Petrology, geochemistry and K-Ar Age determination of De Gerlache Seamount basalts

• Main Authors: Hagedorn, Birgit, Gersonde, Rainer, Gohl, Karsten, Hubberten, Hans-Wolfgang
• Format: Dataset
• Language: English
• Published: PANGAEA 2007
• Subjects: ANT-XII/4; AWI_Paleo; Dredge; DRG; Paleoenvironmental Reconstructions from Marine Sediments @ AWI; Polarstern; PS2693-1; PS35/155; PS35 06AQANTXII_4; Southeast Pacific; Antarctic; Antarctic Peninsula; West Antarctica; Bellingshausen Sea; Pacific; Gerlache; Thurston; De Gerlache; Thurston Island; Peter I Island; De Gerlache Seamounts; Jones Mountains; Antarc*; Antarctica; Polarforschung
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.743234; https://doi.org/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.