence from multiple generations of clinopyroxene. Lithos. ISSN 0024-4937. 340-341, s. 139–151. doi: 10.1016/j.lithos.2019.04.025. Fulltekst i vitenarkiv
• Neumann, Else Ragnhild; Svensen, Henrik; Polozov, Alexander & Hammer, Øyvind (2017). Formation of Si-Al-Mg-Ca-rich zoned magnetite in an end-Permian phreatomagmatic pipe in the Tunguska Basin, East Siberia. Mineralium Deposita. ISSN 0026-4598. Published ahead of print. doi: 10.1007/s00126-017-0717-9.
• Svensen, Henrik; Planke, Sverre; Neumann, Else Ragnhild; Aarnes, Ingrid; Marsh, J.S. & Polteau, S. [Vis alle 8 forfattere av denne artikkelen] (2015). Sub-volcanic intrusions and the link to global climatic and environmental changes. Advances in Volcanology. ISSN 2364-3277. doi: 10.1007/11157_2015_10.
• Neumann, Else Ragnhild; Abu El-Rus, Mohamed Ali; Tiepolo, Massimo; Ottolini, Luisa; Vannucci, Riccardo & Whitehouse, Martin (2015). Serpentinization and deserpentinization reactions in the upper mantle beneath Fuerteventura revealed by fibrous orthopyroxene and mottled olivine. Journal of Petrology. ISSN 0022-3530. 56(1), s. 3–31. doi: 10.1093/petrology/egu069.
• Neumann, Else Ragnhild; Svensen, Henrik; Tegner, Christian Maughan; Planke, Sverre; Thirlwall, Matthew & Kym E., Jarvis (2013). Sill and lava geochemistry of the mid-Norway and NE Greenland conjugate margins. Geochemistry Geophysics Geosystems. ISSN 1525-2027. 14(9), s. 3666–3690. doi: 10.1002/ggge.20224.
• Neumann, Else Ragnhild; Svensen, Henrik; Galerne, Christophe Yann & Planke, Sverre (2011). Multistage Evolution of Dolerites in the Karoo Large Igneous Province, Central South Africa. Journal of Petrology. ISSN 0022-3530. 52(5), s. 959–984. doi: 10.1093/petrology/egr011.
• Galerne, Christophe Yann; Galland, Olivier; Neumann, Else Ragnhild & Planke, Sverre (2011). 3D relationships between sills and their feeders: evidence from the Golden Valley Sill Complex (Karoo Basin) and experimental modelling. Journal of Volcanology and Geothermal Research. ISSN 0377-0273. 202(3-4), s. 189–199. doi: 10.1016/j.jvolgeores.2011.02.006.
• Corfu, Fernando; Svensen, Henrik; Neumann, Else Ragnhild; Nakrem, Hans Arne & Planke, Sverre (2010). U-Pb and geochemical evidence for a Cryogenian magmatic arc in central Novaya Zemlya, Arctic Russia. Terra Nova. ISSN 0954-4879. 22(2), s. 116–124. doi: 10.1111/j.1365-3121.2010.00924.x.
• Galerne, Christophe Yann; Neumann, Else Ragnhild; Aarnes, Ingrid & Planke, Sverre (2010). Magmatic differentiation processes in saucer-shaped sills: Evidence from the Golden Valley Sill in the Karoo Basin, South Africa. Geosphere. ISSN 1553-040X. 6(3), s. 163–188. doi: 10.1130/GES00500.1.
• Neumann, Else Ragnhild & Simon, Nina Simone C (2009). Ultra-refractory mantle xenoliths from ocean islands: how do they compare to peridotites retrieved from oceanic sub-arc mantle? Lithos. ISSN 0024-4937. 107(1-2), s. 1–16. doi: 10.1016/j.lithos.2008.06.003. Vis sammendrag

  Ultra-refractory harzburgitic mantle is abundantly sampled as xenoliths in ocean island magmas. Its occurrence has potentially important implications for both geochemistry and geodynamics, and we therefore need to understand how these unusually refractory compositions form. In this contribution, we compare ultra-refractory spinel harzburgite xenoliths from ocean islands with peridotites collected along active arcs, based on available major element data on rocks and their minerals. The compositions of arc peridotites vary from ultra-refractory to fertile and estimated equilibration temperatures range from about 800 to >1300 ºC. These variations are not directly related to setting (ocean-ocean or ocean-continent collision; forearc, arc or back-arc). In general, however, fertile compositions seem to be more common in continental arcs and to be accompanied by higher equilibration temperatures. Ultra-refractory peridotites appear to be most common along oceanic forearcs and give generally lower temperatures in the range 950-1050 ºC. Ultra-refractory harzburgites sampled in subduction settings are chemically very similar to the ultra-refractory peridotites found as xenoliths in ocean islands. Both rock types compare quite well with the residues from experiments on the formation of primitive arc magmas. The formation of such magmas and their ultra-refractory harzburgite residues requires melting beyond the stability of clinopyroxene. Such high degrees of partial melting are probably achieved in two stages. The first stage is likely to take place as decompression melting along mid-ocean ridges or in back-arc spreading centers, whereas the second stage seems to require fluid-fluxed melting in the mantle wedge. Large degrees of melting may also be achieved in other types of settings if temperatures are sufficiently high. However, the common occurrence of ultra-refractory harzburgites together with melts generated from a strongly depleted precursor in active arcs is an argument in support of a subduction related origin of ultra-refractory harzburgites both in arc settings and in ocean islands. This implies that ultra-refractory arc material is common and may be recirculated by mantle convection. Because of their low density relative to “normal”, more fertile asthenospheric material, these ultra-refractory residues may rise as diapirs and intrude shallower parts of the asthenosphere, where they can accrete to younger oceanic plate.

• Galland, Olivier; Planke, Sverre; Neumann, Else Ragnhild & Malthe-Sørenssen, Anders (2009). Experimental modelling of shallow magma emplacement: Application to saucer-shaped intrusions. Earth and Planetary Science Letters. ISSN 0012-821X. 277(3-4), s. 373–383. doi: 10.1016/j.epsl.2008.11.003.
• Polteau, Stephane; Ferré, E.C.; Planke, Sverre; Neumann, Else Ragnhild & Chevallier, L. (2008). How are saucer-shaped sills emplaced? Constraints from the Golden Valley Sill, South Africa. Journal of Geophysical Research (JGR): Solid Earth. ISSN 2169-9313. 113(B12). doi: 10.1029/2008JB005620.
• Simon, Nina Simone C; Neumann, Else Ragnhild; Bonadiman, C.; Coltorti, M.; Delpech, G. & Gregoire, M. [Vis alle 7 forfattere av denne artikkelen] (2008). Ultra-refractory domains in the oceanic mantle lithosphere sampled as mantle xenoliths at ocean islands. Journal of Petrology. ISSN 0022-3530. 49(6), s. 1223–1251. doi: 10.1093/petrology/egn023. Vis sammendrag

