Basaltic micrometeorites from the Novaya Zemlya glacier

Abstract

Abstract-A large number of micrometeorites (MMs) was recovered from glacier deposits located at the north-eastern passive margin of the Novaya Zemlya glacier sheet. Melted, scoriaceous, and unmelted micrometeorites (UMMs) are present. Unmelted micrometeorites are dominated mostly by chondritic matter, but also a few achondritic MMs are present. Here we report the discovery of four UMMs that, according to their texture, mineralogy, and chemistry, are identified as basaltic breccias. Mineral chemistry and Fe ⁄ Mn ratios of two basaltic micrometeorites indicate a possible relationship with eucrites and ⁄ or mesosiderites, whereas two others seem to have parents, which appear not to be present in our meteorite collections. The basaltic breccia UMMs constitute 0.5% of the total population of the Novaya Zemlya MM suite. This content should be lowered to 0.25% because the Novaya Zemlya MM collection appears to be biased with carbonaceous UMMs being underrepresented.

HED-like cosmic spherules from the Transantarctic Mountains, Antarctica: Major and trace element abundances and oxygen isotopic compositions

“…This proportion is slightly higher than those estimated from other micrometeorite collections: differentiated cosmic spherules represent 0.5 ± 0.4% of the South Pole Water Well micrometeorite collection (Taylor et al, 2007) and basaltic unmelted micrometeorites represent 0.2-0.5% of the Novaya Zemlya glacier collection (Badjukov et al, 2010). This slight discrepancy in the estimated influx of differentiated precursors can be due to the difference in the examined size fractions (200-900 lm for the Transantarctic Mountain collection and <500 lm in the South Pole Water Well collection and in the Novaya Zemlya glacier collection) or to the difference in the proportions of melted versus unmelted particles (98% of cosmic spherules in the Transantarctic Mountain collection and $75% in the South Pole Water Well collection and in the Novaya Zemlya glacier collection; Rochette et al, 2008;Taylor et al, 2000;Badjukov et al, 2010). As stated above, differentiated Mg-poor particles are more likely to melt during atmospheric entry and to be present in higher proportions in micrometeorite collections rich in cosmic spherules.…”

“…Such pyroxene-dominated lithologies have also been recognized among unmelted basaltic micrometeorites (Badjukov et al, 2010). On the other hand, Type 3 spherule compositions can be modeled as bulk eucrite compositions with an excess of orthopyroxene (80-90 vol.%).…”

“…These differentiated particles have been related to vestoids (Taylor et al, 2007;Badjukov et al, 2010;Cordier et al, 2011a) or to new basaltic asteroids, i.e. asteroids that are not represented in meteorite collections (Gounelle et al, 2009;Badjukov et al, 2010). Note that following Burbine et al (2001Burbine et al ( , 2009, we use the term vestoids to refer to near-Earth asteroids with V-type reflectance spectra (i.e.…”

“…Micrometeorites deriving from achondritic precursors are rare, both among the melted (cosmic spherule) and the unmelted micrometeorite populations. So far, five differentiated unmelted micrometeorites have been recognized on the basis of their basaltic mineralogy (Gounelle et al, 2009;Badjukov et al, 2010), and nine differentiated cosmic spherules have been identified on the basis of the relict grains they contain (silica, anorthite) and of their bulk chemical compositions (Taylor et al, 2007;Cordier et al, 2011a). These differentiated particles have been related to vestoids (Taylor et al, 2007;Badjukov et al, 2010;Cordier et al, 2011a) or to new basaltic asteroids, i.e.…”

Microtexture, nanomineralogy, and local chemistry of cryptocrystalline cosmic spherules

“…Cosmic spherules from the Novaya Zemlya Archi pelago were collected in the marginal part of the Novaya Zemlya ice cap (Badjukov and Raitala, 2003;Badjukov et al, 2010). Samples of solid sediment on ice (cryoco nite) were washed to get rid of the clay constituent and subjected to magnetic separation.…”