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. 2020 Mar 25;20(4):475–499. doi: 10.1089/ast.2019.2044

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© Steven W. Ruff et al., 2020; Published by Mary Ann Liebert, Inc.

This Open Access article is distributed under the terms of the Creative Commons Attribution Noncommercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.

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FIG. 13. — Evidence for nodular opaline silica in contact with Halley class rocks at the southern tip of Mitcheltree Ridge. (A) Cropped portion of the Pancam ATC McMurdo panorama looking N from Low Ridge showing context of Halley class buff-colored platy bedrock. Rectangle represents view in (B) and (C). Rover tracks are ∼1 m apart. (B) A false-color Pancam image (sol 1113, P2456) of unnamed rocks includes light-toned nodular rocks, one with pronounced digitate structures, appearing to erode from the layered Halley class outcrop. Bluish rocks include spherical grains, presumably accretionary lapilli similar to those in volcaniclastic rocks at Low Ridge. (C) The Pancam hydration signature supports an opaline silica composition for the nodular rocks and possible silicification of Halley rocks. Blue to red hues show low to high values, respectively, with red corresponding to the value observed for the known opaline silica materials at Gertrude Weise and Elizabeth Mahon.