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Constraining the Texture and Composition of Pore-Filling Cements at Gale Crater, MarsThe Mars Science Laboratory (MSL) rover Curiosity has encountered a wide variety of sedimentary rocks deposited in fluvio-lacuestrine sequences at the base of Gale Crater. The presence of sedimentary rocks requires that initial sediments underwent diagenesis and were lithified. Lithification involves sediment compaction, cementation, and re-crystallization (or authigenic) processes. Analysis of the texture and composition of the cement can reveal the environmental conditions when the cements were deposited, enabling better understanding of early environments present within Gale Crater. The first step in lithification is sediment compaction. The Gale crater sediments do not show evidence for extensive compaction prior to cementation; the Sheepbed mudstone in Yellowknife Bay (YKB) has preserved void spaces ("hollow nodules"), indicating that sediments were cemented around the hollow prior to compaction, and conglomerates show imbrication, indicating minimal grain reorganization prior to lithification. Furthermore, assuming the maximum burial depth of these sediments is equivalent to the depth of Gale Crater, the sediments were never under more than 1 kb of pressure, and assuming a 15 C/km thermal gradient in the late Noachian, the maximum temperature of diagenesis would have been approximately 75 C. This is comparable to shallow burial diagenetic conditions on Earth. The cementation and recrystallization components of lithification are closely intertwined. Cementation describes the precipitation of minerals between grains from pore fluids, and recrystallization (or authigenesis) is when the original sedimentary mineral grains are altered into secondary minerals. The presence of authigenic smectites and magnetite in the YKB formation suggests that some recrystallization has taken place. The relatively high percentage of XRD-amorphous material (25-40%) detected by CheMin suggests that this recrystallization may be limited in scope, and therefore may not contribute significantly to the cementing material. However, relatively persistent amorphous components could exist in the Martian environment (e.g. amorphous MgSO4), so recrystallization, including loss of crystallinity, cannot yet be excluded as a method of cementation. In order to describe the rock cementation, both the rock textures and their composition must be considered. Here, we attempt to summarize the current understanding of the textural and compositional aspects of the cement across the rocks analyzed by Curiosity to this point.
Document ID
20150002843
Acquisition Source
Johnson Space Center
Document Type
Conference Paper
Authors
Siebach, K. L.
(California Inst. of Tech. Pasadena, CA, United States)
Grotzinger, J. P.
(California Inst. of Tech. Pasadena, CA, United States)
McLennan, S. M.
(Stony Brook Univ. Stony Brook, NY, United States)
Hurowitz, J. A.
(Stony Brook Univ. Stony Brook, NY, United States)
Ming, D. W.
(NASA Johnson Space Center Houston, TX, United States)
Vaniman, D. T.
(Planetary Science Inst. Tucson, AZ, United States)
Rampe, E. B.
(Aerodyne Industries Houston, TX, United States)
Blaney, D. L.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Kah, L. C.
(Tennessee Univ. Knoxville, TN, United States)
Date Acquired
March 12, 2015
Publication Date
March 16, 2015
Subject Category
Lunar And Planetary Science And Exploration
Chemistry And Materials (General)
Report/Patent Number
JSC-CN-32873
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: The Woodlands, TX
Country: United States
Start Date: March 16, 2015
End Date: March 20, 2015
Sponsors: Lunar and Planetary Inst., Universities Space Research Association, NASA Johnson Space Center
Distribution Limits
Public
Copyright
Public Use Permitted.
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