  Many peridotite xenoliths sampled at ocean islands appear to have strongly refractory major element and modal compositions. In order to better constrain the chemistry, abundance and origin of these ultra-refractory rocks we compiled a large number of data for xenoliths from 9 different groups of ocean islands. The xenoliths were filtered petrographically for signs of melt infiltration and modal metasomatism and the samples affected by these processes were excluded. Most ocean islands are dominated by ultra-refractory harzburgites. Exceptions are Hawaii and Tahiti peridotites which are more fertile and contain primary clinopyroxene, and Cape Verde, which contains both ultra-refractory and more fertile xenoliths. Ultra-refractory harzburgites are characterized by the absence of primary clinopyroxene, low whole rock Al2O3, CaO, FeO/MgO and HREE concentrations, low Al2O3 in orthopyroxene (generally <3 wt%), high Cr# in spinel (0.3-0.8) and high forsterite contents in olivine (averages >91.5). They are therefore on average significantly more refractory than peridotites dredged and drilled from mid-ocean ridges and fracture zones. Moreover, their compositions resemble those of oceanic fore-arc peridotites. The formation of ultra-refractory ocean island harzburgites requires potential temperatures above those normally observed at modern mid-ocean ridges, and/or fluid fluxed conditions. Some ultra-refractory ocean island harzburgites give high Os model ages (up to 3300 Ma), showing that their formation significantly pre-dates the oceanic crust in the area. A genetic relationship with the host plume is considered unlikely based on textural observations, equilibration temperatures and pressures, inferred physical properties, and long-term depleted Os and Sr isotope ratios of some of the harzburgites. Although we do not exclude the possibility that some ultra-refractory ocean island harzburgites have formed at mid-ocean ridges, we favor a model in which they formed in a process spatially and temporally unrelated to the formation of the oceanic plate and the host plume. They most likely represent residues of ancient large degree melting events, possibly during periods of enhanced arc magmatism and crust formation. Due to their whole rock compositions, ultra-refractory harzburgites have low densities and very high viscosities, and will tend to accumulate at the top of the convecting mantle. They may be preserved as fragments in the convecting mantle over long periods of time and be preferentially incorporated into newly formed lithosphere.

• Ferrando, S; Frezzotti, M.L.; Neumann, Else Ragnhild; DeAstis, P.; Dereje, A. & Gezahegn, Y. [Vis alle 7 forfattere av denne artikkelen] (2008). Composition and geothermal structure of the lithosphere beneath the Ethiopian Plateau: evidence from mantle xenoliths in basanites, Injibara, Lake Tana Province. Mineralogy and Petrology. ISSN 0930-0708. 93, s. 47–78. doi: 10.1007/s00710-007-0219-z.
• Ferrando, S; Frezzotti, ML; Neumann, Else Ragnhild; De Astis, G; Peccerillo, A & Dereje, A [Vis alle 8 forfattere av denne artikkelen] (2008). Composition and thermal structure of the lithosphere beneath the Ethiopian plateau: evidence from mantle xenoliths in basanites, Injibara, Lake Tana Province. Mineralogy and Petrology. ISSN 0930-0708. 93. doi: 10.1007/s00710-007-0219-z.
• Aarnes, Ingrid; Podladtchikov, Iouri & Neumann, Else Ragnhild (2008). Post-emplacement melt flow induced by thermal stresses: Implications for differentiation in sills. Earth and Planetary Science Letters. ISSN 0012-821X. 276, s. 152–166. doi: 10.1016/j.epsl.2008.09.016.
• Galerne, Christophe Yann; Neumann, Else Ragnhild & Planke, Sverre (2008). Emplacement mechanisms of sill complexes: Information from the geochemical architecture of the Golden Valley Sill Complex, South Africa. Journal of Volcanology and Geothermal Research. ISSN 0377-0273. 177(2), s. 425–440. doi: 10.1016/j.jvolgeores.2008.06.004.
• Abu El-Rus, M.; Neumann, Else Ragnhild & Peters, V. (2006). Serpentinization and dehydration in the upper mantle beneath Fuerteventura (eastern Canary Islands): Evidence from mantle xenoliths. Lithos. ISSN 0024-4937. 89, s. 24–46. Vis sammendrag

  Mantle xenoliths from Fuerteventura (spinel-bearing harzburgites, dunites, and rare lherzolites and wehrlites) in the easternmost part of the Canary Islands chain, are highly deformed and show a wide range in textures from protogranular and porphyroclastic with olivine and orthopyroxene porphyroclasts, to rocks with “fibrous textures” (no orthopyroxene porphyroclasts, large, porous clusters of fibrous orthopyroxene, olivine porphyroclasts criss-crossed by stringy trails of fibrous orthopyroxene and fluid inclusions). The whole group of xenoliths covers a wider compositional range (e.g. Fo86.6-92.7, 0.18-0.44 wt% NiO, and up to 0.25 wt% CaO in olivine; <0.01-2.5 wt% TiO2 and 0.7-5.5 wt% Al2O3 in clinopyroxenes in harzburgites and lherzolites, and relatively Ti-Fe3+-rich spinels in some rocks). Rocks with orthopyroxene porphyroclasts cover a restricted compositional range typical of depleted oceanic peridotites (e.g. Fo90.7-91.4, 0.36-0.41 wt% NiO, and <0.10 wt% CaO in cores of olivine porphyroclasts; 0.12 w% TiO2, 1.0-1.8 wt% Al2O3 in clinopyroxene; low Ti and Fe3+, and high Cr in spinel). These rocks are interpreted as pieces of the highly refractory oceanic lithosphere that accreted to the oldest oceanic crust in this part of the Atlantic Ocean, later modified by different processes. This mantle was highly depleted due to melt extraction, and had a composition similar to that of the most refractory peridotites collected along the Mid-Atlantic Ridge. Also the oceanic mantle beneath the other Canary Islands appears to have had similar composition before the onset of the Canary Islands magmatism. The “fibrous textures” in many xenoliths from Fuerteventura are interpreted as the results of partial serpentinization, later followed by heating and dehydration during the formation of Fuerteventura. The Fuerteventura magmatism has also caused metasomatism and reactions in the lithospheric mantle beneath Fuerteventura, leading to decreased Si and increased Fe+Ca+Na±Ti.

• Neumann, Else Ragnhild; Vannucci, R & Tiepolo, M (2005). N-MORB crust beneath Fuerteventura in the easternmost part of the Canary Islands: evidence from gabbroic xenolits. Contributions to Mineralogy and Petrology. ISSN 0010-7999. 150, s. 156–173. Vis sammendrag

  We report on gabbro xenoliths collected in northern Fuerteventura, the Canary Island located closest to the coast of Africa. The xenoliths are very fresh and consist of Ti-Al-poor clinopyroxene + plagioclase (An87-67) + olivine (Fo72-86) ± orthopyroxene. Clinopyroxene and orthopyroxene are markedly depleted in light rare earth elements (LREE) relative to heavy REE (HREE). Estimates imply that the clinopyroxenes formed from highly refractory N-MORB-type melts. Whole-rock Primordial-Mantle-normalized trace element patterns range from mildly S-shaped patterns (mildly depleted in Pr-Sm relative to both the strongly incompatible elements Rb-La and the HREE), to enriched patterns. Estimates show that the trace element compositions of the rocks and their minerals are compatible with formation as N-MORB gabbro cumulates which have been infiltrated to different degrees (&#61603;1% to >>5%) by enriched alkali basaltic melts. The enriched material is mainly concentrated along grain boundaries and cracks through mineral grains, suggesting that the infiltration is relatively recent, and is thus associated with the Canary Islands magmatism. Our data contradict the hypothesis that a mantle plume was present in this area during the opening of the Atlantic Ocean. We have also found no evidence of continental material that might reflect attenuated continental crust in the area. Gabbro xenoliths with REE and trace element compositions similar to those exhibited by the Fuerteventura gabbros are also found among gabbro xenoliths from the islands of La Palma (western Canary Islands) and Lanzarote. The compositions of the most depleted samples from these islands are closely similar, implying that there was no significant change in chemistry during the early stages of formation of the Atlantic oceanic crust in this area. Strongly depleted gabbros similar to those collected in Fuerteventura have also been retrieved in the MARK area along the central Mid-Atlantic Ridge. The presence of N-MORB oceanic crust beneath Fuerteventura implies that the continent-ocean transition in the Canary Islands area must be relatively sharp, in contrast to the situation both further north along the coast of Morocco, and along the Iberia peninsula.

