P024-0009
Trends in Trace Elements from Biogenic and Abiogenic Manganese Oxides

Wednesday, 9 December 2020
Poster
Lauren Judge1, Amy J Williams2, Nina Lanza3, Ann Ollila3, Mike Spilde4 and Virgil Lueth5, (1)University of Florida, Department of Geological Sciences, Gainesville, FL, United States, (2)University of Florida, Department of Geological Sciences, Ft Walton Beach, FL, United States, (3)Los Alamos National Laboratory, Los Alamos, NM, United States, (4)University of New Mexico Main Campus, Albuquerque, NM, United States, (5)New Mexico Institute of Mining and Technology, Socorro, NM, United States
Abstract:
Mn-oxidizing microorganisms (microbes) on Earth facilitate the formation of manganese oxides, which require high pH and Eh conditions to precipitate. Due to the microbial provenance of Mn oxides, Mn oxides on Mars should be explored for their potential as mineral biosignatures. It is possible to distinguish abiogenic and biogenic Mn-oxides with a suite of analyses on Earth. However, rover payload instruments are limited, and using these instruments to test the biogenicity of Mn oxides has not been assessed. As one of the goals of the Perseverance and Rosalind Franklin rover missions is to identify samples containing potential biosignatures (evidence of life recorded in the rock record), it is important to identify the biosignatures that would be detectable with the rover payloads.

Trace element (TE) data were collected from three New Mexico Mn oxide samples with ICP-MS bulk dissolution analysis. Sample MCA is banded Mn-oxide and calcite from the hydrothermal deposit at MCA mine (Socorro County, NM), and is likely abiotic due to the high temperatures experienced by this paleo-hydrothermal environment. TC is a stromatolitic manganese mineralization from the Ellis Mn deposit (T or C, NM), presumed to be biotic because of the unusual “cauliflower-like” textures of the ores. TM is from Tortugas Mountain and is banded Mn-oxide and calcite from a geothermal spring edifice (Dona Ana County, NM), which is likely biotic based on morphologic characteristics similar to the Ellis Mn ores. These samples were compared with two biotic deep-sea Mn nodules (Nod-P and Nod-A). Initial TE data indicate that TC is biotic, while MCA and TM are abiotic. TC and both Mn nodules have higher Mn than Ca, while MCA and TM have more Ca. The nodules and TC also have higher amounts of Ti and Ni than MCA and TM. TC is also elevated in Ba relative to the other samples and the nodules. This data supports the expected biogenicity of TC and abiogenicity of MCA but contradicts the expected biogenicity of TM. On-going analyses with laser ablation (LA) ICP-MS are being conducted to determine how well microscale analyses of these Mn oxides represent the whole sample. Because laser-induced breakdown spectroscopy is available on Mars rover missions, it is important to understand how TE abundance and trends can be linked to biogenicity with laser-based space flight instruments.

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