Alteration of volcanic deposits in the ANDRILL AND-1B core: Influence of paleodeposition, eruptive style, and magmatic composition

Abstract

Alteration minerals, assemblages, and textures were studied in a 175-m-thick volcanic sequence found between 759.32 and 584.19 m below seafloor within the 1285-m-long ANDRILL (Antarctic Geological Drilling project) McMurdo Ice Shelf core (MIS AND-1B). Three main alteration zones were identifi ed through the application of different analytical methods (optical and scanning electron microscopy, electron microprobe, and X-ray diffraction). Alteration zoning is guided by the texture of the volcanic deposits, which is in turn determined by the eruptive style, transport mechanisms, and paleodepositional conditions. In particular, alteration refl ects the evolution of paleodepositional conditions from submarine or shallow water to subaerial due to the growth of a nearby volcanic edifice. The general alteration trend is also infl uenced by the contribution of volcanogenic sediments derived from the reworking of silica-rich pyroclasts from earlier volcanic activity.

Early Miocene Antarctic glacial history: new insights from heavy mineral analysis from ANDRILL AND-2A drill core sediments

“…The composition of most of the deposits from the EVP belong to the strongly silica-undersaturated basanite-tephrite-phonolite alkaline association, although older deposits on Mount Morning are silica-saturated to oversaturated and belong to the alkali basalt-trachyte to rhyolite association (Martin et al 2010). Mount Morning is considered the source of Early to Middle Miocene volcanic material recovered from the Cape Roberts (Barrett 2007), AND-1B (Pompilio et al 2007;Di Roberto et al 2013) and AND-2A cores (Panter et al 2008;Di Vincenzo et al 2010;Di Roberto et al 2012;Nyland et al 2013). However, indirect evidence of an older volcanic activity (Late Oligocene) has been found within sediments of the Ross Sea Victoria Land Basin recovered by the CIROS-1 and the CRP-2A drill cores (Smellie 2000;Sandroni and Talarico 2004;Zattin et al 2012).…”