• Neumann, Else Ragnhild; Wilson, M.; Spencer, E.A.; Obst, K.; Timmerman, M.J. & Kirstein, L. (2004). Permo-Carboniferous rifting and magmatism in southern Scandinavia, the North Sea and northern Germany: A review. Geological Society Special Publication. ISSN 0305-8719. 223, s. 11–40.
• Wilson, M.; Neumann, Else Ragnhild; Davies, G.R.; Timmerman, M.J.; Heeremans, Michael & Larsen, B.T. (2004). Permo-Carboniferous magmatism and rifting in Europe: introduction. Geological Society Special Publication. ISSN 0305-8719. 223, s. 1–10.
• Neumann, Else Ragnhild; Griffin, W.L.; Normann, J.P. & O'Reilly, S.Y. (2004). The evolution of the upper mantle beneath the Canary Islands: Information from trace elements and Sr isotope ratios in minerals in mantle xenoliths. Journal of Petrology. ISSN 0022-3530. 45, s. 2573–2612.
• Frezzotti, Maria-Luce; Andersen, Tom; Neumann, Else Ragnhild & Simonsen, Siri Lene (2002). Carbonatit melt-CO2 fluid inclusions in mantle xenoliths from Tenerife, Canary Islands: a story of trapping, immiscibility and fluid-rock interaction in the upper mantle. Lithos. ISSN 0024-4937. 64, s. 77–96. Vis sammendrag

  Three types of fluid inclusions have been identified in olivine porphyroclasts in spinel harzburgite and lherzolite xenoliths from Tenerife: pure CO2 (Type A); carbonate-rich CO2-SO2 mixtures (Type B); and polyphase inclusions dominated by silicate glass fluid sp silicate sulfide carbonate (Type C). Type A inclusions commonly exhibit a "coating" (a few m thick) consisting of an aggregate of a platy, hydrous Si-Mg-Fe phase, most likely talc, together with very small amounts of halite, dolomite and other phases. Larger crystals (e.g. (Na,K)Cl, dolomite, spinel, sulfide and phlogopite) may be found on either side of the "coating", towards the wall of the host mineral or towards the inclusion center. These different fluids formed through immiscible separations and fluid - wall-rock reactions from a common, volatile-rich, siliceous, alkaline carbonatite melt infiltrating the upper mantle beneath Tenerife. First the original siliceous carbonatite melt separated into a mixed CO2-H2O-NaCl fluid and a silicate/silicocarbonatite melt (preserved in Type A inclusions). Reaction of the carbonaceous silicate melt with wall-rock minerals gave rise to large poikilitic orthopyroxene and clinopyroxene grains, and smaller neoblasts. During the metasomatic processes consumption of the silicate part of the melt produced carbonate-enriched Type B CO2-SO2 fluids which were trapped in exsolved orthopyroxene porphyroclasts. At later stages, the interstitial silicate/silicocarbonatite fluid was trapped as Type C inclusions. At some temperature above 650 C the mixed CO2-H2O-NaCl fluid inside Type A inclusions separated into CO2-rich fluid and H2O-NaCl brine. At T<650 C the residual silicate melt reacted with the host olivine, forming a reaction rim or "coating" along the inclusions walls consisting of talc (or possibly serpentine) together with minute crystals of NaCl, KCl, carbonates and sulfides, leaving a residual CO2 fluid. The homogenization of +2 to +25 C temperatures obtained from Type A CO2 inclusions reflect the densities of the residual CO2 after reactions with the olivine host, and are unrelated to the initial fluid density or the external pressure at the time of trapping. The latter are restricted by estimated crystallization temperatures of 1000-1200 C, and the spinel lherzolite phase assemblage of the xenolith, that is 0.7-1.7 GPa.

• Frezzotti, Maria-Luce; Touret, Jacques L. R. & Neumann, Else Ragnhild (2002). Ephemeral carbonate melts in the upper mantle: carbonate-silicate immiscibility in microveins and inlusions within spinel peridotite xenoliths, La Gomera, Canary Islands. European journal of mineralogy. ISSN 0935-1221. 14, s. 891–904. Vis sammendrag

  Carbonate droplets containing mafic silicate glass+- CO2 occur within mineral inclusions and late microveins in spinel-bearing ultramafic xenoliths (dunite, dunite-wehrlite and pyroxenite) from La Gomera, Canary Islands. Primary carbonates are Mg-calcite (X[Ca] 0.89-0.93) and dolomite X[Ca] 0.46-0.54), with low Na2O (<0.1 w.t%) and variable MnO (0.2-8 wt.%. The mafic glass has high MgO (24-35 wt.%), FeO (1-18 wt.%) and SiO2 (40-55 wt.%), with low Al2O3, TiO2, CaO and alkalis. Mafic glass contains high amounts (> 10 et.%) of volatiles (i.e. H2O). The composite carbonatite droplets represent a quenched liquid, resulting from unmixing within the inclusions of a carbonatite-rich melt into separate carbonatite- and silicate-rich phases. Modeling of initial bulk compositions suggests dolomitic melts, with with high silica (ca. 10 wt.%)and H2O, but low alkali contents. If not protected within inclusions, these melts are ephemeral, unstable in the P-T field of spinel peridotite (10-18 kbar; 900-1000oC). Mafic glass remnants in microveins represent a residual degassed hydrous mafic silicate fraction after decarbonation.

• Neumann, Else Ragnhild; Wulff-Pedersen, Erik; Pearson, Norman J. & Spencer, Elizabeth Ann (2002). Mantle xenoliths from Tenerife (Canary Islands): evidence for reactions mantle peridotite/silicic-carbonatite melts inducing Ca-metasomatism. Journal of Petrology. ISSN 0022-3530. 43, s. 825–857. Vis sammendrag

  Mantle xenoliths from Tenerife show evidence of metasomatism and recrystallization overprinting the effects of extensive partial melting. The evidence includes: recrystallization of exsolved orthopyroxene porphyroclasts highly depleted in incompatible trace elements into incompatible-trace-element-enriched, poikilitic orthopyroxene with no visible exsolution lamellae; formation of olivine and REE-Cr-rich, strongly Zr-Hf-Ti-depleted clinopyroxene at the expense of orthopyroxene; the presence of phlogopite; whole-rock CaO/Al2O3 >>1 (Ca-metasomatism) in recrystallized rocks; and enrichment in incompatible elements in recrystallized rocks, relative to rocks showing little evidence of recrystallization. The "higher-than-normal" degree of partial melting which preceeded the metasomatism most likely results from plume activity during the opening of the Central Atlantic ocean. Sr-Nd isotopic compositions are closely similar to those of Tenerife basalts, indicating resetting from the expected original MORB composition by the metasomatizing fluids. Metasomatism was caused by silicic carbonatite melts, and involved open-system-processes, such as trapping of elements compatible with newly formed acceptor minerals, leaving residual fluids moving to shallower levels. The compositions of the metasomatizing fluids changed with time, probably due to changing compositions of the melts produced in the Canary Islands plume. Spinel dunites and wehrlites represent rocks where all, or most, orthopyroxene has been consumed through the metasomatic reactions.

