Investigating the source of unusual kaolinite-spinel float rocks in Jezero crater, Mars, and their implications for Mars crustal processes. - INSU - Institut national des sciences de l'Univers
Communication Dans Un Congrès Année : 2024

Investigating the source of unusual kaolinite-spinel float rocks in Jezero crater, Mars, and their implications for Mars crustal processes.

Clément Royer
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Résumé

Since Landing in Jezero crater, the Mars 2020 Perseverance rover has encountered over 4,000 light-toned float rocks (“float”) scattered across the dark-toned, mafic to ultramafic crater floor and volcaniclastic Jezero delta. To date (Sol ~1100), no outcrop of these light-toned float has been found. Here, we use imaging, chemical, and mineralogical data from the SuperCam and Mastcam-Z instruments onboard the Perseverance rover to constrain the potential origins of these unusual float. Geochemical data acquired from the SuperCam laser induced breakdown spectrometer (LIBS) shows that these rocks are rich in Al2O3 (up to 44 wt%), with low abundances of MgO, FeOT, CaO and Na2O (averages <2 wt%) and an unusually high abundance of Ni, Cr, and Cu. Al2O3 abundances in these rocks are negatively correlated with SiO2 and hydration. Mineralogical data provided by SuperCam Visible Near-Infrared spectrometer show that the main minerals present in these rocks are likely kaolinite (strong signature in one target) and spinel, with potential accessory sulfates, zeolites, Al-smectite/illite, and hydrated silica or alumina. Kaolinite horizons overlying Fe/Mg smectite clay horizons have been detected in multiple places in the Jezero crater watershed suggesting that a possible formation mechanism for the high Al2O3 abundances and low MgO, FeOT, CaO, and Na2O, and the mineralogical observation of kaolinite could be due to pedogenic leaching in a warmer and wetter ancient Mars [1]. However, the low hydration observed by both LIBS and IR spectra in many of these targets suggests they are rich in metakaolinite, a metastable dehydroxylated kaolinite. Temperatures from 450-700°C are required to form metakaolinite [2]. Spinel is also known to form from high temperature metamorphism of Al-bearing rocks [e.g., 3]. Possible sources of heat in the Jezero crater watershed or crater rim include impact or volcanic processes. Due to the presence of a kaolinite-bearing megabreccia block and several detections of light-toned boulders on the Jezero crater rim in long-distance images, we suggest impact metamorphism of a kaolinite weathering horizon is the most likely source of these light-toned float. [1] Ehlmann et al., 2009 https://doi.org/10.1029/2009JE003339 [2] Sperinck et al., 2011 https://doi.org/10.1039/C0JM01748E [3] Wang et al., 2021 https://doi.org/10.1007/s00710-021-00743-1
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insu-04683181 , version 1 (01-09-2024)

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  • HAL Id : insu-04683181 , version 1

Citer

Candice Bedford, Clément Royer, Roger C. Wiens, Jeffrey R. Johnson, Briony H. N. Horgan, et al.. Investigating the source of unusual kaolinite-spinel float rocks in Jezero crater, Mars, and their implications for Mars crustal processes.. Goldschmidt Conference 2024, Aug 2024, Chicago, United States. ⟨insu-04683181⟩
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