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Further evidence for an impact origin of the Tsenkher structure in the Gobi-Altai, Mongolia : Geology of a 3.7 km crater with a well-preserved ejecta blanket

Komatsu, Goro; Ormö, Jens; Bayaraa, Togookhuu; Arai, Tomoko; Nagao, Keisuke; Hidaka, Yoshihiro; Shirai, Naoki; Ebihara, Mitsuru; Alwmark, Carl LU and Gereltsetseg, Lkhagva, et al. (2019) In Geological Magazine 156(1). p.1-24
Abstract

The Tsenkher structure in the Gobi-Altai, Mongolia is a c. 3.7 km diameter crater with a well-preserved ejecta blanket. It has been hypothesized to be either of impact or volcanic origin in our previous work. Observations during our 2007 expedition and related sample analyses give further support for an impact origin. The evidence includes the presence of a structurally uplifted near-circular rim surrounded by an ejecta blanket, and abundant breccias, some of which are melt- A nd millimetre-scale spherule-bearing. Planar deformation features (PDFs) were found in one quartz grain in a breccia sample. Fe-rich grains are found in a vesicular melt sample that is also characterized by elevated platinum group element (PGE) abundances with... (More)

The Tsenkher structure in the Gobi-Altai, Mongolia is a c. 3.7 km diameter crater with a well-preserved ejecta blanket. It has been hypothesized to be either of impact or volcanic origin in our previous work. Observations during our 2007 expedition and related sample analyses give further support for an impact origin. The evidence includes the presence of a structurally uplifted near-circular rim surrounded by an ejecta blanket, and abundant breccias, some of which are melt- A nd millimetre-scale spherule-bearing. Planar deformation features (PDFs) were found in one quartz grain in a breccia sample. Fe-rich grains are found in a vesicular melt sample that is also characterized by elevated platinum group element (PGE) abundances with respect to the sedimentary bedrock of the area (approximately an order of magnitude). Noble gas analysis of one breccia sample yielded an elevated 3He/4He value of (5.0±0.2) × 10-6. Although not conclusive alone, these geochemical results are consistent with a contribution of meteoritic components. A volcanic origin, in particular a maar formation, would require explanations for the unusual conditions associated with Tsenkher, including its large size occurring in isolation, the structurally uplifted rim and the lack of a bedded base surge deposit. A pronounced rampart structure observed at the eastern ejecta is also unusual for any volcanic origin. 40Ar-39Ar dating of a vesicular melt sample gives an age of the Tsenkher structure of 4.9±0.9 Ma. The rampart structure could provide insights into the formation of similar ejecta morphologies associated with numerous impact craters on Mars.

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published
subject
keywords
breccia, ejecta, impact crater, maar, Mongolia, raised rim, Tsenkher
in
Geological Magazine
volume
156
issue
1
pages
24 pages
publisher
Cambridge University Press
external identifiers
  • scopus:85059911695
ISSN
0016-7568
DOI
10.1017/S0016756817000620
language
English
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yes
id
f8804831-353b-4f1f-8fa3-a07ec6f3192d
date added to LUP
2019-01-24 12:54:48
date last changed
2019-02-20 11:44:24
@article{f8804831-353b-4f1f-8fa3-a07ec6f3192d,
  abstract     = {<p>The Tsenkher structure in the Gobi-Altai, Mongolia is a c. 3.7 km diameter crater with a well-preserved ejecta blanket. It has been hypothesized to be either of impact or volcanic origin in our previous work. Observations during our 2007 expedition and related sample analyses give further support for an impact origin. The evidence includes the presence of a structurally uplifted near-circular rim surrounded by an ejecta blanket, and abundant breccias, some of which are melt- A nd millimetre-scale spherule-bearing. Planar deformation features (PDFs) were found in one quartz grain in a breccia sample. Fe-rich grains are found in a vesicular melt sample that is also characterized by elevated platinum group element (PGE) abundances with respect to the sedimentary bedrock of the area (approximately an order of magnitude). Noble gas analysis of one breccia sample yielded an elevated <sup>3</sup>He/<sup>4</sup>He value of (5.0±0.2) × 10<sup>-6</sup>. Although not conclusive alone, these geochemical results are consistent with a contribution of meteoritic components. A volcanic origin, in particular a maar formation, would require explanations for the unusual conditions associated with Tsenkher, including its large size occurring in isolation, the structurally uplifted rim and the lack of a bedded base surge deposit. A pronounced rampart structure observed at the eastern ejecta is also unusual for any volcanic origin. <sup>40</sup>Ar-<sup>39</sup>Ar dating of a vesicular melt sample gives an age of the Tsenkher structure of 4.9±0.9 Ma. The rampart structure could provide insights into the formation of similar ejecta morphologies associated with numerous impact craters on Mars.</p>},
  author       = {Komatsu, Goro and Ormö, Jens and Bayaraa, Togookhuu and Arai, Tomoko and Nagao, Keisuke and Hidaka, Yoshihiro and Shirai, Naoki and Ebihara, Mitsuru and Alwmark, Carl and Gereltsetseg, Lkhagva and Tserendug, Shoovdor and Goto, Kazuhisa and Matsui, Takafumi and Demberel, Sodnomsambuu},
  issn         = {0016-7568},
  keyword      = {breccia,ejecta,impact crater,maar,Mongolia,raised rim,Tsenkher},
  language     = {eng},
  number       = {1},
  pages        = {1--24},
  publisher    = {Cambridge University Press},
  series       = {Geological Magazine},
  title        = {Further evidence for an impact origin of the Tsenkher structure in the Gobi-Altai, Mongolia : Geology of a 3.7 km crater with a well-preserved ejecta blanket},
  url          = {http://dx.doi.org/10.1017/S0016756817000620},
  volume       = {156},
  year         = {2019},
}