Transtension and alkaline magmatism of the Romanche Fracture Zone

New magnetometric, petrological, and geochemical data on basalts from the central Romanche Fracture Zone (FZ) allow us to classify these rocks into two groups. The igneous rocks from the active part of the fracture zone that experienced transtension are referred to as alkaline rocks. According to some indications, they are younger that the oceanic tholeiites of the southern fault-line ridge, which were affected by elevated pressure in the past. These data indicate with a high probability that the Romanche FZ belongs to a rare group of magmatically active demarcation transform lines that separate large oceanic domains different in structural and geochemical features.