Chemistry:Libyan desert glass
Libyan desert glass or Great Sand Sea glass is an impactite, made mostly of lechatelierite,[1] found in areas in the eastern Sahara, in the deserts of eastern Libya and western Egypt. Fragments of desert glass can be found over areas of tens of square kilometers.
Geologic origin
The origin of desert glass is uncertain. Meteoritic origins have long been considered possible, and recent research links the glass to impact features, such as zircon breakdown, vaporized quartz and meteoritic metals, and to an impact crater.[2][3][4][5][6][7][8] Some geologists[9] associate the glass with radiative melting from meteoric large aerial bursts, making it analogous to trinitite created from sand exposed to the thermal radiation of a nuclear explosion. Libyan Desert glass has been dated as having formed about 29 million years ago.[10] Like obsidian, it was knapped and used to make tools during the Pleistocene.[11]
The glass is nearly pure silica which requires temperatures above 1,600 °C to form – hotter than any igneous rock on Earth. However, few mineral relics survived from whatever caused the melting, including a form of quartz called cristobalite, a rarely occurring high-temperature mineral; and grains of the mineral zircon, although most have reacted to form a higher-temperature mineral called zirconia. Ideas about how the glass formed include melting during meteorite impact, or melting caused by an airburst from an asteroid or other object burning up high in Earth's atmosphere.[12]
See also
- Chemistry:Atacama desert glass – Desert glass found in the Atacama Desert
- Chemistry:Darwin glass – Natural desert glass found in Tasmania
- Astronomy:Hypatia (stone) – Candidate for the first comet nucleus
- Earth:Kebira Crater – Circular feature in the Sahara
- Chemistry:Tektite – Gravel-sized glass beads formed from meteorite impacts
- Physics:Tunguska event – 1908 meteor air burst explosion in Siberia
References
- ↑ "Libyan Desert Glass". mindat.org. https://www.mindat.org/min-39796.html.
- ↑ "First ever evidence of a comet striking Earth". Wits University. 2013. http://www.wits.ac.za/newsroom/newsitems/201310/21649/news_item_21649.html.
- ↑ Kramers, J.D et al (2013): Unique chemistry of a diamond-bearing pebble from the Libyan Desert Glass strewnfield, SW Egypt: Evidence for a shocked comet fragment. Earth and Planetary Science Letters 382, 21-31 doi:10.1016/j.epsl.2013.09.003
- ↑ B. Kleinmann (1968): The breakdown of zircon observed in the Libyan desert glass as evidence of its impact origin. Earth and Planetary Science Letters 5, 497-501. doi:10.1016/S0012-821X(68)80085-8
- ↑ Weeks, R. (1984): Libyan Desert glass: A review. Journal of Non-Crystalline Solids, 67, 593-619. doi:10.1016/0022-3093(84)90177-7
- ↑ Seebaugh, W. R. & Strauss, A. M. (1984): Libyan Desert Glass: Remnants of an Impact Melt Sheet. LUNAR AND PLANETARY SCIENCE XV, 744-745. [Abstract.] Bibcode: 1984LPI....15..744S
- ↑ Barbara Kleinmann, Peter Horn and Falko Langenhorst (2001): Evidence for shock metamorphism in sandstones from the Libyan Desert Glass strewn field. Meteoritics & Planetary Science 36, 1277-1282 doi:10.1111/j.1945-5100.2001.tb01960.x
- ↑ Giovanni Pratesi, Cecilia Viti, Curzio Cipriani and Marcello Mellini (2002): Silicate-silicate liquid immiscibility and graphite ribbons in Libyan desert glass. Geochimica et Cosmochimica Acta 66, 903-911.doi:10.1016/S0016-7037(01)00820-1
- ↑ Greshake, Ansgar; Koeberl, Christian; Fritz, Jörg; Reimold, W. Uwe (2010). "Brownish inclusions and dark streaks in Libyan Desert Glass: Evidence for high-temperature melting of the target rock". Meteoritics & Planetary Science 45 (6): 973–989. doi:10.1111/j.1945-5100.2010.01283.x.
- ↑ Cavosie, Aaron J.; Koeberl, Christian (1 July 2019). "Overestimation of threat from 100 Mt–class airbursts? High-pressure evidence from zircon in Libyan Desert Glass". Geology 47 (7): 609–612. doi:10.1130/G45974.1. Bibcode: 2019Geo....47..609C.
- ↑ "Desert Glass: An Enigma". http://archive.aramcoworld.com/issue/197905/desert.glass-an.enigma.htm.
- ↑ "Libyan desert glass mystery solved" (in en-AU). 23 May 2019. https://cosmosmagazine.com/history/archaeology/mystery-of-libyan-desert-glass-solved-at-last/.
- ↑ Tut's gem hints at space impact, BBC News, July 19, 2006.
Literature
- V. de Michele (ed.): Proceedings of the Silica '96 Meeting on Libyan Desert Glass and related desert events, Bologna, 1997 Contents
- P.A. Clayton / L.J. Spencer: Silica Glass from the Libyan Desert, Vortrag vom 09.11.1933 online
External links
 |  |
