Thermal profiles across a ridge, a trench and a transform fault

- Across a ridge, the temperature decreases from that of the upper mantle (thickness of the oceanic crust is ~ null), i.e. about T = 1200°C, and decreases away from the ridge.

- This temperature decrease follows the law of heat conduction (1/ √ kt) through an oceanic crust increasing in thickness (due to the decrease in T). The heat flow decreases conformably (Figure).

- Across a trench, the isotherms display a complex pattern due to the fact that the cold oceanic crust plunges under the continental crust into the mantle. The re-heating of the subducted slab takes a long time (diffusion in a slow process) such that the thermal « anomaly » persists very deep along the subduction zone. In the following figure, it is also shown (in addition) that the temperatures are modified at the « olivine-spinel » and « spinel-oxide » transitions (~ 400 km and ~ 670 km deep).

- Finally, across a transform fault (TF), due to the translative mouvement along the fault, an abrupt change in temperatures is observed (modeled).

- The following figures show (in (a)) the temperature-profile in cross-section (perpendicularly to TF), and the isotherms in map view (horizontally : b, c and d), at 6.25, 12.5 and 25 km under the surface of the oceanic crust for an age offset of 10 Ma at a rate of 1.5 cm/year.

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Date: 2015-01-29; view: 1461