^1,2S. D. Crossley, ³N. G. Lunning, ⁴R. G. Mayne, ³T. J. McCoy, ⁴S. Yang, ⁴M. Humayun, ⁵R. D. Ash, ⁶J. M. Sunshine, ⁷R. C. Greenwood, ⁷I. A. Franchi
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13114]
¹Monnig Meteorite Collection, Texas Christian University, , Fort Worth, Texas, USA
²Department of Geology, University of Maryland, , Maryland, USA
³Department of Mineral Sciences, Smithsonian Institution, National Museum of Natural History, Washington, DC, USA
⁴National High Magnetic Field Laboratory and Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, Florida, USA
⁵Department of Geology, University of Maryland, , Maryland, USA
⁶Department of Astronomy, University of Maryland, , Maryland, USA
⁷Planetary and Space Sciences, School of Physical Sciences, The Open University, Walton Hall, Milton Keynes, UK
Published by arrangement with John Wiley & Sons

The incompatible trace element‐enriched Stannern‐trend eucrites have long been recognized as requiring a distinct petrogenesis from the Main Group‐Nuevo Laredo (MGNL) eucrites. Barrat et al. (2007) proposed that Stannern‐trend eucrites formed via assimilation of crustal partial melts by a MGNL‐trend magma. Previous experimental studies of low‐degree partial melting of eucrites did not produce sufficiently large melt pools for both major and trace element analyses. Low‐degree partial melts produced near the solidus are potentially the best analog to the assimilated crustal melts. We partially melted the unbrecciated, unequilibrated MGNL‐trend eucrite NWA 8562 in a 1 atm gas‐mixing furnace, at IW‐0.5, and at temperatures between 1050 and 1200 °C. We found that low‐degree partial melts formed at 1050 °C are incompatible trace element enriched, although the experimental melts did not reach equilibrium at all temperatures. Using our experimental melt compositions and binary mixing modeling, the FeO/MgO trend of the resultant magmas coincides with the range of known Stannern‐trend eucrites when a primary magma is contaminated by crustal partial melts. When experimental major element compositions for eucritic crustal partial melts are combined with trace element concentrations determined by previous modeling (Barrat et al. 2007), the Stannern‐trend can be replicated with respect to both major, minor, and trace element concentrations.

^1,2Matthew J. Genge, ^1,2Matthias van Ginneken, ^1,2Martin D. Suttle, ³Ralph P. Harvey
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13107]
¹Department of Earth Science and Engineering, Imperial College London, , London, UK
²Department of Earth Science, The Natural History Museum, London, UK
³Department of Geological Sciences, Case Western Reserve University, Cleveland, Ohio, USA
Published by arrangement wit John Wiley & Sons

We report the discovery of a large accumulation of micrometeorites (MMs) in a supraglacial moraine at Larkman Nunatak in the Grosvenor Mountains of the Transantarctic Range in Antarctica. The MMs are present in abundances of ~600 particles kg−1 of moraine sediment and include a near‐complete collection of MM types similar to those observed in Antarctic blue ice and within bare‐rock traps in the Antarctic. The size distribution of the observed particles is consistent with those collected from snow collections suggesting the moraine has captured a representative collection of cosmic spherules with significant loss of only the smallest particles (<100 μm) by wind. The presence of microtektites with compositions similar to those of the Australasian strewn field suggests the moraine has been accumulating for 780 ka with dust‐sized debris. On the basis of this age estimate, it is suggested that accumulation occurs principally through ice sublimation. Direct infall of fines is suggested to be limited by snow layers that act as barriers to accumulation and can be removed by wind erosion. MM accumulation in many areas in Antarctica, therefore, may not be continuous over long periods and can be subject to climatic controls. On the basis of the interpretation of microtektites as Australasian, Larkman Nunatak deposit is the oldest known supraglacial moraine and its survival through several glacial maxima and interglacial periods is surprising. We suggest that stationary ice produced by the specific ice flow conditions at Larkman Nunatak explains its longevity and provides a new type of record of the East Antarctic ice sheet.