Melt Percolation, Concentration and Dyking in the Hawaiian Mantle Plume and Overriding Lithosphere: Links to the Evolution of Lava Composition along the Volcanic Chain

Abstract Oceanic island basalts and related magmatic rocks from Hawaii are derived a compositionally heterogeneous mantle plume. Here we describe how this heterogeneity results the transport of filaments specific composition in plume, representing relatively small volume (~15 %) interbedded inside dry peridotite mantle. Four types considered: sub-primitive mantle, ultralow-velocity zone, fertilized-harzburgite eclogite type filaments. We present model that describes flow within plume stress field overriding viscoelastic lithosphere can determine, depth to surface, melting rate, trajectory melts produced each filament. Our shows (1) melt at corresponding >5 GPa, where temperature gap between solidus liquidus is narrow (~40–80 °C), (2) relative total which therefore allows latent heat required for partial be provided via conduction hot The primitive filaments, occasionally mixed with an filament, represent comparable expected composed only partially degree ~10 % interface spinel garnet fields (60–70 km depth). In particular, centre produce up 30 tholeiite–picrite melts, whereas completely having meimechite-like composition. A key finding fractional crystallization these probably forms so-called ‘primary mantle-derived alkaline magmas’ along dunites olivine-rich cumulates. divides into two parts. first corresponds flowlines originate ~200 distance less than 25 axis. Along flowlines, when reaches pressure 5 molten horizon sufficiently thick interstitial squeezed out dykes. This eventually ponds as sills subrectangular zone located overlying lithosphere, 70 50 centred over 40 on either side designated shield reservoir. volatile-rich infiltrates surrounding it. After ~0·1 Myr, resumes its vertical ascent dykes differentiates subcrustal magma chambers below active volcanoes. sequence processes matches volume, petrology geochemistry recorded second part does not pond Rather, cold originating 25–35 axis, discharge their through were initially generated deeper, ~5 GPa. Moho 100–150 it bodies differentiates. represents observed pre- postshield Finally, ~70 axis greater 200 km, subvertical. They then deflect ~180 rotate toward horizontal transit 10–20° across reach ~140 depth. mantle/ultralow-velocity elbows by few several per cent. resulting has kimberlite-like Thereafter, excess top filament overcomes threshold dyking thus escape ponding or emerging directly surface. These have similar associated rejuvenated volcanism. use nature whole erupted magmas seismic structure Hawaiian chain validate model.