• Neumann, Else Ragnhild; Dunworth, Elizabeth Ann; Sundvoll, Bjørn A. & Tollefsrud, Jan-Inge (2002). B1 basaltic lavas in Vestfold-Jeløya area, central Oslo rift: Derivation from initial melts formed by progressive partial melting of an enriched, phlogopite-bearing, sub-lithospheric source. Lithos. ISSN 0024-4937. 61, s. 21–53. Vis sammendrag

  The earliest (B1) lavas in Vestfold and Jeløya, in the central part of the Permo-Carboniferous Oslo rift have been divided into four main groups: high-Ti (HT) basalts (TiO2>4.2 wt %), low-Ti (LT) basaltic rocks (TiO2<3.7 wt%), phonotephrites and ignimbrites. They are all highly enriched in strongly incompatible elements, and have high La/Yb ratios. Initial Nd and Sr ratios of whole-rock samples and clinopyroxene separates (assumed age = 295 Ma) are +6.0 to -1.6 and -17 to +57, respectively. Their trace element and isotopic compositions imply that during ascent the magmas were subjected to varying degrees of fractional crystallization, mixing between evolved and mafic magmas, and crustal contamination in the upper crust. Crustal contamination was most likely caused by rocks similar to the metasediments now exposed in the Bamble sector, south of the Oslo rift. The preserved lava sequences represent interfingering of lavas from at least three eruption centers. After extrusion the lavas suffered post-magmatic alteration that led to mobilization of Rb, U and K, and increased 87Sr/86Sr ratios. Interpretation of magmatic signatures inferred to have been preserved through contamination and alteration, allow us to make the following conclusions concerning the mantle sources of the Vestfold and Jeløya B1 basalts. The formation of the HT-basalts involves highly Ti-P-rich, garnet-bearing mantle source rocks, e.g. clinopyroxenites, wehrlites, websterites and amphibolites. The HT and LT basalts may have originated by progressive partial melting of a veined, enriched, garnet-phlogopite-bearing peridotite at the base of the lithosphere. Progressive melting of this complex source initially produced magnesian lavas with high REE and HFSE contents, followed by less enriched, more voluminous lavas. The early basalts were derived from an isotopically-depleted source similar to the PREMA source. Contribution of older lithospheric material to the later basalts produced more enriched Sr-Nd isotopic signatures. As some of the most primitive basalts found within the European Permo-Carboniferous rifting event, these lavas are key to understanding the nature of the sub-lithospheric mantle beneath Europe at this time.

• Andersen, Tom & Neumann, Else Ragnhild (2001). Fluid inclusions in mantle xenoliths. Lithos. ISSN 0024-4937. 55, s. 301–320.
• Dunworth, Elizabeth Ann; Neumann, Else Ragnhild & Rosenbaum, J. M. (2001). The Skien lavas, Oslo Rift; petrological disequilibrium and geochemical evolution. Contributions to Mineralogy and Petrology. ISSN 0010-7999. 140, s. 701–719.
• Simonsen, Siri Lene; Neumann, Else Ragnhild & Seim, Kristin (2000). Sr-Nd-Pb isotope and trace element geochemistry of basaltic lavas in Tenerife: evidence for regional variations. Journal of Volcanology and Geothermal Research. ISSN 0377-0273. 103, s. 299–312.
• Neumann, Else Ragnhild; Sørensen, Vivian; Simonsen, Siri Lene & Johnsen, Kari (2000). Gabbroic xenoliths from La Palma, Tenerife and Lanzarote, Canary Islands: Evidence for reactions between Canary Islands melts and old oceanic crust. Journal of Volcanology and Geothermal Research. ISSN 0377-0273. 103, s. 313–342.
• Wulff-Pedersen, Erik; Neumann, Else Ragnhild; Burke, Ernst A.J.; Vannucci, R.; Bottazzi, P. & Ottolini, L. (2000). Origin and structural character of hauyne(ss) in spinel dunite xenoliths from La Palma, Canary Islands. American Mineralogist. ISSN 0003-004X. 85, s. 1397–1405.
• Wulff-Pedersen, Erik; Neumann, Else Ragnhild; Vannucci, R.; Bottazzi, P. & Ottolini, L. (1999). Silicic melts produced by reaction between peridotite and infiltrating basaltic melts: ion probe data on glasses and minerals in veined xenoliths from La Palma, Canary Islands. Contributions to Mineralogy and Petrology. ISSN 0010-7999. 137, s. 59–82.
• Neumann, Else Ragnhild; Wulff-Pedersen, Erik; Simonsen, Siri Lene; Pearson, Norman J.; Mitjavila, J. & Marti, J. (1999). Evidence for fractional crystallization of periodically refilled magma chambers in Tenerife, Canary Islands. Journal of Petrology. ISSN 0022-3530. 40, s. 1089–1123.
• Neumann, Else Ragnhild; Marti, J.; Mitjavila, J. & Wulff-Pedersen, Erik (1999). Mafic xenoliths from Roca Negra volcano, Catalan Volcanic Zone, Valencia Trough, NE Spain. Mineralogy and Petrology. ISSN 0930-0708. 65, s. 113–139.
• Vannucci, R.; Bottazzi, P.; Wulff-Pedersen, Erik & Neumann, Else Ragnhild (1998). Naturally determined REE, Y, Sr, Zr and Ti partition coefficcients between clinopyroxene and silicate melts under upper mantle conditions. Earth and Planetary Science Letters. ISSN 0012-821X. s. 39–51.
• Neumann, Else Ragnhild & Wulff-Pedersen, Erik (1997). The origin of highly silicic glass in mantle xenoliths from the Canary Islands. Journal of Petrology. ISSN 0022-3530. 38, s. 1513–1539. Vis sammendrag

  Spinel harzburgite, lherzolite, dunite and wehrlite mantle xenoliths from the Canary Islands (La Palma, Hierro, Tenerife and Lanzarote) contain a spectrum of silicate glasses as inclusions in minerals, along grain boundaries, and in interstitial glass pockets. These glasses show a range in composition from basaltic (ca. 44 weight percent SiO2), to highly silicic, TiO2-FeO-MgO-CaO-P2O5-poor types (up to 71 weight percent SiO2). Glasses in spinel harzburgites and lherzolites are generally silica-oversaturated, whereas those in spinel dunites and wehrlites have somewhat lower SiO2-contents and are generally silica-undersaturated. Glasses in xenoliths from La Palma and Tenerife are rich in K2O compared to those from Hierro and Lanzarote. Daughter minerals coexisting with highly silicic glass in polyphase inclusions are similar in composition to the main phases in the host xenoliths (Fo>90, Cr-diopside, chromite), whereas those in less silicic glasses are richer in Al2O3, TiO2 and FeO, and poorer in MgO. The systematic relations found to exist between glass composition, mineralogy of the host xenolith and locality (island) cannot reflect random variations in the geochemistry of "exotic" melts infiltrating the mantle lithosphere, but instead suggest a cogenetic relationship between the melts and their mantle host xenoliths. The silicic glasses are interpreted as the products of reactions at 8-12 kbar between infiltrating alkali basaltic magmas and peridotitic wall-rocks which, in orthopyroxene-bearing rock-types, involves formation of silicic melt + olivine at the expense of orthopyroxene. In xenoliths from La Palma and Tenerife where interstitial phlogopite is commonly present, phlogopite has been partly or totally consumed by the reactions between relatively mafic melts and peridotite, giving rise to silicic glasses with high K2O contents and K2O/Na2O ratios. The low K2O concentrations and K2O/Na2O ratios in glasses in anhydrous xenoliths suites from Hierro and Lanzarote are believed to result from reactions between infiltrating melts and anhydrous and/or amphibole-bearing mantle wall-rocks. The silicic melts appear to have been mobile over distances exceeding the diameter of a xenolith, that is at least 20-30 cm.

