Detailed heat flow measurements over the Juan de Fuca ridge system
Eleven detailed profiles of heat flow measurements have been completed over young oceanic crust of the Juan de Fuca ridge system. Individual measurements were spaced typically 0.4--1 km apart along multiple-penetration lines from 3 to 20 km in total length, and each measurement was located with respect to structural and sedimentary features by simultaneous seismic reflection profiling. In all cases, the average heat flow is well below that predicted by simple conductivity cooled spreading models even when the sediment cover is thick and the nearest basement outcrop is 15 km away. This disparity is attributed to ventilated convective circulation of water in the crust. Large heat flow variability is common along all profiles. Variations are present at two scales. Small-scale variations (from 1 km to a few kilometers between significant heat flow maxima), present in the younger profiles, probably reflect the influence of local venting and permeability variations on permeable layer cellular convection. Large-scale variations (10--20 km between significant heat flow maxima), present in all profiles, may reflect the influence of regional circulation driven by cold water recharge at isolated basement outcrops. Laboratory experimental data indicate that normal celluar convection can coexist with larger-scale bilateral flows, so that there is no simple way to extract the permeable layer thickness from the surface heat flow data. There is a considerable reduction in the amplitude of small-scale heat flow variability over the range of crustal age studied (0.1x12.5 m.y.). This is probably caused by the thermal filtering effects of the sediment cover which increases from about 50 m near the ridge crests to over 700 m on the flanks.
- Research Organization:
- Pacific Geoscience Centre, Earth Physics Branch, Sidney, British Columbia, V8L 4B2, Canada
- OSTI ID:
- 5413045
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 85:B1
- Country of Publication:
- United States
- Language:
- English
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