Petrology, geochemistry and K-Ar Age determination of De Gerlache Seamount basalts, supplement to: Hagedorn, Birgit; Gersonde, Rainer; Gohl, Karsten; Hubberten, Hans-Wolfgang (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

• Main Authors: Hagedorn, Birgit, Gersonde, Rainer, Gohl, Karsten, Hubberten, Hans-Wolfgang
• Format: Article in Journal/Newspaper
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2007
• Subjects: Dredge; ANT-XII/4; Polarstern; Paleoenvironmental Reconstructions from Marine Sediments @ AWI AWI_Paleo; Antarctic; Antarctic Peninsula; Bellingshausen Sea; De Gerlache; De Gerlache Seamounts; Gerlache; Jones Mountains; Pacific; Peter I Island; Thurston; Thurston Island; West Antarctica; Antarc*; Antarctica
• Online Access: https://dx.doi.org/10.1594/pangaea.743234; https://doi.pangaea.de/10.1594/PANGAEA.743234

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.