Imilac meteorite crater

Coordinates: 24 ° 12 ′ 46 ″  S , 68 ° 48 ′ 31 ″  W.

Imilac​

Chile

The Imilac meteorite crater in northern Chile with 8 m diameter of the largest impact craters in about 8 square kilometers extensive Imilac- meteorite strewn field , caused before an estimated 500 years by an already shattered during the approach in the atmosphere stony-iron meteorite type Pallasite .

description

Calama San Pedro de Atacama Sierra Gorda Antofagasta Torment Escondida Paranal observatory Salar de Atacama Bolivia Argentina Imilac crater Monturaqui crater Tilocalar crater Tujle crater

The Imilac meteorite crater is located in a region where meteorites accumulate and impact craters are well preserved because they are exposed to little erosion due to the dry climate that has lasted for several million years . Imilac meteorite crater other meteorite crater other meteorite finds inhabited places

The Imilac meteorite crater is located in the Atacama Desert , in northern Chile, in the Antofagasta municipality . It is located at 24 ° 13 ′  S , 68 ° 49 ′  W , around 170 km as the crow flies from the city, in an extremely dry, vegetation-free zone of the Andes Precordillere at an altitude of 3,050 m, a few kilometers from the Salar de Imilac.

It is a simple, bowl-shaped crater with a diameter of 8 m, bordered by steep walls. The impactor was a pallasite (stone-iron meteorite) which, when approaching from the southwest, broke apart in the atmosphere. This resulted in numerous fragments of different sizes, which hit a primary stray field at least 8 km long and 1 km wide. Slowed down by the atmosphere, the smaller pieces fell first, while the largest fragment flew farthest, to the northeastern edge of the litter field. When it hit, this caused the crater and shattered into tens of thousands of pieces, which flew up to 1000 m apart and formed a secondary stray field.

discovery

Imilac pallasite:
The meteorite consists of a spongy iron-nickel alloy in which the cavities are usually completely filled with olivine . About 50  % by volume of olivine. In this backlit, thin disc, the olivine is transparent and colored, while the surrounding iron appears opaque and dark. When location is 24 ° 12 '  S , 68 ° 48'  W indicated.

There is no recorded observation of the fall of the meteor shower. In 1821, a man named Alejandro Chavez heard a loud noise during the day in the vicinity of the Peine oasis and soon afterwards large quantities of iron were found scattered over a plain. Because volcanism and earthquakes are also possible causes of the noise in the area, it was doubted whether this was related to the meteorite. It could only be determined inaccurately that two local hunters from Peine, José María Chaile and Matías Mariano Ramos, discovered the meteorite field sometime between 1814 and 1824. Because they could cut the meteoritic iron with a knife and the fresh cut looked silvery, they thought their find was silver. A Monsieur C. Lambert reported that on a trip from San Pedro to Coquimbo in 1822 he tried to visit the site called reventason by the indigenous population , but that nobody wanted to show him the way, presumably to keep the supposed silver mine a secret. It is therefore certain that the Imilac meteorite was discovered since at least 1822, making it the oldest documented find from a so-called hot desert. It is believed, however, that the case was several hundred years ago. From geological considerations it could be deduced that the fall could have taken place around 500 years ago.

Exploitation of the meteorite field

While a few Europeans set out to look for the coveted meteorites in the Atacama Desert, mostly the opportunity was used to have them procured by experienced native suppliers. Understandable when you consider that crossing the vast, extremely dry and vegetation-poor desert was an arduous and dangerous undertaking. It is assumed that in the first three to four decades after the discovery, no European was at the site in Imilac. The indigenous population processed the meteoritic iron into useful or ornamental objects.

When Spanish ships blocked the port of Buenos Aires during the War of Independence and iron was scarce due to a lack of imports, the new government there commissioned the procurement of meteoritic iron from the Atacama region. By the time it was laboriously transported overland, the blockade was over. The material acquired up to then was sold in 1825 to the British naturalist and consul general in Buenos Aires Sir Woodbine Parish. Parish sent two of them from Imilac to Great Britain. In the spring of 1827 these were recognized by the mineralogist T. Allan as being comparable to a meteorite found by Peter Simon Pallas in Siberia. The chemist E. Turner determined 10% nickel and 1% cobalt in iron and thus confirmed the meteoritic origin.

