Initiation of the Ferrar LIP, Antarctica: Multiple shallow level sill intrusions into wet sediments associated with hydroclastic eruptions with strombolian components

Category Petrology
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Viereck-Goette, Lothar۱; Abratis, Michael۱; Schoener, Robert۱; Elsner, Martin۱; Schneider, Joerg۲; Bomfleur, Benni۳
Holding Date 29 September 2008

In Northern Victoria Land, Antarctica, the plateau lavas of the Ferrar Large Igneous Province are underlain by volcaniclastic deposits of phreatomagmatic eruptions (so-called Exposure Hill Type events) that are intercalated at two stratigraphic levels with fluvial deposits of Triassic to Lower Jurassic age that overlie crystalline basement in thicknesses of less than 300m. Volcaniclastic deposits are sourced in breccia-filled diatremes which themselves are rooted in sills intruding wet sediments. Abundant scoriaceous spatter (locally welded) indicate a widely distributed hawaiian / strombolian component. The deposits are subaerial expressions of initial Ferrar magmatism involving intrusion of multiple shallow-level sills. Due to magma-sediment interaction abundant clastic dikes are developed that intrude the sediments and sills. All igneous components in the volcaniclastic deposits are of low-Ti andesitic composition, as are the chilled margins of the sills. They are more differentiated than the basaltic andesites of the subsequent effusive section of Kirkpatrick plateau lavas which in northern Victoria Land start with pillow lavas and small volume lava flows from ordinary volcanic necks. Magmatism of the Ferrar Large Igneous Province in NVL was neither preceded nor associated with the eruption of peraluminous dacitic crustal melts as in the North Atlantic Igneous Province.