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Major Element Records of Variable Plume Involvement in the North Atlantic Province Tertiary Flood Basalts |
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| Authors: | SCARROW J H; CURRAN J M; KERR A C |
| Institution: | 1DEPARTMENT OF MINERALOGY AND PETROLOGY, CAMPUS FUENTENUEVA, UNIVERSITY OF GRANADA, 18002 GRANADA, SPAIN 2SCHOOL OF GEOSCIENCES, THE QUEEN’S UNIVERSITY OF BELFAST, BELFAST BT7 1NN, UK 3DEPARTMENT OF GEOLOGY, UNIVERSITY OF LEICESTER, LEICESTER LE1 7RH, UK |
| Abstract: | Major element variations in North Atlantic Tertiary Provinceprimitive, early erupted, alkaline-transitional-tholeiite basalts,recalculated to a restricted value of MgO, give insights intothe process of plume-related magmatism. Basalts primitive enoughto be crystallizing only olivine were recalculated to a proposedprimary magma composition of 15 wt % MgO. The recalculated datasetshows clear inter-element correlations including a strong, significant,negative correlation between Fe and Si indicating polybaricmelt segregation. Overlap between basalt compositions and experimentalmelts from a fertile, Fe-rich, low mg-number (85.5) peridotitesuggests that, relative to normal peridotite with mg-number> 89, the North Atlantic basalt source was Fe rich. Linearregression of the experimental data gives apparent pressuresof magma segregation of 17·5–37 kbar, with intra-regionvariability in the depth derivation from the melt column foreach sample, thus suggesting that lithospheric thickness ‘lid-effect’control on magma generation may have been overemphasized inrecent studies. Comparable source composition, magma segregationdepth and calculated mantle potential temperature (1440–1460°C)throughout the Province supports the previously suggested plumeimpact model, arriving below East Greenland, derived from avariably enriched and depleted lower-mantle source. Given thegood agreement between conclusions drawn from major elementdata and previously published results we suggest that restricted-MgOrecalculated datasets may be usefully applied to study otherlarge igneous provinces. KEY WORDS: basalt; Fe-rich mantle; large igneous provinces; North Atlantic Tertiary Province; restricted-MgO major element datasets |
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