The largest mass of Imilac at 198 kg in the collection of the British Museum was acquired in 1877 by the British explorer George Hicks from a local supplier. It took four men ten days with a cart to get to the port in Antofagasta, around 200 km away.

As a sought-after commodity, numerous Imilac pallasites have found their way into private or institutional meteorite collections under various names (e.g. Ollague ) and with imprecise or even incorrect information about the location.

exploration

The German-Chilean naturalist Rudolfo Philippi came to Imilac in January 1854 on an expedition commissioned by the Chilean government. He was led to the site by José María Chaile, one of the discoverers and self-declared owner of the iron mine. Philippi was the first researcher to investigate the site and publish a description. The meteorite field was already largely exploited. Philippi and his companions were only able to recover numerous, smaller fragments with an estimated total weight of 4.5 kg. He believed the Imilac crater, which was about 6 m deep at the time, to be a pit that earlier iron seekers had dug. Several smaller excavation holes were also found in the surrounding hills.

After that, the Imilac litter field was not rediscovered for science until April 1973. The Imilac crater was about 3 m deep with a diameter of 6 to 8 m at the time. Using a metal detector, 2430 pallasite fragments with a total weight of 4.8 kg were found in the vicinity. For the first time a position was determined and a sketch was published. According to the information published up to that point, it could be determined that a total of 500 kg of material had been recovered from Imilac.

During a geological survey and after indications from locals who knew of earlier finds, three were found in 1987 up to 8 km away from the Iimilac crater, at the foot of the Morro de la Mina mountain ( 24 ° 17 ′  S , 68 ° 54 ′  W ) further Pallasites with a total of 59 kg found. Two of them in intact craters of 80 and 125 cm in diameter.

At the beginning of 1996 the area around the Imilac crater was systematically searched again with metal detectors. Two further, well-preserved impact craters of 2 m and 1.5 m in diameter were discovered in a south-westerly direction, 200 m and 500 m away, respectively. They are on a line with the large crater that corresponds to the direction of flight of the meteorite. Ribbons of metal splinters distributed radially from the crater were found. At least four such radiation patterns extend up to 80 m in eastern directions. It is estimated that there could be a ton of smaller iron particles in this secondary stray field.

