Geophysical constraints on radial and lateral temperature variations in the upper mantle

Journal Article · Thu Jan 01 04:00:00 EST 1976 · Am. Mineral.; (United States)

OSTI ID:7042614

Solomon, S C

Temperatures in the upper mantle may be inferred from measurements of physical properties which are strongly dependent on temperature and by identification of seismic discontinuities with phase transitions of measurable equilibrium boundaries. Temperature at the top of the low-velocity zone, equated with the onset of incipient melting, is generally 1100/sup 0/ +- 100/sup 0/C from a wide variety of evidence. The extensive melting detectable beneath mid-ocean ridges implies temperatures above 1250/sup 0/C in the shallow asthenosphere under spreading centers. Below a thermal boundary layer at the top of the asthenosphere, associated with convection on a scale secondary to plate motions, geotherms in the asthenosphere follow nearly adiabatic gradients and intersect the olivine-spinel transition at a temperature of 1300/sup 0/ +- 150/sup 0/C. The olivine--spinel transition is elevated about 100 km in subducted oceanic lithosphere, implying a 1000/sup 0/C temperature contrast between slab and normal mantle at 250 km depth. Systematic thermal differences between stable ocean basins and continental shields are necessary but are not likely to extend deeper than 200 km. Lateral temperature variations of perhaps 200/sup 0/C do persist deeper than 200 km and are probably associated with convective flow in the asthenosphere.

• Research Organization: Massachusetts Inst. of Tech., Cambridge
• OSTI ID: 7042614
• Journal Information: Am. Mineral.; (United States), Journal Name: Am. Mineral.; (United States) Vol. 61:7/8; ISSN AMMIA
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152004* -- Geothermal Data & Theory-- Isotope & Trace Element Studies
CONVECTION
EARTH MANTLE
ENERGY TRANSFER
GEOPHYSICAL SURVEYS
GEOPHYSICS
GEOTHERMAL GRADIENTS
GEOTHERMOMETRY
HEAT FLOW
HEAT TRANSFER
ISOTHERM
LAYERS
MELTING
PHASE TRANSFORMATIONS
SEISMIC SURVEYS
TEMPERATURE DISTRIBUTION
TEMPERATURE GRADIENTS