• Wulff-Pedersen, Erik; Neumann, Else Ragnhild & Jensen, Brenda Blanche (1996). The upper mantle under La Palma, Canary Islands: Formation of Si-K-Na-rich melt and its importance as a metasomatic agent. Contributions to Mineralogy and Petrology. ISSN 0010-7999. 125, s. 113–139.
• Andersen, Tom; Burke, Ernst A.J. & Neumann, Else Ragnhild (1995). Nitrogen-rich fluid in the upper mantle: Fluid inclusions in spinel dunite from Lanzarote, Canary Islands. Contributions to Mineralogy and Petrology. ISSN 0010-7999. 120, s. 20–28.
• Neumann, Else Ragnhild (1991). Ultramafic and mafic xenoliths from Hierro, Canary Islands: evidence for melt infiltration in the upper mantle. Contributions to Mineralogy and Petrology. ISSN 0010-7999. 106, s. 236–252.
• Anthony, E. Y.; Segalstad, Tom Victor & Neumann, Else Ragnhild (1989). Unusual mantle source regions for nephelinites from the Oslo Rift, Norway. Geochimica et Cosmochimica Acta. ISSN 0016-7037. 53, s. 1067–1076.

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• Wilson, M.; Neumann, Else Ragnhild; Davies, G.R.; Timmerman, M.J.; Heeremans, Michael & Larsen, B.T. (2004). Permo-Carboniferous magmatism and rifting in Europe. Geological Society. ISBN 1-86239-152-1. 498 s.

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• Callegaro, Sara; Svensen, Henrik Hovland; Heimdal, Thea Hatlen; Kjøll, Hans Jørgen; Harstad, Andreas Olaus & Neumann, Else Ragnhild (2022). New insights on shallow intrusions from the early stage of the Oslo Rift. .
• Callegaro, Sara; Svensen, Henrik Hovland; Jerram, Dougal Alexander; Neumann, Else Ragnhild; Deegan, Frances M. & Polozov, Alexander [Vis alle 7 forfattere av denne artikkelen] (2021). Geochemistry of low-Ti Siberian Traps sills from the Tunguska Basin bears evidence of magma-crust interaction.
• Aarnes, Ingrid; Podladtchikov, Iouri; Neumann, Else Ragnhild & Galerne, Christophe Yann (2009). Post-emplacement melt-flow as a feasible mechanism for reversed differentiation in tholeiitic sills.
• Neumann, Else Ragnhild & Simon, Nina Simone C (2008). Ultra-depleted domains in the oceanic mantle lithosphere. Geochimica et Cosmochimica Acta. ISSN 0016-7037. 72, s. A677–A677.
• Neumann, Else Ragnhild & Simon, Nina Simone C (2008). Ultra-Depleted Domains in the Oceanic Mantle Lithosphere.
• Aarnes, Ingrid; Podladtchikov, Iouri & Neumann, Else Ragnhild (2008). Post-emplacement melt flow as possible differentiation mechanism in sills.
• Neumann, Else Ragnhild; Simon, Nina Simone C; Bonadiman, C; Coltort, M; Delpech, G & Gregoire, M (2007). Extremely refractory oceanic lithospheric mantle and its implications for geochemical mass balance. Geochimica et Cosmochimica Acta. ISSN 0016-7037. 71, s. A712–A712.
• Simon, Nina Simone C; Neumann, Else Ragnhild; Medvedev, Sergei & Podladchikov, YY (2007). Isostatic Response of Strongly Extended Continental Lithosphere to Refertilization.
• Neumann, Else Ragnhild; Simon, Nina S. C.; Bonadiman, C.; Coltorti, M.; Delpech, G. & Gregoire, M. (2007). Oceanic lithosphere composition revisited: constraints from major element and modal relationships in mantle xenoliths from ocean islands.
• Galerne, Christophe Yann; Neumann, Else Ragnhild; Planke, Sverre; Aarnes, Ingrid & Haaberg, Kirsten (2007). Geochemical Architecture of the Golden Valley Sill Complex, South Africa: Implication for Saucer-Shaped Sill Emplacement in Sedimentary Basins.
• Aarnes, Ingrid; Podladtchikov, Iouri & Neumann, Else Ragnhild (2007). Formation of D- and I-shaped geochemical profiles in mafic sills due to post-emplacement magma flow induced by thermal stresses.
• Neumann, Else Ragnhild; Simon, Nina Simone C; Bonadiman, C.; Coltorti, M.; Delpech, G. & Gregoire, M. (2007). Ultra-refractory domains in the oceanic lithosphere: evidence from major element and modal relationships in mantle xenoliths from ocean islands. Vis sammendrag

  We have compiled a database for major element and modal data of mantle harzburgite and lherzolite xenoliths from different ocean islands. The xenoliths fall in two main categories. Xenoliths showing no petrographic evidence of metasomatism (OI1) from the Canary Islands, Kerguelen, Cape Verde and Samoa are ultra-depleted spinel harzburgites. These xenoliths formed by high degrees of partial melting leading to total exhaustion of cpx. Small amounts of cpx observed in these rocks (mainly $<$3 vol. percent) have partly formed through exsolution from opx followed by recrystallization, and partly through reactions between mantle wall-rocks and LREE-enriched metasomatic melts. Peridotites from the same islands (and the Azores) which show petrographic evidence of metasomatism (OI2) partly fall within the major element and modal range of OI1 xenoliths, partly they are less refractory. On average, the OI1 xenoliths are significantly more refractory than peridotites collected along mid-ocean ridges and fracture zone (MORP), although the most refractory mid-ocean ridge peridotites fall within the OI1 range. Although the OI1 xenoliths show indications of metasomatism in trace elements, Na2O, and radiogenic isotopes, their major element and modal compositions seem to be essentially unaffected by metasomatic processes. The ultra-depleted nature of the OI1 xenoliths is also reflected in the Fo-contents in ol, and in the HREE and MREE in opx. OI2 xenoliths are OI1 rocks, many of which have been metasomatized to the degree that major element and modal phase compositions have been modified. The other main category, consisting of harzburgite and lherzolite xenoliths collected in Hawaii, Tahiti and Grande Comore (OIcpx) are significantly less refractory that the OI1 xenoliths and show similarities to MORP. Many of these xenoliths contain significant amounts of cpx (up to 20 vol. %), and contain primary cpx, indicating only moderate amounts of partial melting (or extensive re-fertilization). Unradiogenic Os isotopes and high Re-Os model ages suggest that OI1 and OI1cpx rocks from some islands are much older than the abyssal lithosphere in which they are found. P-T estimates of 0.7-1.3 GPa and 850-1200C indicate that the OI1 xenoliths last equilibrated at depths corresponding to $>$80 Ma old oceanic lithospheric mantle. We interpret the ultra-depleted xenoliths as fragments of “exotic” material trapped in the oceanic mantle lithosphere. Major element similarities to some series of oceanic sub-arc mantle, and significant differences from continental xenolith series, makes it most likely that the ultra-refractory OI1 peridotites represent recycled abyssal mantle. The large proportion of ultra-refractory peridotite xenoliths in ocean islands, and the presence of such rocks also along some mid-ocean ridges and in sub-arc mantle, suggest that ultra-refractory material may be important ingredients in the convecting mantle. Because of their ultra-depleted chemistry the OI1 type harzburgites will have relatively low densities and are therefore buoyant relative to less refractory mantle rock types. Their high solidus temperatures make the OI1 xenoliths immune to further partial melting (sterile).

