Composition of conglomerates analyzed by the Curiosity rover: Implications for Gale Crater crust and sediment sources

Mangold, N.; Thompson, L. M.; Forni, O.; Williams, Amy J.; Fabre, C.; Deit, L. Le; Wiens, R. C.; Williams, R. M. E.; Anderson, R. B.; Blaney, D. L.; Calef, F.; Cousin, A.; Clegg, S. M.; Dromart, G.; Dietrich, W. E.; Edgett, K. S.; Fisk, Martin; Gasnault, O.; Gellert, R.; Grotzinger, J. P.; Kah, L. C.; Mouëlic, Stéphane Le; McLennan, Scott M.; Maurice, S.; Meslin, P. Y.; Newsom, H. E.; Palucis, M. C.; Rapin, W.; Sautter, V.; Siebach, K. L.; Stack, K. M.; Sumner, D. Y.; Yingst, Aileen

doi:10.1002/2015je004977

Cited by 57 publications

(67 citation statements)

References 77 publications

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“…The range of modeled plagioclase end‐member compositions (An 30–40 ) were selected to encompass a reasonable range based on orbital, CheMin, and ChemCam observations. These include the normative plagioclase composition for average Martian crust, An 34 ; CheMin analyses of a Sheepbed mudstone and the K‐rich sandstone Windjana, ~An 35–45 [ Vaniman et al ., ; Treiman et al ., ] (Morrison, personal communication); and trends in ChemCam analyses of Bradbury group rocks in SiO 2 ‐Al 2 O 3 space, which are consistent with plagioclase compositions of An 30–40 [ Mangold et al ., ]. Figure shows, in oxide‐MgO space, the mixing lines between An 30 or An 40 plagioclase and average Martian soil.…”

Section: Resultsmentioning

confidence: 99%

Sorting out compositional trends in sedimentary rocks of the Bradbury group (Aeolis Palus), Gale crater, Mars

et al. 2017

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Sedimentary rocks are composed of detrital grains derived from source rocks, which are altered by chemical weathering, sorted during transport, and cemented during diagenesis. Fluvio‐lacustrine sedimentary rocks of the Bradbury group, observed on the floor of Gale crater by the Curiosity rover during its first 860 Martian solar days, show trends in bulk chemistry that are consistent with sorting of mineral grains during transport. The Bradbury group rocks are uniquely suited for sedimentary provenance analysis because they appear to have experienced negligible cation loss (i.e., open‐system chemical weathering) at the scale of the Alpha Particle X‐ray Spectrometer bulk chemistry analyses based on low Chemical Index of Alteration values and successful modeling of >90% of the (volatile‐free) targets as mixtures of primary igneous minerals. Significant compositional variability between targets is instead correlated to grain‐size and textural characteristics of the rocks; the coarsest‐grained targets are enriched in Al2O3, SiO2, and Na2O, whereas the finer‐grained targets are enriched in mafic components. This is consistent with geochemical and mineralogical modeling of the segregation of coarse‐grained plagioclase from finer‐grained mafic minerals (e.g., olivine and pyroxenes), which would be expected from hydrodynamic sorting of the detritus from mechanical breakdown of subalkaline plagioclase‐phyric basalts. While the presence of a distinctive K2O‐rich stratigraphic interval shows that input from at least one distinctive alkali‐feldspar‐rich protolith contributed to basin fill, the dominant compositional trends in the Bradbury group are consistent with sorting of detrital minerals during transport from relatively homogeneous plagioclase‐phyric basalts.

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Section: Resultsmentioning

confidence: 99%

Sorting out compositional trends in sedimentary rocks of the Bradbury group (Aeolis Palus), Gale crater, Mars

et al. 2017

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“…After leaving the Square_Top location, Curiosity traversed east and imaged a pebble conglomerate outcrop named Point_Coulomb. These conglomerates are consistently observed at the base of the stratigraphic section and have been collectively termed the Point_Coulomb member of the Kimberley formation [ Mangold et al ., ; Le Deit et al ., ].…”

Section: Overview Of the Kimberley Campaignmentioning

confidence: 98%

“…As described by Mangold et al . [], the conglomerate outcrops observed by ChemCam on Bradbury rise (prior to sol 540) have a felsic alkali‐rich composition (with a Na 2 O/K 2 O > 5), whereas those observed during the Kimberley campaign have an alkali‐rich potassic composition with Na 2 O/K 2 O < 2. ChemCam observations of the other members of the Kimberley formation are described in detail by Le Deit et al .…”

