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SOME FIGURES FOR UNFINISHED MANUSCRIPTS (CONDENSED; FULL VERSION CAN BE REQUESTED VIA DROPBOX) eclogite harzburgite 410 cold 650 cold RIDGE Shear wavespeed OIB 1 Temperature BL VSH>VSV Observed Seismic profile 6 High-T conduction geotherm 2 220 km ~1600 C Vs for selfcompressed solid along adiabat VSV>VSH 4 1600 C adiabat 5 3 Subadiabatic geotherm 7 Tp=~1300 C 650 km disconnect A mantle circulation model based on anisotropy, anharmonicity, absolute wavespeeds & gradients, allows for, and predicts, non adiabaticity ridge hotspots Tp LIL Sheared mélange 200 LIL LVZ UPPER MANTLE Ancient eclogite cumulates 400 km TZ Modern slab fragments ‘cold’ THE “NEW” PARADIGM “the canonical box” Midocean ridges Intraplate volcanoes Sediments volatiles Residual slab components LOWER MANTLE *Essentially the classical model of Birch, Tatsumoto, Wilson… The Eureka Solution Physics-Based Archimedian Paradigm* OIB squeezin g Superadiabatic boundary layer REGION B MORB source “fixed” Sources deeper than ~ 150-200 km are effectively fixed (e.g.J.T.Wilson) Tp decreases with depth TRANSITION ZONE (TZ) 200 Myr of oceanic crust accumulation (* Birch, Tatsumoto, J. Tuzo Wilson) Shear strain squeezin g Hawaii source Thermal max 300 km k(T), a(V,T), TCMB(t), n(V,T), U(z,t), 600 km 600 km Th(z,t)… Shear-driven magma segregation Pebbles Old Greeks Slabs (RIP) Archimedes & Birch STANDARD CONCEPTUAL MODEL (1988) No physics, no seismology jet ADIABATIC ISOTHERM 100 km ISOTHERMAL HOMOGENEOUS ISOTHERM No U, Th, K No secular cooling Ambient T constrained (<1600K) (used as reference model; Herzberg, Asimow, Humphreys, Schmandt, Victor Camp…e.g…) LID LLAMA subadiabat BOUNDARY LAYER T (oC) Negative Vs gradient 1600 1200 Tp(max)~1600o Tp=1280o 800 Lithosphere 400 0 Cambridge nomenclature Adiabatic Mechani Therm interior cal al boundar bound ary 0 y layer 100 200 300 Depth layer (km) European, African, Asian (Changbai), Yellowstone & most continental intraplate volcanoes (“hotspots”) are underlain by slabs Cold slab Cooled mantle UPPER MANTLE & LOWER MANTLE ARE COOLED BY LONG-LIVED FLAT (STAGNANT) SLABS 49 Fixed hotspot paradox STAGNANT SLABS–A FIXED REFERENCE FRAME Ridges & hotspots No hotspots REGION B LVA 410 WARM COLD 650 COOL TZ SLIP-FREE BOUNDARY There may be a concentration of CaO, Al2O3, K…U, Th…in the upper mantle…Birch 50 Illustrating the thermal bump and subadiabaticity 1600 1400 T oC 400 200 Midplate bump (& backarc) Boundary layer LLAMA(shearing) ridge UPPER MANTLE midplate TZ Plate (conducting) Depth D” T B LOWER MANTLE CMB Depth The highest potential temperature in the mantle is near 200 km. Tectonic processes (shear, delamination) are required to access this. U, Th, K and other LIL are concentrated in the crust & the upper mantle boundary layer during the radial zone refining associated with accretion (Birch, Tatsumoto…). This accentuates the thermal bump. (Lubimova, MacDonald, Ness) SUMMARY Ridges are fed by broad 3D upwellings plus lateral flow along & toward ridges ridge OIB LID LVZ LLAMA 200 400 km subadiabatic Mesosphere (TZ) Cold slabs Intraplate (delamination, CRB, Deccan, Karoo, Siberia) magmas are shear-driven from the 200 km thick shear BL (LLAMA)