Transmission Electron Microscopy of CONCORDIA UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs): Mineralogical properties E. Dobrica ˘ a,⇑ , C. Engrand a , H. Leroux b , J.-N. Rouzaud c , J. Duprat a a Centre de Spectrome ´trie Nucle ´aire et de Spectrome ´trie de Masse (CSNSM), CNRS-Univ. Paris Sud, 91405 Orsay Campus, France b Unite ´ Mate ´riaux et Transformations, UMR 8207, CNRS-Universite ´ Lille 1, 59655 Villeneuve d’Ascq, France c Laboratoire de Ge ´ologie, Ecole Normale Supe ´rieure (ENS), UMR CNRS 8538, 75231 Paris, Cedex 5, France Received 6 April 2011; accepted in revised form 12 October 2011; available online 20 October 2011 Abstract We performed mineralogical and petrographic studies of three UltraCarbonaceous Antarctic Micrometeorites (UCA- MMs) by analytical transmission electron microscopy (TEM). The UCAMMs were identified in the CONCORDIA micro- meteorite collection (2002 and 2006) recovered from central Antarctic snow, and are of probable cometary origin. UCAMMs are dominated by disordered carbonaceous matter that extends over surfaces of up to 90% of the particle. Embedded in this carbonaceous matter, we observed small and complex assemblages of fine-grained mineral phases, isolated minerals, glassy phases that resemble Glass with Embedded Metal and Sulfides (GEMS) that were first found in Interplan- etary Dust Particles (IDPs), and rounded objects containing both glass and crystalline materials. The mineral assemblages are chondritic in composition, within a factor of 2. Crystalline materials represent at least 25% of mineral phases. This value is much larger than the upper limit of crystallinity measured in the diffuse interstellar medium (<2.2 wt%). Crystalline phases are dominated by low-Ca, Mg-rich pyroxenes, Mg-rich olivine and low-Ni Fe-sulfides. Exotic phases such as Mn-, Zn-rich sulfide and perryite have also been found as accessory minerals. The variety of high temperature mineral phases observed in UCAMMs is similar to that reported in chondritic porous IDPs and 81P/Wild 2 samples. The close association of high temperature crystalline phases with the low temperature carbonaceous matter in UCAMMs supports the hypothesis of a large-scale radial mixing in the early solar nebula. This new type of carbon-rich micrometeorites containing crystalline mate- rial provides the opportunity to analyze in situ, without any chemical processing, the association of materials formed at both low and high temperatures in the protoplanetary disk. A better knowledge of these samples is also important to prepare for future cometary missions, like ROSETTA in 2014. Ó 2011 Elsevier Ltd. All rights reserved. 1. INTRODUCTION Extraterrestrial micrometer-sized particles (micromete- orites) can be retrieved from many types of sediment at the Earth’s surface (Taylor and Lever, 2001). In the early 1980s, large numbers of micrometeorites were collected from the bottom of blue lakes in Greenland (Maurette et al., 1986, 1987) and, later on, from blue ice fields in Ade ´lie Land (Antarctica) (Maurette et al., 1991). Over a decade, the group from “Centre de Spectrome ´trie Nucle ´aire et de Spectrome ´trie de Masse” (CSNSM, France) has devel- oped a program to retrieve micrometeorites from ultra- clean snow near the French-Italian station CONCORDIA at Dome C (2000, 2002 and 2006) (Duprat et al., 2007). Other expeditions were made to Antarctica to collect cos- mic dust particles by Japanese and American teams (Taylor et al., 1998, 2000; Yada and Kojima, 2000; Nakamura et al., 2001). 0016-7037/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.gca.2011.10.025 ⇑ Corresponding author. Present address: Department of Earth and Planetary Sciences, MSC03-2040 1, University of New Mexico, Northrop Hall, Albuquerque, NM 87131-0001, United States. E-mail address: edobrica@unm.edu (E. Dobrica ˘). www.elsevier.com/locate/gca Available online at www.sciencedirect.com Geochimica et Cosmochimica Acta 76 (2012) 68–82