• Galerne, Christophe Yann; Neumann, Else Ragnhild & Planke, Sverre (2007). Geochemical architecture of the Golden Valley Sill Complex, South Africa: Implications for the emplacement of saucer-shaped sills in sedimentary basins. Vis sammendrag

  Saucer-shaped sills and dykes are common features in sedimentary basins worldwide and represent important parts of the plumbing system in such areas. In spite their common occurrence, the emplacement mechanisms that lead to the formation of sill complexes are poorly understood. Two main emplacement models have been proposed, based on field observations, seismic imaging, and mathematical modeling: (1) Each sill in a complex is produced by an individual magma batch emplaced through a dyke or a pipe, ending in the formation of a sill. (2) A single batch of magma gives rise to a series of saucer-shaped sills which feed one another, thereby forming a nested sill complex in which the different sills are interconnected. We report on a detailed geochemical study of a complex of nested, saucer-shaped dolerite sills, the Golden Valley Sill Complex in the Karoo Large Igneous Province, South Africa. This well-exposed sill complex consists of four large sills (ca. 100 m thick; long axes: 13-24 km) emplaced at slightly different stratigraphic levels, one small sill (55-80 m thick; long axis: 4 km; forming an appendix to one of the large sills), and two large dykes (15-20 m thick; 25 and 70 km long). The field observations show no physical connections between the large sills, or between the sills and the dykes. The compositions of basalts and dolerites in the Karoo basin are very similar. However, small chemical differences do exist. In order to discriminate between sills and dykes of different geochemical signature in the Golden Valley Sill Complex, that might have formed from different magma batches, we used a Forward Stepwise-Discriminant Function Analysis (FS-DFA). Sample groups which, based on field observations, were found clearly to belong to the same sill or dyke were defined as populations, the variables were forty-seven major and trace elements. The FS-DFA showed that several magma batches of distinct chemical characteristics were involved in the formation of the GVSC. Four different magma batches gave rise to two of the large sills and the two dykes. The exposed dykes thus do not represent feeders to the main sills in the GVSC. One additional, chemically distinct magma batch gave rise to the two other large sills plus the small sill. Our study of the GVSC thus gives support to both the main models proposed earlier to explain the emplacement of sill complexes. Some sills in a sill complex may be fed by different magma batches (model 1); other sills in the same complex may overflow and feed new sills, forming a group of nested sills formed from one single batch of magma (model 2). An important difference between model (2) and our observations is the way sills feed one another. Model (2) proposes that each of the nested sills in a complex is fed from its center, connecting the distal part of one sill to the center of the next sill which floor will be located at a higher stratigraphic level. In the GVSC the nested sills are connected along their edges through lateral overflow, the nested sills are thus located at approximately the same stratigraphic level. The GVSC includes complex areas where two or more sills appear to meet, and where two sills are located above one another. Using the FS-DFA parameters for the main populations, we were also able to assign samples in these areas to specific sills, thus improving the geological mapping of the area.

• Aarnes, Ingrid; Podladtchikov, Iouri & Neumann, Else Ragnhild (2007). Formation of D- and I-shaped profiles in basaltic sills due to post-emplacement melt-flow induced by thermal stresses.
• Neumann, Else Ragnhild & Simon, Nina Simone C (2006). The abyssal Mantle Lithosphere as indicated by Xenoliths from Ocean Islands. Vis sammendrag

  When studying metasomatism and other processes in the abyssal mantle, it is essential to know the composition of the unmodified lithospheric mantle. Most information available on the abyssal lithospheric mantle has been obtained on the basis of peridotites sampled through dredging and drilling along mid ocean ridges and fracture zones. However, the compositions of such samples have been modified through serpentinization, marine weathering, metamorphism, melt infiltration and deformation. Furthermore, such samples represent only the uppermost part of the abyssal mantle, and thus cannot give information about potential vertical zoning. An alternative approach is through peridotite massifs and ophiolites, but also these rocks have experienced a complex set of processes after initial formation, and the origin of a given unit (oceanic or continental) is not always easy to determine. As a matter of fact, it is doubtful if any of the units for which data are available represent abyssal mantle. A third setting where information about the abyssal mantle lithosphere may be obtained is ocean islands where mantle xenoliths are commonly brought to the surface during volcanic eruptions. Although the intraplate magmatism forming ocean islands leads to metasomatism of the underlying abyssal lithosphere, and there is evidence that there may be fragments of continental lithosphere beneath some ocean islands (e.g. Cape Verde), mantle xenoliths from ocean islands are proving to be a fruitful source of information about the abyssal mantle lithosphere. The mantle xenolith series from many ocean islands include samples that have mainly suffered cryptic metasomatism so that their pre-metasomatism chemistry is preserved in the most abundant major elements (SiO2, MgO, FeO and CaO) and in their modal phase proportions. These parameters are most robust against metasomatism. We use major element and modal data on spinel harzburgite and lherzolite xenoliths from different oceanic islands (Canary Islands, Cape Verde, Azores, Kerguelen, Hawaii, Tahiti, Samoa) in order to throw light on the compositional character of the abyssal mantle lithosphere. The least metasomatized xenoliths from different ocean islands are, on average, significantly more refractory (most of these samples fall in the range 44-49 wt% MgO, 0.4-1.1 wt% CaO, 1.5 wt% Al2O3) than peridotites sampled along mid-ocean ridges and fracture zones (40-48 wt% MgO, 0.3-2.5 wt% CaO, 0.3-4.0 wt% Al2O3; with the least refractory suites along slow-spreading ridges). The major element and modal compositions of the mantle xenoliths from ocean islands indicate that they represent residues after partial melting into the olivine+orthopyroxene±spinel stability field. Small amounts of clinopyroxene (<2 volume %) found in these samples appear to have formed as the results of exsolution from orthopyroxene. Comparison with experimental data suggests partial melting at 1 GPa. Samples with >>65 % olivine and significant amounts of clinopyroxene generally show abundant evidence of metasomatism, including clinopyroxene-producing reactions. The peridotite series xenoliths from Hawaii and Tahiti are anomalous as they are less refractory (on the average, lower MgO and modal olivine, higher FeOtotal, CaO, TiO2, Al2O3 and modal clinopyroxene). The observed major element and modal differences between spinel harzburgite/lherzolite series collected in ocean islands and along mid-ocean ridges and fracture zones are interpreted as (1) the result of partial melting at higher pressures of the former (leading to exhaustion of clinopyroxene at a lower olivine-content), and (2) melt infiltration and refertilization which has affected the shallow mantle close to the mid-ocean ridges, but not the deeper parts of the upwelling mantle that has moved away from the mid-ocean ridge zone without being subjected to the refertilization processes in the main ridge zone.

• Galerne, Christophe Yann; Neumann, Else Ragnhild & Aarnes, Ingrid (2006). Geochemical Architecture of the Golden Valley Sill Complex, South Africa: Implication for Saucer-Shaped Sill Emplacement in Sedimetary Basins.
• Neumann, Else Ragnhild (2005). Supervulkaner i Oslo området. [TV]. NRK1, Schrødingers katt.
• Polteau, Stephane; Planke, Sverre; Neumann, Else Ragnhild; Galerne, Christophe Yann; Malthe-Sørenssen, Anders & Podladtchikov, Iouri [Vis alle 7 forfattere av denne artikkelen] (2005). Emplacement of saucer-shaped sill intrusions constrained by detailed fieldwork and AMS analyses of the Golden Valley Sill Complex, South Africa.
• Ferrando, S.; Frezzotti, M.L.; Neumann, Else Ragnhild; Peccerillo, A.; Ayalew, D. & Yirgu, G. (2005). Characterisation of the lithosphere beneath north-western Ethiopian Plateau: Spinel lherzolites from Injibara (Lake Tana Province.
• Neumann, Else Ragnhild; Vannucci, R; Tiepolo, M; Griffin, W.L.; Pearson, N.J. & O'Reilly, S.Y. (2005). A Sharp Continent-Ocean Transition in the Area of the Canary Islands: Evidence From Upper Mantle and Lower Crustal Xenoliths. Vis sammendrag

