Petrology and geochemistry of the 25 MA Mt. Marion dufresne basaltic section on the Kerguelen Archipelago : constraining the transition from tholeiitic to mildly alkalic volcanism on a major oceanic island ...

• Main Author: Annell, Heidi
• Format: Text
• Language: English
• Published: University of British Columbia 2009
• Subjects: Antarc*; Antarctic
• Online Access: https://dx.doi.org/10.14288/1.0052331; https://doi.library.ubc.ca/10.14288/1.0052331

Flood basalts on the - 6500 km² Kerguelen Archipelago in the southern Indian Ocean formed in an intraplate location on the Antarctic plate between 29-24 Ma as the Southeast Indian Ridge migrated from - 225 to - 400 km northeast relative to the Kerguelen hotspot. A - 700 m section of basalts exposed at Mt. Marion Dufresne, in the southern part of the Plateau Central, contains both transitional-tholeiitic and mildly alkalic lavas (A.I. -0.8 to 2.0) that are geochemically and isotopically variable, and captures an important period of time (-1 Myr) near the end of flood basalt volcanism on the Kerguelen Archipelago. The basal 300 m of the section consists of low-MgO (<5.2 wt. %) predominantly aphyric lavas characterized by a limited range of "enriched" isotopic compositions (¹⁷⁶Hf/¹⁷⁷Hf =.0.28282-0.28287; ⁸⁷Sr/⁸⁶Sr = 0.7048-0.7050; ¹⁴³Nd / ¹⁴⁴Nd = 0.5126-0.5127; ²⁰⁷Pb / ²⁰⁴Pb = 15.54-15.56) similar to compositions observed in the enriched 24-25 Ma mildly alkalic lavas to the east and southeast (e.g. Mt. ...