New Late Cretaceous and CAMP Magmatic Sources off West Iberia, From High-Resolution Magnetic Surveys on the Continental Shelf

Abstract

Magma-poor rifted margins can be affected by magmatic occurrences coeval with rifting and post-rifting. Understanding the geological processes that originated these magmatic events requires determining their extent, type and size of magmatic bodies and tectonics. This work investigates the distribution and origin of two large magmatic events off SW Iberia, the Late Triassic Central Atlantic Magmatic Province (CAMP) and the West Iberia Late Cretaceous Alkaline Province (WILCAP). Marine magnetic data were densely acquired over ∼4,400 km2 and new magnetic maps reveal a complex heterogeneous anomaly field with different anomaly zones. A wide number and variety of magmatic bodies are interpreted, from km-scale deeply intruded plutons to small plug-like and dike-like intrusions. Integration with bathymetry and seismic reflection data allows discussing the geometry, extent and age of the magmatic sources. The Cabo Raso complex is a densely intruded zone related to the WILCAP event. The Sines complex comprises the offshore prolongation of the on-land Sines WILCAP magmatic rocks but also the newly mapped Côvo and Milfontes anomalies. Côvo is possibly the largest magmatic intrusion recognized in West Iberia. Milfontes intrudes the non-rifted Paleozoic crust and is the first known evidence of a plutonic source of the CAMP in Iberia. The intrusion of magmatic bodies was mostly controlled by the crustal tectonic fabric inherited from the Paleozoic Variscan orogeny, which was re-worked during the Mesozoic rifting and the Cenozoic Alpine collision.