  A Sharp Continent-Ocean Transition in the Area of the Canary Islands: Evidence From Upper Mantle and Lower Crustal Xenoliths Else-Ragnhild Neumanna, Riccardo Vannuccib,c, Massimo Tiepoloc, William L. Griffind, Norman J. Pearsond & Suzanne Y. O�Reillyd a Physics of Geological Processes, University of Oslo, PO Box 1048-Blindern, N-0316 Oslo, Norway b Dipartimento di Scienze della Terra, Università di Pavia, via Ferrata 1, 27100 Pavia, Italy c CNR - Istituto di Geoscienze e Georsisorse, sezione di Pavia, Via Ferrata 1, 27100 Pavia, Italy d Department of Earth Sciences, Macquarie University, Sydney, NSW 2119, Australia Our present information on passive margins rests almost exclusively on seismic and density data. An important exception is the west Iberia margin where petrological and geochemical information on crustal and mantle rocks have been made available through drilling experiments. In order to increase our information about, and understanding of, passive margins and their mode of formation, more information on crustal and mantle rocks along different types of passive margins are needed. In the area of the Canary Islands such information has been obtained through the study of mantle and deep crustal xenoliths brought to the surface by basaltic magmas. In-situ laser ablation (LA) ICP-MS mineral analyses have enabled us to �see through� the effects of the Canary Islands event and obtain robust information about the original (pre-Canarian) chemical character of the crust and upper mantle on which these islands are built. Our studies show that the lithosphere beneath the Canary Islands originated as highly refractory N-MORB type oceanic mantle overlain by highly refractory N-MORB crust. Both the lithospheric mantle and lower crust have been metasomatized to different degrees by a variety of fluid and melts. The enriched material is commonly concentrated along grain boundaries and cracks through mineral grains, suggesting that the metasomatism is relatively recent, and is thus associated with the Canary Islands magmatism. The original, strongly depleted trace element patterns and the low 87Sr/86Sr isotopic ratios typical of the oceanic lithosphere are preserved in the minerals in the least metasomatized rocks (e.g. LaN/LuN<0.1 in orthopyroxene and 87Sr/86Sr=0.7027-0.7029 in clinopyroxene in mantle xenoliths). The compositions of the most depleted gabbro samples from the different islands are closely similar, implying that there was no significant change in chemistry during the early stages of formation of the Atlantic oceanic crust in this area. Strongly depleted gabbros similar to those collected in Fuerteventura have also been retrieved in the MARK area along the central Mid-Atlantic Ridge. Furthermore, we have found no evidence of continental material that might reflect attenuated continental lithosphere in this area. The easternmost Canary Islands, Fuerteventura and Lanzarote, appear to overlap the lower part of the continental slope of Africa. The presence of normal oceanic lithosphere beneath these islands implies that the continent-ocean transition in the Canary Islands area must be relatively sharp, in contrast to the passive non-volcanic margin further north along the coast of Morocco, along the Iberia peninsula, and in many other areas. Our data also contradict the hypothesis that a mantle plume was present in this area during the opening of the Atlantic Ocean.

• Neumann, Else Ragnhild; Vannucci, R; Tiepolo, M; Griffin, WL & Pearson, NJ (2004). Earliest stages of formation of oceanic lithosphere in the central Atlantic Ocean: The oceanic plate beneath the Canary Islands. Geochimica et Cosmochimica Acta. ISSN 0016-7037. 68, s. A557–A557.
• Neumann, Else Ragnhild; Wilson, Marjorie; Heeremans, Michel; Spencer, Elizabeth Ann; Obst, K. & Timmerman, Martin [Vis alle 7 forfattere av denne artikkelen] (2004). Carboniferous-Permian rifting and magmatism in southern Scandinavia, the North Sea and northern Germany: a review. Geological Society Special Publication. ISSN 0305-8719. 223, s. 11–40. Vis sammendrag

  During the Late Carboniferous and Early Permian an extensive magmatic province developed within northern Europe, intimately associated with extensional tectonics, in an area stretching from southern Scandinavia, through the North Sea, into northern Germany. Within this area magmatism was unevenly distributed, concentrated mainly in the Oslo Graben and its offshore continuation in the Skagerrak, Scania in southern Sweden, the island of Bornholm, the North Sea and northern Germany. Available geochemical (major- and trace-element, and Sr-Nd isotope, data) and geophysical data are reviewed to provide a basis for understanding the geodynamic setting of the magmatism in these areas. Peak magmatic activity was concentrated in a narrow time-span from c. 300 to 280 Ma. The magmatic provinces developed within a collage of basement terranes of different ages and lithospheric characteristics (including thicknesses), brought together during the preceding Variscan orogeny. This suggests that the magmatism in this area may represent the local expression of a common tectono-magmatic event with a common causal mechanism. Available geochemical (major and trace element and Sr-Nd isotope data) and geophysical data are reviewed to provide a basis for understanding the geodynamic setting of the magmatism in these areas. The magmatism covers a wide range in rock types both on a regional and a local scale (from highly alkaline to tholeiitic basalts, to trachytes and rhyolites). The most intensive magmatism took place in the Oslo Graben (ca. 120000km 3 ) and in the NE German Basin (ca. 48000km 3 ). In both these areas a large proportion of the magmatic rocks are highly evolved (trachytes-rhyolites). The dominant mantle source componet for the mildly alkali basalts to subalkaline magmatism in the Oslo Graben and Scania (probably also Bornholm and the North Sea) is geochemically similar to the Prevalent Mantle (PREMA) component. Rifting and magmatism in the area is likely to be due to local decompression and thinning of highly asymmetric lithosphere in responses to regional stretching north of the Variscan Front, implying that the PREMA source is located in the lithospheric mantle. However, as PREMA sources are widely accepted to be plume-related, the possibility of a plume located beneath the area cannot be disregarded. Locally, there is also evidence of other sources. The oldest, highly alkaline basaltic lavas in the southernmost part of the Oslo Graben show HIMU trace element affinity, and initial Sr-Nd isotopic compositions different from that of the PREMA-type magmatism, These magmas are interpreted as the results of partial melting of enriched, metasomatised domains within the mantle lithosphere beneath the southern Olso Graben; this source enrichment can be linked to migration of carbonatite magmas in the earliest Paleozoic (ca. 580 Ma). Within northern Germany, mantle lithosphere modified by subduction-related fluids from Variscan subduction systems have provided an important magma source components.

• Neumann, Else Ragnhild (2004). The upper mantle beneath the Canary Islands: From passive margin to intra-plate magmatism.
• Neumann, Else Ragnhild; Vannucci, R; Tiepolo, M; Griffin, W.L. & Pearson, N.J. (2004). The nature of the passive margin in the area of the Canary Islands, Central Atlantic Ocean.
• Neumann, Else Ragnhild; Vannucci, R.; Tiepolo, M.; Griffin, W.L. & Pearson, N.J. (2004). The earliest stages of formation of the oceanic lithosphere in the central Atlantic Ocean: The oceanic plate beneath the Canary Islands.
• Neumann, Else Ragnhild (2004). The deep crust and upper mantle beneath the Canary Islands: Formation and evolution.
• Neumann, Else Ragnhild (2004). The formation of passive margins: Examples from the Atlantic Ocean and the Red Sea.
• Neumann, Else Ragnhild (2004). The Nature of the Passive Margin outside Morocco in the Central Atlantic Ocean, before the Formation of the Canary Islands.
• Neumann, Else Ragnhild (2003). Megavulkaner. [Radio]. NRK-P2 Verdt å vite.
• Neumann, Else Ragnhild (2003). Progressive changes in melt composition in the upper mantle beneath the Canary Islands: evidence from trace element compositions of minerals in mantle xenoliths.
• Neumann, Else Ragnhild; Wilson, M.; Heeremans, Michael; Dunworth, E.A.; Obst, K. & Timmerman, M.J. [Vis alle 7 forfattere av denne artikkelen] (2003). Permo-Carboniferous Rifting in Europe - magmatism, geodynamics and thermal evolution of the lithosphere.
• Neumann, Else Ragnhild (2003). Recrystallization processes associated with fluid infiltration and metasomatism in the mantle lithosphere beneath the Canary Islands.
• Neumann, Else Ragnhild; Wilson, Marge; Heeremans, Michael; Dunworth, Elizabeth Ann; Obst, K. & Kirstein, Linda (2003). Permo-Carboniferous rifting and magmatism in northern Europe. Vis sammendrag

