Geotectonic evolution of the Oceanographer Transform Fault

The Oceanographer Transform Fault is a 120 km long and E-W oriented transform fault located southwest of the Azores. We have detailed geological and morphological information of the area through high-resolution bathymetry and an extensive collection of rock samples. There we see different seafloor types (magmatic dominated volcanic seafloor, tectonic dominated smooth seafloor and core complexes) that indicate variations in the magmatic productivity. Our results show that seafloor morphology is linked to magma supply rates.

Now, we work at showing a complete geotectonic evolution of the Oceanographer Transform Fault area. The new data presented here, include radiometric age dates, which put constraints on the timing of processes, and magnetic signatures.

The magnetic anomalies were analyzed by 2D profile forward models. Weak magnetic patterns are observed above areas where mainly mantle-derived rocks occur. On the other hand, magmatic robust segments which are predominantly basaltic, are characterized by well-defined magnetic anomalies. Based on these magnetic anomaly analyses, we estimate seafloor spreading rates. Crustal accretion is asymmetric at both axes and varies in space and time.

To verify our magnetic anomaly results, we conducted U-Pb dating on zircons in five gabbroic samples collected by dredging. Obtained crystallization ages range between 3 Ma to 8 Ma. Not all results align with the seafloor ages, some geochemical ages are younger than the dates derived from the magnetic anomaly, which might be due to secondary magmatism.