McClintock and White (2006) introduced the notion of debris jets in a volcanological sense in a study on the Mawson Formation at Coombs Hills, Antarctica (Ferrar Province). They proposed that sub-vertical tuff breccia zones found within the vent complex were formed when jets of “debris + steam + water” passed through unconsolidated vent-filling debris. Based on simple spatial relationships, they buy NSC 146109 found that the majority of the debris jets probably did not breach the surface and erupt, but rather remained in the vents, though they were unable to determine exactly what portion of debris jets remained confined to the vent. Furthermore, the composition of the sub-vertical deposits is indicative of both the lateral and vertical location where they originated (Ross and White, 2006). They hypothesized that deposits filled with country rock-rich lapilli tuff and tuff breccia formed by explosions near the walls or floor of the diatreme, where significant fragmentation of country rock could occur. In contrast, the basalt-rich deposits were formed a distance away from the vent and floor where there was abundant basalt already present. Ross and White (2006) argued that once a debris jet has been formed above a site of explosive magma–water interaction, vertebrae entrains little to no material of the surrounding vent-filling debris as it propagates. Instead, incorporation of clasts takes place directly at or near the site of explosions.
↧