  During late Carboniferous and early Permian time an extensive magmatic province developed within northern Europe. Magmatism was unevenly distributed, concentrated mainly in the Oslo Graben and its offshore continuation in the Skagerrak, Scania, the Baltic Sea, Bornholm, the North Sea, northeast England, and northern Germany. Peak magmatic activity was concentrated in the narrow time span 300-280 Ma. The various magmatic provinces developed basement terranes of different ages and lithospheric characteristics. This suggests that the magmatism in different parts of northern Europe may represent the local expressions of a common tectono-magmatic event with a common causal mechanism. The dominant mantle source component for the most primitive mafic magmas generated within the province (ranging from basanites and alkali basalts to subalkaline tholeiites) is sub-lithospheric; it is geochemically similar to the PREMA component which is widely accepted to be plume-related. Locally, however, distinctive alkaline magma types were generated by partial melting of enriched, metasomatised domains within the mantle lithosphere; in the Oslo Graben this source enrichment can be linked to intrusions by carbonatite magmas in the earliest Paleozoic (ca 580 Ma). Within northern Germany, mantle lithosphere modified by subduction-related fluids from Variscan subduction systems may provide an important magma source component.

• Neumann, Else Ragnhild (2003). Partial melting and carbonatite metasomatism in the upper mantle beneath the Canary Islands: Evidence from trace element compositions of minerals in peridotite xenoliths. Vis sammendrag

  Spinel harzburgite and lherzolite xenoliths in the Canary Islands bear evidence of extensive partial melting followed by metasomatism. The compositions of the xenoliths and their minerals show a higher degree of depletion than average depleted MORB mantle. Modeling based on whole-rock and mineral compositions indicate about 25% fractional melting. Metasomatism is reflected in i) evidence of growth of olivine and clinopyroxene at the expense of orthopyroxene, ii) the common presence of phlogopite in xenoliths from La Palma and Tenerife, iii) enrichment in strongly incompatible trace elements (including light and middle REE) relative to HREE in rocks and minerals, and iv) CaO/Al2O3 >>1.0 in many xenoliths from Tenerife and La Palma. Whereas the degree of partial melting appears to be similar in different parts of the sub-Canarian mantle, the degree of metasomatism varies, being mild beneath the islands of Hierro and Linarite, and strong beneath Tenerife. The trace element compositions of the metasomatizing melts, estimated on the basis of the trace element compositions of Cr-diopside assumed to have formed from or equilibrated with, the melts, imply that the upper mantle beneath the Canary Islands has been metasomatized by carbonatitic melts. On the basis of the xenoliths studied, the evolutionary history of the lithosphere beneath the Canary Islands is summarized.

• Wolff, John & Neumann, Else Ragnhild (2001). Sourcing Phenocrysts in Zoned Eruption Sequences Using Trace Elements: the Diego Hernandez Formation, Tenerife, Canary Islands. Vis sammendrag

  The Diego Hernandez Formation (DHF) consists of several plinian fallout and ignimbrite sequences. With few exceptions, the dominant volume of each eruptive package consists of compositionally variable phonolite with smaller amounts of basaltic and intermediate components. In addition to mixing with the mafic components, compositional variations among the phonolitic component are due to crystal-liquid separation corresponding to up to 60% crystallization of an assumed starting liquid. Sphene crystallization plays a dominant role in controlling abundances of REE and HFSE among Tenerife phonolites. Sphene preferentially sequesters MREE, leading to strongly parabolic REE patterns among residual liquids. We have used this feature of the zoned Tenerife phonolites to match the REE content of individual pyroxene crystals, analyzed by laser ablation ICP-MS, to observed liquids using the elastic strain mineral-melt partitioning model of Blundy and Wood [1]. The strongly parabolic REE patterns of the liquids allow matching solely using the calculated Young's modulus of the host M2 cation site in pyroxene, without any independent constraint on the strain-free partition coefficient D0. For sodian salite pyroxenes in the phonolites, we find that most did not grow from the host liquid represented by the pumice clasts in which the crystals were erupted. Instead, most grew from liquids significantly more evolved, with lower MREE/LREE and MREE/HREE than the observed host. Elevated Zr contents in the salites support this conclusion, although the Zr abundances cannot be modelled with the same degree of confidence as the REE. The required liquids correspond to both the most-evolved phonolite compositions observed within the DHF, and to cognate syenite fragments found in the ignimbrites. Sodian salite also occurs as cores to titanaugite grains that grew from the basaltic component. These observations are consistent with a model in which invading basaltic magma melts syenite, and/or stagnant syenitic crystal mush with highly evolved interstitial liquid, to produce phonolite-dominated mixed magma. [1] Blundy and Wood (1994) Nature 372, 452-454.

• Trønnes, Reidar G; Neumann, Else Ragnhild & Sundvoll, Bjørn A. (2001). Sr-Nd-Pb isotope composition of Oslo Rift basaltic rocks: derivation from old, enriched mantle lithosphere.
• Neumann, Else Ragnhild (2001). Changes in the Oceanic Lithosphere Induced by the Canary Islands Magmatism.
• Neumann, Else Ragnhild (2001). Permo-Carboniferous Rifting in NW Europe.
• Neumann, Else Ragnhild (2000). Changes in the Oceanic Lithosphere Induced by the Canary Islands Magmatism.
• Neumann, Else Ragnhild; Sørensen, Vivian; Simonsen, Siri Lene & Johnsen, Kari (1999). Gabbroic Xenoliths from La Palma, Tenerife and Lanzarote, Canary Islands: Evidence for Reactions between Canary Islands Melts and Old Oceanic Crust.
• Simonsen, Siri Lene & Neumann, Else Ragnhild (1999). Change in apatite chemistry during the evolution of the Diego Hernandez Formation.
• Simonsen, Siri Lene; Neumann, Else Ragnhild; Wulff-Pedersen, Erik & Seim, Kristin (1998). Decoupling between trace element ratios and radiogenic isotope data from Tenerife, Canary Islands.
• Neumann, Else Ragnhild; Simonsen, Siri Lene; Wulff-Pedersen, Erik & Seim, Kristin (1998). Source regions of Tenerife magmatism.
• Neumann, Else Ragnhild; Wulff-Pedersen, Erik; Simonsen, Siri Lene & Pearson, Norman J. (1998). Magma chamber processes and eruptive mechanisms.
• Simonsen, Siri Lene; Neumann, Else Ragnhild; Wulff-Pedersen, Erik & Seim, Kristin (1998). Decoupling between trace element ratios and radiogenic isotope data from Tenerife, Canary Islands.
• Trønnes, Reidar G; Neumann, Else Ragnhild & Andersen, Tom (1996). Samlokalisering av geofagene ved UiO. Uniforum. ISSN 1891-5825. s. 8–8.

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