FISSION-TRACK STUDY - HEATING AND DENUDATION OF MARGINAL RIDGE OF THEIVORY-COAST GHANA TRANSFORM MARGIN

Six sandstone blocks sampled during dives along the southern slope of the Ivory Coast-Ghana continental margin have been studied using fissi on tracks in apatite and zircon. Measurements demonstrate that the roc ks were heated above 120 degrees C but below 390 degrees C and cooled quickly. The ages of cooling recorded by the apatite crystals are 90 M a in the western part of the margin, and 80-70 Ma in the central and e astern part. Heating is interpreted by the heat liberation due to the friction along the active transform fault and by the vicinity of an oc eanic spreading center, which slipped along the margin. Cooling is int erpreted by two stages of denudation due to minor faults and landslide s produced by the increasing of the bathymetric step between the conti nental margin and the oceanic crust.