Publication Date:
2015-07-31
Description:
The causes for the formation of large igneous provinces and hotspot trails are still a matter
of considerable dispute. Seismic tomography and other studies suggest that hot mantle
material rising from the core-mantle boundary (CMB) might play a significant role in the
formation of such hotspot trails. An important area to verify this concept is the South Atlantic
region, with hotspot trails that spatially coincide with one of the largest low-velocity regions
at the CMB, the African large low shear-wave velocity province. The Walvis Ridge started to
form during the separation of the South American and African continents at ca. 130 Ma as a
consequence of Gondwana breakup. Here, we present the first deep-seismic sounding images
of the crustal structure from the landfall area of the Walvis Ridge at the Namibian coast to
constrain processes of plume-lithosphere interaction and the formation of continental flood
basalts (Paraná and Etendeka continental flood basalts) and associated intrusive rocks. Our
study identified a narrow region (〈100 km) of high-seismic-velocity anomalies in the middle
and lower crust, which we interpret as a massive mafic intrusion into the northern Namibian
continental crust. Seismic crustal reflection imaging shows a flat Moho as well as reflectors
connecting the high-velocity body with shallow crustal structures that we speculate to mark
potential feeder channels of the Etendeka continental flood basalt. We suggest that the observed
massive but localized mafic intrusion into the lower crust results from similar-sized
variations in the lithosphere (i.e., lithosphere thickness or preexisting structures).
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
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isiRev