Section: Sediment Provenancementioning

confidence: 99%

Geologic overview of the Mars Science Laboratory rover mission at the Kimberley, Gale crater, Mars

et al. 2017

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The Mars Science Laboratory (MSL) Curiosity rover completed a detailed investigation at the Kimberley waypoint within Gale crater from sols 571–634 using its full science instrument payload. From orbital images examined early in the Curiosity mission, the Kimberley region had been identified as a high‐priority science target based on its clear stratigraphic relationships in a layered sedimentary sequence that had been exposed by differential erosion. Observations of the stratigraphic sequence at the Kimberley made by Curiosity are consistent with deposition in a prograding, fluvio‐deltaic system during the late Noachian to early Hesperian, prior to the existence of most of Mount Sharp. Geochemical and mineralogic analyses suggest that sediment deposition likely took place under cold conditions with relatively low water‐to‐rock ratios. Based on elevated K2O abundances throughout the Kimberley formation, an alkali feldspar protolith is likely one of several igneous sources from which the sediments were derived. After deposition, the rocks underwent multiple episodes of diagenetic alteration with different aqueous chemistries and redox conditions, as evidenced by the presence of Ca‐sulfate veins, Mn‐oxide fracture fills, and erosion‐resistant nodules. More recently, the Kimberley has been subject to significant aeolian abrasion and removal of sediments to create modern topography that slopes away from Mount Sharp, a process that has continued to the present day.

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“…Outcrops encountered in the HP unit correspond to fluvial conglomerates bearing pebbles of various compositions but dominated by plagioclase mineralogy [ Williams et al ., ; Mangold et al , ]. The higher abundance of Mg in clastic fracture fills cutting conglomerates suggests late episodes of postdepositional aqueous alteration possibly coeval with that of YKB [ Mangold et al ., ]. Curiosity also analyzed float igneous rocks containing a significant feldspar component and corresponding to two distinct geochemical series [ Sautter et al ., ].…”

Section: Introductionmentioning

confidence: 99%

The potassic sedimentary rocks in Gale Crater, Mars, as seen by ChemCam on board Curiosity

et al. 2016

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The Mars Science Laboratory rover Curiosity encountered potassium-rich clastic sedimentary rocks at two sites in Gale Crater, the waypoints Cooperstown and Kimberley. These rocks include several distinct meters thick sedimentary outcrops ranging from fine sandstone to conglomerate, interpreted to record an ancient fluvial or fluvio-deltaic depositional system. From ChemCam Laser-Induced Breakdown Spectroscopy (LIBS) chemical analyses, this suite of sedimentary rocks has an overall mean K 2 O abundance that is more than 5 times higher than that of the average Martian crust. The combined analysis of ChemCam data with stratigraphic and geographic locations reveals that the mean K 2 O abundance increases upward through the stratigraphic section. Chemical analyses across each unit can be represented as mixtures of several distinct chemical components, i.e., mineral phases, including K-bearing minerals, mafic silicates, Fe-oxides, and Fe-hydroxide/oxyhydroxides. Possible K-bearing minerals include alkali feldspar (including anorthoclase and sanidine) and K-bearing phyllosilicate such as illite. Mixtures of different source rocks, including a potassium-rich rock located on the rim and walls of Gale Crater, are the likely origin of observed chemical variations within each unit. Physical sorting may have also played a role in the enrichment in K in the Kimberley formation. The occurrence of these potassic sedimentary rocks provides additional evidence for the chemical diversity of the crust exposed at Gale Crater.

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Composition of conglomerates analyzed by the Curiosity rover: Implications for Gale Crater crust and sediment sources

Cited by 57 publications

References 77 publications

Sorting out compositional trends in sedimentary rocks of the Bradbury group (Aeolis Palus), Gale crater, Mars

Sorting out compositional trends in sedimentary rocks of the Bradbury group (Aeolis Palus), Gale crater, Mars

Geologic overview of the Mars Science Laboratory rover mission at the Kimberley, Gale crater, Mars

The potassic sedimentary rocks in Gale Crater, Mars, as seen by ChemCam on board Curiosity

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