We report on the geochemical analyses of glassy spherules from sediments at three Transantarctic Mountain locations and the discovery of Australasian microtektites at two of these sites. Australasian microtektites are present at Mt. Raymond (RY) in the Grosvenor Mountains and Meteorite Moraine (MM) at Walcott Neve, in the Beardmore Glacier region of Antarctica. The microtektites were identified based on their pale yellow appearance, the high concentrations of silica (SiO2 = 60 7 wt%) and alumina (Al2O3 = 23 4 wt%), and a K2O/Na2O > 1, which are all characteristics of microtektites and distinct from spherules of meteoritic origin. Additionally, trace element patterns for these microtektites match the upper continental crust compositions with enrichments in refractory elements and depletions in volatile elements, most likely as a result of melting and vaporization of source material. The presence of Australasian microtektites in RY sediment confirms the recent Australasian strewn field extension to Antarctica and the presence of highly volatile depleted microtektites. In addition to microtektites, thousands of chondritic spherules and a few unique differentiated cosmic spherules were identified in RY, MM, and Jacobs Nunatak sediments. Two unique spherules were calculated to have Fe/Mn ratios similar to micrometeorites assumed to be derived from Vesta (Fe/Mn 33.2 0.5 atom%) and two other unique spherules are extremely rich in refractory components (Al2O3 ~ 30% and TiO2 = ~2%). The three sites examined are evidently successful cosmic dust and impact debris collectors, and thus are useful traps for recording and examining the nature of influx events.
Microtektites and glassy cosmic spherules from new sites in the Transantarctic Mountains, Antarctica
Folco, Luigi;Suttle, Martin D.;
2021-01-01
Abstract
We report on the geochemical analyses of glassy spherules from sediments at three Transantarctic Mountain locations and the discovery of Australasian microtektites at two of these sites. Australasian microtektites are present at Mt. Raymond (RY) in the Grosvenor Mountains and Meteorite Moraine (MM) at Walcott Neve, in the Beardmore Glacier region of Antarctica. The microtektites were identified based on their pale yellow appearance, the high concentrations of silica (SiO2 = 60 7 wt%) and alumina (Al2O3 = 23 4 wt%), and a K2O/Na2O > 1, which are all characteristics of microtektites and distinct from spherules of meteoritic origin. Additionally, trace element patterns for these microtektites match the upper continental crust compositions with enrichments in refractory elements and depletions in volatile elements, most likely as a result of melting and vaporization of source material. The presence of Australasian microtektites in RY sediment confirms the recent Australasian strewn field extension to Antarctica and the presence of highly volatile depleted microtektites. In addition to microtektites, thousands of chondritic spherules and a few unique differentiated cosmic spherules were identified in RY, MM, and Jacobs Nunatak sediments. Two unique spherules were calculated to have Fe/Mn ratios similar to micrometeorites assumed to be derived from Vesta (Fe/Mn 33.2 0.5 atom%) and two other unique spherules are extremely rich in refractory components (Al2O3 ~ 30% and TiO2 = ~2%). The three sites examined are evidently successful cosmic dust and impact debris collectors, and thus are useful traps for recording and examining the nature of influx events.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
