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Hagedorn, Birgit; Gersonde, Rainer; Gohl, Karsten; Hubberten, Hans-Wolfgang (2007): Petrology, geochemistry and K-Ar Age determination of De Gerlache Seamount basalts. doi:10.1594/PANGAEA.743234,
Supplement to: Hagedorn, B et al. (2007): Petrology, Geochemistry and K-Ar Age constraints of the dastern De Gerlache Seamount alkaline basalts (Bellingshausen Sea, Southeast Pacific). Polarforschung, 76(3), 87-94, hdl:10013/epic.28876.d001

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The De Gerlache Seamounts are two topographic highs in the Bellingshausen Sea, southeastern Pacific. Petrological and geochemical studies together with K-Ar age determinations were carried out on four dredged basalt samples collected during a RV Polarstern expedition (ANT-XII/4) in 1995. Minor and trace element composition suggest alkaline basalt compositions. Compared to alkaline basalts of adjacent West Antarctica (the Jones Mountains) and of Peter I Island, the samples have lower mg-numbers, lower Ni and Cr contents and lower high field-strength elements (HFSE)/Nb and large-ion lithophile elements (LILE)/HFSE ratios. Three of the four samples have low K, Rb, and Cs concentrations relative to alkaline basalts. The K-depletion and other elemental concentrations may be explained by 1.1% melting of amphibole bearing mantle material. Additionally, low Rb and Ba values suggest low concentrations of these elements in the mantle source. K-Ar age determinations yield Miocene ages (20-23 Ma) that are similar in age to other alkaline basalts of West Antarctica (Thurston Island, the Jones Mountains, Antarctic Peninsula) and the suggested timing of onset of Peter I Island volcanism (~10-20 Ma). The occurrence of the DGS and Peter I Island volcanism along an older but reactivated tectonic lineation suggests that the extrusions exploited a zone of pre-existing lithospheric weakness. The alkaline nature and age of the DGS basalts support the assumption of plume activity in the Bellingshausen Sea.
Latitude: -65.305000 * Longitude: -90.586000
Date/Time Start: 1995-04-22T21:34:00 * Date/Time End: 1995-04-22T21:34:00
PS2693-1 (PS35/155) * Latitude: -65.305000 * Longitude: -90.586000 * Date/Time: 1995-04-22T21:34:00 * Elevation: -773.0 m * Location: Southeast Pacific * Campaign: ANT-XII/4 (PS35 06AQANTXII_4) * Basis: Polarstern * Device: Dredge (DRG) * Comment: Basalt (max. 50x30x20 cm)
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