Cadamosto Seamount
Coordinates: 14 ° 40 ′ N , 24 ° 55 ′ W
The Cadamosto Seamount is a volcanic deep-sea mountain in the eastern North Atlantic . It closes off the Cape Verde Islands in their south-west and is seismically active.
designation
The Unterseeberg was named after the Venetian explorer Alvise Cadamosto .
geography
The Cadamosto Seamount is located about 20 kilometers southwest of Brava and forms the southwestern extension of the Fogo Brava platform , which includes the islands of Fogo , Brava and the Ilhéus do Rombo . Its foot rests on the sediments of the ocean floor at a depth of around 4400 meters . Its flattened tip is almost 2900 meters deep. The seamount thus reaches a total height of 1500 meters. Numerous smaller volcanic cones have been discovered between the main structure and Brava.
geology
Sampling at the deep sea mountain confirmed that the deep sea mountain was formed volcanically . Petrologically , they are differentiated phonolites that emerged from nephelinitic magmas by fractional crystallization . The Seamount thus takes on a special role within Cape Verde, which is mainly composed of primitive, undersaturated, mafic alkaline rocks ( basanites etc.), together with the nearest island of Brava. Were fractionated clinopyroxene , titanite , apatite and feldspar , and the fractionation of feldspar can be very far advanced. The clinopyroxenes of the nephelinites crystallized under pressures of 170 to 380 MPa, ie in the lower oceanic crust slightly above the Moho , which can be found in the Fogo-Brava platform at 400 MPa or between 12 and 14 kilometers depth. The base of the porphyry rocks and especially the very late crystallizing feldspar representatives were contaminated in the crustal area; so the isotope ratios of Sr, O and S were influenced. The Nd-Pb isotope ratios remained unaffected and unaltered reflect the composition of the original mantle rock . They show that the initial magma of the deep-sea mountain is much more similar to the magmas of the northern archipelago of Cape Verde than to the magmas of its immediate, eastern neighbors. The Seamount magma has at a 206 Pb / 204 Pb ratio of 19.5 to isotopically depleted DM component ( engl. Depleted mantle ) with fairly high εNd developed from +6 to +7 out at the same time but from the DUPAL- Anomaly (positive 208 Pb / 204 Pb ratio) removed, whereas its neighbors have the enriched EM component ( English enriched mantle ) and a positive DUPAL value with +21.
earthquake
In 1998 and 2004 two earthquakes were recorded that originated from the Cadamosto seamount as the epicenter . The 2004 quake had a magnitude of m b = 4.3 and triggered a number of smaller aftershocks. As a result, brittle deformations had occurred on the deep sea mountain, which had been triggered by redistribution movements in the magma chamber or by duct intrusions . The Cadamosto Seamount is seismically most active in the entire Cape Verde archipelago, so it can be assumed that the deep-sea volcano is currently in a growth phase.
Individual evidence
- ↑ K. Abigail Barker et al: Magmatic Evolution of the Cadamosto Seamount, Cape Verde. Beyond the Spatial Extent of EM1. In: Contributions to Mineralogy and Petrology . Vol. 163, 2011, No. 6, pp. 949-965, doi : 10.1007 / s00410-011-0708-2 .
- ↑ Alexandra Lodge, George Helffrich: Depleted Swell Root Beneath the Cape Verde Islands. In: Geology. Vol. 34, 2006, pp. 449-452.
- ^ Bernard Dupré, Claude J. Allègre: Pb-Sr-Nd Isotopic Correlation and the Chemistry of the North Atlantic Mantle. In: Nature . Vol. 286, 1980, pp. 17-22, doi : 10.1038 / 286017a0 .
- ↑ Ingo Grevemeyer include: Seismic Activity at Cadamosto Seamount near Fogo Iceland, Cape Verde - Formation of a New Ocean Iceland? In: Geophysical Journal International. Vol. 180, 2010, No. 2, pp. 552-558, doi : 10.1111 / j.1365-246X.2009.04440.x