Abstract:
New thermal data from 18–24 Ma lithosphere on the
Cocos Plate delineate contrasting subsurface thermal
conditions in adjacent sections of crust. Heat flow through
seafloor created at the East Pacific Rise is generally
suppressed by ~70% relative to conductive lithospheric
cooling models, whereas heat flow through adjacent,
similarly-aged lithosphere generated at the Cocos-Nazca
Spreading Center is consistent with these models. The
transition between thermal regimes is remarkably abrupt,
only 2–5 km wide, indicating a shallow hydrothermal origin.
The transition is more closely associated with differences in
the distribution of basement outcrops than with tectonic
boundaries, demonstrating the importance of the former in
extracting heat from the lithosphere on a regional basis.