Web links

Commons : Imilac  - collection of images, videos and audio files

Individual evidence

1. ^ Joaquin Sanchez, William Cassidy: A previously undescribed meteorite crater in Chile . In: Journal of Geophysical Research . tape 71 , no. October 20 , 1966, p. 4891–4895 ( astro-udec.cl ( Memento from December 4, 2013 in the Internet Archive ) [PDF; 438 kB ; accessed on October 6, 2013]).
2. ^ F. Ferrando A .: Two unknown Meteor Craters in Antofagasta Region, Northern Chile . In: Revista Geográfica . tape 85 , June 1977, ISSN  0031-0581 , pp. 210-212 , JSTOR : 40993113 .
3. ^ The Meteoritical Society , Meteoritical Bulletin Database , accessed November 20, 2013.
4. ^ Monica M. Grady: The Catalog of Meteorites . With special reference to those represented in the collection of The Natural History Museum, London. 5th edition. The Natural History Museum , London 2000, ISBN 0-521-66303-2 ( online database , excerpt ).
5. ↑ Coordinates according to Google Earth 2013, determined with the help of the site plan by Vagn F. Buchwald 1975.
6. ↑ ^{a b c d e f g h} Vagn F. Buchwald: Imilac, Antofagasta, Chile . In: Handbook of Iron Meteorites . Their history distribution, composition and structure. tape 3 . University of California Press, 1975, ISBN 0-520-02934-8 , pp. 1393-1400 ( manoa.hawaii.edu [accessed November 15, 2013]).
7. ↑ ^{a b} BM Killgore: Imilac Strewnfield, Chile, revisited . In: Conference Paper, 28th Lunar and Planetary Science Conference . Houston TX March 1997, p. 725 ( lpi.usra.edu [PDF; 11 kB ; accessed on November 3, 2013]).
8. ↑ ^{a b c d} Holger Pedersen, F. Garcia: Nuevos meteoritos habenrados en Imilac . In: The ESO Messenger . No. 47 , March 1987, ISSN  0722-6691 , p. 1–3 ( eso.org [PDF; 1.7 MB ; accessed on November 3, 2013]).
9. ^ ^{A b} Holger Pedersen, Harri Lindgren, Claudio Canut de Bon: Strewn-fields of Imilac and Vaca Muerta . In: Meteoritics . tape 24 , no. 47 , December 1989, p. 314 , bibcode : 1989Metic..24R.314P .
10. ↑ ^{a b c d e f g} Lazarus Fletcher : On the meteorites which have been found in the desert of Atacama and its neighborhood . In: Mineralogical Magazine . tape  8 , no. 40 , 1889, pp. 223–264 , doi : 10.1180 / minmag.1889.008.40.01 ( minersoc.org [PDF; 2.8 MB ; accessed on November 10, 2013]).
11. ^ ^{A b} Vagn F. Buchwald: The pallasite Imilac, Chile . In: Meteoritics . tape 8 , 1973, p. 333–334 , bibcode : 1973Metic ... 8..333B .
12. ^ ^{A b} William Bollaert: On the geography of southern Peru . Meteoritic iron of Atacama. In: The Journal of the Royal Geographical Society of London . tape 21 , 1851, pp. 126–130 ( limited preview in Google Book Search [accessed November 10, 2013]).
13. ^ ^{A b} Rudolfo Philippi : Memoria sobre el hierro meteórico del Desierto de Atacama. Discursco de recepción del miembro de la Facultad de Ciencias Fisicas i Matemáticas doctor don Rudolfo Philippi. In: Anales de la Universidad de Chile . tape  January 11 , February, March. Imprenta del Siglo, 1854, p. 209–217 ( limited preview in Google Book Search [accessed November 14, 2013]).
14. ↑ ^{a b c} Rudolph Amandus Philippi : Journey through the Atacama desert . Taken and described by order of the Chilean government in the summer of 1853-1854. Eduard Anton, Halle 1860 ( limited preview in Google book search [accessed December 30, 2012]).
15. ↑ Gerald Joseph Home McCall, AJ Bowden, Richard John Howarth: The History of Meteoritics and Key Meteorite Collections . Fireballs, Falls and Finds. Geological Society of London, 2006, ISBN 978-1-86239-194-9 , ISSN  0305-8719 ( limited preview in Google Book Search [accessed November 17, 2013]).
16. ↑ Woodbine Parish: Buenos Ayres and the provinces of the Rio de la Plata . Their present state, trade, and debt; with some account from original documents of the progress of geographical discovery in those parts of South America during the last sixty years. John Murray, London 1839 ( limited preview in Google Book Search [accessed November 15, 2013]).
17. ↑ Woodbine Parish: Buenos Ayres and the provinces of the Rio de la Plata . Their discovery and conquest by the Spaniards to the establishment of their political independence. John Murray, London 1852 ( limited preview in Google Book Search [accessed November 15, 2013]).
18. ↑ Thomas Allan : On a mass of native iron from the Desert of Atacama in Peru . In: The Edinburgh Journal of Science . tape  9 , April-October, 1828, pp. 259–262 ( limited preview in Google Book Search [accessed November 15, 2013]).
19. ^ Edward Turner : Examination of the specimen of native iron from the Desert of Atacama in Peru . In: The Edinburgh Journal of Science . tape  9 , April-October, 1828, pp. 262–264 ( limited preview in Google Book Search [accessed November 15, 2013]).
20. ↑ Meteoritical Bulletin Database - Imilac ( Ollague in the NHM catalog)
21. ↑ Coordinates according to Google Earth 2013.