Magmatic and geodynamic evolution of the King’s Trough Complex – the “Grand Canyon” of the North Atlantic

The King’s Trough Complex (KTC) is a major canyon-like structure in the eastern North Atlantic and consists of several deep basins: The huge King’s Trough in the west is flanked by elongated ridges, while at its eastern opening the smaller Peake and Freen Deeps are separated by the Palmer Ridge. The King’s Trough is located in an area of elevated seafloor covered with numerous seamounts, which transitions to the Mid-Atlantic Ridge (MAR) flank toward the west. Here we present major and trace element and Sr-Nd-Hf-Pb isotope data from submarine volcanic rock samples obtained during RV METEOR cruise M168.

Whereas lavas from the eastern deeps show N- and E-MORB signatures and moderately depleted isotope compositions, samples from the western King’s Trough and surrounding seamounts display predominantly enriched OIB-like compositions. This geographic transition would be consistent with involvement of a mantle plume that was located beneath or near the MAR resulting in elevated seafloor of relatively enriched geochemical composition. The troughs probably formed subsequently by rifting and/or transtension when (36 to 42 Ma) the KTC area represented a temporary plate boundary between the Iberian and Eurasian plates. In the east, the KTC cuts into older (not elevated) crust, presumably formed prior to plume-ridge interaction, explaining why samples obtained from there possesses normal to transitional MORB compositions. Age and further isotope data are pending and will reveal if the ridges on the King’s Trough flanks represent younger, plume-related excess volcanism or simply the tops of tilted graben shoulders along the former plate boundary.