The palaeomagnetic record of the Santiago volcanics (Republic of Cape Verde); multiphase magnetization and age consideration

An 40Ar‐39Ar study of the Cape Verde hot spot: Temporal evolution in a semistationary plate environment

“…Here we present additional direct age information for Santiago, Sal, and São Vicente based on 40 Ar‐ 39 Ar analyses and some inferred ages from Sr isotope analyses of marine carbonates. On the basis of this information we suggest that the main volcanic activity for several of the islands occurred significantly later than the Miocene as suggested by Serralheiro [1976], Mitchell et al [1983], Gerlach et al [1988], Davies et al [1989], and Abranches et al [1990]. We discuss the geological evolution of the archipelago in the context of a hot spot and semistationary lithosphere.…”

“… Abranches et al [1990] considered their paleomagnetic results for CA rocks to be secondary and interpreted them as reflecting a Neogene overprint from the young volcanism on Santiago. They also found that a low‐temperature recrystallization of the CA rocks occurred in the Paleogene, and speculated that their original emplacement was in the Late Cretaceous, and thus older than the Paleogene age according to Serralheiro [1976] and Alves et al [1979].…”

“…The CA comprises mainly intrusions and submarine volcanic rocks with some subaerial volcanic rocks, and it may represent an early, mainly submarine, construction of the island [ Serralheiro , 1976]. Abranches et al [1990] found that the CA is pre‐Paleogene and suggested that it represents uplifted Cretaceous seafloor. This is supported by identification of MORB‐type volcanic rocks at Santiago by Gerlach et al [1988] and Davies et al [1989].…”

“…K‐Ar determinations by Bernard‐Griffiths et al [1975] yielded younger ages, but they largely discarded these because of discordance with other geological information [ Serralheiro , 1976; Alves et al , 1979] and because the analyzed samples were thought to have lost argon during hydrothermal events [ Bernard‐Griffiths et al , 1975]. Abranches et al [1990] found a complex paleomagnetic history of the CA, with the youngest remanence of Miocene age, younger than the expected age for CA rocks, which were interpreted to mainly reflect a Neogene overprint from the young volcanism on Santiago. They also detected low‐temperature recrystallization of the rocks in the Paleogene and speculated that the CA was emplaced in the Late Cretaceous.…”

Alpine remagnetization and tectonic rotations in the French Pyrenees

“…(Steiner et al 1985); 2, 3 Permo-Triassic rocks of the Catalán Range (Van den Berg 1980); 4 Lisbon volcanics (overprinted magnetization; Storetvedt et al 1987); 5 Mesozoic-Lower Tertiary rocks of the Catalán Coastal Range (Pares et al 1988); 6 Eocene rocks from the Ebro basin (Pares et al 1988). In b poles corresponding to directions 1-6 of a are shown in relation to the Upper Cretaceous-Tertiary APW curve for continental Africa and Meso-Caenozoic poles (circles) from the Cape Verde and Canary Islands (Storetvedt et al 1979;Storetvedt 1980;Storetvedt and Løvlie 1983;Abranches et al 1990). See text and Storetvedt et al (1990) for discussion The combined palaeomagnetic and isotopic age studies of alkaline intrusions in Portugal (Storetvedt et al 1987 gave some unexpected results.…”