TY - JOUR
T1 - Alteration of immature sedimentary rocks on Earth and Mars
T2 - Recording aqueous and surface-atmosphere processes
AU - Cannon, Kevin M.
AU - Mustard, John F.
AU - Salvatore, Mark R.
N1 - Funding Information:
We are greatly indebted to Ralph Milliken for suggestions that significantly improved this manuscript, and to Janice Bishop and an anonymous reviewer for thorough reviews. We would also like to thank Janette Wilson, Kwok Wong, Jennifer Bentz, Takahiro Hiroi, Joseph Bosenberg, Sue Wirick, and William Rao for assistance with instrumental techniques. Portions of this work were performed at Beamline X26A, National Synchrotron Light Source (NSLS), Brookhaven National Laboratory. X26A is supported by the Department of Energy ( DOE ) – Geosciences ( DE-FG02-92ER14244 to The University of Chicago – CARS). Use of the NSLS was supported by DOE under Contract No. DE-AC02-98CH10886 .
Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/5/1
Y1 - 2015/5/1
N2 - Rock alteration and rind formation in analog environments like Antarctica may provide clues to rock alteration and therefore paleoclimates on Mars. Clastic sedimentary rocks derived from basaltic sources have been studied in situ by martian rovers and are likely abundant on the surface of Mars. However, how such rock types undergo alteration when exposed to different environmental conditions is poorly understood compared with alteration of intact basaltic flows. Here we characterize alteration in the chemically immature Carapace Sandstone from Antarctica, a terrestrial analog for martian sedimentary rocks. We employ a variety of measurements similar to those used on previous and current Mars missions. Laboratory techniques included bulk chemistry, powder X-ray diffraction (XRD), hyperspectral imaging and X-ray absorption spectroscopy. Through these methods we find that primary basaltic material in the Carapace Sandstone is pervasively altered to hydrated clay minerals and palagonite as a result of water-rock interaction. A thick orange rind is forming in current Antarctic conditions, superimposing this previous aqueous alteration signature. The rind exhibits a higher reflectance at visible-near infrared wavelengths than the rock interior, with an enhanced ferric absorption edge likely due to an increase in Fe3+ of existing phases or the formation of minor iron (oxy)hydroxides. This alteration sequence in the Carapace Sandstone results from decreased water-rock interaction over time, and weathering in a cold, dry environment, mimicking a similar transition early in martian history. This transition may be recorded in sedimentary rocks on Mars through a similar superimposition mechanism, capturing past climate changes at the hand sample scale. Our results also suggest that basalt-derived sediments could have sourced significant volumes of hydrated minerals on early Mars due to their greater permeability compared with intact igneous rocks.
AB - Rock alteration and rind formation in analog environments like Antarctica may provide clues to rock alteration and therefore paleoclimates on Mars. Clastic sedimentary rocks derived from basaltic sources have been studied in situ by martian rovers and are likely abundant on the surface of Mars. However, how such rock types undergo alteration when exposed to different environmental conditions is poorly understood compared with alteration of intact basaltic flows. Here we characterize alteration in the chemically immature Carapace Sandstone from Antarctica, a terrestrial analog for martian sedimentary rocks. We employ a variety of measurements similar to those used on previous and current Mars missions. Laboratory techniques included bulk chemistry, powder X-ray diffraction (XRD), hyperspectral imaging and X-ray absorption spectroscopy. Through these methods we find that primary basaltic material in the Carapace Sandstone is pervasively altered to hydrated clay minerals and palagonite as a result of water-rock interaction. A thick orange rind is forming in current Antarctic conditions, superimposing this previous aqueous alteration signature. The rind exhibits a higher reflectance at visible-near infrared wavelengths than the rock interior, with an enhanced ferric absorption edge likely due to an increase in Fe3+ of existing phases or the formation of minor iron (oxy)hydroxides. This alteration sequence in the Carapace Sandstone results from decreased water-rock interaction over time, and weathering in a cold, dry environment, mimicking a similar transition early in martian history. This transition may be recorded in sedimentary rocks on Mars through a similar superimposition mechanism, capturing past climate changes at the hand sample scale. Our results also suggest that basalt-derived sediments could have sourced significant volumes of hydrated minerals on early Mars due to their greater permeability compared with intact igneous rocks.
KW - Alteration
KW - Mars
KW - Sedimentary
KW - Spectroscopy
KW - Weathering
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U2 - 10.1016/j.epsl.2015.02.017
DO - 10.1016/j.epsl.2015.02.017
M3 - Article
AN - SCOPUS:84924188364
SN - 0012-821X
VL - 417
SP - 78
EP - 86
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -